RONALD FRANK 23701 TIARA ST. WOODLAND HILLS, CALIF. THE FUTURE IS NOW On Friday, October fourth, 1957 (Russian Time), at an unspecified moment, Soviet rockets propelled into outer space the first man-made Moon—first of the artificial Earth {-j upper atmosphere and returned to Earth. The eight-hour trip ' T^ was undertaken for the USAF Aero Medical Laboratory. Numerous tests will soon determine what the effects of the flight were on the tissue and brain—and whether the skull was punctured by cosmic dust, microscopical particles flying about in the universe with speeds so great that one barely visible particle could penetrate a sheet of automobile steel. When a human skull is placed inside a satellite vehicle that circum navigates the Earth, medical researchers will be able to deter mine the effects of space radiations on the brain tissue, and on disease bacilli. It has been suggested that a better understand ing of certain radiations will help us find a cure for cancer. ' 4 This success alone would be worth huge grants of money for satellite science. The first small satellites will be used for determining outer atmospheric densities. They will also be used to obtain more accurate measures of the Earth's equatorial oblateness, of intercontinental distances and other geodetic data. This means that we shall be able to make accurate maps and construct better navigational devices for our ships and airplanes. We shall also investigate the nature and effect of ultraviolet radiations, and the relative abundance of matter, such as hydrogen, in space. In a satellite equipped with Geiger counters, cosmic rays will be studied. These high-speed rays from outer space are not completely understood. Involving the highest energy particles known, the study of cosmic rays is of great interest to the scientist. From a practical point of view, cosmic rays interest the promoters of space flight, for the rays could constitute a potential hazard. As the source of practically all the energy affecting the Earth and its atmosphere, sunlight is of prime interest and importance. The ultraviolet and other regions of the solar spectrum are absorbed at high altitudes causing photochemical activity, heating and winds. Variations in intensity of the solar radiations are associated with corresponding variations of atmospheric and weather phenomena. With photon counters—sensitive instruments for measuring tiny amounts of electromagnetic energy—the ultraviolet regions of the solar spectrum can be monitored above the atmosphere which absorbs these ultraviolet waves. In particular, the opportunity will exist to observe the ultraviolet light curve of the Sun during the occurrence of solar flares. Interplanetary space is not a complete vacuum. Its actual density is not definitely known, although the figure of one atom per cubic centimeter (0.06 cubic inch) has been used. The data on which this estimate is based are meager; to provide a better estimate will be the object of some of the satellite experiments. It might be possible to observe the Sun directly by means of photon counters, and simultaneously to observe radiation emanating from some direction other than that of the Sun. By correlating the intensities observed directly from the Sun with those observed at an angle, it should be possible to estimate the average density of hydrogen atoms in space. While most of us must wait to feel the many effects of satellite science, some people have already been touched. Thousands of engineers are being hired every month by those aircraft manufacturers working in the field of satellite flight. The 5 first basketball satellites have already been bypassed by more courageous designs now on the drawing boards. The guided-missile and rocket divisions of practically every major airplane builder now include departments devoted to satellite and spaceflight projects. The job opportunities are many and fascinating. The most obvious evidence of this new engineering develop- -ment has brought a klondike type of rush to central Florida. A migration of 100,000 people is predicted for this state within the next few years. These include not only engineers but also plumbers, carpenters, milkmen, hotel managers, gasoline-station operators, lawyers, dentists, and others with ancillary interests in the satellite. Real estate values have risen spectacularly near Patrick Air Force Base, chosen as the launching site for the first satellites. This migration is a direct result of rockets and satellites. This base, located near Cocoa Beach, southeast of Orlando, has become Satellite City, U.S.A. Scientists and military personnel travel between Washington and Patrick AFB every day. Meetings are being held constantly, for there is much planning to do. The Air Research and Development Command is responsible for the Patrick facility and for the Bahamas Missile Range, a chain of island observation and instrumentation posts stretching from Patrick via Grand Bahama Island, Eleutria, San Salvador, Mayaguana, Grand Turk, Dominican Republic, Puerto Rico, St. Lucia to the Ascension Island in the Atlantic Ocean, near Africa. Several thousand personnel are stationed on these islands. Their job is to track rockets and missiles as they zoom eastward over the Atlantic Ocean. Pan American World Airways, which has wide experience in operating air bases, was awarded the contract for running the Bahama range stations; the Radio Corporation of America is handling the technical tracking job. Some of the people have lived on the range for several years. They will never go back to the mainland for a different job. In the warm and healthy climate, they live inexpensively, and since they earn high salaries, have free room and board, 30 days' vacation a year and free transportation whenever they visit the mainland, one cannot blame them. One couple on Grand Bahama Island pay only $35 a year to the British Government for lease of the land on which they have built their $1,800 rambler. They have no other expenses, no taxes, no household costs. Besides, they earn up to 50 per cent more than they would in similar positions in the United States. There are all types of job openings. This rocket and satellite enterprise will last for many, many years. To these people, the guided missile has been a blessing—soon their work will embrace the whole area of space flight. Who are these people? Some are bulldozer drivers, some run cafeterias, some handle laundries, some operate fire engines. some watch high-flying rockets in radarscopes. Modern living quarters are being erected, as well as motion-picture houses, clubs and gymnasiums. On Grand Bahama Island, several hundred PAA and RCA people are working intensively to be prepared for the future large-scale missile and satellite operations. Only a few years from now there will be a population of 10,000 on this island. There could be no satellites without a formidable rocket technology and a vast fund of missile science experience. We can now build small or large satellites in our laboratories. We can put highly sensitive instruments into them, and we can test the finished unit to find out whether it will work. The construction of a small satellite designed for telemetering data from the upper atmosphere or from space is no more complicated than manufacturing radios and television sets. Artificial satellites may be made on mass-production basis, if necessary. After all, they are only little lightweight metal spheres containing instruments and electronic gear. But the question of putting a satellite into an orbit outside the Earth's atmosphere is a quite different story. Highly advanced rockets are needed for this task. The guidance and stabilization gear of these rockets must operate with near-perfect accuracy. The flow of propellants into the rocket engines must be synchronized to split-second precision. A task force of engineers and technicians is needed for launching and tracking a satellite rocket. Complex ground facilities are required, including such service units as weather stations, communication centers, radar and camera observation posts, laboratories, fire departments—even field hospitals where men can be treated for injuries such as burns from liquid oxygen. Such systems are currently in use at every guided-missile facility; and since there is overlapping experience between weapon systems and designing, building, handling and launching satellite vehicles, the knowledge we have gathered is highly useful. The engineers who design and build engines for our missiles are being asked to make the engines for satellite rockets. The relationship between satellite science and the intercontinental ballistic missile is so close that the over-all construction, launching and guidance techniques are also identical. The intercontinental ballistic missile has been referred to as the ultimate weapon—if one will grant that there can be such an instrument. Present concepts define these weapons quite clearly. In the clipped terminology of aeronautical engineers they are known as ICBM, which is a guided missile so powerful and accurate that it could bomb New York from Moscow (or vice versa) in little more than an hour. Fitted with a nuclear-fission warhead, such missiles would travel at an estimated speed of 8,000 to 16,000 miles an hour, 7 a velocity so great that any defense against them would be exceedingly difficult. It is for this reason that the ICBM, when it is made operational, might be unbeatable. While very little factual information has been released about this country's work on the ICBMs, the U.S. versions so far are known as Convair's SM-65, or Atlas, and Martin's Titan. Companies like Douglas and General Electric are also working on ICBMs. A missile such as the Atlas will take off vertically from a special platform, under the impetus of multiple rocket motors in its lower section. Soon the missile will begin to tilt. At about 15 miles' altitude, the first section will drop away. Another set of rocket motors in the middle section will push the now smaller missile still higher. About 100 miles above the Earth, the second section will drop away, and the final portion, about 30 feet long and 4 feet in diameter, will hurtle through the upper atmosphere as a ballistic shell. These weapons are indicative of the development trends in missile science today—only 30 years after Dr. Robert Goddard fired his liquid-fuel rocket to an altitude of 41 feet. It traveled a distance of 220 feet and reached a velocity of 60 miles per hour. Since then rocketry has become a science of its own. We are on the threshold of a new aeronautical age—not characterized by adjectives such as supersonic or atomic but by the headings Missiles and Satellites. There is no doubt that the theoretical possibilities of the guided missile in warfare has made it imperative to establish a guided-missile industry. Scientists and engineers in general have become enthusiastic over this development because extraordinary challenges are involved, and persons of imagination and creative talent cannot help being fascinated. Since the German V-2s were aimed at London in 1944, speeding many times as fast as the sound of their coming, their military importance has been obvious. This lesson was clearly understood by every military nation. Even before the first atomic bomb, it took little imagination to picture dozens of deadly duties that missiles could perform. And if they had carried atomic warheads, they would have reduced much of England to radioactive rubble. But the missiles of World War II were not dependable. Effective missiles call for a technology that did not exist at that time; new production methods were needed. Better rocket motors, more reliable and disentangled electronics, more intelligent computers and more sensitive instruments were demanded. New metals, ceramics and high-velocity propel-lants were required. Furthermore, adequate guidance techniques had to evolve. The answering of these needs has 8 resulted in more dependable rocket motors, considerably lighter and enormously more powerful. The electronic computers, the brains of the missiles, have grown rapidly in capability. A missile's tiny gyros, bearings and electronic components must be manufactured with superwatchmaker's precision. The job is sometimes done in a windowless factory. Since no speck of dust can be tolerated, the air is changed by fans and filters every few minutes, and positive air pressure is maintained inside the building so that any air leakage will be outward, not inward. Engineers in the drafting rooms are forbidden to tear paper or use pencil erasers as both make dust, and all employees are required to wear nylon smocks. Physically handicapped men and women who are used to sitting long hours without unnecessary motion are said to be among the best assembly workers. It is a historical phenomenon, although not a strange one, that the development of rockets and, in particular, intercontinental missiles—of their power plants and airframes as well as their instruments and warheads—has led into satellite science. Dr. Eugen Sanger, rocket pioneer and first president of the International Astronautical Federation, says that humanity may soon be in the dilemma of declaring war nonsensical—not only on moral, but also on technical grounds—and at the same time be faced with the problem of trying to avoid dropping the gigantic defense organizations of research and industry, as well as of the military establishments. The most natural way out of this dilemma seems to be satellite science. Satellite science and space flight will far better satisfy the urge for adventure, for discharging vitality, for reaching new horizons than does our present-day military aviation. It will require research institutes, industries and military organizations for its implementation. Yet, by this virtue, space flight will accomplish cultural tasks instead of threatening humanity. Looking into the future, we see rockets used logistically in building artificial satellites, we see nuclear rockets on interplanetary research missions—and one day we may even see atomic-powered vehicles speeding across the farthest reaches of the universe. To accomplish these tasks, we shall require sound development programs employing the best scientists and the best engineers. Maybe Patrick AFB, from being a military establishment, one day will have become a giant scientific center for peaceful space-flight operations. If people become space-minded in the sense that they understand the vast scientific possibilities of cosmic flight, the dream of peace may become a reality. It is interesting to note that more than 30 years ago, the father of space flight, Hermann Oberth, revealed plans for building entire stations in space. At that time, few people took 9 his ideas seriously. But Professor Oberth could prove mathematically that satellites or space platforms could be constructed. One of the most remarkable aspects suggested by Oberth at that time was the space mirror concept. A huge mirror in space would reflect the Sun's radiation in focused beams, its utility aspects including heating and illuminating cities. It could also be used to "boil" the water of our oceans, which in turn would yield vapor and rain during drought periods. Considered seriously by many scientists today, the space mirror was first suggested in 1923. It has been stressed on numerous occasions during the last decade that the achievement of space flight will require fantastic sums of money, amounts that would strain the budgets of even the largest nations. If we talk in terms of large manned-space-station systems, it might be that the solution will be found in global collaboration, and such space projects require an almost perfect level of world peace. Dr. Walter Dornberger, formerly commanding general of Nazi Germany's famous Rocket Test Station, Peenemunde, and now Missile Design Consultant for Bell Aircraft, has said that it is likely that only military reasons could ever muster the vast sums needed for space flight, and that the initial phases of a space-flight program—such as establishing an unmanned satellite and, secondly, launching of manned space ships—could be carried out only on the basis of military advantage. Landing on the Moon and planets would be difficult to sell to the tax-paying public on any grounds. After all, what possible practical advantage could be demonstrated? Dr. Dornberger believes that the constriction induced by building solely for military purposes impedes the thinking of the backers of interplanetary travel. The military engineer deals with hardware and is walled about by secrecy. This secrecy frustrates the space-flight theorist, whose lot is hard enough even with adequate practical data, and he must content himself with topics that in many cases must strike the casual observer as academic trivia. This situation is not likely to change for a long time, but Dr. Dornberger feels that if it did, the theorist could jump ahead about 30 or 50 years, and perform many valuable studies from the viewpoint of space flight as a fait accompli. We do not entirely agree with Dr. Dornberger. The amount of money needed for the first small satellites has been estimated at $35 million. It is quite likely that more money will be spent on these satellites indirectly, but definitely not as. much as $100 million, as has been suggested by many. AlsoTir is established thaftrTe first satellites will not have any active military advantage, although some of the data gathered could be useful for ICBM development. 10 We feel that the taxpayers will not suffer because of these satellites. The projects will not upset the U.S. national budget, or any other budget. The United States certainly can manage to pay for the first American satellite, and the Soviet government for theirs. The research contributing to the satellites has been accomplished as a by-product of other projects—largely military. The Department of Defense works hand in hand with the various scientific institutions involved in the project. We do look forward to the time when some of our scientific talent can be released from the defense task—when the country can afford the manpower and money required to tackle an over-all spaceflight program. There is no reason why we shall not all benefit from the conquest of space. "The knowledge we will have to gain," says Milton W. Rosen, technical director of the Earth Satellite Vehicle Vanguard project, "the techniques we will have to master, the machines we will have to build—all will bring more material benefit to the Earth's population than any gold or uranium we may find on Mars or Venus. The value of space flight is in the doing of it." 2. Planning for the Orbiters We have been close to realizing space flight before now. On December 29, 1948, in a report to Congress, the late Secretary of Defense James V. Forrestal mentioned that a study for construction of artificial space satellites was proceeding. But the so-called Forrestal Project soon died. We were perhaps too optimistic at that time, although optimism is an important ingredient of any philosophy of action. So is caution. The American Rocket Society's Space Flight Committee had both these characteristics in a report they published in 1952, which considered the possibilities and types of action needed to promote space flight. In agreement with the Rocket Society's proposal was a paper presented in 1953 by A. V. Cleaver, a leading British rocket expert and former chairman of the British Interplanetary Society. Mr. Cleaver's work had a great influence on the thinking of our own experts. In brief, he suggested that the first phase of a space program be theoretical and applied work resulting in the establishment of an unmanned satellite. Then we might tackle the operation of a regular manned satellite and achieve some occasional circum-lunar flights. Finally, he visualized landings on the Moon and the nearest planets, and return to Earth. 11 In the American Rocket Society's Journal, the prominent rocket pioneer G. Edward Pendray wrote that World War II brought the society its greatest opportunity—and its greatest hazard. Rockets were being developed wholesale, and rocketry almost overnight was becoming a major industry. "The opportunity presented to the society by all this was growth and leadership; but the hazard was that, among the hundreds of new rocket technologists entering the field, the society was relatively unknown. "And unfortunately to some who did know of it, its technical reputation was not what they felt it should be. For the American Rocket Society (ARS), which had been kept alive these many years by the magic of the interplanetary idea, now stood in danger of extinction because of association with that very idea. Interplanetary flight was still not technologically respectable in the 1940s in many quarters." This danger had been recognized as far back as 1934, when the society—at that time called the American Interplanetary Society—was renamed the American Rocket Society. As the editor of Astronautics explained at the time: "In the opinion of many members, adoption of the more conservative name, while in no way implying that we have abandoned the interplanetary idea, will attract able members repelled by the present name." The significance of this resolution is important. As the approach to space flight became more realistic, and more evident —because of gains in rocket technology—the more careful and conservative the ARS became. As a result, the ARS managed to advance thinking along the line of a scientific and peaceful conquest of space. The society, consequently, became the spark plug that ignited the space-satellite idea. Its work had a tremendous influence on the National Science Foundation when that institution had to decide whether artificial satellites were to be recommended. For several years the American Rocket Society members had tried to convince the various scientific institutions that satellite flight was feasible. In 1953, the chairman of the ARS Space Flight Committee invited Alan T. Waterman, director of the National Science Foundation, to attend a plenary meeting of the committee. Soon thereafter, a confidential report was issued, which stated that the Space Flight Committee proposed that the "National Science Foundation study the utility of an unmanned satellite vehicle to science, commerce and industry, and national defense. Such a study should precede any considerations of feasibility and cost, which could be undertaken if the utility study showed a definite need for a satellite vehicle." The committee stated that "examples of these research uses 12 might be: for a superior astronomical observatory site; for biological and chemical research utilizing nongravity conditions; for electronic research utilizing a more perfect vacuum of unlimited size for microwave research in free space, cosmic ray, and nuclear research, etc." In 1954 the committee submitted to the National Science Foundation an open proposal "On the Utility of an Artificial Unmanned Earth Satellite." The text stated that the study of the utility of an unmanned Earth satellite would be one of the most important steps that could be taken immediately to advance the cause of space flight, and that this step would also increase the country's scientific knowledge. Why call for an unmanned Earth satellite? Although many satellite proposals had been suggested, the small unmanned satellite is the only one for which feasibility could be shown right now. This opinion was held by many responsible engineers and scientists involved in rocket and guided-missile work and in upper-atmospheric research. Most of these people agreed that the unmanned Earth satellite would be the first step toward more ambitious undertakings. Why study utility? Although many claims had been made for the utility of a satellite vehicle and many uses had been proposed, the subject had not been investigated by a responsible organization and had not rested upon a broad foundation. Because of recent advances in guided missiles, the cost of producing an unmanned satellite is not the mammoth sum that was at one time considered necessary. Nevertheless, the creation of even a small satellite is still a major undertaking, and does require a modest expenditure which must be justified. The Rocket Society felt that to build a satellite merely for the purpose of saying it had been done would not justify the cost. Rather, the satellite should serve useful purposes—purposes that would command the respect of the officials who sponsored it, the scientists and engineers who produced it, and the community that paid for it. The society therefore recommended that the study of utility be considered one of the most important tasks to be accomplished prior to building a satellite. It was apparent to the Rocket Society's Space Flight Committee during their early deliberations that the subject of utility could not be entirely divorced from feasibility, and that some concept of feasibility would have to be assumed. This was done not to be restrictive, but to provide a frame of reference from which those investigators considering utility could proceed. It was assumed that it would be feasible to establish a small pay load in an orbit, the difficulty increasing with the size of the pay load, and with the means that could be provided for communicating information from the satellite to the Earth. With this concept in mind, the committee outlined the various fields 13 t of utility, such as astronomy and astrophysics, biology, communications, geodesy, geophysics and many other ones arising from the unusual environment of space flight. Since it was established in 1946, the Office of Naval Research (ONR) has been engaged in supporting basic research —the starting point for every major technical development. Its concern with basic research has necessarily included development of the research tools needed to make these new advances. The scientific frontiers that now confront man are so remote from his usual environment that he cannot explore them without tools of much greater complexity than any he has used in his progress thus far. Development of the tools demands a great deal of difficult and expensive research. ONR has had a strong program of upper-atmospheric research for many years, in fact, the organization was a pioneer in the field. Its primary concern was for the accumulation of scientific knowledge, since we have to progress scientifically if we are to meet the military requirements of the future. During the past few years, ONR has supported work on high-altitude aircraft, such as the two Douglas Skyrocket research planes. It became apparent that aircraft research and development was leading to the point where man would eventually be able to fly an aircraft beyond the atmosphere, into space. ONR realized that science did not have the information about these regions needed to permit such flight. In particular, more accurate data on air density, pressure and temperature were needed. The big problem in this type of research is how to get up very high and stay there. ONR knew that their present methods of gathering data through rockets and balloons were not good enough. Some means had to be found for gathering data over extended periods. After looking over the possible research tools, ONR agreed that the only solution appeared to be the development of an Earth satellite that could stay above the Earth for a long while, especially when compared with rockets or balloons—and relay information back. Although satellite vehicles had been repeatedly proposed, studied and rejected, ONR felt that the need for continuing long-range research and development required an evaluation of the satellite's technical abilities in terms of current and future needs. On June 23, 1954, shortly after the first detailed satellite proposals had been submitted by the Rocket Society, a telephone call to the Office of Naval Research from Frederick C. Durant III, president of the International Astronautical Federation, disclosed that the famous missile expert and spaceflight enthusiast Dr. Wernher von Braun would be in Washington within the next few days. Chief Engineer of ONR's Air Branch, Alexander Satin, and Commander George W. Hoover 14 of that office decided to hold a conference to discuss the subject of satellites to determine how best to set up a research program. Two days later a historical meeting was held in one of the Navy buildings in Washington. In attendance were Dr. Wernher von Braun; Fred Durant; Harvard astronomer Dr. Fred L. Whipple; Dr. Fred Singer, member of the Physics Department, University of Maryland; Mr. David Young of Aerojet-General Corporation; Commander George Hoover, and other ONR personnel including Alexander Satin. When the meeting was opened, the first question placed before the group was whether any scientific satellite project was being studied in the light of the type of research that ONR needed. After considerable discussion of projects dealing with very-high-altitude research, it Was agreed that although many investigations were being conducted, there was no specific satellite program under way. The second question was whether it was possible to launch a satellite within the next few years. At this point, Dr. von Braun suggested the possibility of using a combination of Redstone and Loki missiles to push the satellite into an orbit outside the Earth's atmosphere. He explained that the Redstone missile, a highly advanced V-2-type rocket, might be used as a main booster on which could be mounted a multiple cluster of Loki solid-propellant rockets. After considerable detailed explanation by von Braun, it was concluded that such a program was possible—providing an official project could be established and Army participation effected, since the Redstone was an Army missile. The discussion continued with Dr. Singer pointing out the need for relatively heavy pay loads, and also the desirability of orbits that would permit as much information as possible to be gathered. Fred Durant listed the technological advancements that could be made through the use of an Earth satellite. Dr. Whipple sketched the major areas where new information could be obtained. By making the satellite vehicle visible by means of optical and electronic means, he said that it would be possible to investigate the phenomena connected with ionization, the effects of electrically charged particles in the atmosphere. He also suggested that the decay from an elliptical to a circular orbit of the satellite could tell us much about the density of air at extreme altitudes. It was believed by those present that the program suggested by Dr. Singer was a definite step in the search for upper-air data, but that this must be considered a second phase. It was agreed that enough information could be obtained from a minimum satellite, weighing perhaps five pounds, to warrant proceeding with the first step in a large satellite program. 15 Even a five-pound satellite was thought to be difficult enough to get into an orbit. The venture certainly would require skillfully planned launching and tracking methods. It would be a challenging task. But it could be done, and it could be done within a much shorter time than would be required for a fully instrumented vehicle. There were many possible methods and many rocket combinations that could be used to place the satellite in an orbit, but the Redstone-Loki combination was at that time an arrangement capable of putting a satellite into an orbit without calling for major development work. Following the meeting—which was the first phase of the American satellite project—a presentation was made to the Chief of Naval Research. He gave official approval for further investigation of the project, and authorized conversation with the Army's Redstone Arsenal in Huntsville, Alabama. On August 3, 1954, Navy representatives visited Redstone and a meeting was held with General H. N. Toftoy and Dr. von Braun. After some discussion regarding the possibility of using the Redstone-Loki combination, General Toftoy said that Redstone would co-operate providing General Lesley Simon, at that time Chief of Army Ordnance, approved of the participation. In the sequence of events, General Toftoy went to Washington for a discussion with General Simon, who said he would co-operate with the Navy provided the project would not slow down the Army's missile weapons program, and provided it would not draw excessively upon the Army's missile engineering manpower. The Chief of Naval Research was then notified, and ONR's Air Branch was given permission to proceed with preliminary studies leading to the establishment of a detailed program. Commander Hoover was assigned to the post of Project Officer. Project Orbiter became the code name of the program. It was classified CONFIDENTIAL. The Navy was to handle the design, development and construction of the satellite, which included arranging for tracking facilities, logistic support, and recording and interpreting the scientific data. The Army agreed to carry the responsibility for the over-all design, construction, and launching of the satellite vehicle. It is worth noting that while the Navy supported the satellite studies in order to obtain more data about the upper atmosphere for future high-altitude missile and airplane flights, the Air Force was not even involved in the project. Three contracts were let immediately by ONR. The visibility study was given to Varo Manufacturing Company, who hired Dr. Whipple as a consultant. Alabama Engineering & Tool Company was awarded the second contract; this study was to embrace the design and development of the Loki cluster mount 16 and guidance system needed to place the satellite in an orbit. The third study contract was given to the Aerophysics Corporation. This company was to conduct development of the Loki cluster. A fourth contract was planned for International Business Machines Corporation, which was to study the communication aspect. One problem that became evident quite early in th& study was that of logistic support. Men and equipment would have to be transported to locations practically all around the globe. From material released by the Navy on Project Orbiter there is no indication that any existing base—Army, Navy or Air Force—was considered as a launching site; such a site had to be constructed, as well as tracking stations. Enough supplies had to be made available for the crews to operate for many days and perhaps even a year. For this reason, a presentation was made to the Chief of Naval Operations. His only remark was: "Tell us what you want moved and where you want it moved, and we'll see that it gets there." On January 20, 1955, the proposed program was submitted to the Assistant Secretary of Defense in charge of Research and Development, as the first step in bringing the project to the attention of the Secretary of Defense—and, eventually, to the President of the United States. Five meetings of the Orbiter team were held in all, the last one on May 23 and 24, 1955, at Redstone Arsenal and Patrick Air Force Base, to witness the firing of a giant Redstone missile. Important decisions were made as a result of these meetings. The people involved became busy now, because the program was beginning to take form. An equatorial orbit was considered best for the first satellite. Later a polar orbit and an inclined orbit would be tried. The Naval Research Laboratory, which had some interesting satellite ideas of its own, was asked to participate and submit a backup program. The use of Minitrack, a highly sensitive electronic missile tracking apparatus, was offered by NRL. Representatives of the contractors were frequent visitors to Washington; conference after conference was held in Mr. Satin's and Commander Hoover's offices. Dr. von Braun was traveling back and forth between Washington and Huntsville. To him, the satellite project was a personal victory. Since 1930 he had tried to convince the world that satellites could and should be built. He had devoted his whole life to such studies and had at one time been arrested and jailed by the Gestapo in Germany for suggesting that the Nazi rocket research work would one day be applied to the peaceful conquest of space. In April, 1955, ONR began the planning of an expedition for establishing a launching site. The expedition was scheduled to leave in the spring of 1957, with the understanding that the 17 actual launching of the first satellite would be undertaken by midsummer or fall of that year. But as ONR was planning for the first satellite expedition, an entirely different and unknown (to ONR) satellite project was revealed by the President of the United States—an instrumented satellite would be launched to gather scientific information which in turn would be distributed to scientists of all the world's countries. Scientific and technological break-throughs often come in pairs. The universality of science frequently leads widely separated groups and individuals to arrive at almost identical ideas at the same time. While ONR was studying their Orbiter and its importance for high-altitude-flight research, the National Science Foundation had proceeded to accept the initial proposals by the Rocket Society. The Defense Department had been asked to encourage the "scientific" satellite, and the President of the United States enthusiastically had approved of the venture. Obviously, the Orbiter project could be canceled, since some of the basic information sought by ONR could be expected to result from the other satellite. So Project Orbiter was nudged out by Project Vanguard. A new approach was now in the undertaking. Everything had to be reorganized, and the pioneers and the original backers of the satellite idea, such as Dr. von Braun, Alexander Satin, George Hoover, Fred Durant and others, were almost forgotten. The revelation of Project Vanguard came as follows: on the morning of July 29, 1955, White House Press Secretary, James C. Hagerty, told newsmen that there would be a story of "some importance" given out at 1:30 P.M. When the time arrived, reporters were steered into a conference room which, back in the Roosevelt and Truman days, was known as the "Fish Room." Here they found Hagerty at a table with several prominent scientists from the National Science Foundation and the National Academy of Sciences. Secretary Hagerty announced that President Eisenhower had approved plans for launching an Earth-circling satellite. The President had expressed his personal satisfaction that the American project would provide scientific data that would be made available to all countries, the Soviet Union included. He stressed that the satellite would be constructed strictly for scientific purposes, and not with any war purpose in mind, although the Department of Defense would help with the project. The reporters then began firing questions at the scientists. Did the announcement, one asked, mean that the United States really was capable of putting up a satellite? 18 "Of course," said Dr. Waterman. The scientists had no doubt that all the problems could be worked out. The wires of the world's news bureaus and press agencies flashed the news to every corner of the globe. As an almost immediate reply to the American announcement came the United Press dispatch from Moscow stating that the Soviet Union was preparing to launch a similar satellite. The Eisenhower announcement was followed by more complete statements by the scientists involved. According to Detlov W. Bronk, president of the National Academy of Sciences, and Alan T. Waterman, director of the National Science Foundation, the Vanguard project calls for the construction of a small, unmanned, Earth-circling satellite vehicle to be used for basic scientific observations during the International Geophysical Year (IGY), the period set aside from July 1, 1957, to December 31, 1958, for world-wide observations in the fields of the Earth sciences by about 42 nations. The satellite project is sponsored by these two organizations as part of the United States program of participation in the IGY. The stimulant for such a vehicle was provided, as we have seen, by the American Rocket Society. The final decision was based upon a resolution passed by the Special Committee for the International Geophysical Year, and because of ONR's Orbiter program and long interest and experience in the broad aspects of upper-atmospheric research, the Chief of Naval Research was selected to manage the Defense Department portion of the Vanguard satellite program. Project Vanguard is a three-year project, with a possible year's extension. According to the Martin Company of Baltimore, prime contractor for the project, it is a 6,000-man-hour job. ONR and its agency NRL are using, as contractors or consultants, "nearly all" the nation's leading scientific authorities in geophysics, astrophysics and rocket research. Since the Earth satellite problem differs in several respects from the bulk of NRL's work, the project is being prosecuted outside the division structure of the laboratory. A separate project office reporting directly to the Laboratory Director of Research has been established. It was not felt necessary or desirable to set up a large, complex organization to co-ordinate the project. Much of the necessary co-ordination of the technical program could be carried out on a day-to-day basis by scientists and engineers at the working level in the Navy, the other services and industry. The Army and the Air Force (who came into the satellite program after it was begun) have designated Project Vanguard liaison officers who have official responsibility for keeping their services abreast of the status of the project, and who have kept 19" ONR and NRL workers informed of their services' potential for participation in any given phase of the work. For many years, the Army, Navy and Air Force military and civilian personnel involved in rocketry and other aspects of upper-atmospheric research have used formal machinery and informal contacts for working out mutual problems. This same working level communication network, although it has caused some confusion at times, is also used to attack problems that must be solved before the Vanguard satellite can be launched. The Navy's approach to the management of Project Vanguard has been shaped by the project's mission, which is threefold: First, a satellite is to be placed in an orbit during the IGY. Second, proof of such an achievement must be established by defining the orbit. This means tracking the satellite and providing information by which observers in the United States and other countries can also detect and track it. Third, it must be possible to perform at least one experiment of recognized scientific merit. "We hope to make a precise measurement of the density of air in outer space, the detection of hydrogen in space or radiation from the Sun, or something of equal scientific importance," according to Admiral N. Furth, former Chief of Naval Research. These then are the three primary technical responsibilities that must be discharged by NRL. But they cannot be done without assistance from the Army, Air Force and American science and industry. Before long, several countries will be launching their satellites, and the need for international co-operation in the various areas of satellite science will become increasingly evident. For this reason, rocket and satellite workers are discussing the different international aspects. In order to be prepared for any misunderstandings that may arise among nations, and to boost the peaceful aspects of space flight, the United Nations has been approached. The world's rocket societies, through their international federation, have been interested in establishing a close contact with UNESCO (United Nations Educational, Scientific and Cultural Organization), because the societies' members feel that the United Nations must assist in supervising the world's attempt to explore and conquer space. Clark M. Eichelberger, executive director of the American Association for the United Nations, has also suggested that the UN take over international supervision of the satellite programs to make certain that interplanetary rivalry between the United States and the Soviet does not "mask military projects of frightful destruction." Before we launch any satellites, it is wise that we ask whether 20 we shall experience any international conflicts during the initial phase of the satellites' explorations; and whether political confusion in one way or another between two or more nations would result if a satellite went astray. When dozens of small unmanned satellites are circling the globe in all types of orbits within a few years, the scientific organizations behind them will be interested in world-wide co-operation regarding tracking and exchange of information. Actually, all countries in the world will be involved when circumpolar orbits are used; special tracking vessels will be operating in every ocean. During the IGY we shall experience close international co-operation with respect to tracking; successful achievement of complete scientific studies depends upon this aid. The countries involved, therefore, must agree on the distribution and magnitude of the tracking operations. Many of the territories will be behind iron-curtain or Communist nations. Consequently, West and East must attempt to meet each other on a friendly basis if either is to benefit from satellite science. Since the Soviets are participants in the IGY, we might expect that they will be as interested in international co-oper-tion as we are. This could lead to permanent international harmony in all satellite ventures. In this case, we visualize that one political difficulty will be avoided: the question of occupying the air space—or just space —over another country's territory. Many experts feel that space law—a new form of binding international legal practice and rules—will be required for the peaceful advancement of space flight. Space law, as applied to satellite science, has been studied thoroughly by the well-known Washington lawyer, Andrew G. Haley, past president of the American Rocket Society. According to his analysis of international law and space flight, it is evident that each and every sovereign nation can demand that no man-made object or vehicle shall pass over such a sovereign's territory without permission of the sovereign—and this has no reference to the height at which the passage is made as long as such a passage might be a means of acquiring intelligence concerning the sovereign or a threat in any manner to the sovereign. Historically the sovereign has always asserted exclusive, absolute dominion over the land and everything incident to the land, including the space above the land. While we have an almost complete freedom of the seas, there is actually no such thing as freedom of the air. Air travel between any two nations is still entangled in a complex of bilateral and international rules and regulations. In the light of the rules of law and the idea of untrammeled sovereignty, the inauguration of the unmanned Earth satellite programs stands out as perhaps the most felicitous incident of the generation. 21 The entire Vanguard program could have been stopped by the protest of a single sovereign nation over which the satellite might pass. The entire program could have been endlessly delayed by making it the subject of detailed international negotiation. "The inauguration of the program in a peaceful and uncomplicated manner is a great achievement of scientists throughout the world," Haley says. We might also ask if a satellite could in any fashion go astray, and the answer is yes. During launching, a malfunctioning rocket component would be enough to send the vehicle off course. It could happen that it would crash in another country, causing some physical damage. But judging from past airplane incidents—it has happened many times that foreign aircraft have crashed in this country and vice versa —we can find not one case that has resulted in any international political difficulties. The risk and probability for such accidents are mutual, and they are always unintentional. The same view will apply to satellite flight as long as the satellites are not used militarily. Scientists seem quite confident that complete disintegration or vaporization will kill a satellite spiraling back to Earth. If such vaporization is not complete, however, we might get a fall-out of miniature electronic components scattered over thousands of square miles. Consequently, the chance of finding a satellite component in the back yard is rather remote. Other important aspects of international co-operation are those connected with telecommunications and meteorology. Communications from or to Earth through space must be by radio. Remote control of an unmanned Earth satellite either from Earth or from some spatial point, and automatic imparting of knowledge through instrumentation in the satellite and on Earth by use of radio are comparatively simple problems. But the day is not distant when the problems of remote control will multiply tremendously, and with the advent of the manned satellite, the problems of communication will become quite complicated. They will call for more and more use of the radio spectrum. It follows that distribution and use of channels and frequencies must be governed on an international basis. Quite logically, the International Astronautical Federation has already approached the International Telecommunications Union (ITU) for a thorough investigation of the problems expected. The program submitted to the ITU calls for the ITU's International Radio Consultative Committee to undertake a study of communication requirements for travel in space. It was also requested that the International Frequency Registra- 22 tion Board advise as to the availability of frequencies for such purposes. UNESCO, IAF, and rocket and astronautical organizations throughout the world were requested to co-operate in all phases of the basic study made by the ITU. After such co-operative studies are completed, the ITU will initiate formal steps to effect the allocation of radio frequencies, not only for travel in space but also for communication to and from satellites. It is well that lawyers and political experts have become interested in satellite science. It is also significant that the international aspects of satellite science are being considered and studied; thus we shall be prepared to meet any difficulties that may arise when satellite traffic becomes heavy. Our more immediate problems, however, such as how to get the satellites up, are of greater concern right now. We will leave it to the experts to discuss who owns the universe. We want to convince ourselves that our rocket and missile techno-ology really permits us to advance into space. 3. Long Playing Rockets Today, the rocket is the only engine that is usable for flights in the very upper layers of the atmosphere or in space, where air-breathing engines are useless. The rocket carries with it the oxygen needed for the combustion of its fuel, and in addition develops the greatest thrust per unit of engine weight with the smallest frontal area per pound of thrust of all propulsion devices. Although we take tremendously powerful rockets for granted, it is necessary to review a bit of rocket technology to understand how it is applied to satellite vehicles. Also, it is important to stress that a vast number of instability factors and difficulties still are encountered in connection with launching and firing large liquid-propellant rockets. The first V-2 was launched from Peenemiinde in the spring of 1942. It rose slowly, gathered momentum and roared into the clouds. Then, suddenly, the motor stopped. The large rocket came tumbling out of the clouds and crashed into the sea with a tremendous explosion. Something had gone wrong, and something went wrong with all except one of the first 8 V-2s fired. A German color movie, released after the war, shows in detail the disastrous effects of one such mishap. The revenge weapon, the 46-foot V-2, is erected on its launching stand with the usual layer of frost covering the skin around the liquid-oxygen tank (temperature of LOX, liquid oxygen, is —297 degrees 23 Fahrenheit). The operator pulls the igniter switch and the first stage of the starting is in process: liquid oxygen and alcohol flow by gravity into the motor and burn to produce seven tons of thrust, insufficient to lift the rocket. When the operator is convinced that the burning is normal, and that the flames are licking around the rocket base and launching platform smoothly, he pushes the button for the second firing stage. Inside the rocket, hydrogen peroxide and permanganate are mixed, forming a steam that drives the turbine pumps, which in turn force the fuels into the combustion chamber. The rocket is rising slowly, uncertainly. Standing still for a moment, only a foot above the stand, it tilts over and its nine and one half tons of liquid fuels explode with a tremendous force. A huge ball of fire engulfs the launching site. Of our own Viking rockets, quite similar to the V~2s, only seven out of twelve firings can be said to have been successful. Viking Number 6 executed violent maneuvers in flight because the steering fins failed; Number 8 broke loose on a static firing test and destroyed itself; Number 10 did not leave the ground at all, the motor exploding on the first flight attempt. Every rocket designer and manufacturer will confirm that any high-thrust liquid rocket motor, even of the most advanced design, is likely to hold a few sinister surprises. In the early days of German rocketry, and more recently, at our current testing facilities, all types of accidents have occurred and still occur during testing of engines. The rocket engineer keeps his fingers crossed before every firing, asking himself whether the thing will work—and hoping that it will. Before any Viking rocket was launched from the White Sands Proving Ground in New Mexico, the instrumentation, the fuel system and the rocket motor had been tested and retested many times. And still the rocket engineers from the Naval Research Laboratory, which was responsible for the venture, were always uncertain whether the rocket would take off and fly successfully. Besides being the most efficient propulsion device, the rocket motor is usually considered the simplest of all combustion engines. An aircraft gas turbine contains thousands of precision parts while a liquid rocket is essentially made up of a combustion chamber, two propellant tanks, and a turbine pump system for driving the fuels under pressure into the motor; other than the pumps, there are no moving parts involved. Why is it, then, that so many failures and incidents have been recorded? And since a Viking-type rocket is just the type device that will be used for the early satellite vehicles, is it not likely that we are taking quite a chance? Will it work? When we examine the general characteristics of a rocket of the kind that might be used for putting up a satellite, we soon find that there are quite a few difficulties involved in designing 24 the vehicle, as well as in launching it. Such a rocket represents a most intricate and expensive apparatus. A perfect rocket flight depends on a great many factors, the two most important being successful operation of the rocket motor and faultless functioning of the.automatic stabilization system. Growing out of these requirements are the specifica tions that electrical and other equipment must operate at pres sures ranging from atmospheric to near vacuum. Because the launching velocity of a large rocket is so slow—starting from zero—initial guidance is difficult without the use of a launch ing tower, or either graphite steering vanes in the exhaust stream or a gimbaled motor. This type of power plant is mounted in a swivel structure that permits tilting of the motor in any direction. - Another problem is the fact that portions of the rocket's skin will heat up at supersonic speeds; also, even though a rocket is a one-shot proposition, components must be designed with reliability approaching 100 per cent. So much depends on each element in the chain of events that each must operate successfully. Rockqt flight is not particularly smooth. Equipment, therefore, must not only be self-powered, self-running, and self-controlled, but also must be stable under conditions of high accelerations, vibration, heating and considerable tossing. Gas temperatures in the rocket motor run from 5,000 to 6,000 degrees Fahrenheit. (A jet aircraft turbine operates at about 1,800 degrees Fahrenheit.) Therefore, the motor must be cooled. In a regenerating cooling system the motor parts are cooled by means of a built-in coil in which the propellant is used as the coolant fluid. The heat absorbed by the coolant is therefore not wasted but rather augments the initial energy content of the propellant prior to injection, thereby increasing the exhaust velocity slightly. Without cooling, the wall in the rocket combustion chamber acts as a heat sponge, absorbing heat energy. When the wall temperature approaches the melting point of the wall material, it will be only a matter of seconds before the motor explodes. An important factor in the stability of rocket combustion is the matter of continuous flow of the propellant and oxidizer. In a large missile, the fuel system involves several valves. Since the temperature of liquid oxygen is -297 degrees Fahrenheit, it is quite possible that some of the valves will stick and shut off the flow. This may result in nothing but motor cutoff, but if fuel alone is allowed to accumulate in the rocket, the situation could easily lead to a catastrophe. Control of instability in rocket burning is an art that rocket engineers have tried to master. It involves many problems connected with the combustion and flow of gases through the 25 rocket nozzle, fuel pressure, shock waves and other phenomena. These are essential problems that rocket engineers must consider carefully in order to make the large vehicle fly. Even though supersonic rocket motors are available, it is obvious that they are useless unless they can be used to perform an assigned mission with high accuracy, such as a satellite project requires. In the area of rocket power-plant installations are included such items as fuel systems, lubrication systems, lines, fittings, seals and cooling systems. The most aggravating factor in supersonic flight is the temperature that is encountered. The increase of rocket skin temperature with increasing velocity is considerable, and this increase can critically affect the various systems. At relatively moderate speeds, the usefulness of rubber materials, aluminum and titanium ends. Our earnest hopes are with engineers who work on the development of new materials. These men are trying to solve many rocket problems through the use of superalloys, ceramics and cermets, part metal, part nonmetal. Of paramount importance and a predominant source of concern for the engineer who must consider supersonic installations is the problem of the effects of high-speed flight upon fuel systems. It is estimated that rocket flying at twice the speed of sound at an altitude of 50,000 feet will lose almost 20 per cent of the propellant as a result of vaporization. A big problem in stabilizing a rocket arises because the rocket's center of gravity changes as the propellants are burned. Also, it is not easy to guide a rocket remotely, since certain exhaust gases absorb, reflect and diffuse radio waves. This makes it difficult to send information from the missile and send guidance signals to it. At high altitudes the problem is particularly onerous because the exhaust tends to grow bushy or blossom out as atmospheric pressure decreases. If the rocket has no electronic equipment for guidance, it must rely solely upon its built-in equipment for steering. One would imagine that a rocket aimed straight up would have no difficulty in following a vertical path. But tests have proved differently. We remember that Number 6 Viking roared aloft out of control because the steering fins did not function. Many White Sands engineers recall with horror the time that a V~2 screamed into a hillside cemetery at 3,000 miles per hour outside Juarez, Mexico. No international fuss developed, but the incident did point up the initiative of the Mexican townsfolk. Concession stands were established at the site and small boys were peddling pieces of the "missile" as souvenirs. Unwary tourists soon found that their purchases were distressingly similar to odd pieces of wrecked automobiles, easily procurable at any city dump. 26 It is the external sleekness of a missile that has led to the tacit assumption that there seems to be nothing to the problem of designing and flying large rockets. This idea is understandable, especially in view of the apparent simplicity of the rocket concept. Upon analyzing the stabilization of a large rocket, however, we find that an intricate and expensive system is required. This problem is made more complicated by the variation of missile dynamics during flight. At take-off, the forward velocity is so low that aerodynamic forces are negligible and the rocket behaves as a wingless body would. As the speed increases, aerodynamic forces become significant and the equations of motion of the vehicle become more complicated. Later the lack of air at the upper altitudes reduces these forces until the rocket again behaves as a wingless body. N. E. Felt, Jr., Martin's operations manager for Project Vanguard, says that Martin engineers, when designing the Viking, initially proposed that the control forces be obtained by the deflection of vanes placed in the jet stream. The chief advantage of this system was based on the experiences obtained with the V-2. However, the disadvantages of this system became apparent when an investigation of alternate control methods was conducted. When a gimbaled motor system was compared with the jet-vane method, the latter system showed a considerable weight penalty, a difficulty connected with vane durability because of the heat, a reduction of propellant burning-rate due to vane drag in the jet stream, and a high complexity. The gimbaled motor with its swiveling structure appeared to be the better unit. Deflection of a rocket motor during flight is not a simple task. The complex steering system consists of electrical and hydraulic components, delicate valves and precision fittings. The most important mechanical unit in a stabilization system is the automatic pilot, whose main component is the gyroscope. The gyroscope has the property, like a child's spinning hoop or top, of always pointing in the same direction. In a satellite-carrying rocket, the gyroscope—mounted in the nose section— points upward. If the rocket tends to depart from the desired line of flight, perhaps because of wind gusts or turbulent air, the gyroscope immediately sends a message to the gimbaled motor, which tilts over slightly to bring the vehicle back on course. The gyroscope remains spinning in the original position of setting, in this case, vertically. It sounds rather uncomplicated when we say that the gyroscope "sends a message to the gimbaled motor." And it would not be fair to refrain from sketching what takes place during a corrective maneuver. If the rocket attitude differs from the desired flight path, an error voltage appears at the output of the vertical gyroscope. The error voltage, a tiny amount of 27 electrical pressure proportional to the off-course angle, is sent to an amplifier, a component that builds the current up to a power that through mechanical and hydraulic links is capable of deflecting the gimbaled motor. The amount of deflection is proportional to the error voltage. In its tilted position, the motor begins correcting the rocket's attitude error. When the rocket has returned to its desired attitude, the motor returns to its normal position. The rocket engines for the early satellites will be similar to the Viking rockets but improved in two principal ways. First, the new rockets will be more efficient. Second, the new rockets will have no fins; in this way we can design a vehicle that is completely stabilized by the thrust of its motor. The gimbal mounting usually is designed to permit a tilt of ±5 degrees from the center line of the vehicle. The gimbal structure was built into the first Viking, and into all the subsequent ones, although they also had fins to assist in stabilization. The finless rocket has been under study for several years and a few small finless rockets have been fired experimentally. The Martin and NRL engineers have performed much analysis that has proved the finless rocket theoretically workable, and they had sufficient confidence in this work to suggest large finless rockets for the first satellite vehicles. Actually, it was known in 1946 that the use of fins for longitudinal rocket stabilization produced unwanted movements and added weight to the rocket's structure. They give no assistance to the rocket's course at the moment of launching, when its forward speed is low, nor near the end of the powered flight, when the rocket is above the Earth's atmosphere. Having examined some of the more vital aspects of a typical liquid-propellant rocket, we should consider velocity. The speed required, after all, is the most essential element in getting a satellite into an orbit. There are only two ways to achieve the most in velocity for a rocket. We can increase the exhaust velocity of the gases by using more powerful propellants and more efficient rocket motors, because the exhaust speed determines the velocity of the rocket itself. Or we can improve the rocket's mass ratio (ratio of the total rocket weight to the weight after fuel is expended) by reducing dead weight to a minimum. As far as improving mass ratio is concerned, tremendous difficulties are involved. A rocket with a total weight of 272 pounds and a final weight of 100 pounds after all fuel is consumed would have a mass ratio of 2.72 to 1. It has been calculated that, no matter what type fuel is used, this is the mass ratio needed to drive a rocket at the exhaust velocity of its own fuel. If a rocket with this mass ratio uses liquid hydrogen and liquid oxygen as fuel, the rocket 28 would eventually travel at the exhaust velocity of the fuel, about 12,000 miles per hour. Assume, however, that we want the rocket to go twice as fast as its exhaust velocity. To attain this speed, the mass ratio is not doubled but squared. The mass ratio required is now 7.4 to 1. If we want to travel at three times the exhaust velocity, the mass ratio (2.72) must now be cubed—which means a mass ratio of about 20 to 1. Such a rocket would have to be 95 per cent fuel and only 5 per cent rocket and pay load. When we get to a mass ratio of this size, the size of the over-all rocket is gigantic. A new fuel with a higher exhaust velocity than is possible today would of course mean that a much lower mass ratio would be required to get the same final speed. Thousands of propellant combinations have been examined for this purpose. Propellants ranging from aluminum powder to turpentine have been tried. The development of a pure and safe ozone, a potential superoxidizer, has been reported. The product might prove to be a major step forward in the development of rocket travel of the future, if the claims for the ozone are true. While one scientist says that for years he thought he had a safe pure form of ozone gas only to have it blow up without any apparent provocation, another scientist predicts that the new liquefied gas may help speed Earth satellites out to the fringe of Earth's gravity. Gerald W. Platz, head of the ozone technology group at Armour Research Foundation, says that the past history of ozone research has been full of reports about spontaneous, unpredictable explosions. But the ozone developed in purified form at Armour has the characteristics of a safe product. Ozone has been called supercharged oxygen. It forms naturally in the atmosphere along the path of a lightning bolt, but quickly reverts to stable oxygen. What happens is that the normal molecule of oxygen containing two atoms is broken up by the electrical discharge, forming ozone, which contains three oxygen atoms. The hitchhiking atoms, hungry to get back in their proper places, quickly latch on to other free oxygen atoms to form stable oxygen. In laboratory production, ozone formed by the passage of an electrical discharge through oxygen is trapped to prevent reunion of its extra atom with free oxygen atoms. A report by Platz and his associate, C. K. Hersh, indicates that ozone is hazardous only when not completely purified. The new processing, they say, makes their ozone "100 per cent pure"; since the ozone is pure, it can be produced and handled without mishap. Such pure ozone has remarkable stability against heat, impact and vibration—all trigger mechanisms blamed for lab-shattering explosions. Stored in specially 29 cleaned containers, the chemical can be dropped from great heights or withstand great vibration forces over a long period of time. This development is significant; it is just what the rocket propellant experts have been looking for. We are also waiting for certain exotic propellants, powerful nonhydrocar-bon fuels with high exhaust velocities. These fuels and certain superoxidizers are currently being tested in our laboratories. In the meantime, however, we shall be confined to the use of the more proven and conservative propellants. A powerful rocket propellant is the combination of liquid oxygen and liquid hydrogen. However, this is also the most dangerous and difficult combination to handle. Liquid oxygen at a temperature of -297 degrees Fahrenheit, is cheap to produce and is abundant. It can be handled safely when stored in vented and well-insulated containers. Liquid hydrogen, on the other hand, has a temperature of -423 degrees Fahrenheit, which presents extremely difficult storage and handling problems. A rocket with liquid-oxygen liquid-hydrogen propellants would require very large and well-insulated tanks and comprise an extremely hazardous vehicle even when not in use. Dr. Dornberger says he would want to stand several miles from a launching site if someone were to attempt the fueling of a rocket with liquid hydrogen and liquid oxygen. The most widely used rocket fuel at the moment is liquid oxygen and alcohol, which produces fairly high thrusts and exhaust velocities. The performance of this propellant combination is considerably lower than that of the liquid hydrogen-oxygen combination but the alcohol is simple to store and handle and presents no special hazards that ordinary care will not accommodate. Some of the early satellite rocket propellants will be a combination of about 95 per cent gasoline, 4 per cent alcohol and one percent silicone oil, which will act as a flow coolant. Liquid oxygen will be used as the oxidizer. The more practical problems of propellant selection include low price, abundance of raw materials, availability, stability in storage, high density, ease of handling, nontoxicity and convenient freezing and boiling points. These factors exert a more powerful influence on propellant selection, particularly for military field operations, than does propellant performance alone. There are several schools of thought as to how a satellite can be placed in its orbit. Writing in a semimonthly Moscow journal, Professor Kirill Stanyukovich, of the USSR Academy of Science Commission for Inter-Planetary Communication, recently reported that Soviet engineers "believe it is possible to build larger satellites than those now being discussed in the Western press." His article in the political journal, the News, said that the present level of automatic and remote-control en-30 gineering makes entirely practical the idea of a composite-stage rocket that can climb to a height of 250 miles, come to a stop at its maximum altitude and, at this precise moment, explode from its side an 18-inch-diameter satellite having an initial velocity of about five miles per second. The Soviet doctor of technical sciences observed that such a satellite can be given an initial speed of 18,000 miles per hour in two ways: "A three-stage rocket, the satellite being the third stage, could be constructed. But this is extremely complicated. The simpler way is to shoot out the cosmic ball with an explosion that will at the same time break up the remainder of the rocket. Calculations show that in order to obtain such a speed with the use of the powerful explosives TNT or hexogen, the explosive force has to be 10 times the weight of the body to be ejected. It is, of course, difficult to say now which method scientists in different countries will choose. Both methods, it seems to me, are valid." In this country, three different launching methods have been discussed and they will probably all be tried within the next few years. Professor P. E. Sandorff of Massachusetts Institute of Technology, five weeks prior to President Eisenhower's announcement of the Vanguard project, offered interesting details of what he termed the airplane-launching method. Sandorff considers the possibility of launching a satellite vehicle with a 500-pound pay load from an aircraft (such as the B-52) at 9.5 miles' altitude. In this way, by lifting the vehicle through much of the atmosphere and adding the aircraft's speed \o the vehicle, a satellite could be launched with a lower weight and cost than would be the case for a ground-launched vehicle. Sandorff shows that a two-stage rocket weighing 100,000 pounds with 200 pounds' pay load could achieve a 200-mile altitude orbit. In comparison, a three-stage-rocket vehicle launched from the ground would weigh about 250,000 pounds with a corresponding increase in cost. A significant advantage of the airplane-step arrangement is the improved reliability of the entire system, according to Sandorff. Rocket-powered space vehicles, being new and highly automatized instruments, do not yet compare in dependability with aircraft. The separation of two stages is an operation involving considerable difficulty. The rocket-powered lower step would probably contain several motors and consequently show a higher probability of malfunction. Sandorff thinks that the chance for success for a three-stage rocket is about one in three while for a two-stage rocket using the airplane step the chances for success are about two in three. A program to put 10 satellites into orbit would cost $170 million if the larger, all-rocket design were used, while if the airplane step were adopted, the 31 cost would be $48 million plus the cost of airplane modification, operation and attrition. Significant advances are being made in the efficiency of air-breathing engines, as evidenced by the advent of purely thrust-borne aircraft in the past few years. Aerodynamics has kept pace with airplanes designed for 1,100 miles per hour at 7.5 miles' altitude. If these trends continue, Sandorff visualizes an airplane step that will launch the rocket at 7.5 or 9.5 miles' altitude at an initial speed of perhaps 3,000 miles per hour. The aircraft in combination with its load might have the external appearance of the Douglas X-3 Stiletto research airplane. The power loading would be relatively high, so that take-off would be an easy operation, but the climb to the service ceiling of the aircraft—10 or 11 miles' altitude—would still take perhaps an hour. A straight launching run then would be made, with full engine power, employing afterburners and auxiliary ram-jets mounted in the wings. The sonic barrier would be passed quickly, but it would take an hour to reach full speed. Meanwhile the airplane would dive to the lowest permissible altitude for rocket efficiency, which would also be the optimum design performance altitude for the airplane. Here, at top speed, a pull-up maneuver would be made to place the rocket into the optimum flight path. JATO rockets might be used for an additional boost. The cargo would be dropped, it would fall away 50 to 100 feet, until its rocket engines developed full thrust, at which time the rocket vehicle would accelerate swiftly ahead. "If such designs materialize it seems unlikely that space vehicles will ever take off from the Earth's surface under rocket power," Sandorff says. It is likely that the concept will be tried in the future. With tomorrow's B-58 supersonic delta-wing bombers, it might be possible to launch a satellite rocket from approximately 13 miles' altitude. The second launching concept, the balloon-launching method, has intrigued the U. S. Air Force. Even though the Air Force has a five-year satellite project under way, small balloon-launched vehicles might be built first. The man behind the balloon method is Kurt R. Stehling, formerly with Bell Aircraft, now in charge of power-plant development for Project Vanguard. The idea actually has been tried with a small solid-propellant rocket, the Deacon, by Dr. James A. Van Allen of the University of Iowa's Department of Physics, under an ONR contract. While the Deacon was not an orbital vehicle, Van Allen was able to explore altitudes up to 65 miles with very inexpensive equipment—balloon and vehicle cost about $2,000. Because a large liquid-propellant-powered vehicle would be costly and difficult to build, Stehling, in collaboration with R. M. Missert, of the University of Iowa's Department of Physics, has concentrated on the possibility of launching a small orbital vehicle from a high altitude. In an Aviation Age article Stehling writes that his minimum vehicle could be the forerunner of larger and more complicated ones. It could obtain information on ballistic flight paths, supersonic high-altitude aerodynamic drag, guidance and radio propagation. The success of the Deacon project led to Stehling's consideration of a larger vehicle (30-pound pay load) launched from a balloon at near-drag-free conditions and capable of an orbital flight path at an altitude of 150 miles or more. He says the main features of the vehicle, which he calls Saloon, are low total weight, and simple construction with a minimum number of parts that could fail—necessary because launching takes place away from human control. The rocket may be designed without streamlining because of the low drag involved when launching from great altitudes. This means that standard, nonstreamlined powder-booster rockets are immediately possible. Stehling also stresses the use of high acceleration rates and relatively short burning times. These were deliberately chosen so that less power would be required to lift the rocket plus its propellant load against gravity. Reasonable mass ratios and thrust-weight ratios are also possible. These were chosen to permit the application of techniques that are available now or will soon be developed, rather than of hypothetical future ones. Only 50 pounds of controls are built into the second stage to permit small adjustments of the ballistic flight path during the powered phase. The third stage is assumed to be able to reach an elliptical orbit without further guidance. The 50 pounds of controls will include a timer or a chamber pressure sensor to actuate the third-stage blowoff device at the moment the second-stage rocket reaches the burn-out point, the moment when all propellants are consumed. A thrust-weight ratio of 3 has been chosen by Stehling to give a firing period long enough to permit application of some control, if needed. The third stage is the orbital vehicle, the actual satellite. It is fired at the moment of second-stage burnout. No control is provided since the second stage is expected to have entered the free-fall or orbital path. The third stage will enter an elliptical orbit. The 30-pound pay load is equal in weight to that of the Deacon vehicle and somewhat more than the weight of the Vanguard satellite. The advantages of the balloon-launched satellite vehicle include low cost and simple construction, which is made possible because of the reduction of aerodynamic drag. This is due to 33 launching the vehicle from higher altitude. An upper limit of 21 miles has been mentioned as the launching altitude; this would require a balloon with a capacity of six million cubic feet. A minimum of complex hardware is required, and the pay load is high enough to get a useful minimum satellite into an orbit. The proposed vehicle is a possibility for the near, rather than the distant, future. The third launching concept, of course, is the method that will be used for the Vanguard satellites, often referred to as LPR, or Long-Playing Rockets. The basketball satellites will be brought up to their proposed orbits between 200 and 800 miles above the Earth by multistage rockets launched vertically. When we build a rocket capable of carrying a certain pay load, and make that pay load another rocket carrying the same percentage of propellants, when the smaller vehicle has burned its propellants it will have achieved twice the speed that either rocket could attain by itself. A three-step rocket will do even better; a rocket vehicle consisting of a sufficient number of steps could literally reach any desired terminal speed. This is the reason that an improvement in rocket propellants is not of paramount importance for the successful launching of a small satellite. In the case of the Vanguard vehicle, a three-step configuration will be sufficient, the first finless stage carrying the other two rockets and the satellite as its pay load, the second stage carrying the third rocket and the satellite, and the last one carrying only the satellite. The main-stage engine will be more efficient than the Viking engine, and therefore more powerful. It will have a thrust of 27,000 pounds at sea level (about the same as three jet engines) and an operating time of 131 seconds. Built by the General Electric Company, the engine consists of a regeneratively cooled thrust chamber, a gimbaled mounting, propellant valves, turbopump and high-pressure lines. Liquid oxygen and a mixture of gasoline, ethyl alcohol, and silicone oil will be forced into the thrust chamber by turbine-driven pumps. The turbine will be powered by the decomposition products of hydrogen peroxide. In this type turbine, liquid peroxide is converted in a steam generator into hot steam, which is forced against the turbine blades, thereby driving the pump. The second-stage rocket, as well as the first-stage, will be finless. The subcontract for construction of the second stage was awarded to the Aerojet-General Corporation. This power plant will also consist of a regeneratively cooled thrust chamber mounted in a gimbal. Nitric acid, which contains quite a bit of oxygen, will be the oxidizer and unsymmetrical dim-ethyl-hydrazine the fuel. Flow of these propellants to the thrust chamber will be effected by helium pressurization of the 34 Schematic view of propulsion system in a three-stage satellite vehicle of the Vanguard type. No gyromechanisms or stabilization components are shown. The propellants used for the second stage are hypergolic, that is, oxidizer and fuel ignite upon contact, no battery or ignition system being required. propellant tanks, rather than by a steam turbine, as in the first-stage motor. The third stage of the Vanguard rocket will be powered by a solid-propellant motor, and will consist of the motor, a struc- ture for attaching it to the second stage and for imparting spin to the third stage, and the satellite package and mounting structure. Builders of the third-stage rocket are the Grand Central Rocket Company and the Allegany Ballistics Laboratory. The whole Vanguard configuration is close to 70 feet high. With a main-stage thrust of 27,000 pounds, we get the following approximate weight specifications for a Vanguard satellite vehicle: Satellite (including nose cone] 1 30 pounds Third-Stage Structure 60 pounds Empty Weight 90 pounds Gross Weight 270 pounds Second-Stage Structure 540 pounds Empty Weight 810 pounds Gross Weight 2,430 pounds First-Stage Structure 4,860 pounds Empty Weight 7,290 pounds Gross Weight 21,870 pounds While these figures should not be taken as exact, they probably will not differ much from the actual ones. The total gross weight of 21,870 pounds represents about the same weight as that of a Sabrejet fighter. Dr. Martin Summerfield, professor at Princeton University, has revealed some specifications for a three-stage rocket required to put a Vanguard-type, satellite into an orbit as far as 400 miles above the Earth. His calculations are based on the performance that might be achieved by each stage of the satellite rocket and on the characteristics of the Viking Number 11 rocket plus expected advances in the state of the art since this rocket was designed by Martin in 1951. His specifications included the following data: 12 per cent 15 per cent 2,000 pounds 200 pounds 5,200 miles 12,500 miles per hour per hour Gross Mass Thrust Burning Time Structure Mass Ratio of Structure to Gross Mass Pay Load Total Velocity at Burnout 1st Stage 15,000 pounds 38,000 pounds 70 seconds 1,800 pounds 2d Stage 2,000 pounds 8,400 pounds 50 seconds 300 pounds 3d Stage 200 pounds 730 pounds 50 seconds 30 pounds 15 per cent 30 pounds 19,500 miles per hour Dr. Summerfield is counting on a first-stage thrust of 38,000 pounds for this operation, while the actual Vanguard rocket will have a thrust of only 27,000 pounds. Regardless of the satellite pay load, it is obvious that more thrust is needed to bring the satellite up to more distant orbits: a satellite destined for a 500-mile orbit needs a greater initial push than if the orbit 36 were to be 250 miles, even though the orbital velocity is less at 500 miles. If the satellite package were to be the nose of the vehicle, it could become too hot, probably in excess of 1,000 degrees Fahrenheit. One alternative would be to build the satellite with a heavy skin and insulation, which would incidentally present a problem of excess weight. Another alternative would be to shelter the satellite with a conical, disposable nose for the third-stage rocket. Since the heating would occur during the last part of the first-stage flight and the first part of the second-stage flight, that is, after high speed has been reached and before the denser portion of the atmosphere is left behind, the conical nose could be jettisoned near or at the end of the second stage. The use of such a cone would provide a weight penalty for the first and second stages of the flight, and this penalty is one of the many that are being considered in the weight studies. The first-step rocket is the most critical portion of the Vanguard vehicle; if this rocket fails, the entire attempt will fail. Furthermore, the guidance of the main rocket is vital to the success of the venture, since any deviation in the steering of this rocket automatically puts the second and third rockets off course. The flight path of the first-stage rocket may be conveniently divided into three phases. During the first phase the engine accelerates the rocket vertically to a maximum speed of approximately 3,000 to 4,000 miles per hour. In the second phase, the rocket coasts through the upper atmosphere. At an altitude between 30 and 40 miles, in the third phase, the motor in the second rocket is started automatically and the first rocket drops off and falls into the ocean. The second rocket, having been given an initial velocity of almost six times the speed of sound, and flying in the upper layers of the atmosphere where the air resistance is negligible, will have a simple task compared to the first rocket. The second rocket will soon fly at a velocity close to 11,000 miles per hour. Its path will curve somewhat, its gyro control system being set so that this event will occur automatically. The third rocket will then take over from an altitude of approximately 300 miles and bring the satellite out to its orbit. At this time, the third rocket releases the satellite, either through a powerful mechanical spring kickoff or through the use of an explosive charge; the velocity is now in the neighborhood of 18,000 miles per hour. At the same time, the third rocket has been flying almost parallel to the Earth's curvature. As we see, the attainment of an orbit just outside the atmosphere is really not an insurmountable task, even when considered in terms of present rocket performance. The development costs involved in the Vanguard project are of course 38 considerable, but a great deal of this money will represent capital investment and various nonrecurring expenses. As long as rockets of present-day performance can form the basis for designing satellite vehicles, and in view of the estimated $35 million allocated for the project, we might well see 15 satellites being built for use during the IGY. Some of them might go astray, but we are convinced that most of the satellites ("birds," to their designers) will reach their orbits successfully. The velocity will be fast enough for the satellite to circle the Earth in about 90 minutes; the altitude may be anywhere between 200 and 800 miles. This will be too low for escape into outer space. Gravity and drag will finally have their effects. The satellite will descend in a shallow spiral. After some days, or, if we are lucky, weeks, the satellite will crash into the heavier atmosphere and quickly disintegrate. 4. What Is Space? Go up a few miles and life as we know it ends. There, we would no longer have an atmospheric blanket to protect us. High temperatures exist but would not be sensed. X rays and cosmic rays would penetrate our bodies and dissociate our cells. The air pressure would decrease below our blood pressure until our bodily liquids began to boil. Time is always a relative concept. Skyward all is darkness. At sea level, the molecules comprising air are packed tight together. In every cubic inch there are about 400 quintillion particles. A molecule can barely move without colliding with another one, and its obstacle-free path is only one millionth of an inch. Because the air at sea level is so dense, scientists at one time believed that nature abhorred a vacuum. Yet we need rise only 70 miles to see that nature prefers a vacuum, for at this altitude, the obstacle-free path of a molecule is 51 inches. The higher the altitude, the farther a molecule can travel before meeting another. At 250 miles' altitude the free path is 43 miles. In outer space there are about 16 particles per cubic inch, and they hardly ever collide. They exist in a vacuum far less dense than the best we can get in our laboratories, which is thought good at five billion molecules per cubic inch. The free path of particles in space is not known, but is judged to be enormous. It is interesting to learn how much matter there is in a given 39 volume of outer space. For a volume as large as that of Earth, there is about a quarter of an ounce of meteors and two to three ounces of hydrogen. These figures give an idea of what emptiness is. Connected with this emptiness are unfamiliar concepts of temperature and heat. At 600 miles' altitude, the temperature is about 1,200 degrees Fahrenheit—the melting point of aluminum. Yet aluminum would not melt at that height because there is temperature without heat. Temperature, as we are most familiar with it, is measured with a thermometer. If we wish to know the temperature of a room, then for ordinary accuracy it does not matter where we mount the thermometer. Its bulb is constantly being bombarded by molecules, which carry energy to the instrument. The hquid level rises or falls depending upon the speed of the molecules. They are in constant motion, with the temperature being highest when their speed is highest. Temperature is simply the measure of molecular speed. At sea level the molecules are so closely packed together that they no sooner get up speed than they lose it in collisions. But in space, where particles probably travel for millions of miles before they are stopped, they can move at tremendous speeds. The temperature of these particles can reach 10,000 degrees Kelvin and even higher. The temperature scale using degrees Kelvin is based on the point at which a body is entirely devoid of heat and molecular motion ceases; this is marked zero degrees Kelvin, or absolute zero. At 273 degrees Kelvin, water freezes; at 373 degrees, water boils. This makes one degree Kelvin equivalent to one degree Centigrade. The story is told of a young journalist who had read that in space the temperature is several thousand degrees Kelvin. Using this fact as a lead, he wrote a sensational article describing the belt of fire that was surrounding Earth. An instructive experiment for the journalist would have been one in which he was surrounded by interstellar hydrogen traveling at a speed corresponding to 10,000 degrees Kelvin. He would have quickly discovered the difference between temperature and heat. Though each hydrogen particle possesses a tremendously high temperature, it takes a vast volume of them to furnish enough heat to boil a thimbleful of water. One should not get the impression that a body set in space would immediately freeze. The Earth, for example, is kept warm by its atmosphere, which is heated by the Sun's rays or radiant energy; these rays travel much like light, whose presence is known only when reflected or absorbed by a body, thus the Sun's heat is not felt until it passes through space and becomes absorbed by our atmosphere and planet. When any body in space intercepts the Sun's rays, then it too is warmed— 40 At sea level, the air molecules are packed closely together. In space, they travel many miles before colliding, and being slowed down. As a result, the temperature of a molecule, which is a measure of its velocity, is high in outer space. (Martin, Baltimore) but if no atmosphere surrounds the body, then it quickly loses heat. The amount of radiant heat falling upon a body in the upper atmosphere is called the solar constant. Its value is 440 BTUs per square foot per hour. One BTU, British thermal unit, is the quantity of heat needed to raise one pound of water one degree Fahrenheit. If the body were painted black, then it would almost completely absorb the radiant energy hitting it, while if it were painted white, it would reflect the most radiant energy. We see then that a one-foot-square black body located in space could absorb enough radiant energy in one hour to raise the temperature of 440 pounds of water one degree Fahrenheit. Because of losses caused by moisture in the atmosphere, dust, and the air mass itself, the solar constant at sea level is 220 BTUs per square foot per hour, half of its upper-atmospheric value. This figure is quite variable: it changes with latitude, time of day and year, and tilt of the body with respect to the solar beam. The temperature and density of the air change as altitude changes. A graph of air temperature versus altitude appears as a zigzag curve because of the varying absorptions of the Sun's energy in different air layers. At low altitude, there is a "normal" relationship between the actual temperature and the temperature that we feel. At high altitudes, there is no such direct relationship. As we have seen, the few air molecules present cannot convey their heat to us, and the Sun's radiations heat us on one side while the other side remains cold. The various layers in the atmosphere have been defined according to their temperature characteristics by the Air Force Cambridge Research Center. This agency sees the atmosphere divided into five concentric spheres around the Earth. These are chiefly distinguished by their temperature gradients, which change with altitude. Each shell has the suffix sphere. In the order of increasing height we have the troposphere, the stratosphere, the chemo-sphere, the ionosphere, the mesosphere, and the exosphere. The top of any sphere is given the suffix pause. The upper boundary of the troposphere is called the tropopause; of the stratosphere, the stratopause, and so forth. Actually, at no altitude does the temperature gradient change suddenly. If one wishes to mark the spheres according to temperature gradients, then the bounding surfaces or pauses must be allowed to have considerable thickness. At some latitudes, the defining temperature gradient occasionally does not exist, which leads to the elimination of the corresponding sphere. Our weather is generated in the lowest layer, or troposphere, which is about seven miles high—a mile higher than Mount Everest but equal in height to the mushroom-shaded cloud resulting from an atomic explosion. The troposphere is in thermal equilibrium with the stratosphere above it and the Earth be-42 low. When the troposphere absorbs more heat than it reflects, it uses this excess to warm and mix itself. This gives rise to the winds, rains, and displays of summer lightning. Man has already flown in the stratosphere, the second atmospheric layer above Earth. In its record-breaking flight, the Douglas Skyrocket climbed to about 16 miles' altitude, only 4 miles below the stratopause. High-altitude balloons have traveled through the stratosphere into the next layer. Strong air currents of high velocity, the newly discovered jet streams, are found in the lowest portion of the stratosphere. Here also are the delicate and threadlike cirrus clouds. The air in the stratosphere is clear but turbulent. Occasionally, rare nacreous (mother-of-pearl) clouds are seen, their origin and composition still wrapped in mystery. Streaking across the stratosphere are the ends of meteor trails bright enough to mark the sky even in the daytime. Above the stratosphere is the chemosphere, which acts like a huge photochemical laboratory. It processes the Sun's incoming ultraviolet energy, and also gives rise to the recently perceived enormously intense, infrared night airglow radiations. It is in this region that ordinary meteors reach their fiery end, and it is here that a layer of electrified particles sometimes captures radio waves, the capture on occasion causing radio blackouts. Though it lies in the interval between 50 and 250 miles' altitude, the ionosphere is our most probed layer. We have explored this region with powerful high-frequency radio waves. Rocket research, and observations of meteors and auroras have given us vital data. An instrumented Wac Corporal fired from a V-2 rocket in the chemosophere reached the ionopause. In the early days of radio, Watson Watt coined the word ionosphere because of the region's electrical characteristics. The ionosphere is that portion of our atmosphere capable of conducting electricity. This characteristic makes long-distance radio communications possible, and accounts for the small but daily variation in compass readings. The formation of ions in the atmosphere is a dynamic phenomenon. During the daytime, ultraviolet radiation and X rays from the Sun constantly pass through our upper altitudes. These radiations hit the molecules in the atmosphere, which are tiny and numerous, sometimes sufficiently hard to break them down into atoms. When this occurs, one atom is apt to steal an electron from its former companion. Sometimes, just an electron is knocked loose. In either case, free electrons and atoms with too few or too many electrons are formed. Such atoms are called ions, and the process of making them is called ionization. The particles have two quite important properties: first, unlike neutral particles, they generate an electromagnetic field about themselves, and second, when they form in layers as they do in the ionosphere, the free electrons act as mirrors and reflect certain types of jadio waves. It was through its electromagnetic characteristic and electrical conductivity that the ionosphere was first hypothesized. About 75 years ago, the Scottish physicist Balfour Stewart made an important but then unnoticed contribution to science. He knew that there were daily variations in the strength and direction of the Earth's magnetic field. He also knew that a magnetic field is distorted when an electrical current passes over it. He concluded that there must be a layer someplace in the atmosphere that is conducting electricity. Not until the beginning of this century was Stewart's theory revived. Physicists agreed that radio waves travel in straight lines much like light. Today, this phenomenon explains our receiving FM and TV broadcasts only within a radius of 25 to 30 miles of the sending station, unless repeaters are used. But, the physicists asked, if radio waves travel along line-of-sight paths, how is it that we can receive broadcasts from across the Atlantic Ocean? It was necessary to rehypothesize the iono-44 Different layers in the ionosphere reflect different type radio waves. The low frequency or standard broadcast waves are sent back to Earth from a layer low in the atmosphere, while high-frequency programs such as FM and TV pass easily into outer space. (Martin, Baltimore) sphere, an atmosphere region that conducts and reflects electrical waves. Experimental proof was given in 1924. Short-pulsed radio waves that had been sent straight up into the atmosphere had returned microseconds later. This experiment not only proved that the ionosphere is real but also indicated its height—from the time delay of the radio waves traveling at the speed of light. Today it is known that the ionosphere extends from an altitude of 50 miles to 250 miles, that it is made up of many horizontal layers, and that each layer contains a seething ocean of electrons easily churned by solar activity, cosmic rays, meteors, and gravitational tugs of the Moon and Sun. Even the time of day, the season, and the year have major effects in this region. What counts most in the ionosphere is the electron density, normally measured in number of electrons per cubic inch. The higher the density, the more effectively a layer of electrons reflects radio waves. It is natural to characterize each layer with respect to its electron density. This has been done, the chief layers being named D, E, and F. The layers have thickness, and vary in the type radio wave they will reflect. The D layer, which is the lowest one and has the lowest electron density, reflects long waves such as the standard-broadcast ones but allows the shorter waves to go by. A useful analogy is to look at the three layers as sieves, the grid size of each being proportional to the electron density of each. In this view, the D layer has the coarsest grid; above it lies the E layer with a less coarse grid; and finally we have the F layer with the least coarse grid. The long waves of the standard-broadcast band being blocked by the D grid are reflected back to Earth. The shorter waves of the police-broadcast band stream through the D grid but are stopped and reflected by the E one. Short-wave broadcasts pass through the D and E grids to be reflected by the F grid. FM and television signals, being shortest of all, scurry through all three grids to provide entertainment for inhabitants of artificial satellites and other planets. The E and F layers sometimes each split into two layers; then subscripts are given to the letter names and the split layers are called £„ E„ and F„ F,. It is not yet known why these splits occur. Having gone this far into the mechanics of the ionosphere, and seen its apparent simplicity, we can appreciate the time and work scientists have put into its study. Their theories have received convincing experimental confirmation. Radio probes have shown the existence and heights of the various electron layers. Spectroscopic studies have proved that speeding atomic particles (corpuscles) leave the Sun at times of solar flares and bombard our atmosphere, causing variations in the layers of the ionosphere. Recently, rocket probes of the 46 ionosphere have confirmed the existence of ultraviolet radiations and X rays in this region. It would be fine if the ionosphere behaved in a consistent fashion, for then, we could soon wrap up the problem for all time and move on to the next. But superimposed on the general pattern are varying ones. These change from day to day, even from minute to minute. For example, during a solar flare, when ultraviolet and X-ray radiations are at their highest intensity, the D layer gets a sudden increase in ionized atoms. These, unlike electrons, absorb short waves, and we experience several hours of radio fading and blackouts, the length and severity depending on the nature of the solar flare. Sometimes sporadic clouds of electrons hover in the E layer. Why, we do not know. Suddenly, waves that ordinarily would pass right out of the atmosphere are reflected, and we begin receiving FM and TV programs from great distances, programs that should have been cut off at the sending station's line of sight. Between the ionosphere and the exosphere, which is the outermost atmospheric layer, lies the mesosphere. No man-made vehicle has yet explored this space which stretches from 250 to 600 miles' altitude. Even its temperature gradient is not known, though the region is believed to be one of high but decreasing temperature. Because it experiences the Sun's radiations before the ionosphere does, the mesosphere is probably proportionately more highly ionized, yet since its air density is so much lower, its electron density must also be quite low. Having so few electrons, the mesosphere's influence on radio communications is considered negligible. At the exosphere we stand on the fringe of outer space. Low in this region some of the neutral atoms and molecules speeding upward never experience a collision, thereby escaping from Earth. This level is called the critical level and is believed to be at about 625 miles' altitude. The smaller and faster particles such as hydrogen and helium have lower critical levels, while the heavier particles such as nitrogen have higher ones. Quite gradually, the exosphere diffuses into interplanetary space. Fortunately for us, from the surface of the Earth it is not possible to see all the sunlight—even with instruments. Most of it is absorbed by our atmosphere. In this way, the atmosphere shields us from the Sun's more intense radiations. As we rise in the atmosphere we perceive strongly the infrared rays at 25 miles' altitude, and then the ultraviolet at 70 miles. Instruments must be used to recognize these radiations because none of our senses can. Biologically we have no need for this ability because none of the ultraviolet and only a minute fraction of the infrared ever reach the Earth. Violet light is the lower limit of visibility, with a wave length of about 3,850 Angstrom units. (The Angstrom unit 48 is a convenient length measure, particularly in the atomic field. The diameter of an atom of hydrogen, for example, is about one Angstrom unit or 0.00000001 centimeters.) Nevertheless, we can easily prove the existence of light below this lower limit. Ordinary photographic paper responds quite readily to exposure to ultraviolet. Instruments show the existence of ultraviolet in the electric arcs thrown by welding rods and arc lights. The concept of infrared light is quite familiar to us. It is by this light that we take pictures in the "dark." Also, by this light "infrared broilers" cook our food. We can appreciate the existence of these radiations, particularly when they emanate from hot bodies, yet we cannot see them. Neither can we feel the entire band of infrared, which stretches from the normal upper limit of visible light (7,600 Angstrom units) to the region of high-frequency radio waves. The rays emitted by the Sun are not bounded by the short ultraviolet waves nor by the long infrared ones. There are ones far shorter and far longer. Above the infrared is the wide band of radio waves extending from radar to the standard-broadcast waves. On the other side, below the short-waved ultraviolet, are the X rays and gamma rays. All these radiations are cut of similar cloth: they travel with the speed of light, are electromagnetic phenomena, and have characteristic wave lengths. Back in 1900 when research in physics was being done in earth-bound laboratories, British and German scientists noted a strange occurrence: the charge in an electroscope leaked away no matter how well it was shielded and insulated. (An electroscope is simply a metal cylinder containing a conducting rod. At one end, the rod is insulated from the cylinder, at its other end, the rod holds two thin gold leaves. When the cylinder is given an electrical charge relative to the rod, the leaves spread apart; when the cylinder and rod have the same charge, the leaves hang freely.) To explain the mysterious leaking, scientists said that somehow the Earth emitted radioactive rays that were neutralizing the charged electroscope. This theory was proved wrong in 1910 when a scientist took some electroscopes up to altitude in balloons; he found that rather than the leakage decreasing, it increased. Later it was observed that the loss reached a peak at 17 miles' altitude, and then slowly lessened. (Recent rocket studies indicate that the leakage becomes constant at 35 miles' altitude.) It was realized that the Earth was not the origin of the phenomenon. Strange radiations called cosmic rays were designated as the culprits. Further research showed that these rays can pierce three feet of lead or 3,000 feet of water. The physicists claimed that anything coming in from space with that much energy must 49 certainly originate in the Sun. They added that cosmic rays are radiations similar in nature to light; this theory was quickly disproved when it was shown that cosmic rays, unlike light, are deflected by a magnetic field. Today it is believed that cosmic rays are electrically charged particles bearing extremely high energies. They are said to include protons and atomic nuclei stripped of their electrons. The cosmic nuclei probably exist in the same relative numbers as do the different atoms on Earth, in fact, cosmic-ray particles as heavy as iron and tin have been identified. Primary cosmic rays enter the atmosphere near the speed of light. They arrive with energies higher than any other known in nature, ranging up to one half a foot-pound per particle. When cosmic rays collide with oxygen or nitrogen atoms in the atmosphere, the energy of the ray is dissipated as the atom is disintegrated, and mesons and other types of particles are formed. (Mesons are particles with either a positive or negative charge and with a mass about 200 times that of an electron.) These are the cosmic-ray secondaries whose energy and mass are absorbed by the atmosphere and Earth. Compared with the energy sent to us by the Sun, the total energy of the cosmic rays is equivalent to that of starlight, yet the cosmic-ray mass falling to Earth per minute can easily be contained in a pinpoint. It is not known where cosmic rays come from. They could originate in the Sun or in interstellar space or in both places. Neither is it known why mainly high-energy cosmic rays arrive here; the rays seem to be cut off below a certain energy level. Does this mean that they are deflected by the Earth's magnetic field, or that the low-energy rays do not exist? In studying cosmic-ray densities from the equator to 56 degrees latitude, scientists find that the density increases tenfold, yet from 56 degrees to the geomagnetic pole, the density is constant. It is not known why. The answers to these questions could perhaps give us the key that would unlock the structure of the nucleus and lead to an understanding of the true nature of elementary particles. Daily variations in the ionosphere cause variations in the strength and direction of the Earth's magnetic field. Quite independent of these are variations caused by magnetic storms. The reasons for these storms are being studied, and a connection with sunspots has already been shown. Looking at the Sun through a telescope, suitably shaded, we often see its surface pockmarked with sunspots. These are dark circular patches sometimes reaching a diameter of 100,000 miles. They are cooler regions than the rest of the Sun, and are sources of great magnetic fields. What is interesting about the sunspots is that sometimes we can see many of them, sometimes none at all. These periods correspond to the sunspot maximum and the sunspot minimum. The entire sunspot cycle takes 11 years. The odd characteristic about magnetic storms is that they occur most strongly during a time of sunspot maximum. Yet they do not appear at the moment a sunspot is seen, and this fact could be said to be an odd coincidence, except that the storms come in a series. They start with a small magnetic disturbance, then 27 days later there is a larger disturbance, and so on, building up to a maximum in 27-day steps, and then back down to a minimum. The rotational period of the Sun is 27 days. Despite our present inability to see them emerge, it is thought that just 51 before magnetic storms take place, vast clouds of ionized particles speed out from the Sun. These storms are world-wide, and could be produced by the electromagnetic effects of these particles streaming past the Earth's magnetic field. One manifestation of magnetic storms, often of great beauty, is known in the Northern Hemisphere as the aurora borealis, "in the Southern Hemisphere as the aurora australis. We shall speak of the aurora borealis, as that one is the more familiar. Although these auroras are usually confined to the upper northern regions, they can sometimes be seen as far south as Washington, D. C, though not in anywhere near their full glory. A typical aurora appears at dusk. It tints the sky with a yellowish-or greenish-white almost eerie glow. Later the glow brightens, gathers itself into a band and arcs east to west across the sky. Soon part of the band may break away into sweeping curves, or may wind around in the sky in serpentine formation; the other part falls into many smaller bands and dancing segments. Sometimes fans of pink, purple and red appear, complete with darkened centers. Around midnight we can see long beams of light falling toward the horizon like folds in a thick drapery. A few hours from dawn the light slowly diffuses and quickly fades away. A generally accepted theory is that the auroras are located in the ionosphere. Like the magnetic storms, of which the auroras are the visible part, they are caused perhaps by protons speeding from the Sun into the Earth's magnetic field. These particles sweep into the magnetic funnels at the poles. The protons unite with free electrons to form hydrogen, emitting light rays in the process. The later kaleidoscopic patterns are formed by beams of charged particles bombarding the ionized gases in the ionosphere, an action similar to the ionic bombardment of neon in a neon tube. Closely associated with the auroras is the night air glow. Though usually perceived by instruments, it accounts for 40 per cent of the light in the night sky, apart, of course, from moonlight and starlight. This figure does not take account of the invisible radiations present. It is said that if our eyes were sensitive to the infrared, the air glow would make the night sky as bright as mid-twilight. As with the aurora, the air glow is caused by ionized particles in the atmosphere, probably in the ionosphere. Some authorities believe that it results from the transfer of some of the energy stored up from sunlight during the day into radiations in the infrared, visible, and ultraviolet during the night. As an example, during the day the sunlight dissociates molecular oxygen. Partial recombination of the resulting atoms during the night involves processes in which light may be emitted. One 52 criticism of this theory is that it is difficult to imagine only such a small part of the Sun's daylight energy being reconverted. If the process is going to take place at all, it has the entire energy in the ionosphere to draw upon. The Sun holds sway over a number of satellites—planets, asteroids or minor planets, comets, and meteors. Of these, the meteors or "shooting stars" caU for our attention for we shall certainly have to contend with them minutes after artificial satellites leave the Earth. The origin of meteors and of their larger brothers, the meteorites, which are different only because they had the good fortune to reach the Earth, is open to speculation. One idea about which many science-fiction writers like to wrap their plots, and that has some scientific backing, says that the asteroids, comets, and meteors were once part of a planet between Mars and Jupiter. Long ago this planet was destroyed either by the tidal forces of Jupiter or by some other catastrophic force. Left in the lost planet's orbit was a ring of asteroids, particles of which sometimes enter our atmosphere as meteors. This theory is somewhat plausible, because if we assume a planet in the orbit of the asteroids then, except for Mercury, the distance between each planet is always double the preceding distance. The chemical composition of meteorites also suggests that the material originated in the interior of some large body. Meteors enter our atmosphere at speeds of about 40 miles per second, a rifle bullet travels less than one mile per second. Turned incandescent by air friction, they streak across the sky with fiery tails up to 30 miles long. They appear much larger than they are because of their envelopes of glowing gases and irradiation effects. Nearly all meteors have diameters far less than one tenth of an inch and weigh less than a few thousandths of an ounce. Of the two types, the stony meteors outnumber the iron meteors ten to one. Although 750 billion particles weighing upwards of one hundred-millionth of an ounce shower the Earth every day, few meteors ever reach the ground. Most of them are so small that despite their great speed, a paper-thin steel body could possibly cruise in space for about a year without ever being pierced. It is doubtful that most meteors could do more harm than dull the surface finish of a tiny orbiting Earth satellite. The nature of our atmosphere and outer space has been only briefly sketched by science. There are so many questions that man has not answered that those he has seem trivial. It may be better that he not know how much there is still to be known. Still, to be able to live adequately in our environment and to turn to advantage the energies nature has given us, it is vital that some of the problems be solved. We want to know about 53 the photochemical reactions taking place in the atmosphere. With this information we shall be on our way toward long-range weather forecasting. We want to know the mechanism of the ionosphere and the distribution of ion densities in order to improve radio communications. Cosmic ray, aurora and air-glow studies could give us valuable data about the ultimate nature of particles, and incidentally more information about the generation of nuclear energy. For satellite science and space travel, we need to learn about the winds and turbulences in the upper atmosphere, and about general circulation patterns. It would be a brave crew that would set out on a space journey without also knowing the magnitude and probable frequency of meteor showers. Upper-atmospheric studies through rocket research have already yielded valuable data. But they are insufficient, and in view of the results, such research has reached the point of diminishing returns. 5. New Moon Among the stimulants for raising an Earth satellite are national pride and technical achievement. Those who say that the country that builds the first one will be building military superiority must mean psychological superiority. It is clear that the first satellites will be only probes into the higher altitudes. We cannot use them for guiding missiles. They are too small for tactical mapping, too light for carrying bombs, and too unpredictable for accurate homing. Later, satellites could be part of a weapons system—but now, no. The United States and the Soviet Union will not have the satellite field to themselves. Other countries will soon begin building their own orbiters. Although the goals will be the same, the means will vary, in fact, the means will vary within a country. For this reason, engineers cannot prescribe a single satellite design and say this is to be. An artificial Earth satellite is an object that leaves the Earth's surface, ascends to a high altitude where it is held by centrifugal force, and then perhaps descends into the lower atmosphere or to Earth. We say "perhaps" because the satellite may reach an altitude where gravity is not strong enough to bring it back. Then, as with our Moon, the satellite could circle our Earth forever—or at least as long as there is an Earth. In view of the dimensions of our solar system, the current satellites will not rise very high, only a hop. We know that their return flights to Earth will be disintegrating ones, marked by 54 fiery evaporation as they rush at hypersonic speeds down through the denser atmospheric layers, and a handful of unidentifiable dust will be their remains. When satellites larger than the minimum ones are sent aloft, engineers may try to save them. The main problem in establishing a satellite is thwarting the pull of gravity. It may be said that our aircraft experience gives us a substantial lead in solving this problem. This statement is not entirely true because the airplane depends for its lift upon the air, which conducts the airplane's weight back to Earth. With this vehicle, we have no more overcome gravity than has a ship's builder whose vessel is kept afloat by a depth of water. At best, we have constructed a pair of quite high stilts. On the other hand, a satellite in its orbit cannot cry to the atmosphere or to Earth for support; the vehicle must be self-sustaining. The interplay of gravity and centrifugal force can be pictured if we consider a mass being rotated at the end of a long rubber cord. Given sufficient angular velocity, the centrifugal force keeps the mass in a circular orbit in the plane of the rotating cord. For larger orbits, additional energy must be put into the system to oppose the increased pull of the lengthened cord. A point is finally reached where the amount of energy put into the system is more than the system can contain. The string then tears apart and the freed mass goes speeding off in a way similar to that of a satellite escaping from the Earth's gravitational field. It must be remembered that the Earth's gravitational field has no sharp boundary; rather its influence is strongest at the Earth's surface; with increasing altitude, the field slowly becomes weaker. This observation is expressed by Newton's inverse-square law, which states that the gravitational force between two bodies varies directly as the product of their masses and inversely as the square of the distance between them. From this law, the acceleration effect of gravity on a 200-mile satellite is 29 ft/sec2, which is nine tenths of its sea-level value of 32.2 ft/sec2. For a 4,000-mile satellite, gravity's effect has decreased to 8 ft/sec2, one quarter of its sea-level value. At the mean altitude of the Moon, which is 238,000 miles from the Earth, the pull of the Earth's gravity on a small mass is practically zero. We are not seeking to escape the Earth's gravity. That we can is voiced by some of the more optimistic scientists. That we want to, even if we could, is open to serious question. The outer fringes of our atmosphere offer enough data to keep all of today's available scientists busy for all their available time. With our present technology, we could possibly send a small slug of matter bounding into space. Beyond the satisfaction we 55 would get by knowing that we had added a particle to the cosmic dust, there would be little that we could learn from the costly experiment—except lessons in rocket architecture. The escape velocity (speed needed for a body to escape from the Earth's gravity) for a sea-level vehicle leaving for outer space is 25,000 miles per hour. This velocity may be produced entirely at the moment of launching or in stages during the vehicle's travel through the atmosphere. We have seen that the stage principle is the preferred one. The escape velocity is calculated through an equation in which the vehicle's initial kinetic energy, energy arising from the vehicle's speed, is set equal to the vehicle's final potential energy, energy needed to raise the vehicle through the Earth's gravitational field. Since the pull of gravity decreases with increasing heights, the required escape velocities also decrease with height. On this basis, we might ask for a powerful first-stage rocket that would propel its vehicle to perhaps 100 miles' altitude, followed by a second-stage rocket that could then operate on a smaller escape velocity. However, the weight penalty incurred by using such a powerful first stage would more than offset the small decrease in escape velocity; in fact, this velocity is far less than one would intuitively expect, having decreased from its sea-level value only 5 per cent. For a launching site 1,000 miles high, the decrease in gravity still would prescribe a formidable 22,000 miles per hour for escape. Gravity causes only a part of the resisting force. Another one, almost as great, is air resistance, or drag. This factor depends on the vehicle's shape passing through the atmosphere, the vehicle's velocity and the air density. For a given vehicle and velocity, the drag varies directly with air density, which is small at 100 miles' altitude. Although at this altitude the escape velocity is not significantly changed, the low air drag appreciably lessens the energy needed by a vehicle we want to leave the Earth. These same factors affect the satellite, and its launching at altitude, as in balloon launching, is therefore being studied. Provided its kinetic energy were high enough to overpower gravity and drag, an object could orbit at any altitude around the Earth. For a sea-level orbit, the gravity requirements call for an 18,000 mile-per-hour velocity, a speed at which atmospheric drag consumes in just a few seconds all but the most robust meteors. However, air density decreases rapidly for relatively small increases in altitude; at 200 miles the density comes close to zero. Since gravity lessens only slightly at this altitude, we can expect a 200-mile satellite to travel around the Earth at a speed slightly less than 18,000 miles per hour. It would be strange indeed if the actual orbit of a satellite were a circle. For it to be a circle, we must be assured of two 56 quite difficult happenings: first, when a satellite is launched from its vehicle at orbital altitude, it is launched precisely parallel to the Earth's surface, and second, its launching velocity corresponds exactly with that required to balance the gravitational field. A deviation in either of these factors would result in an elliptic orbit. If a satellite is not launched parallel to the Earth, then the perigee, orbital point nearest Earth, will be closer to the Earth than the launching point, and the apogee, orbital point farthest from Earth, will be at a greater altitude than the launching point. If the launching angle is projected up from the horizontal, then the satellite will pass through the apogee before it passes through the perigee. The reverse happens if the launching angle is downward. If the angle is too great, then the orbit will go through the denser atmosphere or into the Earth. When a satellite is launched parallel to the Earth but slower than is required, its launching point will be its apogee, and its perigee will be halfway around the world—unless the velocity is too slow, in which case the satellite will fall to Earth. When the velocity is more than the altitude requires, then the launching point will be the perigee. Should the velocity exceed the escape velocity, then the satellite will leave the jurisdiction of the Earth never to return. We are now in a position to appreciate some of the problems that face the creators of an artificial satellite. One of these men, Homer Newell, Jr., director of scientific experiments for Project Vanguard, points out that first the satellite must be carried above the appreciable atmosphere, to about 200 miles' altitude. Then the satellite must be projected as close to the horizontal plane as guidance accuracy permits, and with sufficient velocity to assure the satellite's remaining at altitude throughout its orbit. By designing the propulsion system to give with certainty more than enough velocity, engineers can solve the altitude problem. The guidance problem is more difficult. If, for launching altitudes in the range from 200 to 300 miles, the angle of projection misses the true horizontal plane by as little as 1.5 degrees, the perigee altitude will be roughly half the launching altitude. Such an error occurring with a launching altitude of 200 miles or less would cause the satellite to dip into the denser parts of the atmosphere, and would cut short the satellite's lifetime. For launchings between 200 and 300 miles, which are the likely altitudes for early experiments, engineers will be seeking guidance accuracies well within the 1.5 degree bench mark. Atmospheric drag, although extremely small in the higher atmosphere, nevertheless collects a toll in energy from every orbiting body. Over a period of time, these payments detract from the speed of the body bringing it closer to Earth. How 57 long a satellite can remain in the sky before spiraling down is an intriguing question. One scientist says that a 200-mile satellite will begin its final descent at the end of 15 days, while another scientist says the interval will range between one and 100 days, depending on the type satellite. Since the characteristics of the atmosphere at extreme altitudes are not accurately known, and since a satellite's orbit will not be learned until it is formed, we can understand the difficulty in making an estimate. On the basis of upper-atmospheric data gained from rocket research, Dr. Newell believes that a 100-mile altitude satellite would last about an hour. First approximations of the lifetimes of various satellites in near-circular and elliptic orbits have also been calculated by N. V. Petersen of Sperry Gyroscope Company. He estimates that a cylindrical satellite with a cross-sectional area of one square foot and weighing 44 pounds would remain in a 190-mile circular orbit for 47 days. In an elliptic orbit, 62 miles at the perigee and 621 miles at the apogee, the lifetime would be about five hours; for the same apogee but for the perigee increased to 124 miles, the lifetime would jump to about 33 days. Different orbits are desired for different experiments. These orbits have been roughly classified into three types: equatorial, polar, and intermediate. For the first type, the satellite would orbit in the equatorial plane, and the Earth's rotation would simply cause a change in the satellite's apparent time of revolution. The placement of observing stations on the ground would be particularly easy here because the satellite would always be above the equator. For the polar orbit, the Earth's rotation would cause the satellite's track over the ground to spiral around in a complicated fashion. Only at the poles could we always count on a passage of the satellite overhead once per revolution. It is clear that locating observing stations for a polar orbit would present some difficulties. For the intermediate orbit, the satellite's track over the ground would wind around in a sort of sine wave between a maximum latitude north, and an equal maximum latitude south. The equatorial crossing points, or nodes, would move along the equator in a way depending mainly on the Earth's rotation, but also somewhat on the rotation of the orbital plane caused by the Earth's oblate-ness. In the intermediate case, also, the setting up of ground stations would be troublesome, the difficulty becoming more pronounced as the inclination of the orbit to the equator was increased. The early satellites will probably be sent on pole-to-pole or on near-equatorial orbits. In the first-type orbit, a 200-mile satellite would travel once around the world every 90 minutes. 58 In the second-type orbit, if the satellite were launched eastward from the equator, the period would seemingly be greater than 90 minutes owing to the 1,000 mile-per-hour eastward rotation of the Earth, while for a westward equatorial launching, the satellite's period would appear to be less than 90 minutes. The 200-mile orbit is noteworthy only because it is the easiest to attain. Other orbits of particular value include one at 1,075 miles, which represents the two-hour orbit proposed for the von Braun space station. Petersen considers this altitude the lower limit for a permanent orbit. The 24-hour orbit, which would have the satellite appearing stationary to an observer on Earth, is found at 22,300 miles, and a satellite in this orbit could serve as a radio or TV relay station since three such stations could see more than four fifths of the Earth's surface. Especially valuable for geodetical measurements would be an elliptic orbit stretching 238,000 miles to the Moon. A satellite in this orbit could make one of these round trips every 27M> days. Minimum instrumented satellites have been suggested ever since World War II. On May 4, 1954, the Mouse satellite design was revealed at the American Museum-Hayden Planetarium in New York. Although Dr. Fred Singer did not know it at the time, his proposal was destined for world-wide attention. In several ways, Project Vanguard differs from Dr. Singer's concept of the satellite—but that the project is worth while and feasible he proved to everyone's satisfaction. He named the satellite the Mouse, which not only gives an indication of its unpretentious size but also, if one wishes to interpret its initials, stands for Minimum Orbital Unmanned Satellite of the Earth. He said it would be expendable. It would circle the Earth at a low altitude of about 200 miles, and its life would be short, perhaps only a few days. But above all, the satellite would weigh less than 100 pounds. In brief, the proposal consisted of the concept of an instrument-carrying satellite that would pursue astrophysical and other upper-atmospheric studies. At the time, the orbit of the Mouse was different from the orbits being proposed for other satellites. The Mouse would not follow the equator but instead would travel over the poles on a great-circle route and in a plane perpendicular to the Sun-Earth line. It would also cover the whole range of latitudes, as this type of survey is important for determining the energy spectrum of cosmic radiations. In this orbit, too, the satellite would traverse the auroral zones surrounding the poles. The poles and the regions in the vicinity of the poles would represent the logical places for observing the Mouse and for checking its orbit; and most important, for receiving data from the satellite, or for influencing its operation by means of a signal transmitted from the ground. The orientation stability of the Mouse was to be achieved by rotating it about a horizontal axis before take-off. After the third-stage rocket had burned out and the nose tip opened, the spinning cylinder which would be the Mouse would be ejected into its orbit around the Earth. During flight, the spin axis would always be horizontal and at right angles to the direction of motion of the center of gravity. Through the law of conservation of angular momentum, it 60 can be shown that the spin axis will stay horizontal without using any further controlling forces. The instruments would be mounted in two short rods extending through each side of the Mouse along the spin axis. The instruments, therefore, would stay fixed in space, which is important from the point of view of interpreting the observations. The suggested orbit was such that the satellite would always be exposed to the Sun, and a particular half of the satellite 61 would always see the Sun. This would make the use of a solar power supply look quite promising. Since the Mouse would pass over the poles every 45 minutes, we could have patrol planes operating in each polar region. When the satellite appeared overhead, the nearest plane would send an interrogating radio signal to the vehicle, which would automatically turn on its radio transmitter. For the next half a minute the satellite would transmit the information it had recorded during the preceding 45 minutes, which means it would transmit during one per cent of the time of its travel. Thus, it would collect data for 45 minutes in its travel from pole to pole, and would transmit for the half minute it was in the vicinity of each pole. The technical problem could be solved in a simple way by recording the information on a magnetic tape moving slowly at 1 /30 of an inch per second; 45 minutes could be recorded on only IVz feet. Played back at three inches per second, all the information would be transmitted in 30 seconds. In a later report, Dr. Singer proposed general principles for designing minimum orbital satellites (MOS). These principles were based on the need for making best use of the available pay load and of the orbit type. From these two factors would stem the satellite's instrumentation and resulting data. MOS was divided into three groups of increasing propulsion difficulties: I, II, and III. In general, pay load would be traded for a polar orbit (instead of the easier equatorial orbit), or for a means of orientating (for example, by spinning), or for telemetering storage. This is not a rigorous division, but depends to a great extent on changes in the art of instrumentation. Dr. Singer's classification given below is based on the use of a solar battery. MOS Difficulty Pay load Type Orien- of Propulsion (approx.) Orbit tation Telemetering I 101b equatorial no continuous II 301b equatorial no continuous 251b equatorial no triggered or stored 251b equatorial yes continuous 201b polar no triggered or stored 151b polar yes triggered or stored III 501b equatorial no triggered or stored 501b equatorial yes continuous 401b equatorial yes triggered or stored 401b polar no triggered or stored 301b polar yes triggered or stored One way to keep a satellite's weight low, but still have it instrumented, is to do away with its housing. Dr. I. M. Levitt, 62 director of The Fels Planetarium, has proposed a satellite weighing about 10 pounds. It would consist of a large deflated rubber balloon or plastic bag in which a carbon-dioxide cartridge similar to that used to charge water would be placed. A timing mechanism would be fastened to the carbon-dioxide cartridge and at a preset instant a triggering mechanism would release the gas in the cartridge, permitting it to inflate the balloon. This would take place after the pay load had attained circular velocity. Surrounding the balloon would be a layer of thin aluminum foil with the shiny surface on the outside. When the balloon expanded to about 10 feet in diameter, an aluminum shell of the same diameter would be formed. After the shell had been inflated, the gas would leak out. However, since there would be no forces acting on the distended aluminum shell, it would persist as a sphere. Built by Popular Science Monthly after consulting with scientists connected with Project Vanguard, an 18-inch model of an artificial Earth satellite was put on display in late 1955 at the Hayden Planetarium and at the Museum of Science and Industry in Chicago's Jackson Park. One of the problems being solved by the designers of the Vanguard satellites is the method of installing much necessary equipment into such a small sphere. The model made by editors Herbert Johansen and Herbert Pfister showed the equipment mounted on three mutually perpendicular intersecting disks. Comprising a unit, these disks were place into a hemisphere and locked home by a mating hemisphere. The 25-pound models used standard sub-miniature electronic parts to denote instrumentation able to make five upper-atmospheric studies. A simulated mercury battery was shown as the power source. The model, displayed on a truncated third-stage rocket, was attached to the top of the rocket by an explosive bolt. When we come to the Vanguard satellites, probably the first practical orbiters to be launched, we enter an area necessarily characterized by compromise. Many conflicting requirements must somehow be reconciled. Commander Hoover has indicated some of these. The satellite must be as large as possible, in order that it be easily tracked by optical means—the larger the object, the greater its visibility. On the other hand, weight considerations demand that the satellite be as small as possible. Thus a compromise must be reached in order to build an object light enough to be successfully placed in an orbit, large enough to be useful scientifically, and yet small enough to fit into the nose of the third-stage rocket. Other considerations in designing the satellite develop from the physical stresses it must undergo. The satellite must be strong enough to withstand the loads imposed upon it by each of three stages of rocket firing, and this strength must be gained without excessive weight. It is known that meteoric dust at the altitudes to be traversed by the satellite will cause some deterioration of the vehicle's surface. The rate and extent of the harm are not known, and in fact, one of the objects of the experiments is to learn the density of meteoric dust in space. This dust might score the satellite's surface to an extent that would affect its ability to reflect light, thereby affecting the inside temperature of the satellite and hampering optical tracking. The engineering assumptions that have been made to arrive at design specifications might be changed when the satellite gets beyond the atmosphere and is acted upon by meteoric dust. We cannot know until after the first satellite is fired. Project Vanguard calls for sending six instrumented satellites above the Earth's sensible atmosphere during the IGY. The probability that all six will be successfully launched and installed in their orbits is extremely small. But the chance of getting at least one into its orbit is quite good. Vanguard satellites are hollow spheres, 20 inches in diameter, and each weighing HY2 pounds when fully loaded. It was with great difficulty that Navy researchers were able to make such lightweight scientific vehicles. At first, the designers tried using aluminum for the shell. They built a paper-thin prototype, but they could not get the weight, which includes structure, below six pounds. They tried many other materials, but it was not until they tried magnesium, which is one-third lighter than aluminum, that they could see a solution. In January, 1956, representatives of a Detroit magnesium concern, Brooks & Perkins, Inc., were summoned to the Navy Laboratories in Washington to discuss the company's qualifications for constructing satellite spheres. During these conversations, technicians at the company's plant fashioned a rough prototype. Brooks & Perkins got the contract. They reduced the shell's weight to four pounds. The magnesium skin of the Earth satellite sphere is 0.OS-inches thick and is somewhat thicker at its attachment point to the third-stage fuel chamber. Each half of the sphere is first drawn from a single piece of magnesium alloy. The two halves are then machined and polished to mirror brightness. After the polishing operation, the hemispheres are never again touched by human hands. The shells are handled by the padded fingers of mechanical conveying devices, and are packed more carefully than even highly sensitive instruments. Another of the company's plants gold-plates the shells, inside and out, to provide corrosion protection to the instru-64 ments the satellite will be carrying. The thickness of the gold is only 50-millionths of an inch. Four more films are then successively deposited on the gold, the last film being a silicon monoxide layer. This layer is transparent, and is used to insulate the satellite from the Sun's heat as well as to prevent the satellite's temperature from falling too low. Beneath this outer silicon monoxide layer is one of aluminum, which provides the highly reflective surface needed for seeing the satellite. Under the aluminum is another silicon monoxide layer, which is needed to prevent inter-diffusion between the aluminum and a layer of chromium, which lies beneath the silicon monoxide. This chromium layer provides adhesion between the silicon monoxide layer and the gold. Total thickness of all coatings is only about 0.001 inches. With four pounds of the satellite's weight being given to structure, only 17V4 pounds remain for instrumentation and the telemetering system. Still, 17Vi pounds of small electronic components appropriately devised can yield much vital data. While in their orbits, satellites undergo extreme temperature changes, being alternately in full sunlight and in the Earth's shadow. The temperature swings from 400 degrees Fahrenheit to below zero. Since transistors and other miniaturized electronic components are usually designed for a much smaller temperature range, part of the Vanguard program comprised developing rugged electronic components and effective insulating methods. Because the satellite's orbit is expected to be an ellipse with a 200-mile perigee and an 800-mile apogee, the final projectile must be launched in a direction as nearly horizontal as possible. This fact was already emphasized when it was mentioned that a satellite launching error greater than 1.5 degrees would cut the perigee altitude roughly in half, in this case to 100 miles. At this altitude, the satellite would dip into the denser atmosphere, probably never to rise again. In choosing Patrick Air Force Base at Cocoa, Florida, as the launching site, the Navy and Air Force have the advantage of a near-equatorial orbit and projecting the satellite in an eastward direction adds the speed of the rotating Earth to that of the satellite. The orbit of the satellite will make about a 40-degree angle with the equator. "Both technical and functional considerations were involved in the choice," according to Dr. Kaplan, IGY chairman. "Because optical measurements will play an important role in observations of the satellite, intermediate latitudes appeared desirable, because the opportunities to observe the satellite by many nations over 65 its entire course are thereby enhanced. In terms of observational stations, a true equatorial orbit provides simplicity as against a true polar orbit." The near-equatorial orbit of a Vanguard satellite will send it around the Earth in a latitude range about 40 degrees on each side of the equator. While the satellite revolves about the Earth about once every 90 minutes, the Earth rotates beneath. Since the Earth revolves about its axis once every 24 hours, it would have presumably made about one sixteenth of a revolution every time the satellite orbits once. If the orbit of the satellite were circular, then this one-sixteenth-of-a-revolution figure, or 22.5 degrees, would be about right. However, since the orbit is to be elliptical, more than one sixteenth of a revolution will be made by the Earth during one revolution of the satellite. The total displacement of the satellite during succeeding passes across the equator will be about 25 degrees. Thus after one revolution, the satellite will appear about 25 degrees west of its launching point, 50 degrees west on its second passage and so forth. This means that over the course of many revolutions, the orbit of the satellite will shift within a band between 40 degrees north and 40 degrees south of the Earth's equator. The Denver-Philadelphia line lies close to 40 degrees north latitude. For an orbit angling across the equator, the bulge of the Earth introduces a complication. Because it is not round but oblate, the Earth's diameter is 26 miles longer at the equator than at the poles. This excess mass attends a slightly larger gravity pull, which will distort the orbital plane such that it will gradually rotate in space. This factor and that of having an intermediate orbit compound the tracking problem. Two important advantages stem from the proposed satellite's orbit. First, the satellite's instruments will be able to record observations over a broad expanse of the high atmosphere. Such coverage is important in the IGY program, since the primary objective of this co-operative study is to secure data over the Earth and its atmosphere. Second, the excellent band-width coverage will permit the scientists from a large number of countries to make observations and take measurements. Radio observations will extend the range for observing the Vanguard satellites. The system calls for a satellite transmitter whose signals can be picked up for tracking purposes by the IGY participating nations. The nature and design of the radio system, as well as the frequencies, are to be furnished to all nations. The probable maximum range of these signals is expected to be between 1,000 and 3,000 miles in all directions, depending upon the satellite's altitude. Reasonably good position determinations of a satellite's location could probably be 66 obtained when the transmitter is within 800 miles of the receiver. In his book Nineteen Eighty-Four, the English novelist George Orwell sketched a satirical picture of people living in a totalitarian world. Watching the citizens was the government, which knew all and saw all that happened, and was "affectionately" called Big Brother. In the same vein of grisly humor, the engineers working on a proposed reconnaissance satellite have given it the code name Project Big Brother. The companies reported to be working on this satellite are the Radio Corporation of America, the Columbia Broadcasting Company, and Lockheed Aircraft Corporation. According to the syndicated columnists Joseph and Stewart Alsop, this satellite could be of direct military aid. It could fly over Communist bloc countries, take pictures of ground in- 67 stallations, telemeter the facsimiles back to the military in the United States. "The images, it is believed, will be sufficiently clear and detailed to register such major military activity as air base construction or fleet movement. And it will give a sure 'fix' on existing Communist bases, whose location cannot be determined with absolute certainty by present methods." The target date for completion of Big Brother is 1961. The problems that must be solved before this strategic satellite is launched are difficult. They encompass severe technical and diplomatic questions, whose answers must be learned within the next five years. The satellite will be heavy, much heavier than the Vanguard satellite. One hundred pounds would be an optimistic guess. In this weight, besides the structure, will be included the weight of the camera and telescope. The camera will be programed to take pictures only when it is over militarily important terrain. There must be a means of storing the pictures until they are ready to be sent to ground observers. Then, the pictures will be telemetered to Earth. Beyond these requirements is the need for a sure source of relatively large power. A solar battery, which derives its energy from the Sun and in turn feeds a storage battery, might suffice. Nuclear energy could be used, but can we quickly build an atomic power plant weighing less than 50 pounds, which is probably the upper limit for this component? Next we ask about the orbit. If we use a polar orbit, which is the best one since we shall be able to get a complete traverse of the Earth's area, we shall not be able to take advantage of the Earth's rotation as the Vanguard satellite will be doing. This factor bears directly on the power of the rockets that must be used—more powerful ones for nonequatorial orbits. Finally, we ask the diplomats' question. Will the launching of Big Brother also launch President Eisenhower's "open sky" policy? Or will it create an international rift? Of more immediate importance to us are the scientific data that our small basketball satellites will be sending to Earth. These data will be used throughout our technology to ease and add more years to our lives. For these benefits, we must learn much. Before we learn, we must devise the instruments. 6. Telegram from Outer Space Hopefully, man shoves his tiny ball of gadgets into space. Crudely it samples the crisscrossing energies, some of which come to it from infinity. The data are sent down to Earth, where scientists begin sorting and interpreting the information. 68 With this beginning, from this microcosm set in the cosmic vastness, a new theory of the universe and of creation may begin to evolve. Our first venture into space began in June, 1946, when the first V-2 that was instrumented for upper-air research rose 67 miles into the sky. It was launched by the Naval Research Laboratory, which, on the basis of its experience, was chosen for instrumenting the satellite for Project Vanguard. The background that NRL had for this responsibility is quite impressive. Starting with the inception of its upper-atmospheric research program in early 1946, the scope and intensity of NRL's work increased to a point where now the laboratory has two branches, Rocket Sonde and Rocket Development, actively engaged in high-altitude projects research. In addition, the Optics Division conducts a full research program of its own on solar radiation and the upper atmosphere. These and other divisions collaborate freely in providing the instrumentation and services required for the continued success of the program. Approximately 60 scientists are involved in different phases of NRL's work—about 40 physicists, and 20 others including electronic scientists, electrical engineers, radio engineers, electronic engineers, and mathematicians. On January 16, 1947, a meeting of about 50 representatives of more than a dozen interested agencies was convened at NRL to discuss a continuing V-2 program and to devise a means for co-ordinating the work. This group organized itself into the V-2 Upper Atmosphere Rocket Research Panel. Membership was restricted to persons actually working on the program. Since the initial formation of the panel, the Aerobee and Viking rockets have become available, and in March, 1948, the scientific group became known as the Upper Atmosphere Rocket Research Panel. After six years, the V-2 phase of the program ended for a very practical reason. There were no more flyable V-2s left. The V-2 had not been designed to be stored, but to be used as a weapon within a few days after it had been assembled. That it could be stored for years and still be usable is a tribute to the Germans' technical abilities. It has been estimated that during their research activities, the V-2s carried more than 20 tons of instruments to altitudes ranging from 50 to 100 miles. Because of the original design concept, the V-2 was far from an ideal upper-air research vehicle. When instruments replaced the V-2's warhead, the center of gravity of the missile moved aft and its stability was destroyed. To bring the center of gravity forward, lead ballast had to be put into the nose, thereby taking up valuable instrument volume. When the Navy saw that the V-2 stockpile was almost exhausted, they initiated the design of a new rocket—the Viking. 69 The Martin Company of Baltimore was called in to help develop the vehicle. This was to be the first practical rocket specifically designed to probe the upper atmosphere. Much valuable data were taken during the Viking tests. Knowledge was gained about the electron density in the ionosphere. Solar radiations were investigated away from the blinds of the lower atmosphere. Cosmic rays left their traces on specially treated film. Pressures and densities were measured up to 80 miles' altitude. Despite the success of the Viking project, a twig had been fashioned to do the work of a crowbar. Since at the higher altitudes the obstacle-free molecular path is of the order of magnitude of the Viking's length, the rocket was enshrouded in its own exhaust. The instruments were constantly being asphyxiated by the vehicle's gases, which escaped from the thrust chamber and from other unpressurized chambers into the rarefied atmosphere, and they came from seething battery fluids and from unconsumed propellants. Above 90 miles, the temperature, pressure, and density data taken by the Viking are meaningless. The Aerobee project, sponsored by the Navy Bureau of Ordnance and the Office of Naval Research, and directed by the Applied Physics Laboratory of The Johns Hopkins University, called for an inexpensive rocket, ten of which would equal the cost of one Viking. The Aerobee was devised to carry 150 pounds to about 70 miles. The design philosophy stated that if only one investigation were carried out on each flight, then ten investigations could be run for the cost of one Viking launching. All efforts could be concentrated on the study at hand. With different instruments being installed to measure and check the same physical phenomenon, no conflicting interests would jam the data-taking. Propulsion is carried out in two stages, first by a solid-propellant booster rocket that falls away when spent, and then by a liquid-propellant sustaining rocket motor that is spent at about 18 miles' altitude. The rocket motor burns a mixture of red-fuming nitric acid and an alcohol solution. Since 1948, NRL has directed 20 firings, and conducted 31 upper-air experiments, which include five cosmic-radiation, 14 solar radiation, three pressure, three temperature, four composition, one ionosphere, and one photographic. There are drawbacks to the Aerobee. It is a low-altitude probe. It is fin-stabilized, which means that wind and ballistic calculations must be made and must be optimum to assure successful launching. In addition, the required minimum pay load of 120 pounds prevents a weight-for-altitude trade. During 1953 and 1954 the small Deacon rocket was joined with the giant Skyhook plastic balloon to produce the Rockoon. 70 The Deacon rocket has a severely limited pay load of 50 pounds. Yet with fair accuracy, physicists have been able to devise experiments giving data on upper-atmospheric pressure, temperature, density, and solar radiations. Since Rockoons are cheap—only $2,000 each—and can be launched from nearly any accessible location, 120 of them are scheduled for use during the IGY. The drawbacks of the Aerobee led to the development of the Aerobee-Hi. Sponsored by the Air Force and the Navy, and designed by Aerojet-General Corporation, this vehicle could be the last rocket sounding device before a satellite is launched. The Aerobee-Hi ascended to 180 miles with a pay load of 150 pounds. To lessen the amount of gas escaping from its interior, the vehicle is completely pressure-sealed. Since the Aerobee-Hi is equipped with nose and body parachutes, there is the possibility that the same vehicle can be used for several flights. This arrangement means that compact recording equipment is able to replace the more bulky and weight-consuming telemetering equipment. The handling and launching of the Aerobee-Hi is much simpler than that of the original Aerobee, which in turn is vastly simpler than the techniques needed for the Viking. Forty-five Aerobee-Hi's are scheduled to be used for the Upper Atmospheric Research Program of the IGY. Despite the success of our upper-atmospheric research programs, as long as we have to depend solely on rocket vehicles for our data we shall have to be satisfied with astigmatic glimpses of the higher altitudes. For mere minutes of data-taking if we are successful, technicians must put in months and years of work. The information we get from the experiments is to a large extent haphazard, depending as it does on good weather for launching, and is often gravely hampered by the mechanics of flight. To move our present concept of the upper atmosphere toward reality, our Pogo-stick research is being replaced by a semipermanent laboratory in the sky. Any artificial satellite circumnavigating the Earth can give us vital physical data. However, even with a thousand satellites flying, there still would not be enough for their students. Nearly every scientist has a proposed study for a satellite, which investigation is held to be the most important. Perhaps the most difficult problems to solve will be diplomatic ones working out which studies are to be made first. If a country which is unwilling to share its satellite data is able to install an orbiting vehicle, then, before we establish our own vehicles, we shall have to accept passive data—data derived purely by observing the satellite. Information gained this way would be by no means trivial. The satellite loses speed and altitude when it enters the Earth's atmosphere, and know- 71 ing just how much would help us fill the gaps in our table of upper-atmospheric densities. Perhaps the upper atmosphere is not a region of steadily decreasing densities but rather is one composed of peaks and valleys. If the satellite should behave erratically then this "peak-valley" theory would have backing. Dr. Newell writes that if the satellite's orbit can be accurately determined, then the satellite can be used as the Moon is used for geodetic measurements. Observations made of the artificial moon at different spots on the Earth, either simultaneously or at precisely related times, can be used to determine the distance on the ground between the observing sites. Also, by measuring the effect of the Earth's oblateness on a satellite moving in an orbit inclined to the equator, it should be possible to determine the actual amount of bulging at the equator. It may be that the nonuniformity in the distribution of mass in the Earth's crust will also cause an observable perturbation in the satellite's orbit; in this event, the effect, which will be much smaller than that caused by the Earth's oblateness, will be analyzed. When we launch our own satellites, we can count on their active participation in a program contributing essential data to every field of science. We would get the data through the telemetering equipment on board, which would read the instruments for us and relay the information by radio to receivers on Earth. When larger satellites are built, we shall load some of them with cameras and film packets to obtain data difficult or impossible to telemeter. Before it became interred during the last minutes of the satellite, the exposed film would have to be rescued. One method would be that used in the V-2 and Aerobee rocket tests. The exposed film was spooled into a hardened steel container. Although the rocket upon impact with Earth would be found crushed and twisted, the film container would be safely guarding its contents. It has been proposed that just before a satellite enters the Earth's atmosphere, an explosive charge be triggered and released inside the satellite. The film package would then be shot free and parachute slowly to Earth. Appropriate for this procedure is the jingle: "I shot an arrow into the air. It fell to Earth, I know not where." It may be that radar tracking would help keep sight of the container, but with the chances of accurate tracking of so small an object being so slim, it is doubtful that the effort is worth the reward. The more prudent procedure would be to miniaturize further the telemetering equipment in order to send more data per satellite. If photographs taken from the satellite are needed, and it is still not possible to guide the satellite back to Earth, then what may be used is televised transmission of the pictorial data, or facsimile transmission similar to that used for sending news 72 photographs across country. In view of today's technology, facsimile reproduction would probably be used because television transmission demands a satellite power source far greater than we have available. Before we can derive any data from a satellite, we must know where it is, and we must be able to keep constant track of it. Radar and optical trackers appropriately placed beneath the orbit can do this. When the satellite passes out of the line of sight of one tracking system, the next one takes over. This procedure requires close international co-operation, much closer and more rigorously adhered to than most diplomatic alliances. Conventional radar tracking stations can tell us the location of the satellite. These stations will not give us the aspect of the satellite, which knowledge could be quite important if some of the instruments had been designed to face the Sun during predetermined intervals. Neither will these stations be able to determine the satellite's velocity or acceleration. For these data, investigators will use a doppler-radar system. The doppler principle can be described by reference to our perception of sound waves. When a sound source approaches a listener, the wave frequency or pitch appears to increase because the number of waves per second encountered increases. Similarly, as a sound source leaves the listener, its pitch appears to decrease. By measuring the apparent change in the waves' frequency, which is equivalent to measuring the change in pitch, the listener has a measure of how fast the sound source is traveling. In an analogous manner, a doppler-radar transmitter sends a high-frequency wave to the satellite and to a ground-based receiver. The satellite retransmits the wave to the same receiver. By comparing the frequencies of the two waves, engineers at the ground-based receiver can learn the satellite's velocity. From the changes in velocity, the engineers can also derive the satellite's acceleration. Optical tracking is often the most satisfying. By this means, operators can see the satellite, know its aspect, and be assured they are not watching ghosts on a radar screen. An optical instrument that has been used quite frequently for this purpose is the theodolite. One version consists of a 25-power telescope that conveys its horizontal and vertical deflections to a magnetic recorder. A more advanced version of the same instrument, the cine theodolite, photographs the flight of the vehicle. A combination of research stations and of conventional radar, doppler radar, optical and special tracking facilities will be used to establish the orbits of satellites. One combined system proposed to the Air Force is called the "Automatic Tracking Theodolite and Data Analyzing System." First, a radar beam locates and locks itself on a satellite. The theodolite, now know- ing where to look so to speak, tracks the satellite. The tracking data are sent from the radar and the theodolite to a magnetic recorder for a permanent record. The recorder then passes the data on to a computer which turns the raw data into information amenable to analysis. Another method, and one that will be used for determining the positions of Vanguard satellites, is called Minitrack. This system involves a highly sensitive radio, designed and built by NRL. In its orbit around the world, a 12-ounce radio transmitter in the satellite emits a radio signal on a frequency of 108 mc— at the upper end of the standard FM broadcast band—with a power of from 10 to 50 milliwatts. This power is only one ten-thousandth the power consumed by a 100-watt bulb, or one-millionth as strong as the signal of a standard radio broadcasting station of 10 to 50 kilowatts rating. The NRL Minitrack receiver system, along with 11 other similar receivers produced by the Bendix Aviation Corp., is to be strategically placed to tune in on satellite signals. A typical Minitrack radio receiving system occupies six racks, each about the size of a filing cabinet. Each system is housed in an air-conditioned mobile trailer and receives signals picked up from eight antennas, separated by a few feet to 500 feet. By measuring the minute differences in the time required for a satellite's signal (traveling at the speed of light) to reach each of several antennas, observers will be able to pinpoint a satellite's position in space and describe the vehicle's orbit. The satellite's sub-miniature radio transmitter can operate continuously for at least two weeks. Without Minitrack information telling the position and J course of a satellite, observing it in flight would be comparable to trying to track a golf ball dropped from a jet plane flying at the speed of sound at 60,000 feet altitude. Along with the instruments needed to measure the phenomena being studied, and the tracking and power equipment, a satellite must carry a highly compact telemetering unit. Telemetering is the process of transmitting data from a remote source, usually from an inconvenient or highly inaccessible one. Any gauge on an automobile dashboard displays telemetered data—fuel level, for example, can be seen without the driver's ever having to look into the fuel tank. Telemetered information must be accurately transmitted, received and displayed. Any convenient transmission line can be used, and depending on the circumstances, the line may be hydraulic, ^ pneumatic, electrical or electronic. The transmission line for the satellite is electronic (radio). The part it plays in a telemetering system can be illustrated by one method of sending temperature data from a satellite 74 to Earth. It is known that the electrical resistance of a wire varies with the temperature of the wire. Through suitable circuitry, the change in electrical resistance of the wire is related to a change in electrical current. This changing current produces corresponding changes in a radio wave which is sent from the satellite to a receiving station on Earth. Here the signal is recorded, and analyzed, and the temperature in the satellite is learned. This process is the same as that of ordinary radio broadcasting. The microphone changes sound energy into electrical energy. The electrical energy modulates a radio frequency wave which is picked up by home receivers, and is heard as program material. Telemetering systems can be divided into two major types: the time-division system, and the frequency-division system. In the first system, the physical quantities to be measured are done so on a time-sharing basis. In sequence, each quantity is looked at for a short period of time. When all have been seen, the process is repeated. In the frequency-division system of telemetering, a continuing transmission of each physical quantity being measured is made. This method is similar to that of radio broadcasting where each station transmits its individual program on its assigned frequency; the link is radio, and the receiver is the radio set tuned to the station of choice. A source of electrical power is needed for the instrument and telemetering activities on the satellite. To ask today for enough power to operate continuously all the equipment on board would be to ask for a satellite too heavy to launch. Therefore, it has been agreed that only for short intervals during satellites' travels will full power be demanded. In the intervening time, stand-by power will be used. A pretiming device in the satellite could be designed to turn the power on and off at stated intervals. This is a ticklish method; for its correct functioning it requires that we know precisely when a satellite will be in the range of a receiving station. The difficulty is clearer when we realize the problem of even knowing how long the satellite will remain aloft. A second method, and the one which probably will be adopted, involves the satellite's using its stand-by power to store data; then when a receiving station sends an interrogating signal to a satellite, it uses its full power to send these data to Earth. It has been estimated that a maximum power requirement of 50 watts for three minutes, and a stand-by power of one watt per revolution would be sufficient for most satellite experiments. On the basis of present power equipment, engineers are able to incorporate more than 500 watt-hours of energy into a satellite, which would keep its equipment functioning for about eight days 75 If no satellite were expected to live more than a few days, then the power package could be easily furnished by a bank of lightweight batteries already on the market. When a hoped-for life of later satellites is months or even years, then other sources of electrical power must be considered. The nuclear reactor has been proposed as a power source, but even though its shielding could possibly be eliminated for an unmanned satellite, such a reactor with its associated equipment would be far too heavy. From the physicist's point of view, another disadvantage would be the reactor's emission of radiations which would obscure the data being picked up by the instruments. A second scheme proposes taking advantage of the temperature difference between the shaded and unshaded surfaces of a satellite. Then by appropriate electrical circuits the difference could be converted into electrical energy. Because of its inefficiency, this system has not received much backing, though a related idea has—and this hinges on the solar battery. As implied by its name, the battery derives its energy from sunlight, which every 48 hours pours more energy onto the Earth than is contained in all the known supply of the Earth's fossil fuels. The newest solar batteries can develop a potential of one-half volt, and can deliver about 90 watts for every square yard of exposed surface. It is estimated that this is only half the power that an optimum design could deliver. Made of a layer of individual silicon wafers, the solar battery has no moving parts or corrosive chemicals. Even in poor light, it can generate energy but at a lower power. Those that are in use now are at least 15 times more efficient than the best solar energy converters. In Americus, Georgia, a solar-battery installation is powering a rural telephone service. Excess current, not needed for immediate telephone use, is fed into a storage battery, which provides power at night and over periods of bad weather. In contrast to the storage battery, the solar battery has only low power, but it can deliver power for an indefinite length of time. Because a large source of sure power for the lifetime of a satellite is essential, early satellites will be using storage batteries instead of solar batteries. When larger satellites are launched with expected lifetimes measured in months, then a chemical storage battery fed by a solar battery will probably be specified. To conserve battery requirements and therefore battery weight, Vanguard satellites will be using continuous power only for tracking purposes. Upon radio command from a ground station, a satellite will gather its data and simultaneously telemeter the information to the commanding station. The data will be sent through a radio transmitter, which will be turned 76