In the conception of the United States Air Force, "space" is part of an operationally indivisible medium called "aerospace," a continuum from the surface of the earth through the atmosphere to the limits of the solar system- - or the universe. In the years preceding that October 1957 day when the first Sputnik radioed from orbit, and in the furor following that day, a great many specialized definitions of "space" were foisted on a confused public. Such terms as cis-lunar space, trans-lunar space, interplanetary space, near space, deep space, and cosmic space were employed loosely, each defined by its employer. Subsequently there emerged a better understanding of such terminology, and "space" came to mean that near-airless regime above which vehicles could not maneuver by aerodynamic processes. As time passed, that altitude was informally defined as 25 to 50 miles above the earth. A different working formula derived from experience with early satellites, and in that context "space" came to mean the height above which it was possible for an object to remain in orbit for significant periods without catastrophic degradation of performance because of aerodynamic drag. The minimum height for such performance was informally defined as being about 100 miles above the earth's surface. Between, in the altitudes from 50 miles to 100 miles above the surface, there existed insufficient atmosphere to support aerodynamic flight and too much to permit orbital flight.

None of these considerations was of any moment when the first technical discussions of space flight began to appear at the start of the twentieth century. Such discussions preceded by many years the first consideration of rockets as long-range bombardment devices.

The earliest serious proposal for a space ship emerged from the mind of Hermann Ganswindt, a German dabbler in science and invention, who in 1890 contributed the notion of a reaction-powered vehicle based on reasonably sound theory but impossibly impractical engineering details. Ganswindt apparently preferred to argue the theory rather than improve the details, and apart from stimulating some heated but skeptical discussion in minor technical journals had no lasting influence.

Konstantin Tsiolkovski (also Ziolkovsky) was a Russian, a teacher largely self-educated in physics and mathematics, who first mentioned the possibility of space flight in an 1895 article which, somewhat to his surprise, was accepted and published. By 1898 he had carefully refined his ideas on the subject--which had fascinated him for perhaps 20 years- -and had arrived at a workable rocket theory involving liquid fuels based on kerosene, the only then-apparent means of producing the exhaust velocities he knew to be essential. He devoted another 25 years to further studies, with little or no experimentation, before receiving any general recognition. Even then, that recognition came because the Soviet state was interested in demonstrating that a native Russian had been the first to propound mathematical formulae for rocketry.

Tsiolkovski knew nothing of Ganswindt, and neither of the two pioneers who followed Tsiolkovski heard of him before their own work became rather well advanced. The creation of useful interest in rocketry- -and in space flight- - was the achievement of a German- - Hermann Oberth- - and an American- - Robert H. Goddard- -whose work was for practical purposes entirely independent of outside influences. Oberth was a theoretician, and Goddard, an experimenter. Oberth had space flight in mind from the start; Goddard was interested in rocketry almost as an end in itself. Oberth never succeeded in transforming his entirely sound concepts into a functioning rocket engine; Goddard did virtually no public theorizing until he had proven the validity of his concepts by demonstration. Goddard was a proponent and practitioner of pure research; with Oberth, the object of space flight far overbore considerations of science in the abstract. Goddard published only two significant items, and one of these was a 1919 paper which evoked enough public ridicule (because it gently suggested the theoretical feasibility of hitting the moon with a payload of flash powder) to cause its author deliberately to seek obscurity for 16 years. Oberth was more interested in obtaining support for his ideas than in proving or trying them, and he was entirely willing to employ such unprofessional media as pseudo-science motion pictures in the process. Goddard was the first man to build and successfully test a liquid-fuel rocket (November 1923), and by May 1935 had succeeded in sending a gyroscope-stabilized rocket to an altitude of 7,000 feet. (The best of the pre-Peenemunde rockets created by the German research group that eventually developed the V-2 was much heavier but attained an altitude of only 6,500 feet in about the same time period.) Oberth's efforts resulted in the formation, in July 1927, of a German Society for Space Flight which promptly set about recruiting enthusiasts, seeking publicity, and collecting funds to support experimental work. Goddard carried his objections to publicity so far as to refuse to answer letters from such groups. In 1929 Oberth reworked his 1923 book, which had started the enthusiasm in Germany, and produced as a result the most authoritative of the early treatises on experimental rocketry. Goddard made no effort to circulate the results of his work until 1936, when it was largely complete (at least he carried it little further).

Indirectly, Goddard's work led to the formation of the Aerojet Engineering Company through the Guggenheim Foundation (Jet Propulsion Laboratory of the Guggenheim Aeronautical Laboratory at California Institute of Technology), the interest of Dr. Theodore von Karman, and Army Ordnance Department desires to use high altitude rockets to prove-out missile designs. Very much the same thing came from Oberth's efforts, which led with similar indirection to German Army sponsorship of the experimental work being conducted by the "Society for Space Flight." The Wehrmacht, of course, was not interested in space flight but was very much interested in long range artillery that did not come under the ban of the Treaty of Versailles. As it happened, that treaty became inconsequential shortly after the German Society for Space Flight did the same; Hitler's seizure of power in January 1933 coincided with the start of Army-funded rocket research, and the indifferently concealed rearmament of Germany thereafter obviated the need for any particular disguise. By that time, however, the well financed experiments had been transferred to Peenemunde, on the Baltic coast, and had produced results which encouraged the Wehrmacht to continue research toward the objective of a long range bombardment rocket. Wernher von Braun, a boyish latecomer to the Society for Space Flight, became the principal civilian manager of the Peenemunde work and converted to his way of thinking--that missiles were a step toward space flight, not an end in themselves--the unlikely figure of the military chief, Captain (later Lieutenant General) Walter Dornberger. With resources that at one time accounted for at least one third of Germany's entire aerodynamic and technological research establishment, they moved with relative rapidity from the primitive rockets of 1933 to the operationally ready V-2 bombardment missiles of 1943. Development of the V-2, or properly the A-4, began during the winter of 1938-1939 as the climax of five years of applied research. The first successful operational prototype, and the third test vehicle in the series, completed a field trial on 2 October 1942; more than 100 production versions were tested in Poland in the early months of 1943. The first combat firing at London came on 8 September 1944, and by March of the following year more than 1,300 V-2's had followed the first to England.

Unfortunately, from the standpoint of the scientist and the space flight enthusiast, concentration of attention on bombardment missiles neatly eliminated serious work on space research. At least four people (Tsiolkovski, Oberth, Goddard, and Dr. Walter Hohmann of Hamburg) had worked out perfectly valid data on exhaust velocities, mass ratios, and trajectories before 1930. The decade of the 30's was spent in carrying rocket technology to the point of practical application, and during the first half of the 40's, rocket technology was applied to the art of war. There were some few exceptions, concentrated largely in Germany, where the only propulsion systems with sufficiently high thrust to promise eventual space applications were being perfected. Walter Dornberger recalled several years after the fact that "our aim from the beginning was to reach infinite space, and for this we needed speeds hitherto undreamed of. Range and velocity were the great landmarks that guided our thoughts and actions." In another context he remarked, "With our big rocket motors and step rockets we could build space ships which would circle the earth like moons. Space stations . . . could be put into orbit around the earth. An expedition to the moon was a popular topic too." He also conceded, however, that most German scientists were not interested in anything beyond the atmosphere.

In point of fact, Oberth was the first practicing scientist to have a clear concept of a useful artificial satellite, although his theorizing, carried to the point of detailed formulae, was concentrated about the notion of man-carrying satellites, and space ships. Lacking any appreciation for the probable growth of guidance and control technology to match what he anticipated for rocketry, Oberth largely ignored the possibility of robot vehicles. He saw specific applications in observation, mapping, and communications-- among other fields. Interestingly enough, he clearly foresaw, in 1924, the probable need for rendezvous satellite stations to carry additional fuel for true extra-terrestrial expeditions.

In the immediate postwar years, only two serious mentions of satellite programs received much public notice. Defense Secretary James V. Forrestal's brief mention of the possibility of military satellite applications in his 1948 report on the state of the National Military Establishment drew slight- -and sometimes condescending- - attention. The publication of a short article (later called the Grimminger Report) in the October 1948 issue of the Journal of Applied Physics drew notice to the concept of a scientific satellite, but, except among devotees of space flight, it had little lasting influence. Popularization of the space flight thesis had its start in the early 1950's, with Wernher von Braun' s impassioned advocacy of the need for manned space stations for military purposes--an obvious outgrowth of the Oberth thesis- - and with a gradual growth of interest in instrumented satellites - -an evolution of the Goddard theme- - among physical scientists in general. A slim 1951 volume entitled The Artificial Satellite constituted the first public circulation of an entire book devoted to discussion of the subject. Its emphasis was on a "minimum space vehicle," a favorite 1953-l955 project of several prominent British and American scientists. At that point, the "open" aspects of satellite work began to merge again with the military aspects. The "minimum" satellite became the core of a classified Army-Navy project, Project Orbiter, and the whole blended imperceptibly with International Geophysical Year proposals then gaining adherents. Almost inevitably, the feasibility of experimentation with satellites and space vehicles became associated with the only available launch vehicles: the military rockets then under development. Private enterprise had neither the means nor the motivation to support multi-million dollar space research.