On Friday evening, 4 October 1957, man's long dream of spaceflight became reality with the launching of Sputnik I. Most Americans were surprised, not only by the feat itself but that the Soviets had done it first.
There was no lack of public forewarning about the coming age of spaceflight, however. In July 1955, the United States had announced its intention to launch satellites as part of the scientific activities of the International Geophysical Year which was to begin in mid-1957, and this was immediately followed by press articles that the Soviets were making similar plans. In the United States, the satellite activity became Project Vanguard, authorized in September 1955.
Vanguard was the culmination of a decade of scientific research of the upper atmosphere using balloons and sounding rockets, of increasing pressure by groups who saw the feasibility of spaceflight and made realistic proposals, and finally, of the interest and backing of the scientific community through the National Academy of Sciences. The last was essential, for many earlier and sound space proposals had been treated with disdain. Some of this attitude may have come from longtime exposure to grand and impractical schemes and science fiction. Even the ideas of such scientists and engineers as Tsiolkovskiy, Goddard, Oberth, and von Braun had failed to arouse much more than transient public interest. The wartime scare caused by the German rockets had long since receded, and by the late 1940s even the the military services were hard pressed to justify space projects-in spite of the obvious advantages of reconnaissance, communications, and meteorological satellites. International interest in cooperating to study the upper atmosphere and space phenomena using high-altitude probes and satellites became a major driving force, but it evolved so gradually during the early 1950s that the public scarcely took notice. After the 1955 announcement, Project Vanguard proceeded slowly and with little publicity.
Parallel with scientific interest in space was military interest. During the heyday of ballistic missile development during the 1950s, effort was concentrated on long-range missile capability, but engineers were well aware that the same missiles, more powerful than Vanguard, could be modified to provide the additional velocity needed to launch satellites.
The Soviet Sputnik I provided the spur for action in this country. The news media reflected astonishment, dismay, and fear. American pride was hurt, competitive spirit  aroused, and a determination to "catch up" with and exceed the Russians became evident.
In previous parts, we have examined the growth of liquid hydrogen technology and its potential application for rockets and aircraft. In this final part, we will examine the events leading to the decision to use liquid hydrogen in two launch vehicles for the great space accomplishments of the 1960s and 1970s. To do so, we need to understand something of the antecedents of these vehicles-the ballistic missiles of the 1950s. Also pertinent is the competition among several government organizations for a role in space and the formation of the National Aeronautics and Space Administration. Throughout this discussion, emphasis will be on launch vehicles and the considerations that led to the use of liquid hydrogen.