Part II : 1950 -1957
 During 1949-1950, changes in international relationships led to accelerated research in weaponry and aeronautics, both of which involved liquid hydrogen technology.
In the early postwar years, the United States was supremely confident of its superiority in atomic weaponry and did little to advance the technology. In September 1949, President Truman announced that Russia had exploded an atomic bomb; with it, went U.S. complacency. Relations between the two countries had been steadily deteriorating. Late in 1948, the Russians announced the withdrawal of occupation forces in Korea north of the 38th parallel and the establishment of a North Korean communist government. The North Koreans soon added to the tension by conducting raids south of the parallel. In June 1950, after massive invasion by North Korea, Truman authorized U.S. armed forces to assist the South Koreans.
Unlike the stagnation in weapons technology, U.S. progress in aeronautics during the postwar years had been significant. Effort concentrated on exploring transonic and supersonic flight regimes. The Air Force's Bell X-1 was flying at supersonic speeds in 1948, and a year later so was the Navy's Douglas D-558-11. Both were part of a military-industry-NACA flight research program which, by 1949, included more than a half dozen advanced experimental aircraft. In NACA's 1949 Annual Report, the chairman, Jerome C. Hunsaker, reported that this program had "given aeronautics perhaps the greatest impetus in its history." The same year, Congress passed the unitary windtunnel bill to coordinate and expand the nation's aerodynamic research.
In this environment of international tensions and greater emphasis on weaponry and aeronautics appeared three different research and development activities that involved liquid hydrogen. Each drew upon the technology developed by Ohio State University, Aerojet Corporation, and the Jet Propulsion Laboratory of the California Institute of Technology during the second half of the 1940s. And in the next seven years each added significant contributions to hydrogen technology. One, beginning in 1950, was the crash effort to develop a thermonuclear weapon, the hydrogen bomb. The second was research on high-energy rocket propellants by the National Advisory Committee for Aeronautics, which began to focus on liquid hydrogen in 1950. The third, started in 1952 or perhaps earlier, was an escalation of interest in high-altitude aircraft by the Air Force, which led to considerations of liquid hydrogen as an aviation fuel by both the Air Force and the NACA. The first and third activities dwarfed the second in terms of  funding and manpower, but all three provided the basis for later development of launch vehicles using liquid hydrogen. The three activities will be described in the five chapters of this part.