Part I : 1945 - 1950

3. Hydrogen-Oxygen for a Navy Satellite



North American Aviation Study


[41] On 26 September 1946, North American Aviation reported the results of its study. The Navy had specified an initial mass of 45 360 kilograms with a 454 kilogram payload. From the GALCIT report series, an initial-to-final mass ratio of 9.09 was assumed (which meant a propellant mass of 40 370 kg and an engine and structural mass of 4536 kg). Aerojet was asked for an estimate of the rocket engine mass and gave a range of 1361 to 2268 kg. North American used the higher number, leaving an equal mass for the structure-comprising the tanks, supporting structure, external vanes, controls, and skin. R. G. Wilson, the principal structural analyst, found that a structure with a mass of 2903 kg-635 over the limit-was the lightest that could be designed for the propellant mass specified. This increased the initial mass of the vehicle (to 45 995 kg), and Wilson concluded that the use of a single-stage rocket to achieve orbit was not possible with the specifications given. This not being what the Navy wanted, Wilson added that if the initial mass was increased to 59 000 kg and rocket burning time to 165 seconds, the vehicle could achieve orbit with a single stage.22


The North American Aviation study reloaded the Navy's guns. A 59 000 kg vehicle could place 454 kg in orbit with a single-stage vehicle, whereas the Air Force with the RAND study needed from 2 to 4 stages and initial masses 11/2 to 2 times greater to place half as much payload in orbit. One reason for the light North American design was pressure-stabilized tanks with a common bulkhead separating the liquid hydrogen and oxygen. Pressure-stabilized tanks are thin-walled vessels without bracing which depend upon internal pressure for rigidity in the same manner as does a balloon. The technique had been proposed by Oberth in 1923 (p.262) and was a controversial design in the 1940s and early 1950s.


Concurrent with the North American study, RAND was proceeding with its second phase of satellite studies scheduled for completion by the end of January 1947. The RAND engineers selected vehicle mass, volume, and complexity as criteria for evaluating a number of propellant combinations. Hydrogen-oxygen was still the best on the basis of initial mass, but considering all three criteria, RAND liked hydrazine-fluorine better. The study was far from complete when the North American Aviation report came out. In the interim, James Lipp of RAND wrote a special report on the advantages of satellites. Using an estimate of $50-150 million to orbit a satellite in the 1950s, Lipp urged a quick start so that the United States could maintain superiority over possible enemies. He recommended that the AAF be given priority for a research program leading to a satellite.23 This recommendation was strengthened a week later when Army Ordnance launched a V-2 from White Sands. The missile reached an altitude of 120 kilometers arid took motion pictures of 100 000 square kilometers of the earth's surface. Lipp's arguments, however, fell on barren ground, for the country was complacent in its atomic bomb superiority-a complacency that was to last until the Russians exploded their bomb in 1949.