Origins of Navy Interest in Satellites and Hydrogen
 Considering the Navy's involvement in solid rocket research and development during the war, the rising interest in jet propulsion as German developments became known, the Navy's sponsorship of OSRD's Jet Propelled Missiles Panel, and the Lemmon report on jet propulsion fuels (p.4), the interest in hydrogen would appear to be an evolutionary step. In fact, these prior events had little influence. The proposal to use liquid hydrogen to place a satellite into orbit with a single-stage-to-orbit rocket came from Comdr. Harvey Hall, a Navy physicist who had educated himself quickly in jet propulsion, had not heard of the Wright Field contract with Ohio State University on liquid hydrogen (p.18), and had not read the Lemmon report. Neither was he acquainted with the proposals of Tsiolkovskiy, Goddard, or Oberth to use hydrogen in rockets (appendix A-2); but like Tsiolkovskiy, he had gone to chemistry textbooks in search of the most energetic fuel. Not surprisingly, Hall found and selected liquid hydrogen, and in his quest for more information on its use in rockets, he met Robert Gordon of the Aerojet Engineering Corporation, who also had gone to his textbooks and was thinking about hydrogen at about the same time.1
The train of events that led to the Navy's interest in satellites and the use of liquid hydrogen as a fuel in the booster rocket was triggered by information brought to the Bureau of Aeronautics in July 1945 by a young Marine officer, Lt. Abraham Hyatt. The Bureau of Aeronautics was aware of German developments in jet propulsion and rockets from intelligence reports during the war. Hyatt had been part of a technical intelligence team in Europe following closely in the wake of the advancing armies early  in 1945 to interrogate German scientists and technicians and gather documents. Among the Germans interrogated in May 1945 were Wernher von Braun and his associates who had developed the V-2 at Peenemunde. Among the documents Hyatt brought to the Bureau of Aeronautics in July 1945 was a summary by von Braun of liquid propellant rocket developments in Germany and his view of future prospects. Von Braun listed five future possibilities: (1) rocket-propelled transports for intercontinental travel; (2) multi-stage, piloted rockets orbiting the earth; (3) a large space station orbiting the earth; (4) a large orbiting mirror to concentrate solar energy and beam it to the earth for various purposes, including weather control;* (5) travel to other planets but "first of all to the moon," possibly by harnessing atomic energy. Von Braun saw the rocket as having the same impact on future scientific and military activities as the airplane.2
Among those in the Bureau of Aeronautics who were most excited over the potential of satellites were Lt. Robert Haviland and Comdr. Harvey Hall. By the first part of August, Haviland had written an internal memorandum proposing that the Navy initiate a program leading to a manned space station. He developed the Tsiolkovskiy equation** relating vehicle velocity to exhaust gas velocity and mass ratio, but referred only to available fuels, with no mention of hydrogen. A British report of March 1945 on the mass of various components of the V-2 was used by Haviland to calculate the terminal velocity of a two-stage rocket based on these masses. The result was disappointing; the second stage velocity was too low to achieve orbit. To get out of this dilemma, Haviland drew on a 1934 publication of E. Sanger to assume that an exhaust gas velocity of 3500 meters per second was achievable with gasoline and oxygen.*** This is highly optimistic even at altitude: the V-2 exhaust gas velocity, using alcohol-oxygen, was only about 2/3 that value. However, his conservative mass and optimistic rocket performance assumptions led him to the correct conclusion that a satellite could be launched with a two-stage rocket booster using gasoline-oxygen. He wisely included a recommendation that more research be undertaken to secure a high-energy fuel. As a further assurance of success, he suggested that the launch be made from a mountaintop, to gain altitude, and in the direction of the rotation of the earth, to gain rotational velocity.3
In spite of his excitement over satellites, Hall took a slower and more deliberate course than Haviland. For one thing, he was not well acquainted with jet propulsion, but having a doctorate in physics, he went to basic concepts to work out the flight and energy relationships for himself. In the process, he also obtained the Tsiolkovskiy  equation. He then began to explore the extremes of its two variables-exhaust gas velocity, determined by the energy of the reactants and expansion through the nozzle; and mass ratio, determined by the structure. He could have obtained excellent data on exhaust gas velocities of various propellants from the Lemmon report which had been issued in May, but it had not come to his attention. Instead, he simply went to his chemistry textbooks in search of the most energetic fuel he could find to use as a yardstick in comparing the performance of various fuels. There he found the hydrogen-oxygen combination, whose heat of combustion had been measured numerous times since Lavoisier and Laplace first measured it in 1783. Hall was totally unaware that he was repeating the same steps Tsiolkovskiy had taken almost a half century earlier (appendix A-2).
In considering the ratio of initial to final mass, Hall thought of very light structures, somewhat analogous to Oberth's, and his structural design was as optimistic as Haviland's was conservative. Hall's calculations led him to believe that, using liquid hydrogen and oxygen and very light structures, he could put a payload in orbit with a single-stage vehicle, eliminating the complications of multiple staging. Hall wanted to discuss his calculations with rocket experts, so he visited the Jet Propulsion Laboratory (JPL) of the California Institute of Technology where he met with Martin Summerfield, Frank Malina, and Homer Joe Stewart.**** Encouraged by his visit, Hall went on to the Aerojet Engineering Corporation to talk about rocket propellant experiments.