The origins of Air Force interest in liquid hydrogen as a fuel are obscure, but researchers were well aware of hydrogen from general studies and from occasional external suggestions. One of the latter came to Robert V. Kerley on a warm July day in 1942 and, at the time, made no sense to him. As chief of Wright Field's fuels and oil branch, Kerley was the Air Force's leading expert on aviation fuels and its representative on the fuels and lubricants subcommittee of the National Advisory Committee for Aeronautics (NACA). The subcommittee, under the chairmanship of Professor W.G. Whitman of the Massachusetts Institute of Technology, played a key role at the beginning of the war by coordinating aviation fuel needs and stressing the imperative of increased production.*
Kerley's branch at Wright Field had a long tradition of leadership in improving aviation fuels. Although fuels research can be traced to the establishment of the aeronautical engineering laboratory at McCook Field in 1917, the first systematic fuels research program dates from 1928 when studies were started to determine the relationship between fuel composition, engine performance, and knock. As engine designers sought increased power output per unit volume of engine piston displacement, fuels had to be improved to keep pace. During the 1930s, the fuels and oil branch at Wright Field was the recognized leader in promoting research and production of improved aviation fuels. As a result, the United States was the only one of the Allies at the beginning of the war having a significant capacity for producing high-performance aviation fuel.
Kerley was up to his ears in practical problems of increasing aviation fuel production and operating problems in July 1942 when he was requested to comment on a British suggestion forwarded by the NACA. It was a ten-page proposal by F. Simon to use-of all fuels-liquid hydrogen as a means for increasing aircraft range. Kerley knew that hydrogen produced knock; further, hydrogen liquefaction capacity in the United States was on the order of a few hundred liters per day, and those plants were in scientific laboratories. If the exasperated Kerley considered Simon a nut and his suggestion ridiculous, it would be understandable. Although the suggestion was  impractical at the time and indicated Simon's naivete with respect to fuel production and aviation, he was anything but a nut. F. Simon was Franc Eugen Simon (1893-1956), a thermodynamicist and ingenious experimenter with liquid hydrogen at Oxford University. He had earned his doctorate under the famous Nernst and worked in Germany on low-temperature phenomena until 1933 when, disturbed by rising Nazi power, he accepted an invitation from F.A. Lindemann (Lord Cherwell) to come to Oxford. Simon managed to bring a hydrogen liquefier with him and was instrumental in building an outstanding low-temperature laboratory at Clarendon; in August 1940, he was placed in charge of isotope separation research in Britain's nuclear fission effort.1
Kerley immediately recognized the utter impracticability of Simon's suggestion to use liquid hydrogen, but was not so pressed that he could not respond with a bit of humor:
Simon, who had an impish sense of humor and laughed at jokes on himself, would have been delighted with the verses, if not the disposal of his suggestion.
Simon was not alone in considering hydrogen for aviation fuel. Much earlier, P. Meyer had written an article entitled "Is There Any Available Source of Heat Energy Lighter than Gasoline?" which the NACA translated as Technical Note 136 in the early 1920s. Meyer noted that hydrogen had a greater heat content than any other known fuel. Apparently considering it only in gaseous form under pressure, he also noted that the containers had to be strong and heavy, which counterbalanced the energy advantage.
Both Meyer and Simon, therefore, found that hydrogen in any form was an aviation fuel whose time had not come. Interest in hydrogen, however, was not lost entirely and surfaced when war pressures eased in late 1944 and 1945 and the men at Wright Field began to think again about future projects. Opie Chenoweth, chief civilian engineer of the power plant laboratory, suggested that research be sponsored on increasing the energy content of aviation fuels.3 Hydrogen was not a good fuel for piston engines because of the tendency to knock, but what about using it in jet engines? Over at Ohio  State University in nearby Columbus was a professor who had built a cryogenics laboratory during the war and was one of a few experts in liquefying hydrogen and studying its properties. Why not have him study liquid hydrogen for aircraft and rockets? The professor's name was Herrick L. Johnston.
* In July 1940, when President Roosevelt announced a goal of 50000 airplanes, the subcommittee estimated that current production of 100-octane aviation fuel must be increased twelvefold but could not convince the military services, who agreed only to a fourfold increase. By war's end, Allied production of 100-octane aviation fuel was 40 times greater than in 1940. Sam D. Heron, "Development of Aviation Fuels," in Development of Aircraft Engines and Fuels (Elmsford, NY: Maxwell Reprint. 1970), pp. 631-34.