Part II : 1950-1957

6. NACA Research on Hydrogen for High-Altitude Aircraft



Flight Propulsion Conference


[107] The Bee project of flying an airplane fueled with hydrogen was part of a broader investigation of advanced engines for airplanes and missiles at the NACA Lewis laboratory. The broader vein was presented at a second research conference held on 21-22 November 1957, with 300 attendees. Hydrogen was the chief fuel discussed. The papers were presented by a series of eight panels, five of which were on air-breathing engines. The other three were on rockets (p.91). Edgar M. Cortright, J. Howard Childs, DeMarquis D. Wyatt, and David S. Gabriel led, describing the air-breathing engine concepts. They pictured military planning as being at a critical stage. The choice of deterrent weapons included the manned bomber, unmanned missile, glide bomber utilizing aerodynamic lift, intercontinental ballistic missile, and satellite bomber for flight beyond the atmosphere. Development of each was expensive and time consuming; the purpose of the first five panels of the conference was to present "an appraisal of the ultimate performance capabilities of aircraft and missiles powered by air-breathing engines" -range, speed, weight, and payload were used as criteria of merit. Flight at very high speed heats aircraft surfaces and requires cooling for sustained flights. Cortright's panel found that only liquefied methane and hydrogen had significant cooling capacity at flight speeds above Mach 5. Hydrogen was the best [108] fuel for cooling, primarily because it was thermally stable and useful up to the maximum allowable temperatures of the vehicle surfaces.31


Fuel heating value was also examined and not surprisingly, the panel singled out the superiority of hydrogen, noting that it was 70 percent better than diborane. Hydrogen's high heating value, combined with its greatly superior cooling capacity, made it extremely interesting as a fuel for long-range hypersonic flight.


The first panel noted the disadvantages of hydrogen's low density-a problem considered by a later panel. Also noted was possible dissociation loss that might limit the realization of full heating value of the fuels considered. These and other considerations provided the basis for detailed discussions of two applications: a manned bomber flying at a speed of Mach 4, to be powered by a new engine; and an unmanned ramjet missile-with all surfaces glowing red hot from air friction at its flight speed of Mach 7-cooled and fueled by hydrogen.