Part II : 1950-1957
Mach 4 Configurations and Missions
 Another panel at the NACA 1957 conference on propulsion, headed by Roger W. Luidens, bridged the papers on propulsion with an analysis of the range capabilities of airplanes using the advanced propulsion concepts; it was followed by another panel led by S. C. Himmel that tied all the previous discussions of air-breathing engines, airplanes, and missiles together.* One mission selected for discussion was a speed of Mach 4, altitude of 30500 meters, a payload of 4500 kilograms, with airplanes using turbojet engines. When designed for hydrogen, the airplane was 91 meters long and had a gross mass of 136000 kilograms of which about 1/3 was hydrogen. The airplane using JP-4 fuel was half as long, but had a mass 40 percent greater than the hydrogen configuration, with the JP-4 making up 60 percent of the mass. The hydrogen-fueled airplane had a range of just over 5000 kilometers compared to 3050 for the JP-4 airplane (fig. 24). While the hydrogen airplane had the greater range, it was short of the goal of 10 200 kilometers. Use of an air-turborocket increased the range 13 percent, but this was not enough to warrant the cost and time of development. Even with additional engine improvements and by using advanced airframe design, the range of the hydrogen-fueled airplane could be increased to only 7600 kilometers, still short of the goal.
The airplane designs using turbojets were outclassed by a hydrogen-fueled ramjet missile. With a mass of 17400 kilograms and boosted to its cruising speed, it carried the same payload (4500 kg) at Mach 7 for a distance of 16700 kilometers. Liquid methane and diborane were both inferior to liquid hydrogen.
The November 1957 propulsion conference at NACA-Lewis proved to be the climax of efforts to promote air-breathing hydrogen-fueled engines as competitors to rocket-powered intercontinental ballistic missiles. Strangely enough, the rich amount of experimental data on hydrogen from Lewis ground and flight experiments was not apparent to members of the audience. What came across strongly from the papers were concepts and trends of what the future could be like with hydrogen in advanced turbojet and ramjet engines. These potentials, however, came too late to catch up with...
...ballistic missile development. As a final clincher, Sputnik had ushered in the ballistic Missile development. As a final clincher, Sputnik had ushered in the space age seven weeks earlier and turned attention to space, where the rocket was the undisputed propulsion system.
The many research scientists at the Lewis laboratory who worked on hydrogen as a fuel for high-flying aircraft were completely unaware that a huge and highly secret effort on hydrogen for high-altitude flight had been started in the Air Force the previous year. That work was managed by Col. Norman C. Appold, who attended the NACA conference. The Air Force project will be described in a later chapter.
* With Luidens were J.H. Disher, Murray Dryer, and T.W. Reynolds; with Himmel were E.W. Conrad, R. J. Weber, R.R. Ziemer, and W.E. Scull.