Part II : 1950-1957

8. Suntan



Lockheed CL-400


[144] The initial contract with Lockheed called for two prototype reconnaissance aircraft, with the first to fly in 18 months. Hard on its heels, also in 1956, Lockheed received a contract for six of the aircraft. The design Lockheed selected was designated CL-400 and was capable of a speed of Mach 2.5 at an altitude of 30 300 meters.11 The CL-400 was described openly for the first time in 1973 by Ben Rich at a symposium on hydrogen-fueled aircraft at the NASA Langley Research Center. Figure 34, taken from his paper, shows the characteristics of the CL-400. It had a fuselage diameter of three meters and a length of 49 meters to accommodate the 9740 kilograms of liquid hydrogen. The retractable ventral (bottom) fin improved directional stability at supersonic speeds.


The engines, designated 304-2, were to be supplied by Pratt & Whitney and will be described later. Each weighed 2850 kilograms, provided 42 kilonewtons at sea-level, and 27 at Mach 2.5 and 29000 meters altitude.


The mission profile is shown by figure 35. The range was 4070 kilometers and could be extended only by a considerable increase in airplane size. Airplane sizes with lengths as long as a football field, as well as other variables, were studied at the Skunk Works. The relatively short radius of 2000 kilometers was later to become a matter of great concern.


front, side and top view drawing of CL-400 with statistical information

[145] Fig. 34. Lockheed CL-400 reconnaissance aircraft using liquid hydrogen as fuel, ca. 1955. Ben R. Rich, "Lockheed CL-400 Liquid Hydrogen-Fueled Mach 2.5 Reconnaissance Vehicle," read at a symposium on hydrogen-fueled aircraft, NASA Langley Research Center, 15-16 May 1973.


illustration of the CL-400's flight plan

Fig. 35. Mission profile for the Lockheed CL-400 using liquid hydrogen as fuel. (Source same as fig. 34.)


Clarence L (Kelly) Johnson

[146] Fig. 36. Clarence L (Kelly) Johnson, aircraft designer and builder extraordinary, father of the U-2 reconnaissance airplane and its first proposed successor in 1950-19S8, the hydrogen-flueled CL-400 (Courtesy of Lockheed Aircraft Corp.)