Part II : 1950 -1957
Second Attempt to Use Liquid Hydrogen
 In December 1955, the Lewis rocket team resumed experiments with liquid hydrogen but with slight success. Seven runs were made on the 8th and 10th of December; two engines burned out. A successful run was made on 16 February 1956, followed by three more two weeks later. Preparations were then made to operate with liquid hydrogen-fluorine. On 9 March, the first attempt was made, but the engine burned out in four seconds. This was long enough, however, to measure performance: thrust and pressure were near design values and exhaust velocity was 3510 meters per second, or 93 percent of theoretical.26 This was the highest rocket performance value obtained at the Lewis laboratory up to that time. Cooling, however, remained an obvious problem, and emphasis was placed on it.