Part II : 1950 -1957
First Regeneratively-Cooled Hydrogen-Fluorine Rocket
 For many months-since the first run of hydrogen-fluorine in March 1955- Howard Douglass, Harold Price, and Glen Hennings* had worked to design, build, and operate a rocket engine of 22 kilonewtons using liquid hydrogen and liquid fluorine, with the liquid hydrogen serving as a regenerative coolant. Edward Baehr worked with them in designing and fabricating the engine. Two kinds of injectors were designed and fabricated: a showerhead type and an impinging-jet type with two jets of fuel impinging on one of oxidizer (fig. 18). The face of each injector was fuel-cooled.
Hennings was operations chief. A perfectionist ideally suited to cope with the hazards of handling fluorine, he made many equipment changes. Operations with....
....fluorine were scheduled for weekends to minimize possible hazards for laboratory personnel working nearby. In a series of attempted runs, an incredible number of problems arose which Hennings doggedly attacked and solved one by one in his careful, methodical fashion. Time was running out, however, and with the conference only a few days away, Douglass drafted his part of the propellants paper around the cooling aspects of hydrogen-fueled engines and hoped for the best.
An attempted run on the weekend before the conference was aborted and prospects appeared grim. Hennings cleared up several vexing problems, determined to operate the engine as soon as possible. On Wednesday evening, 20 November-the day before the conference began-a run was attempted but again problems halted operations. The crew worked all night to solve the problems and through the day Thursday, aiming for another try Thursday night. Douglass was to speak on Friday. The author, fearing that fatigue could cause a misjudgment and an accident, urged the crew to give up, take a rest, and try another day. They continued, however, and worked all through Thursday evening. Finally, at 5:59 Friday morning, they succeeded with a beautiful run that lasted eight seconds, with no sign of overheating. The exhaust velocity measured was 3400 meters per second, 96 percent of theoretical performance. But these values were not known to the tired crew when Douglass went home for a short rest and freshening before his appearance with the panel at 9:30. Harold Price remained to work up the data as fast as possible and bring it to Douglass at the conference.
When the propellants panel began its discussion, Price had not appeared; he was having trouble with security guards because his name was not on the list of those permitted to attend the classified conference. Finally he managed to convince them, hurried to the projection room, marked a data point on Douglass's slide, hurried  downstairs and up the aisle to the stage where he handed Douglass a note with the data and the engine itself, which had been dismounted to display at the conference. He was in the nick of time, for Douglass was the next to speak. Some in the audience thought the entrance was staged, but it was the real thing and a great moment of triumph for the NACA rocket group.41
Two other panels at the conference also made a persuasive case for high-energy propellants, particularly liquid hydrogen for rockets. The turbopump panel found no great obstacles in developing turbopumps for hydrogen-oxygen or hydrogen-fluorine combinations and estimated that the mass of such a turbopump would be comparable to one for conventional propellants. The panel on performance and missions found that the greater the energy requirements for a mission, the greater the need for highenergy propellants. For the case of a moon landing and return, the difference in initial mass between vehicles using kerosene-oxygen and those using hydrogen-fluorine or hydrogen-oxygen could be a factor as high as 8 to 1. Silverstein and the Lewis rocket group were convinced that liquid hydrogen was an extremely attractive fuel.
* Hennings had been in charge of liquefying hydrogen until a liqud plant in Painesville, Ohio, built by the Air Force, made liquid hydrogen available to the laboratory in quantity.