>But something more potent than alcohol was needed for the X-15 rocket-driven supersonic research plane. Hydrazine was the first choice, but it sometimes exploded when used for regenerative cooling, and in 1949, when the program was conceived, there wasn't enough of it around, anyway. Bob Truax of the Navy, along with Winternitz of Reaction Motors, which was to develop the 50,000 pounds thrust motor, settled on ammonia as a reasonably satisfactory second best. The oxygen-ammonia combination had been fired by JPL, but RMI really worked it out in the early 50's. The great stability of the ammonia molecule made it a tough customer to burn and from the beginning they were plagued with rough running and combustion instability. All sorts of additives to the fuel were tried in the hope of alleviating the condition, among them methylamine and acetylene. Twenty-two percent of the latter gave smooth combustion, but was dangerously unstable, and the mixture wasn't used long. The combustion problems were eventually cured by improving the injector design, but it was a long and noisy process. At night, I could hear the motor being fired, ten miles away over two ranges of hills, and could tell how far the injector design had progressed, just by the way the thing sounded.
>Even when the motor, finally, was running the way it should, and the first of the series was ready to be shipped to the West Coast to be test-flown by Scott Crossfield, everybody had his fingers crossed. Lou Rapp, of RMI, flying across the continent, found himself with a knowledgeable seat mate, obviously in the aerospace business, who asked him his opinion of the motor. Lou blew up, and declared, with gestures, that it was a mechanical monster, an accident looking for a place to happen, and that he, personally, considered that flying with it was merely a somewhat expensive method of suicide. Then, remembering something he turned to his companion and asked. "By the way, I didn't get your name. What is it?"
>The reply was simple. "Oh, I'm Scott Crossfield."