Ignition!: An Informal History of Liquid Rocket Propellants by John D. Clark

Author:John D. Clark
Language: eng
Format: epub
Tags: Aeronautics & Astronautics, Liquid Propellants, Technology & Engineering
Publisher: Rutgers University Press
Published: 1972-06-15T03:00:00+00:00

2. The classification of hydrogen, as a fair contributor of energy even though it, naturally, has a zero heat of formation, is explained by the fact that the molecule is so light. At 25° it has a sensible heat, or heat content of 2.024 kilocalories per mole above absolute zero, and since the molecular weight is only 2.016, its H/M, even at room temperature, is 1.0 Kcal/gm.

8

Lox and Flox and Cryogenics in General

While all this was going on, liquid oxygen was still very much in the picture. The sounding rocket Viking burned it with ethyl alcohol, as had the A-4, and so did several experimental vehicles of the early 50’s, as well as the Redstone missile. Most of these, too, used the auxiliary power source of the A-4, hydrogen peroxide, to drive the feed pumps, and so on. The X-1, the first supersonic plane, was driven by an RMI Lox-alcohol rocket motor.

Other alcohols were tried as fuels to be used with oxygen—methanol by JPL as early as 1946, and isopropanol by North American early in 1951—but they weren’t any particular improvement over ethanol. Neither was methylal, CH3OCH2OCH3, which Winternitz, at RMI, was pressured into trying, much against his will (he knew it was a lot of foolishness) early in 1951. It seems that his boss had a friend who had a lot of methylal on hand, and if only some use for it could be found—? And at NARTS we did some studies for Princeton, using LOX and pure USP type drinking alcohol—not the denatured stuff. The only difference we could find was that it evaporated a lot faster than denatured alcohol when a sailor opened a drum to take a density reading. We had some very happy sailors while that program was going on.

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.

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