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Originally Posted by Wim Libaers
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Originally Posted by LoBlo
Come to think of it though, I do remember hearing that the SR-71 used liquid hydrogen as its fuel source (becuase its combustion properties were desirable at Mach3), but is hampered by its low density, a cubic meter of liquid H2 only holds 70kg of fuel iirc.
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While it woulf be possible to use hydrogen, the SR-71 used JP-7, a high flash point hydrocarbon fuel developed for high temperature use. Also used as coolant and hydraulic fluid.
http://en.wikipedia.org/wiki/JP-7 |
SR-71 did use JP-7 and it had such a high flash point that a lit match could not make it burn. The reason this was used is because the SR-71 leaked fuel when on the ground. It's structure had to be built to expand at Mach 3 due to the heat, so there was no way to avoid this. JP-7 was used simply because it was a bad idea to have a wet leaky airplane that could go up in smoke at a moments notice.
By the way - to keep liquid hydrogen in a liquid state would require cryo temps - so this is not a possible fule source for future engines. Hydrogen stored as a gas on vehicles is also no desired since there is no way to store enough of it to power a car for as along a range as you can get out of a normal gastank - same size gas tank as found in a car of pressurized hydrogen would give you about 150 mile range. I heard however that the designer of the nickel metal hydrad battery has found a way to make hydrogen into a 'solid' state that could be used as a fuel. He calls it (guess this one) solid hydrogen.
-S
PS. the gas form of hydrogen may even be less - like 80 miles.