Re: Methane and other winds (was Re: alternatives to big oil andifthey can ...

From: Doug Jones (
Date: Sat Feb 05 2000 - 13:13:24 MST

Spike Jones wrote:
> Ok, I nominate hydrogen and flourine. I havent the energy per reaction,
> but later Ill get off my lazy ass and look it up. {8-] spike
> Stirling Westrup wrote:
> > Okay, I am working on a chemical model for futuristic role-playing purposes.
> > What I am trying to find out (in my naive way) is what is the maximum amount of
> > energy you can get from a chemical reaction. Any reaction. It doesn't matter if

Actually, lithium-fluorine takes the cake with the highest enthalpy release
per unit mass- 23078 J/g, versus 15862 J/g for H2/O2 burning to water and
13665 J/g for HF. Li-F2-H2 was once tested in an experimental engine at
542 s vacuum specific impulse, an all time record far better than the 485
claimed for the most advanced high pressure, high expansion H2/O2 engine.
Interestingly, the hydrogen does not react with significant amounts of the
fluorine- the Li and F2 burn, and the H2 is simply heated by that reaction,
thus the apellation "poor man's NERVA".

The highest energy density for *practical* air-independent propellants is
lithium with sulfur hexafluoride, used in steam engines in torpedoes- the
boiler is a coil of tubing with lithium cast around it, and the SF6 is
throttled to control the heating power. The reaction ignites
spontaneously, so simply opening the SF6 valve starts the boiler, and all
the reaction products are liquids or solids- no exhaust to get rid of. This
delivers only 4384 J/g, but is actually storable under realistic

Doug Jones
Rocket Plumber, XCOR Aerospace

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