On Sun, 26 Jan 2003 16:56:38 -0800, Sean Lynch <[EMAIL PROTECTED]> wrote:
>What I found was that it would be good for a monopropellant, but you'd >still need an oxidizer to compare to hydrogen+oxygen. I guess this is >what people were saying? I don't see why this would be so. Isp is Isp. Compare those, right? >The heat of formation of liquid H2 (it only gets worse as you get warmer) >is -8123 J/mol. Presumably your exhaust then would have around 8123 >joules per mole, or 4061500 joules per kilogram. A mole of H2 is 2 grams? Chem 101 is a distant memory, but that doesn't ring true. Let's see... Wow. H2 is so light that a mole of GH2 weighs 1.9 grams at STP. OK. Far out. >Since E = (1/2)mv^2, >v = sqrt(2E/m), so you get an exhaust velocity of 2015.3164 m/s, or >around 291 seconds. Here, you lost me. Isp measured in seconds is simply v/g, so 2015 m/sec would be 205.4 seconds. >I'm guessing if you added oxygen to the mix you >could add the specific impulse from LOX/LH2 to and get something >in the range of 740 seconds. Not bad. I don't think you can add the Isp numbers directly. Don't you have to add the numerators, add the denominators, and then divide again? I'm also a little fishy about getting all the benefit of LOX/LH2 by adding LOX to a monatomic hydrogen engine. IIRC, LOX/LH2 is run fuel rich to exhaust a lot of atomic hydrogen and drive the molecular weight through the floor, since exhaust velocity wants to go up as the inverse square root of the molecular weight. >Either frozen equilibrium problems are really easy to do when you've >only got one exhaust product, or I did it wrong :) Frozen equilibrium assumes the reaction rates outside the chamber are zero. With a single exhaust product, it should be fairly easy. :-) This all begs the question of how you keep it monatomic, of course... -R -- "We've all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare. Now, thanks to the Internet, we know this is not true." -- Robert Wilensky, UC Berkeley _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
