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May 11, 2007
Greener Spaceflight?
When you see a title like this and you have to scratch your head. The space program has never been known for their eye toward green living. Then I read that it's about replacing Hydrogen with Methane. For those of you that don't know, Methane is a green house gas that's 23 times more effective at trapping heat than carbon dioxide. So needless to say I was having trouble buying this argument on the surface. Then I looked at the critical thing you look at when dealing with rocket fuel, energy density. At 286 kJ/mol versus 802 kJ/mol, suddenly you have my attention. Add in the fact that methane is easier to store because it's boiling point is so much higher than hydrogen and this idea doesn't seem so crazy at all. 70.8 kg/m³ versus 464.54 kg/m³ tells you the storage story as well, liquid hydrogen just isn't good about being stored compactly. Then you look at -164 degrees Celsius versus -259 degrees Celsius and it really put it over the top. So let's compare, almost a hundred degrees warmer storage, 2.8 times the energy per mole of fuel, and nearly 6.6 times fuel storage per cubic meter. So why weren't we doing this from the beginning?
And that's where we get into a totally different set of discussions. Rocketry is about running a controlled explosion. It's actually a lot harder than it looks believe it or not. Hydrogen, for all it's issues, gives us quite a few advantages. First of all, we pump it through the nozzle of our rockets to keep them from melting down. Since it's so much colder, it can do stuff like that with few problems. The other big problem is the fact that isn't an auto igniting fuel, which is NASA's excuse, but the reality is that that only becomes an issue in space when you shut the engine off and try to turn it back on. It's good to think that way, because a standardized fuel would be great.
[via EcoGeek]
Read more over at NASA, Discovery, and XCOR.
Posted by Jamison at May 11, 2007 1:17 PM
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