Carbon Hydrogen Rocket

[scott712]

I want someone with a little more chem-mystery under their belt to check this out for me.

How much energy is relased when Hydrogen combines with Carbon and how does this compare with Hydrogen and Oxygen PER WEIGHT OF REACTANTS? The motivation behind this question is this: Even if this ratio were improved only by a few percent, the benefit would compound itself many times over since every pound of rocket fuel you don't need is another pound of payload you can carry. If you do it the other way you have to add hundreds, maybe even thousands of pounds of fuel to add just one pound of payload.

On the one hand, to burn Oxygen and Hydrogen in a rocket one loses energy breaking up the O2 molecule into two O1's that each combine with one H2 this gives us two molecules of water. On the other hand, one carbon atom can combine with two H2's. The carbon atom not only combines with twice as many Hydrogen atoms as the oxygen molecule, but it weighs less in the first place, having an atomic weight of 14 vs. 16 for oxygen. It looks like it might be as good as two and a quarter to one improvement.

[kashi]

I have a sneaking suspicion that burning carbon in oxygen would yield more energy (which is what we do now obviously).

[Guest]

Nope. Carbon is much, much less reactive than oxygen. Carbon-hydrogen compounds are easily reduced (aka burned) in oxygen, leaving lumps of the stuff (aka ashes) sitting around doing nothing. In contrast, there would be no free oxygen on Earth at all if it weren't for plants constantly pumping it out. There just isn't much energy in a carbon bond, tho because it makes nice long chains of itself more easily than any other element, we're all here to talk about it.

[Greg]

Yes, Carbon is very good at making more stable covalent bonds, often with other carbon atoms. As a result carbon can be quite sturdy. This is part of the reason that the hardest naturally occuring substance is diamond. A pure diamond is made up exclusively of what element? Take one guess. Hydrocarbons make pretty good fuels, but burn much less cleanly and efficiently than O2 and H2 as fuel. Even a hydrocarbon based rocket (petrol fueled) is too inefficient to achieve as good a specific impulse to compete with what we have now.