Could a rocket burn liquid hydrogen and hydrogen peroxide? If so, what would be the exhaust velocity/specific impulse of an engine burning that combination be?
Could a rocket burn liquid hydrogen and hydrogen peroxide? It could be done, but it doesn’t make a lot of sense. Liquid hydrogen is a pain to work with, because it is a cold cryogenic fuel. It doesn’t help that hydrogen flame is almost invisible, but will burn you nevertheless. Finally, the molecular weight of hydrogen is so low, it will go through things it shouldn’t be able to, and work its way into metals and cause embrittlement. The boiling point of hydrogen is 20K, while the melting point of hydrogen peroxide is 272K (just below that of water). Houston, right there we have a problem that would make it unattractive. You want to store your fuel as a liquid, and this combination isn’t liquid at the same temperature. Although this is a show-stopper, the reason it doesn’t make sense is that the only reason to use hydrogen is to get a high specific impulse, and you get a lower specific impulse with this combination than you would with hydrogen-oxygen, and it’s actually harder to work with. The melting point of oxygen, by comparison, is 54K, so even it has trouble staying liquid next to hydrogen, but as you increase pressure, you increase the liquid range. You can increase the boiling point of hydrogen to 33K by increasing the pressure. Apparently, even SpaceX, which uses kerosene/LOX in their current generation craft, has concerns about freezing their oxygen (because they use helium as a pressurant, and they load it liquid into a tank that’s inside the LOX tank).Hydrogen peroxide’s principal advantage as an oxidizer is that it is liquid at room temperature. Unfortunately, it will pretty much blow up all on its own if exposed to organic material (think insects, leaves, rodents, …), at least at rocket fuel concentrations.I haven’t tried to figure out the exact Isp (specific impulse) or exhaust velocity. I know they would be lower than LH2/LOX, and it would be a lot harder to do.