Jet engines on Eve (and Jool)

[Starman4308]

There's also hydrogen-oxygen engines, which are run very fuel-rich. They're typically run as hot as possible without melting the combustion chamber, so there's no real point to trying to increase burn intensity, and hydrogen is the best possible exhaust gas, having less molecular mass (2 g/mol) than anything else we could feasibly use... unless you can somehow figure out how to eject monoatomic hydrogen out an exhaust, anyways.