One thing I always wanted to ask
is what colour should the exhaust be?
E.g., if it is hydrazine/N2O4 based, on Earth it is violently brown. RP-1/LOX exhaust is a bit more into the yellow and red parts. BUT: what about exhaust in space? Specifically, what would hydrogen (about 2700K) exhaust in space look like - do I simply need to dig out the black body curve and calculate the spectrum from there (and possibly convert to visible colours)?