I was replying to this: "Fuel is almost ALL the cost of launching a rocket." Also, how did your hardware get out of the thick lower atmosphere? Someone paid th

I was replying to this: "Fuel is almost ALL the cost of launching a rocket." Also, how did your hardware get out of the thick lower atmosphere? Someone paid the cost of lofting that mass. Not much about rockets is trivial, except in theory. Practical issues: * heat dissipation: your fuel / oxidizer combo probably burns hotter than the nozzle material can tolerate. This needs to be tested (not for on orbit, for the first time) * fuel supply -- it's non-trivial to design tankage and feed systems that can supply fuel and oxidizer at the rate needed, in vacuum * propellant storage -- non-trivial unless you go for the really nasty "storable" propellants Pretty much every piece of the problem is non-trivial.