>>11082285Hey, Raptor IS amazing, amazingly high performance and low cost and high TWR and amazing for all the other features it has. Raptor should in theory be a much harder engine to pull off because it uses two cryogenic propellants that don't auto-ignite, AND it gets a higher chamber pressure, all while having to be as highly reusable as a commercial air-breathing jet engine. Raptor is simply smaller than RD-270 was.
Also, pentaborane is a shit propellant for rockets other than pressure-fed or tri-propellant, because of the fact that when it burns it makes boron-oxide dust, which is very hard and highly abrasive. It would have absolutely gutted the engine after a single firing due to erosion of every surface, IF the engine's oxygen-rich turbopump didn't catch fire due to the boron oxide rubbing the protective metal oxide layer off of the turbine alloys faster than it could form.
A tri-propellant hydrogen-oxygen-pentaborane rocket would be quite kino, though. Bright green exhaust plume at launch, fading slowly to a nearly invisible hydrolox plume in the upper atmosphere (except for the blue-white glow of the inner walls of the engine nozzle), high thrust and good efficiency at sea level changing to low thrust and great efficiency in vacuum. Could be possible to do an actually-useful SSTO from Earth with that kind of engine, though I hesitate to say it because SSTO are a shitty meme technology.
