Nuclear propulsion would likely need to be assembled in space and when needed, the spacecraft would need to attach to it in orbit. Critical malfunction tends to happen in atmosphere.

Theoretically ion engines are the pinnacle of propulsion. Far more efficient than normal combustion engines. And doesn't satellites already use small ion engines for realignment?

Was about to say integza just recently made a video about this.

Damn there seem to be alot of protomolucule on the moon.