Shaped charges using normal explosive via explosions perpendicular not
behind path of travel "fingers on watermellon seed" squirt a molten
bunch of formerly solid materials to 6 - 10 km/s. Not efficient I
think, but maybe benefits make it worth it.

1. Any way to have this on repeating system, so maybe methane powered
cannon (like Gerald Bull's supergun, which is another issue, so maybe
this issue already covered so ignore), thus maybe squirting molten
metal or even water in solid stream across solar system to wherever
needed? Not an accurate sytem, but moon with its gravity well is big
target, maybe terraform it by dumping 10 meters of water over surface.
Sorry to raise crazy idea, just is a novel and working method of launch
maybe worth exploring.