This question is inspired by two existing spacecraft propulsion concepts.
- Beam-powered propulsion involves a spacecraft being propelled by a beam of some kind, and one potential type of beam would consist of particles moving at high speed (e.g. the MagBeam concept). This means that the spacecraft would not have to carry its own reaction mass or power supply, it would just need a magnetic sail to reflect the particle beam, making it faster and/or increasing its payload. A downside to using a particle beam is that the beam-producing facility would experience recoil and also need to be refuelled.
- Powdered regolith propulsion is similar to ion propulsion, except that it involves accelerating solid powder instead of ions. The isp is lower than ion propulsion but the thrust is higher. And the powder would be made by grinding up lunar or asteroidal regolith, making it a widely available resource. However, spacecraft using powdered regolith propulsion would still have to carry their own reaction mass plus an engine and power supply.
It seems to me that these two concepts could be merged into one: "beamed regolith propulsion". Basically, you would have facilities on moons or large asteroids that process regolith into powder and beam it towards spacecraft. The spacecraft have much better performance than if they had to carry their own reaction mass, engines and power supplies. The beam-producing facilities have access to effectively infinite supplies of powder, and the moon/asteroid absorbs the recoil of their beams.
Would this be a useful method of propelling interplanetary spacecraft? And on a related note, would it be viable for launching spacecraft off the surface of airless bodies like Earth's Moon?