matterbeam

ToughSF has a look at starships propelled by photon drives, and why they have been relegated to a relic of the 1950s.

It's modest when you compare it to the 36,000km+ geostationary tether or the 200,000km+ lunar elevators we see proposed!

That is similar to the concept of the Aldrin Cycler.

Tiny projectiles can be accelerated to speeds so high that fusion reactions are ignited upon impact. This means you can get more energy out than you put in... from a distance. Like most technologies in space, it can be a weapon and/or propulsion system.