Editing Beam-powered propulsion (section)

=== Mass beam systems ===
Another beam-pushed concept uses pellets or projectiles of ordinary matter. A stream of pellets from a stationary mass-driver is "reflected" by the spacecraft, cf. [[Mass driver#Hybrid mass drivers|mass driver]].<ref>{{Cite web |first=Paul |last=Gilster |url=https://www.centauri-dreams.org/2014/07/16/smart-pellets-and-interstellar-propulsion/ |title='Smart Pellets' and Interstellar Propulsion|work=Centauri Dreams |date=July 16, 2014}}</ref> The spacecraft neither needs energy nor reaction mass for propulsion of its own. For craft at sub-relativistic velocities, mass beams would be more efficient than photon beams. Nordley and Crowl point out, "A photon must travel at the speed of light and until relativistic velocities are reached, a reflected photon carries away almost as much energy as it started with. A massive particle’s velocity, however, can be tuned so that the reflected mass is left almost dead in space relative to the beam generators, having surrendered almost all of its kinetic energy to the starship."<ref>{{Cite web |title=(PDF) Mass beam propulsion, an overview |url=https://www.researchgate.net/publication/303682465_Mass_beam_propulsion_an_overview |archive-url=http://web.archive.org/web/20230307141056/https://www.researchgate.net/publication/303682465_Mass_beam_propulsion_an_overview |archive-date=2023-03-07 |access-date=2025-01-17 |website=ResearchGate |language=en}}</ref>