4 ms·

I was thinking about the propellant problem a couple of days ago. Is there a reason we can't use electrons? It's relatively easy to accelerate them to high perc

• taneq 7y ago
  Where would you get stray electrons from?
• ben_w 7y ago
  You can, but: 1) the more reaction mass you conserve, the more energy you need, so relativistic exhaust (electrons or anything else) asymptotically approaches an overly complicated photon drive. 2) using only electrons puts a large cloud of negative charge behind you while giving you a positive charge, which will act as drag slowing you down. Ion drives spray out equal + and - currents of ions and electrons (or equivalently a neutral plasma) to avoid that.
• gus_massa 7y ago
  It is essentially a Ion thrusters. https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster It's better to accelerate the nuclei, because you get more momentum for the same energy. You need to send the electron in the same general direction. From the Wikipedia page: > Ion thrusters emit a beam of positively charged xenon ions. To keep the spacecraft from accumulating a charge, another cathode is placed near the engine to emit electrons into the ion beam, leaving the propellant electrically neutral. This prevents the beam of ions from being attracted (and returning) to the spacecraft, which would cancel the thrust. Most device use Xenon, but other devices use Hydrogen instead. Perhaps you can try to collect the Hydrogen from the almost vacuum (there are a few Hydrogen atoms per cubic feet), but I don't know if it will work in real life.