For greater thrust you could do what has been proposed for the polywell fusion call a quite electron discharge, which act by you dumping something in front of the particle beam and it would in effect blow it out the back of the ship for a lot of thrust, comparable to a rocket but of course the isp for what ever you dumping out wouldn’t be much better then a rocket.
since space is filled with junk it wouldn’t be to hard to slow down in the asteroid belt, near a passing comet, or whatever and mine it a bit for the afterburner mix. this is basically the idea in a lot of since fiction books, 2001 a space odyssey just to name one.
