There's a writeup here that you may be interested in, if you haven't seen it already: https://toughsf.blogspot.com/2019/10/the-expanses-epstein-drive.html http

There's a writeup here that you may be interested in, if you haven't seen it already: https://toughsf.blogspot.com/2019/10/the-expanses-epstein-drive.html https://toughsf.blogspot.com/2019/10/the-expanses-epstein-dr... The author suggests creating a fusion reaction well behind the ship, but channeling the useful parts of it in an electromagnetic field tunnel to create thrust while dissipating the heat more effectively. Vaguely like Project Orion, but with a more-or-less continuous external fusion reaction instead of a series of nuclear explosions. I am not a physicist, but they seem to have done their homework.