Basically a controlled thermo nuclear reaction blasting out the back.
"One design would generate 13 meganewtons of thrust at 66 km/s exhaust velocity (or 6,730 seconds ISP compared to ~4.5 km/s (450 s ISP) exhaust velocity for the best chemical rockets of today)."
You certainly wouldn't want to use this to take off from Earth. But we could use it for deep space travel.
https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket
Scott Manley video on the subject: https://www.youtube.com/watch?v=cvZjhWE-3zM
Basically a controlled thermo nuclear reaction blasting out the back.
"One design would generate 13 meganewtons of thrust at 66 km/s exhaust velocity (or 6,730 seconds ISP compared to ~4.5 km/s (450 s ISP) exhaust velocity for the best chemical rockets of today)."
You certainly wouldn't want to use this to take off from Earth. But we could use it for deep space travel.