The Soviets literally launched reactors into space in the late 70s for very high RF power radar satellites (intended to track US navy, among other things). One

The Soviets literally launched reactors into space in the late 70s for very high RF power radar satellites (intended to track US navy, among other things). One deorbited over northern Canada. https://www.google.com/search?client=firefox-b-d&q=soviet+rorsat https://www.google.com/search?client=firefox-b-d&q=soviet+ro... Of course anything related to hall effect/ion thrusters isn't going to get you off the earth even with some of the theoretical/bench-tested-only 100kW (electrical load) thrusters under development. These are things with very low thrust at any instantaneous moment in time but very high specific impulse from 3800 to 6000 ISP or more. Meant to be used in vacuum only.