https://www.newscientist.com/article/2218685-nasa-engineers-helical-engine-may-violate-the-laws-of-physics/amp/

So this is a cool concept for an inertia engine. Basically, you have a closed system. Start movement in one direction and get equal movement in the other direction, so far so Newtonian. But if your movement reaches relativistic speeds then your moving object becomes more massive and stopping it creates more motion than starting it. The concept is more complicated than that, but I thought it was awesome

let's do it

Biggest problem I see is the power requirement. It would basically take a full size nuclear reactor to generate enough power to do anything meaningful. While that's theoretically possible, the engineering and political challenges to having a nuclear reactor in space seem prohibitive. It would be neat to test it small scale on the space station, but I'm not sure how far you can scale down what is basically a particle accelerator

How would you keep something like that cool in space?

Also, it sucks it cannot be tested at a small scale as it's a neat idea.