Ronald Held wrote:
Controlled fusion has been a decade away for several times that, so I am skeptical that it will occur any time soon.
The thing is, UNCONTROLLED fusion is relatively easy. Controlled fusion is hard because of the "control" part: superheated metallic plasma is hard to control and nearly impossible to extract useful energy from it.
technique is essentially a very small fusion bomb being detonated inside of a rocket nozzle and so the working principle is pretty simple. It only needs to be controlled well enough to not obliterate the entire engine, and that's just a matter of conventional rocket science.