Nuclear fusion? I can see this thing in 20 years http://news.mit.edu/2015/small-modular-efficient-fusion-plan...
You mean deuterium? Because plain hydrogen is quite easy to obtain.
> fusion at terrestrial scales is extremely complex
Lockheed Martin is allegedly working on a fusion reactor about the size of a truck payload: http://www.lockheedmartin.com/us/products/compact-fusion.htm... - But of course, I cannot judge from such a webpage whether that is real in any way.