https://lockheedmartin.com/en-us/products/compact-fusion.html

Lockheed started years ago working on compact Fusion tech and THAT will revolutionize sea, air and space travel. They aren't the only ones either. There are no rules in physics that say you can't have a small fusion reactor but Nature seems to favor rather large ones, I'll admit (eg. The Sun). Who knows maybe an antimatter engine that feeds on atoms and anti-atoms will be here on 100 years. AI will help us design such things.