The tried it in the 50’s, spewing the radioactive coolant into the air. The problem here will eventually be regulatory and political, not technical. Cooling, what happens in a crash etc.
Fusion reactors are different from fission reactors. They don’t require any cooling (indeed the technical problem with fusion is keeping the temperature high enough), the reaction isn’t self-sustaining so it will immediately stop if there is a failure of the reactor and there are negligible radioactive byproducts – the reactor vessel itself being the most important one.
I’ve always believed fusion is the future, and that they will achieve it one day, but I wasn’t aware that the current state of the art was beyond sustaining the reaction for more than a few seconds…
It has often been said that we have been 20 years away from achieving a viable fusion reactor for the past 50 years…
One of my colleagues, a mentor for years, just retired in his early 70s. He smiled a lot at his retirement party when remembering his excitement about the coming twenty years in fusion energy (in 1974)
Lockheed are either pursuing some fancy dream which will come to nothing, or they know something which the researchers who have blown away tens of billions over the last 50 years have not discovered.
I don’t know which it is, but if I had shares in oil companies I would be selling them as soon as they make something work 
“Our compact fusion concept combines several alternative magnetic confinement approaches, taking the best parts of each, and offers a 90-percent size reduction over previous concepts,” said Tom McGuire, compact fusion lead for the Skunk Works’ Revolutionary Technology Programs.
Wow, so their non-working fusion reactor is 90 percent smaller than any other non-working fusion reactor!
It has often been said that we have been 20 years away from achieving a viable fusion reactor for the past 50 years.
Yes, the “fusion constant” has been one of the fundamental constants of physics 
Obviously, it has just been cut in half… But it doesn’t matter if it is 20 or 10 years away because it will always remain “away”.
I have an even smaller non-working fusion reactor. Built it this afternoon! Was really simple
