Gotham Central wrote:
Anyone ever consider what the "Mr. Fusion" on the back of the DeLorean (and presumably a power source used all over in 2015) is really capable of? Forget that it's capable of providing cold fusion in a small space and is "stable" enough to be mounted on a car. But what we see it do is simply incredible, on some levels it's more powerful than any other natural fusion reaction in the universe.
In massive stars hydrogen is fused together to form helium, then helium to form carbon, and some of the other elements are mixed in there but once a star (if its big enough) gets to iron it cannot go any further. At that point there's not enough energy in the star to fuse two iron molecules together to from the next element, at this point the star is so heavy and dense that it collapses into itself likely forming a black-hole.
When we see Doc use the Mr. Fusion at the end of BTTF 1/beginning of BTTF 2 we see him dump inside the Mr. Fusion chamber some eggs, beer, an aluminum can, styrofoam and some other pieces of garbage. "Somehow" the Mr. Fusion is capable of taking these materials that not only contain elements much more complex than hydrogen or helium but alos contains chemical compounds. Rather than pretty much doing nothing because it doesn't have the power to, the Mr. Fusion is able to take the stuff dumped into and convert it into raw, pure, energy. (Also I'm sure some number crunching of what we see Doc put into the device would equal far more than 1.21 GW.)
Yet that super powerful fusion reactor managed to collide with a locomotive without exploding.
A true fusion reactor not dependent on a fission reactor to operate would be extremely stable and not prone to explosion. Which is an "error" in TDKR where the fusion power reactor is used as a bomb. In reality the fusion reactor would simply become a paper weight once disconnected from a fuel/power source. The fusion reaction would also simply stop if no longer controlled or being maintained, also any loss of containment would result in minimal radioactive waste. Fusion requires a very precise and specific set of circumstances to control and maintain, it's a pot of food that needs to be constantly monitored and maintained. If everything doesn't go perfectly it'll simply not work.
Besides, when the DeLorean collided with the train it had just arrived back to the future and likely had spent its fuel, powering down the fusion reactor.