A offshoot of the Space Shuttle reentry question, it is possible to have a object enter the atmosphere (of earth or some other planet) so fast that the compressed gas to start nuclear fusion even just for a nuclear ‘fizzle’ effect?
Is that in theory possible, and if so what would be needed to make it so, or perhaps it already is known to happen?
It probably does happen. Nuclear fusion is actually really easy to achieve. What’s hard is to achieve it on a significant enough scale that it’s self-sustaining.