Now I'm familiar with how nuclear fission works to produce thermal energy and alpha/ beta/gamma radiation, but how do they work in the bomb? When is the high energy neutron fired into the uranium-235, and when does the chain reaction producing the heat begin? Why is it that there's a huge explosion all of a sudden when the bomb impacts with a surface with high force? If 0.1% of the uranium's mass is converted to energy, what happens to the uranium after the bomb explodes? Is it just melted and dissipated? I understand these are not really good questions, but I'd like to better understand the practicality of the bombs. Also, are the answers the same thing for plutonium-239 bombs? Much appreciated.