: You keep making statements like this, but you keep neglecting to link to decent citations. Cite your sources, and make them good ones, and you'll find people may accept your data more. In particular, you may also find that the actual numbers differ from what you'd thought. 200 km/sec is the upper bound to fission plasma velocity if neutrons are produced (and they are, big time). If you have enough matter around the bomb to thermalize them and redistribute their energy, you have enough inert matter to drop the temperature and slow the shockwave by a comparable amount. I'd show you the calculations if I'd thought it would do any good, but you seem to have already decided what to believe regardless of what is actually the case.