> This assumes nuclear warheads only and not a doomsday device. If Teller Ulam scales with additional hydrogen stages needed only, and not fissile ones beyond t

> This assumes nuclear warheads only and not a doomsday device. If Teller Ulam scales with additional hydrogen stages needed only, and not fissile ones beyond the primary, then a doomsday device is possible that does kinectic damage to the entire earth, wiping everyone out. There is an upper limit on the power of a bomb. At some point the radiation pressure starts to blows away the new fuel faster than it can detonate.