It would depend on the proportion of energy carried away from the blast as kinetic energy of material vs. electromagnetic. I would think that such a bomb would be designed to yield a barrage of high speed matter impinging on the asteroid, a shaped charge of lead or depleted uranium to the asteroid side. I’m confident that we would not send a neutron bomb to do the job.
My “grenade” is designed to have such heavy shrapnel thrown out a head of it with a heavy push of super heated steam/gas/plasma behind that..
The idea is to send a nuke with atmosphere/compressed gas or water all incased in a shell. The nuke goes off sending shrapnel ahead of it followed by a “push” of superheated gases that provide anough energy to push a fairly large asteroid off its collision trajectory. Smaller asteroids, especially those of ice and rock variety or comets might well be obliterated.
The talk has been why the experts won’t consider nukes against asteroids; nukes by themselves are just a quick flash heat, light and radiation and aren’t useful against really large asteroids...especially iron/nickel/rock types.
But send out a nuke(a 100 megaton minimum) incased in water/compressed gas or other combination...enhanced with heavy water dueterium/tritium all encased in anouter shell of metal/rock and then you’ll get a weapon that will well be effective. The technology is well within our capabilities...just massive in scale and there-fore expensive. The question is are the risks for asteroid collision large enough justify the costs of building such systems? These systems would be large anywhere from 300 feet to 10000 feet in circumference depending on the size of asteroid and the distance/time factors in volved in meeting the asteroid far enough out to do any good.
They would have to be pre-positioned in space in various La Grange points and in the short term chemically powered to begin to accelerate them toward their targets using gravity sling shot planetary assist where possible. Ion engines have been tested and could after a few months of gentle acceration propel a weapon to almost relativistic speeds 100’s miles a second but the difficulty is providing the power and drive mass to keep the engines running unmanned.
Ultimately how many would we need?... Tunguska type impacts happen once a century. Smaller objects have put holes in roofs of houses, but surely the cost analysis would preclude defending against those. Extinction level events happen evey 50 million years or so, regional or continental devestation events happen perhaps sooner.
The only real option is that this world finds a way to settle its internal squabbles and learn how to launch into space in a big way, finding new raw resources ...”out there”! Once there we would have a better handle as to the bigger threats that face our Earth and what we would need to do to prepare for them!