I guess it depends on how big the pieces are. If you break a very large asteroid in 3, still large, pieces that might not be an improvement. A nuclear weapon exploding in a vaccum is likely to be a lot less destructive than one exploding in the atmosphere.
Enough energy is going to be dumped into the atmosphere either way it doesn’t make much difference. Further, even fist sized fragments are going to penetrate deep into the atmosphere so all options are effectively ground level detonations.
Suppose over one second you can be hit the earth with with either 1 30 gigaton weapon, 3 10 gigaton nuclear bombs. 3,000 100MT weapons, or 3 million 10 KT weapons etc. All of those suck in ways that are hard to comprehend.
Given multi-kilometer asteroids like mentioned above, I'm starting to think neither method (fragment/push) sounds viable. The amounts of energy required just seem off the scale? Maybe pushing (multiple?) smaller but still massive enough to have decent kinetic energy into its path would be more feasible. Sorta like pool balls bouncing off each other..I generally end up missing the pocket (earth) when that happens :-)
yeah - how do you keep it out gassing long enough to hit 0.1 m/s though? I would imagine you'd need to nuke it every couple of days or say every week to keep it out gassing long enough to generate that big a change speed?
Hmm - I guess not! According to [1] it would take less then a ton of TNT to accelerate 1 million tonnes (eg like asteroid 12932-zephyr) to 0.1 m/s...So its probably a good thing I'm not responsible for these things!
Let’s go to the extreme and think 10 km wide ball of sand.
Normally when a single bit of sand hits the atmosphere it dissipates energy in every direction. So you a tiny fast moving glowing dot radiating energy in every direction. However you can’t dissipate energy when you’re right next to another particle at the same temperature. Thus energy from each bit of sad can basically only go in 2 directions down or up and you’re not transferring energy through the entire thing before a crust of plasma followed by ~10km wide ball of sand hits the surface.
Hell it could be a ball of water that size and the same basic effect kicks in.
Spread a 10km wide ball of material into a 1,000 km wide diffuse cloud and you are basically slapping the earth with 1,000 km wide disk with an average width of ~17 cm (maximum width ~1m) going 10’s of thousands of km/h. Again things don’t go well, you may be shifting how many minutes various people survive but it’s not actually addressing the issue.
