Last month’s Acta Astronautica covered a lot, so this month (vol. 221 Aug 2024) is not so packed:
Bailey, B. Cohen, A. N. Lubin, P. et al. Optical and acoustic ground effects simulations from termi… p. 230 .2024.05.002
The research group is putting numbers on a concept for asteroid defense, taking chunks off the body- the “PI method.” The issue with this concept, of course, is that a bunch of smaller bodies is still nothing to dismiss. Would you rather get hit with a rifle, or a shotgun? Not much of a bargain to be had. If the body was small enough to begin with, one option is to simply evacuate that area as hopeless, but take trivial damage (á la Chelyabinsk) to its surroundings. But if you fragment the body, it’s now worse than Chelyabinsk everywhere… and it’s your fault that you fragmented the (natural) object. (See also: trolley problem. Would you throw the switch on the railroad track, if you then saved one life but then…)
Of course, if all this is taking place YEARS in advance of the Earth-impact time, then things unfold (mostly) nicely. Given enough time, the fragments disperse, and the ‘shotgun blast’ becomes ‘hailstorm’ becomes… oh, less hail. In this field, the answer is (has always been) ‘more warning time.’ That’s why Pan-STARRS/Vera Rubin/etc. got funded- there is no Step 2 without Step 1, detection. Certainly, no good Step 2s, only trolley problems and other dilemmas. Step 1, once you consider the issue, is then a slam-dunk: build the darn scopes already. They’re useful for other things.
Now assuming an impactor is found, and the warning time is (for whatever reason) just not that long, what’s the rundown on PI as our mitigation strategy? PI would still require some advanced notice, pre-planning, and flight time. Assuming the chunk-removal mechanism is serious as well, then this could still work. Remaining effects would be nonzero, though- “minimal damage.” I’m sure it wouldn’t feel minimal if it were you at the predicted point, but you’d live to complain. We’re talking about disaster planning here; there is no happy ending, only “you live.”
By the way, PI is yet another acronym from geeks. It stands for “Pulverize It.” Simple.