BTW, the reason we need to experimentally slam a spaceship into an asteroid rather than simply *calculate* how much it will deflect the asteroid, is because regolith physics is UNSOLVED and too hard to calculate! The splash of regolith on impact determines the deflection. 1/2https://twitter.com/CNN/status/1463541705995702276 …
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2/2 Because the splash flies *back* the opposite direction that the asteroid is being nudged, so it actually increases the change of momentum of the asteroid. But how much? Nobody can calculate a splash of sand. Sand physics is unsolved and super hard. https://www.nytimes.com/2020/11/09/science/what-makes-sand-soft.amp.html …pic.twitter.com/cRD5fRmpUt
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The factor of the momentum change due to regolith splash is known as the “beta” of the impact. It is super important to measure so we can deflect an asteroid enough to miss the Earth, considering that spacecraft kinetics are not infinite.https://www.nasa.gov/feature/nasa-s-first-planetary-defense-technology-demonstration-to-collide-with-asteroid-in-2022 …
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Sample the math in this seminal paper. This is sand (in a simplified case). https://www.eweb.unex.es/eweb/fisteor/vicente/publicaciones/preb07.pdf …pic.twitter.com/UkB6b9gFAs
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