3 ms·

Yes the energy is identical, but the volume across with the energy is dispersed is the benefit. Even if you "only" break up an asteroid so that the rubble falls

by burnte 3y ago

Yes the energy is identical, but the volume across with the energy is dispersed is the benefit. Even if you "only" break up an asteroid so that the rubble falls all over the world across a few days or weeks, that's nothing compared to the asteroid in one piece hitting. It's not the fall, it's the sudden stop at the end. Make that fall over days/weeks and a million times the area, you're fine.

mcbutterbunz 3y ago
Still depends on the amount of energy being released. Burning up a large enough asteroid would cook the planet, even at days/weeks/months. I guess it really depends on the rate at which heat is lost to space.
LorenPechtel 3y ago
It's all going to fall at basically the same instant. At small rocks destroying them is a good thing. At big rocks destroying them is worse than not shooting: Blast radius goes at the cube root of energy, blast area goes at the square of blast radius. Thus if you were to break an incoming rock into 8 equal parts the blast radius of each impact would be halved, the blast area quartered--but there would be 8 hits, for a final result of doubling the blast area. The smaller the pieces the worse the effect until you get down to the point where they burn rather than hit. (And that brings it's own problems with flash heating.) Thus big rocks must only be deflected, not destroyed.
- EthanHeilman 3y ago
  All of this depends on the actual parameters we are talking about > last radius goes at the cube root of energy, blast area goes at the square of blast radius. Only up to the point at which the blast wave touches atmosphere then strange things happen because the blast is now being tunneled into a vacuum. This likely reduces the blast of very big asteroids by channeling most of the energy back into space. However blast area isn't the only concern. An ice age can be triggered if enough matter is blasted into the upper atmosphere. You might increase the blast area by breaking the asteroid into smaller pieces but completely eliminate the risk of depositing light blocking particles in the upper atmosphere. It is by no means guaranteed that if you break a big asteroid into eight pieces, they will all hit. The energy to split an asteroid may confer sufficient momentum that small if not all the pieces miss the Earth.
- burnte 3y ago
  > It's all going to fall at basically the same instant. No, not for any sane definition of "at the same instant". See Shoemaker-Levy 9 as a great analog. Completely natural forces broke it up and it fell across a huge swath of Jupiter. An engineered breakup would of course be much more fine tuned to create both chunks and vectors of our choosing. If something were to head at us, and we took it from one big chunk to multiple smaller chunks but with such a terribly small explosion that we turn it into a closely-spaced fleet of rocks, then yes, but hopefully if we go through the effort of trying to destroy/deflect, we'd use a reasonable amount of explosive. While your energy dispersal functions in a vacuum are correct, you're completely neglecting everything else about the situation. All the energy we're putting into the system to change the vectors to start with, you're acting like we barely tap it. Look at what happened with DART and that had zero explosive, that was _purely_ ballistic. You hit a rock several months out and send pieces flying in 18,000 directions, some hit us, some don't, they hit across weeks, they hit across the world, and you get the benefit of our atmosphere. Presuming optimal angle of attack for the interloper, everything under 100 meters in diameter is vapor. More acute angles take that number up, and at really steep angles the objects skip off the atmo. Larger rocks will airburst from the entry into atmo, and lots of stuff will make landfall, but again, ALL THAT ENERGY IS DISPERSED ACROSS SPACE AND TIME. I know you said it won't, but the math, and real-world examples, say it will. > Thus big rocks must only be deflected, not destroyed. The problem is most things aren't just big rocks, the things that endanger us also consist of rock piles and slush balls, which you cannot deflect. So we MUST engineer for destruction as well. And this discussion itself also ignores a hundred other variables such as orbital mechanics, how much time we get, composition, etc. To just say "It'll all hit at the same time and we can only deflect" is only correct, pardon the pun, in a vacuum. There's more to consider.

by burnte 3y ago

mcbutterbunz 3y ago

Still depends on the amount of energy being released. Burning up a large enough asteroid would cook the planet, even at days/weeks/months. I guess it really depends on the rate at which heat is lost to space.

LorenPechtel 3y ago

It's all going to fall at basically the same instant. At small rocks destroying them is a good thing. At big rocks destroying them is worse than not shooting: Blast radius goes at the cube root of energy, blast area goes at the square of blast radius. Thus if you were to break an incoming rock into 8 equal parts the blast radius of each impact would be halved, the blast area quartered--but there would be 8 hits, for a final result of doubling the blast area. The smaller the pieces the worse the effect until you get down to the point where they burn rather than hit. (And that brings it's own problems with flash heating.) Thus big rocks must only be deflected, not destroyed.

EthanHeilman 3y ago
All of this depends on the actual parameters we are talking about > last radius goes at the cube root of energy, blast area goes at the square of blast radius. Only up to the point at which the blast wave touches atmosphere then strange things happen because the blast is now being tunneled into a vacuum. This likely reduces the blast of very big asteroids by channeling most of the energy back into space. However blast area isn't the only concern. An ice age can be triggered if enough matter is blasted into the upper atmosphere. You might increase the blast area by breaking the asteroid into smaller pieces but completely eliminate the risk of depositing light blocking particles in the upper atmosphere. It is by no means guaranteed that if you break a big asteroid into eight pieces, they will all hit. The energy to split an asteroid may confer sufficient momentum that small if not all the pieces miss the Earth.
burnte 3y ago
> It's all going to fall at basically the same instant. No, not for any sane definition of "at the same instant". See Shoemaker-Levy 9 as a great analog. Completely natural forces broke it up and it fell across a huge swath of Jupiter. An engineered breakup would of course be much more fine tuned to create both chunks and vectors of our choosing. If something were to head at us, and we took it from one big chunk to multiple smaller chunks but with such a terribly small explosion that we turn it into a closely-spaced fleet of rocks, then yes, but hopefully if we go through the effort of trying to destroy/deflect, we'd use a reasonable amount of explosive. While your energy dispersal functions in a vacuum are correct, you're completely neglecting everything else about the situation. All the energy we're putting into the system to change the vectors to start with, you're acting like we barely tap it. Look at what happened with DART and that had zero explosive, that was _purely_ ballistic. You hit a rock several months out and send pieces flying in 18,000 directions, some hit us, some don't, they hit across weeks, they hit across the world, and you get the benefit of our atmosphere. Presuming optimal angle of attack for the interloper, everything under 100 meters in diameter is vapor. More acute angles take that number up, and at really steep angles the objects skip off the atmo. Larger rocks will airburst from the entry into atmo, and lots of stuff will make landfall, but again, ALL THAT ENERGY IS DISPERSED ACROSS SPACE AND TIME. I know you said it won't, but the math, and real-world examples, say it will. > Thus big rocks must only be deflected, not destroyed. The problem is most things aren't just big rocks, the things that endanger us also consist of rock piles and slush balls, which you cannot deflect. So we MUST engineer for destruction as well. And this discussion itself also ignores a hundred other variables such as orbital mechanics, how much time we get, composition, etc. To just say "It'll all hit at the same time and we can only deflect" is only correct, pardon the pun, in a vacuum. There's more to consider.