What would happen if a government, say the U.S. captured a huge asteroid, say a couple miles across and brought it into near earth orbit. Don’t ask how, just assume it is done.
Now, if something goes wrong and the asteroid loses orbit and hits the Earth…how bad would it be?
I imagine it would be no picnic but it shouldn’t be as bad as the same asteroid slamming into the Earth ‘naturally’ because the relative speed difference between the 2 is huge and so it has much less kinetic energy, right?
How bad would the difference in damage between the two be?
It depend upon the size of the asteroid and its speed. One would assume some sort of terrible accident or incredible miscalculation for something deliberately placed in orbit to fall to earth. But that much matter fallingeven from orbital height will release an awful lot of energy, and it would be Bad. Pick up a copy of The Moon is a Harsh Mistress sometime (features moon rocks launched at earth, so it’s more than orbital speed and potential energy, but I think the results could be comparable.
Back when they knew less about the nature of the Tunguska meteorite, someone calculated the mass based on the known released energy and assuming it had the maximum velocity and object could have without escaping the solar system. It was asteroid-sized, and produced atmic bomb-type explosions.
Sending asteroid material down to the eartyh should drfinitely be done in small pieces, under extreme control.
An asteroid that was originally in orbit and then accidentally “de-orbited” would actually impact the Earth at about 7.8 km/s (the speed of an object in low Earth orbit), not 11 km/s. Here’s the revised calculation (the new interface doesn’t allow velocities below 11 km/s.)
FWIW, the energy involved in even your ‘modest’ 1st collision, ~1X10^21J, is roughly twice the World’s total energy consumption for 2010. Or, the energy that a moderate hurricane would use for 20 days to evaporate water. It is enough energy to boil roughly 110 cubic miles of water; a staggeringly great number. Lopping the velocity to ~8 km/s chops the energy roughly in half, so it’s only coming in with the entire globe’s energy consumption for one year. Well O.K. then.
While I love, and have cited before to, the impact calculator you’ve cited, I don’t think they adequately account for the systemic global effects of dumping that much energy into the global weather system. Faster impacts are that much worse, of course. Especially since their model doesn’t break out the nasty heat effects until the impactor exceeds 15 mi/sec, IIRC.
How one is supposed to impart enough delta-V to an asteroid to cause it to enter a close Earth orbit, without resorting to some exotic means of harnessing the energy from a nuclear explosion, I’ve no idea. The “gravity tractor” is for deflecting the asteroid very slightly, so as to cause it to miss a particular ‘keyhole’. There’s no way it has the energy to move a large mass into Earth orbit.
Powerful stuff, isn’t it? Thankfully, I don’t think we’re going to have to confront this issue quite just yet.
