12 thoughts on “Rubble Piles”

  1. Or use the recent information gained from the DART mission. The energy delivered by an impacter can blast many times its’ own mass away at velocity creating far more push than than one would expect. As before, I suggest nudging another much smaller asteroid onto a collision course.

    1. I wonder how big an impactor a dedicated anti-asteroid Starship could send? You could just fill it with water and let it freeze or use concrete. Something easily hundreds of times the size of DART.

      I am thinking water ice. It should phase change into steam under the pressure of the impact if it strikes hard enough. It will act as a giant steam thruster.

  3. Bennu was no solid rock either…OSIRIS-REx sank quite a ways into that rock and made quite a crater.

  4. As to moving the rubble piles aside, the least dispersive method I’ve heard of doing the job in less than decades, is the W71.

    https://en.wikipedia.org/wiki/W71

    The method with this X-Ray warhead is that it is placed opposite the side you wish the rubble piles to move toward, maybe 200 meters away from the surface, and detonate it. The X-Rays flash the entire side of the Asteroid, generating a shockwave moving outward perpendicular to the surface of each piece of rubble. That pushes all the rubble pieces*together*, rather than pushing them apart.

    This combined shockwave push on the asteroid changes its velocity in a direction that can be watched from several 10 of kilometers away, measured, and then the position of the next flash bomb adjusted. Repeat until the entire rubble pile has a net velocity vector that misses Earth.

  5. The gravity tractor or the nuke would have to be tested on a “rubble pile” asteroid first. You don’t want to make a first attempt when you absolutely have to have it work and have it fail. The thing is nukes are banned by the UN Outer Space Treaty. Would signatories to the treaty be okay with such a test?

    On another note – what if the Chicxulub impactor, 66 million years ago, was a rubble pile? Would it have been larger than a solid asteroid? Would that change any of the results of the impact? I wonder if anyone will look into it.

  6. A gravity tractor probably would work without a net – and certainly counts, I think, as the “least dispersive” method available. (Of course it should be tested.) The referenced article appears to make a basic error in presuming that “destroying” dangerous asteroids (as opposed to diverting them) was ever a viable strategy – and thus it should be no disappointment to learn (further) that we can’t do that and shouldn’t try.

  7. Why all the concern about “least dispersive”? I would think that dispersing a rubble pile as widely as possible would be the ideal outcome. How deeply an asteroid penetrates the atmosphere depends very strongly on its size. Breaking up a rubble pile into lots of little rocks may result in a very spectacular meteor shower, but one that would cause very little (if any) damage on the ground.

    I thing the ideal “kill vehicle” would consist of large tanks of water, capable of penetrating the surface of the rubble pile asteroid before firing linear shaped charges to open the tanks lengthwise. The second and third Saturn 1 flight test rockets were designated as part of “Operation Highwater”: their second and third stages were loaded with a total of 109,000 liters of water, and were split open at an altitude of 150 km. Observers reported seeing the rapid formation of ice clouds several kilometers in diameter.

    Hitting s rubble pile with a tank of water at a closing velocity in excess of 2,300 m/s would ensure that much of the water would be heated beyond the critical temperature. The resulting pressure would blow the object apart with prejudice. And no nukes would be required.

    You’re welcome.

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