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To: Sam Cree
But are you saying that there is nothing that humanity can do to defend earth from such an event?

Not at all; there's just not much we can do about it now. The two things we need are deliverable propulsion mechanisms (I recommend nuclear rockets for the near term) and a lot of lead time. The longer the lead time, the less integrated thrust we need. The best method would be to identify all of the potential doomsday rocks and affix solar sails to them. Small amounts of thrust could be applied continuously to the rocks without the need to replenish the fuel supply. The sails could be tacked by commands from Earth so that the thrust is always in a useful direction. After enough time, all of the rocks so equipped could be steered into orbits that don't ever cross Earth's orbit. (It is also possible that some of them could be steered so that they enter into orbit about the Earth someday.)

As for the rock that will potentially hit us in 2019, I doubt we could deliver enough delta-v to it to change the probability of collision. We don't have an efficient method of exerting thrust upon it, we don't have a vehicle capable of hauling such a thrust mechanism to it, the lead time is short enough that the integrated thrust requirements are already substantial, and those requirements are increasing as the inverse of the remaining lead time.

Then again, necessity is the mother of invention.

81 posted on 07/27/2002 12:20:07 PM PDT by Physicist
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To: Physicist
Thanks for your fascinating reply. I hope the damn thing misses.
82 posted on 07/27/2002 12:33:17 PM PDT by Sam Cree
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