Spy Satellite to Hit Earth by late February to March |
Spy Satellite to Hit Earth by late February to March |
Guest_Bobby_* |
Jan 27 2008, 04:47 AM
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Guests |
Just read at MSNBC that a large U.S. spy satellite will hit Earth by the end of February or early March.
Better keep our hard hats ready??? Here is the article: http://www.msnbc.msn.com/id/22857051/ |
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Feb 20 2008, 03:09 AM
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
http://www.space.com/news/080219-satellite-shootdown.html
The collision between the fired missile and the satellite would not only break the massive hunk of metal into pieces but would also speed up its tumble through Earth's atmosphere. "If you want to bring something down, you slow it down. You apply a force on it which results in it being slowed down and decrease in its orbit," Carrico told SPACE.com. "Right at that point where they want to engage [the satellite] is at the edge of the atmosphere, so you're bringing it down faster." I believe that was the point I was trying to make above. -------------------- If Occam had heard my theory, things would be very different now.
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Feb 20 2008, 06:05 PM
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Member Group: Members Posts: 321 Joined: 6-April 06 From: Cape Canaveral Member No.: 734 |
http://www.space.com/news/080219-satellite-shootdown.html [i]The collision between the fired missile and the satellite would not only break the massive hunk of metal into pieces but would also speed up its tumble through Earth's atmosphere. I believe that was the point I was trying to make above. The force that is going to bring down the fragments is drag, not the impact. The fragments have a lower ballistic coefficent |
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Feb 20 2008, 07:07 PM
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#4
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
The force that is going to bring down the fragments is drag, not the impact. The fragments have a lower ballistic coefficent You left out this part: "If you want to bring something down, you slow it down. You apply a force on it which results in it being slowed down and decrease in its orbit," This is what I have been saying, and they weren't referring to atmospheric drag. The impactor will slow it down and it will begin to drop. -------------------- If Occam had heard my theory, things would be very different now.
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Feb 20 2008, 08:22 PM
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#5
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
If I'm understanding ugordan's explanation of the dynamics correctly what will actually happen is that the ASAT will slow it all down a little. That situation is unstable so the debris cloud will fall lower into the atmosphere and speed up in the process as it swaps gravitational potential energy for kinetic energy.
The satellite is (believed to be) about 2600kg and is currently orbiting at around 7.8km/sec. I've no idea how the ASAT intercept is supposed to work but lets assume that they put it into a similar orbit moving in the opposite direction. The impact head of the ASAT is not likely to mass much more than 100kg and probably will mass less than 25kg if it's similar to the earlier US ASAT tests. For a perfect collision where a 100kg ASAT warhead transferred all it's momentum into the satellite the resulting object would be moving at 7.22km/sec. That's now unstable at that altitude and so it will fall until its rising velocity matches the orbital velocity at the altitude it finds itself. My [highly unreliable and full of gross simplifications] back of the envelope calculations put that at about 18 km lower down. That alone will significantly increase the drag but the really important factor is that the end result of a successfull intercept will be a debris cloud that has a massively increased effective cross section compared to the original satellite and that is what will really bring it down fast. |
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