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Spy Satellite to Hit Earth by late February to March
Jim from NSF.com
post Feb 17 2008, 02:24 AM
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QUOTE (nprev @ Feb 16 2008, 06:17 PM) *
wink.gif ...NRO might see it differently, Jim; bet that they're just loving all this wonderful publicity...


Doubtful. Adding more penetrations to a tank that could jeopardize a mission would be frowned upon
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nprev
post Feb 17 2008, 02:47 AM
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I wouldn't advocate adding more penetrations to a tank; understand how difficult it can be to design those things to hold pressure & pass the structural integrity requirements. (The bimetallic valves I was thinking about would be on the main feed line before the pump & shut-off valve, making it effectively one penetration topologically).

I would, however, really like to know if there's some sort of substance out there that's safe to fly to coat the tanks with, something that might promote intense spot-heating during reentry. I don't know; maybe a layer of magnesium coated with plastic to keep the O2 out pre-launch, or even just a few strategically-placed patches of same?

One other thing about such "vent-patches" is that they might blow under some circumstances during a launch failure & dump the crap before it's anywhere close enough to habitable areas to cause problems.


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Jim from NSF.com
post Feb 17 2008, 07:08 PM
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QUOTE (nprev @ Feb 16 2008, 09:47 PM) *
1. I wouldn't advocate adding more penetrations to a tank; understand how difficult it can be to design those things to hold pressure & pass the structural integrity requirements. (The bimetallic valves I was thinking about would be on the main feed line before the pump & shut-off valve, making it effectively one penetration topologically).

2. I would, however, really like to know if there's some sort of substance out there that's safe to fly to coat the tanks with, something that might promote intense spot-heating during reentry. I don't know; maybe a layer of magnesium coated with plastic to keep the O2 out pre-launch, or even just a few strategically-placed patches of same?

One other thing about such "vent-patches" is that they might blow under some circumstances during a launch failure & dump the crap before it's anywhere close enough to habitable areas to cause problems.


1. It is still a propulsion system penetrations. Also Range safety wouldn't like like them since there is no insight or intentional control of them

2. Since the weight and range safety issues.
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Guest_Sunspot_*
post Feb 18 2008, 07:33 PM
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Guests






Some questions:

The intention is to break the space craft up in to many smaller pieces, increasing the likelihood of most of it disintegrating upon re-entry. Will this debris spread out after the impact producing dozens or possibly hundreds of re-entry "events" spread out over days maybe weeks?
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Guest_PhilCo126_*
post Feb 18 2008, 07:39 PM
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I'm a bit amazed that anti-satellite missiles can be fired to such altitudes from the ground (sea) up. I remember that the US Air Force had anti-satellite missiles but these were fired from an F-15 fighter jet flying at maximum altitude...
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tty
post Feb 18 2008, 09:34 PM
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Firing a missile to 200 km altitude isn't that difficult (after all the Germans did it back in 1942). Launching from an aircraft at 50,000 feet does help, but the reason ASAT was aircraft-borne was mainly for the flexibility and quick-reaction capability. An aircraft can launch almost anywhere in the wrld and in any direction.
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nprev
post Feb 18 2008, 10:50 PM
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QUOTE (Sunspot @ Feb 18 2008, 11:33 AM) *
Will this debris spread out after the impact producing dozens or possibly hundreds of re-entry "events" spread out over days maybe weeks?


Maybe...but the prime intent per Ed's analysis of the intercept is to rupture that full hydrazine tank on-orbit so that it's not a hazard after impact.


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jaredGalen
post Feb 19 2008, 10:37 AM
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Do we have any idea what the debris field will be like and how long it will persist in orbit? The satellite is almost out of orbit anyway but the energy of a missile strike will surely boost the orbit of a lot of the debris?


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Tman
post Feb 19 2008, 11:10 AM
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http://spaceweather.com/ (19. Feb) reports that rumor has it that the US Navy may make its first attempt to hit USA 193 this Wednesday evening as the satellite passes over the Pacific Ocean. Because of Ted Molczan has drawn attention to a NOTAM issued by the US Government that might point to a possible ASAT attempt on USA 193 on Feb 21, between 2:30 and 5:00 UTC.

If they hit exactly the tank with the hydrazine, at that great combined speed, I would think the missile (without a warhead) penetrates the tank and maybe other parts entirely without larger impact on the orbit of the rest of the satellite.


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ElkGroveDan
post Feb 19 2008, 04:28 PM
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QUOTE (Tman @ Feb 19 2008, 03:10 AM) *
If they hit exactly the tank with the hydrazine, at that great combined speed, I would think the missile (without a warhead) penetrates the tank and maybe other parts entirely without larger impact on the orbit of the rest of the satellite.

As we all know it's all about mass and velocity. If that impactor arcs up and strikes the satellite at a high velocity opposite to the direction of travel then it will indeed impact the orbit of the doomed satellite. I suspect that this is part of the plan, or if not it has been calculated for. Not knowing the impactor mass and it's expected impact velocity it would be difficult for us to even pencil it out here, but the orbital effect will be significant (with a small number on the mass side of the equation, but a very large multiplier on the velocity side.)


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NGC3314
post Feb 19 2008, 05:54 PM
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QUOTE (nprev @ Feb 16 2008, 05:17 PM) *
wink.gif ...NRO might see it differently, Jim; bet that they're just loving all this wonderful publicity...


Wondering why Michael Griffin is so prominent in all these public statements. Hey - I have an idea. Maybe he's thinking this offers a way to avoid HST's eventual reentry violating NASA debris footprint rules, and a lot cheaper than developing a (probably still one-off at that point) robotic module for controlled deorbit.
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Jim from NSF.com
post Feb 19 2008, 06:45 PM
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QUOTE (ElkGroveDan @ Feb 19 2008, 11:28 AM) *
As we all know it's all about mass and velocity. If that impactor arcs up and strikes the satellite at a high velocity opposite to the direction of travel then it will indeed impact the orbit of the doomed satellite. I suspect that this is part of the plan, or if not it has been calculated for. Not knowing the impactor mass and it's expected impact velocity it would be difficult for us to even pencil it out here, but the orbital effect will be significant (with a small number on the mass side of the equation, but a very large multiplier on the velocity side.)



The impactor's velocity is not really part of the "equation", it could be zero. The bulk of the energy is from the satellite. The velocity differences are on the order of several km/sec.
The impactor just has to get in the path of the satellite at the right time. Sort of like throwing up a baseball glove to knock down a fly ball.
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ElkGroveDan
post Feb 19 2008, 08:42 PM
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I get your point, but come on now there is no such thing as a zero velocity except with respect to another body. If the velocity is zero with respect to the satellite then there will be no damage (and no impact for that matter). Even if the impactor is moving in the same direction of travel, albeit slower, its momentum must be factored in to the final momentum of the system after the impact. And in every instance I can imagine, the result will be greater decay in the orbit of the satellite and it's fragments.


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Jim from NSF.com
post Feb 20 2008, 12:49 AM
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QUOTE (ElkGroveDan @ Feb 19 2008, 03:42 PM) *
I get your point, but come on now there is no such thing as a zero velocity except with respect to another body. If the velocity is zero with respect to the satellite then there will be no damage (and no impact for that matter).


Didn't say with respect to the satellite , I was referring with respect to the earth (basically hovering)
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ElkGroveDan
post Feb 20 2008, 03:09 AM
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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.


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