reply to post by hildar
The 'shot' -- that’s what Ambassador James Jeffrey called the decision to use an an Aegis SM-3 to try to shoot down satellite USA 193 in the next
Holding the aside the politics of this — which are terrible — the briefing on debris risk left me cold. I have to say that I am very, very uneasy
about this decision — our missile defense tests have been heavily scripted to minimize debris creation and modeling of debris creation isn’t an
The burden of proof really should be on these guys to demonstrate that the risks to the ISS and other objects in space are minimal.
General Carwright, to his credit, provided enough technical information to model the intercept. David Wright is working on that right now — for
those of you who can’t wait, the important numbers are:
1. The intercept will occur at 240 kilometers (130 nautical miles)
2. The mass of the satellite is 2,300 kg (5,000 pounds)
3. The mass of the interceptor is 20 kg. (From CBO)
4. The closing velocity will be 9.8 km/s (22,000 mph), suggesting a virtually head-on collision.
Other pertinent observations. At 240 km, the satellite should be traveling 7.8 km/s; the SM-3 has a burnout velocity of 3 km/s.
I am very worried about the debris creation — particularly the debris that the light-weight interceptor will kick into higher orbits when it hits
the massive (bus-sized) satellite. Think, as Geoff Forden suggested, of a ping pong ball hitting a superball.
Virtually all the debris should come down quickly. Cartwright said 50 percent would come down within two orbits, with the rest coming down in weeks
and months. That seems plausible, at first blush.
But those two orbits could be hairy and some of the debris will remain in orbit. Michael Griffin, NASA Administrator, said there are “good times and
bad times” to conduct the intercept, based on the position of the ISS but that “bad times are not all that bad” comparing the risk to an order
of magnitude lower than flying the shuttle.
Last I checked, the Space Shutle's PRAN (probability risk assessment number, of complete loss of life) was 1 in 100. Extrapolating, there would be
only a 1 in 1000 chance of wiping out the ISS.
Anyway, we should be able to get some real numbers in the next 24 hours.
-- Jeffrey Lewis, cross-posted at ArmsControlWonk.com
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Falling Spy Sat: Don't Panic
Spy Satellite Will Plummet to Earth
How China Loses the Coming Space War (Pt. 1)
How China Loses the Coming Space War (Pt. 2)
How China Loses the Coming Space War (Pt. 3)
Ukraine Big: We Can Spot Your Sats, Control Space
How to Blow Up a Satellite
"Autonomous" Mini-Spacecraft Team up to Replace Big Sats
Video: Double Hit for Missile Interceptors
Missile Defense's Tight Fit
Missile Defense: Ready Now, or Ready Never?
Let's be honest here, you'd rather see them just let this thing land wherever it may, than have them successfully use a weapons system that you've
been railing against.
I mean, why are you more concerned about the extremely small risk to those in space, versus the unknown risk to the rest of us, including the release
of 1000 gallons of poisonous chemicals.
Your article is an embarrassment. Even things you disagree with can have positive aspects.
Posted by: Tor B | Feb 14, 2008 2:05:28 PM
Excellent analysis - an especially good point IRT the risk being one order of magnitude lower than flying the shuttle. The risk to all artificial
satellites should be considered, before a crucial communications or weather satellite, or the ISS.
It is easy to understand that the spy agencies want the spy satellite utterly
destroyed, but how much risk are they placing