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US To Shoot Down Dying Satellite
A user writes "US officials say that the Pentagon is planning to shoot down a broken spy satellite expected to hit the Earth in early March. We discussed the device's decaying orbit late last month. The Associated Press has learned that the option preferred by the Bush administration will be to fire a missile from a U.S. Navy cruiser, and shoot down the satellite before it enters Earth's atmosphere. 'A key concern ... was the debris created by Chinese satellite's destruction -- and that will also be a focus now, as the U.S. determines exactly when and under what circumstances to shoot down its errant satellite. The military will have to choose a time and a location that will avoid to the greatest degree any damage to other satellites in the sky. Also, there is the possibility that large pieces could remain, and either stay in orbit where they can collide with other satellites or possibly fall to Earth.'"
Is this really anything else? The US is willing to protect it's secrets, China was trying to ensure they could protect theirs. Both are sovereign nations with the technology and ability to make these decisions.
The only way issues like this will ever be resolved is by allowing some intra-national body to have either approval or veto powers, but nobody wants to be told what they can/can't do.
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That's probably unlikely. Keep in mind that a higher orbit requires more than just altitude, it also requires angular velocity. The explosion would have to impart enough kinetic energy to not just overcome the gravitational potential to reach the altitude of other sats, but also to impart the necessary angular velocity about the earth.
The US military is probably aware of the max velocity of debris from their different ordinance. As much as the US administration is full of morons, the physicists designing the ordinance and planning stuff like this are quite competent.
I thought it was obvious, but none of the posters so far seem to have picked up on it. This is a further test of the ballistic missile defense program we've been spending $$$ for the last decade. In particular, the SM-3 Aegis Missile Defense System. One of the bonuses is this will be testing the missile under less strictly defined conditions.
The program has been in the development and test phase since about 2000, and undergoing tests of increasing difficulty, but always under predefined conditions. The tests are also expensive to orchestrate, typically involving several naval vessels, and a lot of ground support from both the navy and contractors, a lot of documentation, and a target missile that itself probably costs several million dollars. Here they've got a target that won't behave as predictably and costs nothing (well sort of...It's a spy satellite that failed to reach the proper orbit). I'm not sure they even know when or where it will come down yet.
This isn't necessarily a good demonstration of our ability to shoot down satellites. The officially released specs say it has a maximum altitude of 160 km. Most satellites orbit higher than that. However, the actual performance is classified and probably somewhat greater.
It's also not something new. We tested anti-satellite weapons in the 80's, although those are now past their shelf life and the response time was slow. In the 60's we developed a system called Nike Zeus that had an altitude ceiling of about 300 km. It wasn't accurate enough to directly hit a ballistic missile or satellite to achieve a kinetic kill like the SM-3 does, but with a 40 kiloton nuclear warhead, that didn't much matter. It was never tested with a live warhead and it would have been messy to use (damages anything else nearby, terrible EM interference on the ground, etc), but it was something.
Letting the satellite re-enter atmosphere unbroken would be the only way to make sure it does NOT create a debris field.
A satellite is not an airplane, there's no way to "shoot" it down. Breaking it in pieces will not bring it down, it's atmospheric drag that's doing it. All the Pentagon is doing is trying to make sure that it breaks down into pieces small enough to protect their military secrets.
By blowing up the satellite with a missile they have no control on how it's going to break, all they can do is estimate on the most probable breaking patterns. They cannot be sure that the remaining pieces will be of such sizes and shapes to re-enter the atmosphere in a predictable manner and time.
There is still the possibility that some of the largest fragments will hit some populated area. The fuel tanks, which are compact and very strongly built, will have a rather good chance of surviving, and reaching the earth's surface still containing some of that extremely toxic hydrazine (so toxic that a drop can kill a person). Besides, the explosion will inevitably send some fragments into a higher orbit, and possibly damage other satellites.
Blowing up a decaying satellite with a missile is, IMHO, the stupidest thing to do, and I have been an engineer working with satellite control systems for nearly 24 years by now.