US: Broken satellite will be shot down

Yahoo/AP ^ | 2/14/2008 | Lolita Baldor

[mojito]

WASHINGTON - President Bush decided to fire a military missile to bring down a broken spy satellite because of the potential danger to people from rocket fuel it is carrying, officials said Thursday.

Deputy National Security Adviser James Jeffries, briefing reporters at the Pentagon, did not say when the attempted intercept would be conducted, but the satellite is expected to hit Earth during the first week of March.

Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, said at the same briefing that the "window of opportunity" for such a shootdown, presumably to be launched from a Navy ship, will open in the next three or four days and last for seven or eight days. He did not say whether the Pentagon has decided on an exact launch date.

He said a Navy missile known as Standard Missile 3 would be fired in an attempt to intercept the satellite just prior to it re-entering Earth's atmosphere. It would be "next to impossible" to hit the satellite after that because of atmospheric disturbances, Cartwright said.

A second goal, he said, is to directly hit the fuel tank in order to minimize the amount of fuel that returns to Earth.

Cartwright also said that if an initial shootdown attempt fails, a decision will be made whether to take a second shot.

[TexanToTheCore]

The shot will most likely attempt to decelerate the satellite annd break it up in pieces. Probably an easy shot.

[sappy]

“rocket fuel” righhhhht! should be an interesting display of our missle tech and if successful, a nice message to enemies.

[353FMG]

“..wouldn’t all the fuel burn up on re-entry.”

Don’t you know that that would only add to the CO2 level in our atmosphere causing an increase in global warming?

[b4its2late]

I was hoping it would hit some middle eastern Arab country myself.

[samtheman]

Are you watching China? All your satellites are belong to us.

That was my thought EXACTLY.

[Bogie]

Really, target practice that is in the public interest.

What could be better?

[Yo-Yo]

These "small pieces" will establish their own orbits, creating a nightmare for other orbiting bodies (like commercial communitication satellites.)

What will be the altitude of intercept?

Not to worry. The satellite is in a polar orbit, and the SM-3 will intercept at around 100 miles altitude. At that altitude, atmospheric drag will ensure that all fragments will de-orbit. Heck, the reason everybody is worried about this satellite is because it's going to de-orbit iself due to atmospheric drag.

As you know, commercial communication satellites are at 22,300 miles altitude.

Much closer is the International Space Station at about 220 miles altitude, but still way too high to be affected.

Remember Skylab deorbited itself due to atmospheric drag and it was at 260 miles.

(The ISS get a periodic re-boost to maintain it's Low Earth Orbit.)

[Yo-Yo]

That’s a damn lie. It’s better to leave it intact and let it burn up. Atmospheric heating during reentry is all about mass/surface area ratio. The frictional heating will be much higher on the intact satellite than on the individual pieces. They’re creating more a hazard to people on the ground and in LEO by doing this.

You're right that it's all about mass/surface area ratio, but you're wrong that it's better off left intact. Which burns better, a log or a bunch of wadded up newspaper made from the same mass of wood?

Leaving the satellite intact will shield the innermost "guts" of the satellite, with the possibility of some secret stuff possibly surviving intact to be discovered by wandering eyes.

Break it up, and it will mostly burn up or at least become unrecognizable chunks on the ground.

[plsvn]

It’s better to leave it intact and let it burn up. Atmospheric heating during reentry is all about mass/surface area ratio. The frictional heating will be much higher on the intact satellite than on the individual pieces. They’re creating more a hazard to people on the ground and in LEO by doing this.

I'd rather take my chances on more smaller pieces allowed to decay than a single piece, perhaps protecting components deep inside the spacecraft, making it through the atmosphere essentially still intact. And I wouldn't worry about operational satellites in LEO, this is taking place well below them.

[archy]

wouldn’t all the fuel burn up on re-entry. That would make a nice view coming back down to earth.

Depends on whether the fuel is *merely hazardous* [like the anhydrous hydrazine emergency geneerator aboard F16s] or really hazardous like that aboard the former Soviet Union's radar ocean reconnaissance satellites, AKA RORSATs.

Which is aboard our naughty NRO launch 21 bird, and do the Future Imagery Architecture program cameras aboard utilize a nuclear radioisotope thermoelectric generator as their powerpack? Sorry, that info's classified.

However, you might want to try some websearching for NORAD Catalog Number 29651 In which case, you'll come across *this.*

[Desron13]

"B.S. It is a loud and clear message to China, in reply to their anti-satellite program."

Agreed. Or, they might be testing a new secret star wars type technology and using this as cover. Possibly both.

[RedCell]

Apparently. Thanks, professor.

[SaxxonWoods]

Hahahahha! Exactly. Shootdown? Please. How about smash? Pulverize. Deconstruct. Gravity is already on the job of bringing it down.

[nonsporting]

Commercial communications satellites are far, far higher.

Not all are geosynchronous (20,000+ miles). The Iridium constellation is in low earth orbit at about 400 miles. (thermosphere/exosphere locale).

It's not necessarily the big pieces which will be problemmatic. They will. Something the size of a grain of sand can destroy critical systems. I'm sure Iridium would prefer a "comfortable" margin of several hundred miles.

[plsvn]

“With the debris field so low, it will decay shortly and more completely” if you go to the link in post 17, china’s debris was still in space 11 months later. How short is shortly?

I think it's already been said the Chinese satellite was orbiting much higher than USA-193 will be when it's targeted. I bet the USA-193 debris lasts only weeks in orbit. Remember that Shuttle mission where a tether experiment went bad and a couple km long cord was left in orbit? That cord remained in orbit for not many weeks afterward, and presumably USA-193 will be in a lower orbit that the Shuttle was in at the time.

[Yo-Yo]

“With the debris field so low, it will decay shortly and more completely” if you go to the link in post 17, china’s debris was still in space 11 months later. How short is shortly?

If you read the link in post 17, you will have seen this:

"Updating the initial analysis by CSSI just after this event was first reported shows pieces in the debris cloud ranging from below 200 km in altitude up to almost 4,000 km"

4,000 km is just over 2,400 miles high. Stuff at that height will be around a long time. Nothing from this satellite, shot at from below 100 miles up, will make it anywhere near that height.

[Hunton Peck]

I’m pretty sure that “shootdown” is the journalist’s word, not that of anyone who’s supposed to know what’s going on.

[pgyanke]

Glad to see someone understands basic thermodynamics.

[orinoco]

Decelerating the satellite would cause it to fall to earth and burn up in the atmosphere with no debris left in orbit. Hopefully this is how they will bring it down!

[Atlas Sneezed]

How do you “shoot down” something that is in orbit. The best you can do is smash it into a bazillion pieces. Newton made these things quite clear.

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It works because all the pieces now have different orbits. Thos different orbits may be sufficiently elliptical and intersect with the earth, or unstable, and degrade into intersection with the earth. Getting something into a stable low-earth orbit is the challenge. Having it fall back is easy. Entropy tends to pull everything back “into the well,” eventually (the mechanism being the drag of the limits of the atmosphere.)