What's behind the US plan to shoot down a satellite?

[Ball Lightning]

This always seemed a bit fishy, what do you think?

Link

Is the peril of a tank full of hydrazine the whole story behind the Pentagon's decision to shoot down a defunct spy satellite, which could occur as early as Wednesday night? Probably not, but you really wouldn't want it dropped in your yard anyway.

Like its chemical cousin ammonia, hydrazine can cause lung damage, but a whiff of it won't kill you on the spot. It's also corrosive, dissolves hair, and can do nasty things to your skin. The rocket fuel can also ignite when it makes contact with rusty surfaces, earth, wood, or cloth.

But if you spill a little of the stuff on most surfaces, after a day or so it will go away if it's outdoors or if you open the doors and windows. A modest spill outdoors won't create a long-term toxic waste site requiring a cleanup crew in moon suits, although spills of large amounts or indoors could be a different matter.

And that's the problem - the falling satellite's tank contains about half a tonne of frozen hydrazine. If the satellite were allowed to simply fall on its own to Earth, military and NASA officials expect the full tank to survive the fall and hit the Earth's surface. That's because a hydrazine tank from the space shuttle Columbia made it all the way to the ground after the shuttle broke up over Texas. Fortunately, the Columbia tank was nearly empty, but the spysat's tank could disgorge its hazardous contents over an area as large as two football fields.

Even so, the risk that the hydrazine would actually spill in your yard - or for that matter in the Pentagon's inner courtyard - is miniscule. But President George W Bush says he doesn't want to take that chance.

The Pentagon and NASA figure they might as well take a shot at the satellite - as NASA chief Mike Griffin (pictured, far right) said last week, missing the satellite completely or just denting it wouldn't make matters worse - at least in terms of a hydrazine spill.

Pentagon officials say the satellite makes a tough target for its interceptors, which were designed to hit much hotter targets - nuclear missiles. But that claim may be intended to reduce expectations. If the Pentagon sounded too confident, missing the target could very well make the US a laughing stock in the eyes of the world.

After all, China shot down one of its own satellites last year using relatively simple technology. Most saw that move as a warning to the US, whose controversial global missile defence system depends on satellites - including the ubiquitous GPS network.

Just last week, China and Russia backed a treaty banning space weapons, though the US has said such pacts would prevent it from handling any future threats to its space assets.

Is the latest decision to shoot down the falling spy satellite a demonstration that the country can and will defend those assets if the need arises? Or is the Pentagon's itchy trigger finger coming from a desire, shared by the automated systems on Magrathea, to "take the occasional pot shot to relieve the monotony"?

Jeff Hecht, contributor

 

[IamJohn]

They just want to show off the fact that they can shoot down a satellite just was well as China, that's all. (And for your information they did successfully hit it). I don't see why everyone is making a huge deal out of the US doing it when China already did...

 

[Serutan]

Yes, I thought the Chinese and Russian protests of this were pretty hilarious
in light of both countries' anti-satellite activities in the past. But I also believe
that the US government didn't want to risk the hardware coming
down intact into the hands of people who could reverse-engineer it.
Not to mention it's a Heaven-sent opportunity to test out the anti-missile
system under real conditions.

 

[IamJohn]

Nah, real conditions are when they're shooting at you at the same time.

 

[a_propagandist]

No, but the US and Russia did this stuff in the 80s. Nothing new, really.

 

[Speedo]

I really can't see much ulterior motive behind it. ASAT has existed for 25 years or so now, so it's not like they're making some bold demonstration of new technology.

 

[Tee Kay]

Well, an opportunity to save the world and test a new space weapon at the same time. I mean, who wouldn't miss the chance?

 

[Zhuge_Liang]

Maybe another WW i guess...

Just joking!

Maybe they want other countries to have envy in their technologies.

 

[Sir Matzee]

It would be better if we had a video of missile hitting the satellite

 

[Joe Harker]

I think it was a test, but not planned, they certainly wouldn't have wanted to do it without a good reason, and this broken heap of junk was the perfect target for this test.

I don't think it changes anything, as it was believe that the US was capable of this anyway.

 

[Cutlass]

And now there's millions more fragments of metal to route everything else is space around to avoid damage

 

[raketooy]

This stuff always increases the risk of a "space war", countries shooting down each others' satellites. I read in a Finnish science magazine that should it happen, it could create millions and millions little fragments that could effectively destroy most of the satellites in orbit, halting much of world's connections.

 

[Ball Lightning]

And now there's millions more fragments of metal to route everything else is space around to avoid damage

It actually created much less fragments then the chinese strike as it incinerated most of the satellite.

 

[BasketCase]

No, but the US and Russia did this stuff in the 80s. Nothing new, really.

Second. The first time the U.S. shot down a satellite (that I know of, anyway) was in 1989. The method was a modified air-to-air missile launched from a jet fighter at 80,000 feet.

 

[Evie]

It actually created much less fragments then the chinese strike as it incinerated most of the satellite.

Didn't I read that most of the debris would burn down in the atmosphere anyway?

 

[Cutlass]

Didn't I read that most of the debris would burn down in the atmosphere anyway?

the fragments that enter the atmosphere will burn up. the fragments that remain in orbit will be a hazard to navigation for anything else in orbit.

 

[carmen510]

Well, you've probably heard already, but the US shot down the satellite.

 

[Kennigit]

It basically was the US Navy wanting to play with their new-ish toys (or bring back their toys from the 80's).

 

[Falcon02]

the fragments that enter the atmosphere will burn up. the fragments that remain in orbit will be a hazard to navigation for anything else in orbit.

The US Satellite was shot at a low altitude (~250 km). There are really no satellites operating at that altitude, for a very good reason, atmospheric drag. The atmosphere at the altitude that this debris is at is quite dense. The Debris is going to come down sooner rather then later (within about a month, which is relatively manageable). Mostly what will be impacted will be launches of missions, I'm not aware of any missions that operate at such a low altitude for any long period. (Prior to Columbia some Shuttle missions would orbit around this altitude since they only planned to orbit for a week or so.

The Chinese ASAT test on the other hand was at a relatively high altitude (~528 km). This is an altitude with operational satellites, and above operating satellites (ie. ISS 407 km, Hubble 590 km). The Atmosphere at such altitudes is much less dense then 250 km. As such instead of estimates of about a month for all the debris to return to Earth, the estimation is on the order of decades.

Also at higher altitudes, smaller changes in velocities are needed to change an object's orbit. What this means is when the Chinese Satellite shattered a piece that got "hit" and pushed away from the original orbit would move further off the original orbit then a similar sized piece that got hit with the same acceleration at a lower altitude. In short, for a similar "bang" a higher altitude satellite would have a much larger scatter effect then one at a lower altitude.