The concept of this missile shooting down that dead spy satellite falling out of orbit is fascinating. How high is that dead satellite orbiting at? 160 miles? Space Shuttle orbit?

What would be the satellite's orbital velocity at the time of missile impact? Are they trying to hit it while its orbit is decaying or while its still high?

Will the missile go straight up and hit the satellite at the point where the trajectories intersect or would the missile go into a partial orbit and try to chase the satellite by coming in from behind?

What I'd really like to know is if this satellite is out of control and coming down, how in control will those rockets be once they're up there? Will we then have to worry about them falling on us as well? What if they not only miss but land somewhere blowing up the place? I might not know a lot about all that could or couldn't happen, but most are in my position and quite concerned.
This whole thing just seems crazy to me that any of us are even having to worry about this. It's not the size of whatever comes down, it's the hazardous materials that will kill us. Unless of course it's those rockets adding so much more fun to an already wonderful crash.
ama

Don't fret, the missiles can be exploded remotely.

As for "shooting it down", that's not actually what they're doing. They're just shooting it to pieces, to disperse the hydrazine before it crashes, and to a lesser extent, perhaps to make the pieces smaller and likelier to burn up in reentry.

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Interesting question. According to http://www.nytimes.com/2008/01/27/us/27spy.html?em

Since it was launched, the experimental satellite has been in a slowly decaying orbit. As of Jan. 22, it was moving in a circular orbit at about 275 kilometers [~171 miles]above the Earth, Mr. McDowell said. In the last month, its orbit has declined by 15 to 20 kilometers.

It has dropped a bit from that by now, so 160 miles probably is close. The shuttle is about 340 km (~211 miles up (currently).

Well, according to:

http://www.chicagotribune.com/news/n...1,387878.story

At the time of the launch, officials said the satellite would be about 150 miles above the Earth.

So, circular orbital velocity at 150 miles would be about 27,936 km / 17,359 miles per hour.

Its orbit is already decaying. Again, according to the Chicago Tribune:

If the satellite is not intercepted, it is expected to enter the atmosphere in late February or early March.

"This has no aerodynamic properties," Cartwright said of the satellite. "Once it hits the atmosphere, it tumbles, it breaks apart. It is very unpredictable and next to impossible to engage. So what we're trying to do here is catch it just prior to the last minute, so it's absolutely low as possible, outside the atmosphere, so that the debris comes down as quickly as possible."

It's a suborbital missile. I doubt the trajectory would be quite straight up, but it certainly isn't going to be able to catch up from behind, so it has to hop up and get in the way. I'd guess it would get in position a little ahead of the satellite, make final position adjustments and let the satellite catch up with it.

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Exactly. I was even reading that the missile would be aimed to strike the portion of the satellite where the hydrazine tank is. Pretty remarkable to think at the precision and technology involved in intercepting something at such an altitude and speed. This is supposed to take place anywhere from 3-10 days from now, so let's see how it goes.

SPACE WEAPON QUESTION.

If a shuttle was in reentry, would it be really, really easy to hit with a heat seeking missile fired from the surface?

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20 years ago I splashed perhaps an ounce of hydrozene on my pants leg, but I have seen no symptoms, so the danger of hydrozene is likely exagereated. I'll guess, the satellite will be at an altitude of about 80 miles when it crashes into the missile. Assuming the missle warhead explodes the hydrozine will be scatter widely above Earth's atmosphere. The hydrozine will likely be scattered by the kinetic energy of the collission even if the war head does not explode. Hydrozine is a reducing agent, so it will mostly make oxygen compounds before it reaches Earth's surface. Most of the new chemicals are less hazardous than the hydrozine and are chemicals typically found in trace amounts in Earth's atmosphere, such as water.
The Navy has assured us that they will deliberately avoid the collision at the last second, if there is any reasonable chance of making matters worse. If we do nothing, odds are about a million to one that zero humans will be injured.The Navy hopes to improve the odds to about a billion to one. Most of us are more likely to be injured by something many minutes per day, so our personel hazard is only increased minutely by this re-entry. As the others posted, there is no reason to worry. Neil

Most Heat Seekers have far too short of a range to reach the Shuttle. Like under 15, with many even less. Sidewinders are listed in Wiki with an 11.3 mile range at Mach 2.5. Stingers are the little shoulder fired ones, and they are listed with a range of 4800 meters, or about 3 miles.

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You've still got time - best get busy on the bomb shelter.

amachristian,
The missiles they will use will be in control once they are launched to explode the satellite. The satellite was launched many years ago, and has had very little ability to change its directions since then, so it has been in a constantly decaying orbit ever since it was placed in orbit. The missile(s) (rockets are not guided, missiles are guided) will leave the atmosphere acquire the target, lock-on, run under constant burn (not drift) to the target, and explode both themselves and the target into many very small pieces. If the whole evolution is successful, then all of these small pieces will burn up during re-entry. If the missile(s) should miss, those missile(s) may have the ability to re-acquire and make another attempt. If they do not have that ability, they would drift out into space, once their fuel runs out. The worst thing that could happen with this would be the missile(s) would hit an asteroid, the moon, or another planet some time in the distant future. There would be no chance of those missile(s) returning to Earth, since they would be aimed away from Earth and under thrust on a tangent away from our gravity field.
Having said all of this, the HYDROZINE is liquid rocket fuel, and should burn up in re-entry, or better yet, cause the satellite to explode due to the heat building up in the unit containing the HYDROZINE. I think the only reason they are proposing this whole deal is because they want to test this new missile. Originally, they claimed this satellite would not cause any problems more than Skylab (being that because it was so large a big piece may survive to hit something). Let's face it, the current administration in the US is not capable of telling the truth about anything.

Hmm, are you sure?

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Not correct at all. The missile would eventually reenter earths atmosphere and burn up. It would never run long or fast enough to escape earths gravity.

Surely the missiles are sub-orbital. If we had missiles capable of reaching escape velocity we would be using them now to put micro-payloads in orbit.

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The article I read said that although the range of the missile was classified, it could not reach a "normal" satellite orbit. If they can't make it to 250 miles, the odds of hitting another planet are (hopefully) very remote. Nibiru... I'm looking at you there. The missile won't have the speed to get away from the Earth, and probably won't have the shape to survive re-entry.

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A rocket is the engine or the entire propulsion system used to propel
the vehicle. A missile is anything which is thrown, such as a spear, a
rock, a hand grenade, or an ICBM. A "guided missile" is a missile with
some kind of guidence after it has been launched. It may be guided
all the way to the target, or only during the first part of the flight.

No, they don't have that ability. The missile and the target will pass
each other at enormous speed. It would take many times as much fuel
as the missile actually carries to turn around and head in the opposite
direction, and it would take far longer to catch up to the target again
than the time available.

Good grief! Nothing like that. This missile will coast upward perhaps a
few hundred miles, possibly over a thousand miles, then will fall back
down on a parabolic trajectory. The impact point will be known fairly
accurately at the time of launch, and will be known very accurately at
the time the engine stops firing.

Hydrazine, N₂H₄.

-- Jeff, in Minneapolis

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Endeavor, Tog,

If the missile misses its target -- which I think is more likely than not --
it probably will not burn up on re-entry. It will not be moving anywhere
near as fast as a satellite in orbit. It is the orbital speed that gets ya.

-- Jeff, in Minneapolis

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"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

Hydrazine is supposed to be highly poisonous. If it is part of a bipropellant system, then the nitrogen tetroxide would also be very poisonous. I think the idea is to break the tank up, because they expect the tank to survive re-entry fairly well, and don't want trace amounts of fuel everywhere where it lands.

On the other hand, the danger is probably exxagerated in the first place because hydrazine has a very low flash point. (It is a monopropellant after all). It would probably all burn off on re-entry provided the smallest break in the tank.

Still, it would be interesting to see if we could hit the target. Probably not an easy one to get.

PS- side-note - all low earth orbits decay if they aren't maintained by thrusters. The rarified atmosphere drags on the sattelites over time. My understanding is the sattelite lost power after being deployed and hasn't been in communications or under control since. Since it is a low orbit, the space debris from such an engagement would also likely decay within a few weeks and burn up.

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I'm glad you were not hurt, but I do not agree that the hazards of hydrazine have been exaggerated. Here is the MSDS for it.

The National Fire Protection Association, which rates chemicals as to the hazards for emergency personnel, lists it as 3 for health, flammability, and reactivity, on a 0 to 4 scale (0 being safe).

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You mean the atmosphere isn't a blazing wall of death? Bah. Sooo didn't think that through.

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They (the briefing) are saying that is unlikely because the hydrozene is currently frozen solid. If there is a small break in the tank, some will burn off, but most will stay intact.
What they are expecting is that it survives, and the connections will provide the leak points, and will slowly escape as it thaws.

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Oh. In that case, by all means, try to blow it up.

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I have it on good authority that the missle uses a secret German guidance system. It has a self adapting neuroptical interface to control the thrust vanes. The delay is due to an O2 supply to the control interface..

In laymans terms it’s a pigeon pecking on different areas of the display screen. Right now they can’t get them to hold their breath above 3 miles. And they are awaiting special high altitude Israeli pigeons.

Blowing up the satellite is all about safety. It has nothing to do with the various secretive components of the spy satellite that might survive an uncontrolled entry into an unfriendly country....

Sure, that's what they say...but we're also talking about the gubmt

Seriously though, it does seem entirely plausible that the damage is enough to be useless. Besides, I would assume a lot of the secrecy is in the construction techniques needed, and without those, the other stuff is useless.

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Well, that's not a trivial motive either. I'd be all in favor of blowing it up in that case too, though they said the sensitive electronics wouldn't be likely to survive re-entry into another country in any sort of useable or reverse-engineerable form.

The missile they are trying to shoot it down with isn't a short-range air to air missile. It's an anti-ballistic-missile missile, more than capable of the necessary ranges and speeds.

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And, all it has to do is burst the fuel tank on a target the size of a short school-bus on a very well known path, whereas it is designed to be able to hit a basketball sized object trying to hide its whereabouts. I think the odds of success are pretty good.

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With sufficient technical expertise, examining the remains of the
satellite could yield information about its spying capabilities, thus
telling an enemy what it needs to do to avoid being spied on by
other, similar satellites, or to feed them false data. It could also
reveal communications system details that would enable an enemy
to receive data from them or send control messages to them.

-- Jeff, in Minneapolis

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"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

Like what? Duck?
I think these techniques are already well known.
Now, that part, I could see, but I also think that some of that stuff is already known, and that there are safeguards in place to protect from it.

Maybe the enemy can learn something, but I would think the amount of information would be so small in comparison, that the risk factor just fades away.

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My comment was tongue in cheek. I think the gubmt was more than willing to let nature take its course until some NASA scientists noted the frozen block of (hazardous) fuel might survive re-entry.

Not that long ago...from the LA Times:

http://www.latimes.com/features/heal...,1788175.story

Which just goes to show how quickly LEO objects can de-orbit on their own.