Missile shootdown

Is this not perhaps a cover story for a demonstration to China that we have the capability to shoot down satellites too, just like they demonstrated last year?

More than likely:

The Pentagon says it has to shoot down a malfunctioning spy satellite because of the threat of a toxic gas cloud. Space security experts are calling the rationale highly unlikely. "Having the US government spend millions of dollars to destroy a billion-dollar failure to save zero lives is comedic gold," one tells DANGER ROOM.

http://blog.wired.com/defense/2008/02/fishy-rationale.html

Is this not perhaps a cover story for a demonstration to China that we have the capability to shoot down satellites

I haven't followed this story, but when I first heard about the planned shootdown, I thought, "Interesting, SDI is testing a new ASAT system." What's news to me isn't _that_ rationale, but rather the proferred one. Toxic gas cloud? Well, at least it's worth a few laughs.

If this is what deterrence is all about, then stop bitching about Iran's nuclear program.

I don't care if it was No. 1 or No. 2 ... but I would be happier to think it was No. 2, given how expensive this thing was to shoot down.

You may be right about the demonstration part of this hit.

The physical consequences of the space junk created by the two missle hits are quite different, however. The Chinese satellite was in a much different orbit meaning that the space junk will be flying around up there for years and maybe even decades posing a risk to manned and unmanned space flight. The very low orbit of the Pentagon's junk satellite means that the debris will re-enter and burn up in a matter of days or several weeks at most. The low orbit also means that the debris created poses no threat to any manned or unmanned space flight because nothing orbits that low (for long).

It is a good target for such a demonstration, whether or not that is what it is about.

Actually, the ful was hydrazine...quite different.

While the shootdown was fairly impressive, it is important to remember that shooting down a satellite whose exact trajectory has been known for years, which was the size of a bus, and which carried no counter measures is quite different from hitting a vastly smaller warhead, whose trajectory is not as well-known to us, and which may be carrying countermeasures and stealth technology to help it evade destruction.

The suitcase nuke is pretty much a myth.

I'm no expert, but compact, low-weight nuclear weapons seem at least somewhat plausible; see here, for instance:

www.milnet.com/nukeweap/suitbomb.htm

a state would be beyond foolish to turn one over to a third party to use for their own purposes, especially since the party at the receiving end could figure out where it came from.

I was referring not to terrorists, but rather military or intelligence agencies of the various "nuclear pipsqueaks". By "suitcase nuke" I was simply referring (rather sloppily, in retrospect) to a nuke covertly delivered, e.g., aboard a civilian cargo aircraft or container ship. Such methods would seem to be well within the capabilities of the "nuclear pipsqueaks".

ex-Soviet weapons that may have gone on the black market have long exceeded their shelf life.

If the fissile material can be extracted from such weapons in usable form, then they are still problematic. As I understand it, the availability of HEU or Pu, not technical expertise or non-fissile components, is the main stumbling block in nuclear weapons acquisition.

My guess is that it was simply a ripe target for a series of killsat tests. The US has been developing anti-satellite weapons for decades now, and, hey! there's a dying Keyhole floating around (and it's big!), so let's shoot that one down.

The hydrazine rationale is a bit weak to me. The tank would likely rupture, and the fuel would burn up in re-entry. The risk of human casualties seems microscopic. Keeping our tech out of curious hands seems more likely.

As for the political dimension, it doesn't hurt as a demonstration. It's going to suck, though, for our satellite-networked troops someday if an enemy starts popping our satellites (developed in a killsat arms race).

Greg covered this, I'm filling in a few details.

First, the Chinese shootdown. The target was the FY-1C at 865 km / 537 mi above sea level, in a polar orbit. There is hardly any atmosphere at this altitude, and the debris will stay in orbit a very long time.

For the American shootdown, the satellite was USA 193, aka NROL-21. It was in a decaying orbit. It was intercepted at an altitude of only 247 km / 153 mi. This was much lower, and the air was much more dense (though I still wouldn't want to try and breathe up there). The pieces will be subject to atmospheric drag, and from what I've read, should be just about all down in about forty days.

In 1985, the US conducted an ASAT test against the Solwind P78-1 satellite orbiting at 555 km / 345 mi. Debris was predicted to still be in orbit through the 1990s. The additional solar heating in 1985 accelerated the decay of the debris as well.

For comparison, the space shuttle operates from 185 to 960 km, or 115 to 596 mi. The ISS orbits at 350-460 km or 189-248 mi. The US operation will not endanger shuttle operations as the debris will clear itself; the Chinese one may, especially as the orbital debris drifts further and further apart.

Based on the construction of USA 193, it could be realistic for the fuel tank to survive entry intact. First off, the entire satellite was, according to what I've heard, about the size of a bus. The fuel tank could have been roughly central to the satellite, which would mean that when re-entry did occur, there would be a lot to burn off before the tank started getting hot. Also, the surrounding structure could act like the ablative heat shields on our Mercury, Gemini, and Apollo spacecraft (it loses pieces to carry heat energy away from the capsule). That could make for an intact tank hitting the ground, and bad news for where ever it happened.

That being said, I think there were additional motivations for the destruction of USA 193. First, a "we still got it" thumb-in-your-eye to China; second, avoiding giving up technical secrets to any who would use them against us; and third, a great propaganda point in favor of ballistic missile defense.

All in all, a great success for the US military.

My thinking is it was shot down because it has sensitive tech that we don't want in the wrong hands.