Syzdekistan

The Shuttle has undocked from the Space Station and is scheduled to land in Florida or California tomorrow. The Navy is probably going to take its first shot at the satellite on Thursday. Meanwhile, some modeling on population densities where the satellite could come down (basically between 58° N and 58° S latitude), agree with my earlier estimate that any danger to humans is very remote (link):

Overall, Tim finds the chance that the satellite’s debris will fall in an area with a population density of one or more persons per 1/4 hectare — about the size of the hydrazine contamination zone — to be no more than one-half of one percent. That’s about 5 chances in 1,000. The probability that the debris will come down in an area with 3 persons per quarter hectare is about 2 chances in 1,000.

Here is an interesting description of the SM-3 missile. The SM-3’s warhead contains no explosives. It destroys its target with sheer kinetic energy. It has been tested against short and medium ballistic missiles and has hit its target 12 out of 14 attempts. Interestingly, the Pentagon only has 21 SM-3 missiles in its inventory and will changing the software to intercept a satellite in low earth orbit versus a ballistic missile. Ballistic missiles move much slower. Although they are launched into space, they are sent on a suborbital trajectory which is basically an ellipse that intersects the earth at the target. A satellite, however, is moving much faster and has a trajectory that “misses” the earth at its low point. A satellite is basically moving so fast horizontally that as it falls it misses the earth. (The difference in suborbital and orbital velocity is so large and so difficult to achieve and is why Virgin Galactic is selling suborbital flights and not orbital flights. Yet.) The SM-3 is designed to intercept hot (heated by atmospheric friction on launch) ballistic missiles moving 3-4 kilometers per second and not cold (only heated by the sun) satellites moving at 7-8 kilometers per second. This does make for a more challenging test because functional satellites in higher orbits are moving more slowly.

The shoot down is set for the evening on Wednesday at about 7:30 P.M. PST just west of Hawaii. The Navy issued a Notice to Airman closing the airspace. The attempt will take place during the total lunar eclipse which should make tracking the fragments easier as they head towards central Canada. The NOTAM is to protect aircraft from the reentry of the first and second stages of the SM-3 (and the third stage if there is a miss). The fragments (again, if there is a hit), will generally continue on the same orbit of the satellite but many of them will be slowed and will be dropping out over the next orbit or so which doesn’t pass over many populated areas (link). Here is an animated map of the orbits of the satellite and the Space Station.

Finally, here is a compelling argument on why this whole thing is bad policy (link):

I don’t know how to express the political risk. Not knowing the risk, however, is different from it being “zero” — which is how the Bush Administration, at best, seems to count it. At worst, some members seem to assign a positive value to conducting an ASAT test.

The Chinese will use this to excuse their January 2007 test and, perhaps, future ones. The Russians seem interested in playing along, too. I’d like to be able to argue that they’re wrong; That this is different.

I have argued, in the past, that we have a strong interest in constraining the development of debris-creating anti-satellite weapons. Sadly, our intercept will make that outcome harder to achieve, not easier.

Given the extremely small risk to people on the ground, as well as the three people in orbit, these risks — though difficult to quantify — almost certainly should dominate the discussion.

But what loser is going to go to bat for confidence building measures in outer space when there is a giant tank of hydrazine bearing down on a Cub Scout Jamboree and one really awesome, heroic chance to blow it out of the sky? Hell, I bet the thing explodes into fireworks with red, white and blue stars and streamers like over the Mall on the Fourth of July.

Let’s face it, supporting the shot is the “safe” thing to do. After all, the debris risk will probably work out ok, while we’ll never know if the satellite would have hit a populated area. The cost, in terms of space security, is so difficult to identify, that one can simply explain it away with facile counterfactuals. “Oh, the Russian’s were just looking for an excuse, they would have done it anyway.”

Also, the government hasn’t released the name of this operation yet. Help them out here: The current leaders are: “Operation Hey, We Didn’t Sign a Treaty Against This Shit”, Operation Weenie Wave, and Operation Space Cowboy’s Last Rodeo.

Technorati Tags: Satellite, NASA