February 15, 2008

Space, The Final Frontier

From the New York Times:

“If we fire at the satellite,” he said, “the worst is that we miss. And then we have a known situation, which is where we are today. If we graze the satellite, we’re still better off, because likely we’ll still bring it down sooner, and therefore more predictably. If we hit the hydrazine tank, then we’ve improved our potential to mitigate that threat. So the regret factor of not acting clearly outweighed the regret factors of acting.”

Some time in the next two weeks the U.S. is going to try to intercept a misbehaving spy satellite with a missile fired from a ship stationed in the North Pacific and smithereen the thing before it falls to earth. Doing so will represent a field test of the U.S.'s anti-ballistic missile system.

The Chinese will be watching. Like the United States, China is gung-ho on militarizing space. It shot down a satellite last year without feeling the need to give the test of its ballistic missile capabilities the humanitarian spin the United States seems to feel so necessary as it goes forward with its own forthcoming test. The implied position of the United States is that it is doing the world a favor by attempting to rid it of the danger posed by the satellite, destroying it there before it destroys us here, which is a known inclination of its foreign policy lofted up to space in this instance.

The rationale for shooting at the satellite instead of letting it descend to earth on its own inevitable path trades on the supposed danger of allowing the fuel tank, full of hydrazine, to crash to earth unimpeded. Hydrazine is a colorless toxic liquid with basic properties similar to those of ammonia, though 15 times weaker. In nature hydrazine is ready to do chemical business at a moment's notice with a wide range of commonly available elements, recombining rapidly in air and water with other loose molecules to form a characteristic batch of less toxic compounds and give off a lot of energy to boot. Well, it's an explosive. Prolonged exposure to hydrazine is bad. Acute exposure to a bunch of it is definitely not recommended.

Those of us who remember the equanimity with which the United States greeted the anticipated reentry of the 83 tons of Skylab back to earth in 1979 will appreciate the marked shift in official U.S. policy represented by this new approach. Back in the day, technology and the ABM treaty did not allow for the deployment of missile systems capable of blasting satellites out of the sky. But Ronald Reagan gave the giddyapp to the technology by his Star Wars initiative, and George Bush removed the United States from the ABM Treaty in 2002, so that now, fruit of all that effort, the United States is going to give itself a few tries at plinking the satellite as it passes overhead, a defining moment in its march to space.

In the Times article, David C. Wright of the Union of Concerned Scientists allows as how the proposed missile strike could create 100,000 pieces of debris, some "small as a marble but still dangerous to vehicles in space." It's unquestionable that if the satellite is destroyed by a ballistic missile strike, some of its debris will be propelled into higher orbit around the earth, though presumably not into the path of working satellites up there (speed up an object in space and it assumes a higher orbit. Slow the thing down and it goes to ground. This rule of thumb is repeated over and over again in some novel or other of Heinlein's). Should the test succeed it remains to be seen how long it will take for the sky to rid itself of these 100,000 or so pieces, which will presumably slow and fall to earth of their own accord sooner or later, creating in the meantime their own little region of danger for any object that might care to cross it, a new neighborhood of space populated by small marbles of material traveling in some alternate direction at relatively great speed. Travel is likely to be harmful in that neighborhood for some time.

The worst case of course would be for the ballistic missile to merely wound the tank of hydrazine, causing it to spit its load of caustic liquid in a fine mist onto the ozone layer below, although I'd be willing to be told that this is chemically and indeed astronomically impossible.

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