Better Safe than Sorry
The news item about the U.S. blowing up a defunct spy satellite in orbit, rather than letting it crash back to Earth, has bugged me since I heard about it. At issue is the fuel tank of the satellite, which contains a chemical named hydrazine, which the government said is poisonous. The government claimed a successful mission, according to various news reports, the other day.
The government's logic (if that isn't an oxymoron) is that, rather than allowing the satellite to crash to Earth, with the potential of the fuel tank not burning up as it passes through the atmosphere, and with the potential of fuel contaminating soil or water or causing injury to humans or other life forms, blowing up the satellite will create small pieces of debris, which almost certainly will burn up upon reentry into the atmosphere. I'm all right with this so far. It's much like the reason why very few meteorites reach the ground vs. the Skylab crash in Australia in 1979. (Humorous note: according to Wikipedia, "An Australian municipality, the Shire of Esperance, fined the United States $400 for littering.") What bothers me is this: what if the unspent fuel is vaporized rather than combusted? Will molecules float through the atmosphere? Will they settle to the ground? Maybe Betty, my astrophysics friend, can educate me.
This article is a follow-up, but note that it includes the phrases, "if not eliminating the risk" and "high degree of confidence". That doesn't sound like 100% to me. Is that still safe?
posted by Captain Chlorophyll @ 12:36 PM
2 Comments:
That's more chemistry or something than astrophysics, so I couldn't tell you for sure, but my sense is that if this stuff disperses high enough in the atmosphere, when it settles to the ground it's going to be diffused so much that it'll be practically undetectable.
And nothing's ever 100% safe. I mean, there's a non-zero chance of all the air around you suddenly ending up on the other side of the room and leaving you to suffocate in unexpected vacuum. Admittedly, that's a googly-squintillion times less likely than things going wrong with shooting down spy satellites. But it's good to keep in mind that perfect safety is a physical impossibility. :)
The hydrazine dispersed in the upper atmosphere. It is a HIGHLY reactive chemical and breaks down before ever reaching the surface.
Hydrazine on the surface is a bad thing. It can make iron oxide burn. If you come into contact with it, please seriously consider never having children; it tends to play with your genetics.
That being said, it does break down rather rapidly and there is no lasting effect to environmental contamination.
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