Monday, September 26, 2011

UARS: Why Another Uncontrolled Satellite Crash?

Saturday, the 6-ton UARS satellite crashed. No one is sure exactly where: the odds say it crashed in the Pacific Ocean, but the uncertainty says some debris might have come down over the Pacific Northwest.

Official estimates were that about half a ton of this satellite would crash to Earth in 26 pieces, one as large as 300 pounds or so. My own estimate of surviving debris mass is larger.

I’ve been watching satellites and satellite re-entries all my life. In all those years, no person has been hurt, because most of these hit the sea (the only victims being fish).

But the risk is still there. So, why do we continue launching satellites that can crash uncontrolled? That's a good question!

Our 85-ton Skylab space station crashed onto Australia in 1979, leaving lighter debris on rooftops in a coastal town, with the heavier pieces carrying further inland. About 75 tons were eventually recovered!

Before that crash, the “official wisdom” was that it would mostly “burn up”. It clearly didn’t do that. Had its debris field been more centered on that Australian town, it is likely someone would have been hurt or killed.

That same year, the 10-ton Pegasus 2 satellite also came crashing back to Earth. This one hit the ocean, as do most.

In 1978, the Russian satellite Cosmos 954 crashed to Earth in north-central Canada. This one was the special case of a nuclear reactor-powered satellite, for which the preferred disposal method (a really high, decay-proof orbit) failed. There was serious radioactive contamination over an area of back-country Canada hundreds of miles wide.

And, most folks remember vividly the crash of Space Shuttle Columbia in Texas in 2003. Again, there were a lot of pieces, some quite large, on the ground from Dallas to Tyler. No one on the ground was hurt, but they very easily could have been.

In contrast, the Russians deliberately crashed their Mir space station into the Pacific in 2001. They used a rocket motor to de-orbit the station and put it down exactly where they wanted: away from land and people.

Excepting disasters and reactor disposals, most satellites could (and should) be equipped with a small rocket motor for a controlled crash in a safe place. Small solid rocket motors are cheap, light, compact, widely available, and they last for decades without any maintenance, waiting to be used.

So why don’t we do this, especially considering the nail-biting experience with Skylab?

Simply because no rule says we have to. That’s something very easy to fix, and without a new law.

For civilian / commercial satellites, the Federal Aviation Administration (FAA) should simply require controlled de-orbit provisions. It’s their jurisdiction and they already have rule-making authority. A word from the President to do it, is all it would take.

For military satellites, a simple order from the Commander-in-Chief is all that is needed.

Mr. President, fix this. Give the word to the FAA and the Joint Chiefs. I bet most of the other satellite-launching nations would soon follow suit.

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