I think you are largely correct that the safety of people on the ground
is a minor component of the decision to fragment this satellite. That
said, however, the behavior of decaying space debris isn't all that
different from the behavior of a meteor. Just as the interior of a
meteorite isn't significantly heated during its passage through the
atmosphere, the interior of debris need not reach high temperatures
during decay. We know nothing about the location of the fuel tank in
this satellite, but if it's buried inside, I think it is at least
possible it could survive to the ground intact.
I recall that nematodes for biological experiments aboard the Columbia
shuttle survived reentry.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
----- Original Message -----
From: "Francis Graham" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Saturday, February 16, 2008 1:51 PM
Subject: Re: [meteorite-list] DoD To Engage Decaying Satellite
There is just something not right about the
assumptions in this press release; take it from an old
amateur rocket man.
Hydrazine boils at 114 Celsius. If the tank
containing it re-enters, it is almost certain to heat
up and boil the material, overpressure the tank and
explode long before reaching the ground.
If a fissure develops in the tank, and hydrazine is
exposed to the oxygen in the air, even in the
stratosphere, it will blow up at just above body
temperature, 37 Celsius.
The chances of any hydrazine reaching the ground,
and spilling out after impact, is zero I would think.
It's not really a credible danger.
There may be other perfectly valid reasons why the
DoD might want to destroy this satellite. Target
practice is one. And there may be perfectly good
reasons why they might not want souvenir hunters
picking over the wreckage if it lands. It's a
top-secret spy satellite, after all. Photos of the
wreckage could be used to understand surveillance
limitations and abilities. This is something the North
Koreans probably would like to know. These are very
good reasons for asking the public to stay clear.
But hydrazine after re-entry? No, I don't think so.
I realize I'm a bit controversial on this. So if any
of you folks want to point out why I could be wrong,
please do. But I think that hydrazine simply would not
survive re-entry.
Francis Graham
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