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From: Mark Sienkiewicz (no email)
Date: Tue Jun 04 2002 - 15:17:34 EDT
At 02:09 PM 6/3/2002 -0500, Keith wrote:
>I'd be a bit skeptical about this thing. While it's better than nothing,
>it doesn't really have any insulation. Looks like "space blanket"
>material to me, essentially metallized mylar with some backing and
>reinforcement. Technically, it'll reflect radiated heat back to you, but
>without any type of insulation, I still think the heat loss will be
>pretty darn close to what you would experience just being in the water
>with a trash bag around you.
If you have a typical sheet of mylar against your skin, it provides almost
no insulation at all. To make it work, you have to keep some air in the
bag with you. Of course, you will still lose heat through contact with
whatever you are sitting on, but that's a lot better than losing heat all
around. And it is very good at keeping the wind off.
This device is not just a sheet of mylar, though. There is a sheet of
mylar in it, but also other material around it, which apparently helps
insulate against conductive heat loss. Their specs only show "body
temperature was maintained during 90 minute live tests" in 50 F / 10 C
water. We don't know the actual survival time in various conditions, but
as you said, it is better than nothing.
>Another bothersome thing on their website is the ad for the same product
>being able to totally hide you from infrared scanners. They claim that
>if you sleep with the camo side out (metallized side in) that there is
>ZERO IR emission, making you invisible to IR scanners. Hey, guess what
>some rescue units use? IR scanners to see a heat signature.
Of course, anything that insulates you well is going to reduce your IR
signature. If you want to radiate some heat, you can always keep part of
your body outside the bag. (In fact, there is such a thing as being "too
well insulated", so you might want to do that anyway.)
>They also claim that radar can pick up the metallized surface. Under the
>water? Sounding a bit like snake oil to me.
It doesn't say underwater; it says "in the marine environment". They are
acknowledging that you don't use radar for search and rescue of hikers in
the mountains, but you do use it when you're looking for a life raft.
Of course, it all comes down to economics. This bag is better than
nothing, but not better than the solution that costs 10 times as much (i.e.
a gumby suit). I suspect for 100 times as much, you could have a James
Bond style escape pod constructed. For even better safety, you could stay
on land. When you look at all the options, none is perfect.
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