[time-nuts] temperature stability basics

Bob Camp lists at rtty.us
Sat Nov 27 00:03:38 UTC 2010


Hi

The ones I'm talking about aren't used anywhere there's air to create any wind....

Bob


On Nov 26, 2010, at 6:52 PM, J. Forster wrote:

> Not leaf in the ones I've seen. It's very clearly a metalized plastic
> film. Gold leaf has virtually no structural strength. A breeze will tear
> it. I also doubt any tissue paper usage.
> 
> Best,
> 
> -John
> 
> =================
> 
> 
>> Hi
>> 
>> The gold color in a space thermal blanket is from - gold. The normal
>> formula is to use gold leaf and tissue paper (not quite the Kleenex
>> variety, but similar) in layers. The gold leaf is *very* good for IR
>> reflection. The tissue paper is porous  enough that there's very little
>> air trapped in it. The real insulation is the vacuum (courtesy of mother
>> nature). The gold leaf and the spacer material just take care of the IR
>> part of the equation without adding a lot of conductivity.
>> 
>> Bob
>> 
>> 
>> On Nov 26, 2010, at 5:43 PM, J. Forster wrote:
>> 
>>> That's what those golden thermal blankets are on spacecraft and in
>>> cryostats. I'm not quite sure whether the golden color comes from a
>>> deposited film of Au, or whether it's color comes from the Mylar. It's
>>> more likely the former. I've seen the stuff up close, but have not
>>> worked
>>> wit it personally.
>>> 
>>> Anyway, the blankets are made of a mulit-layer sandwich of the film and
>>> something like spider web as spacers between layers. In vacuum there is
>>> no
>>> convective transfer, the spider spacers reduce conduction, and the
>>> metalization reduces radiation.
>>> 
>>> Best,
>>> 
>>> -John
>>> 
>>> ============.
>>> 
>>> 
>>>> 
>>>> namichie at gmail.com said:
>>>>> Find some closed cell polyethylene that is quite thin and some very
>>>>> light
>>>>> aluminium foil and you could make many layers.
>>>> 
>>>> How about aluminized Mylar?
>>>> 
>>>> If the many-reflective-layers idea really works, I'd expect somebody to
>>>> sell
>>>> foam built that way.  Why don't they?
>>>> 
>>>> --
>>>> These are my opinions, not necessarily my employer's.  I hate spam.
>>>> 
>>>> 
>>>> 
>>>> 
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>>> 
>>> 
>>> 
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> 
> 
> 
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