[time-nuts] temperature stability basics

[J. Forster]

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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