[aprssig] Balloon warmth

[david Vanhorn]

Look up stablcore.  Carbon fiber lam.  I did some 10 layer boards with this for heat spread and surviving 2000 g impacts..  30 ft drop to concrete.




-- Sent from my Palm Prē
On Mar 24, 2010 9:27, Scott Miller <scott at opentrac.org> wrote: 

The sodium acetate ones are heavy, though.



If I can find board space for the traces, I'm thinking of scattering a 

few big flat SMT resistors around the board.  The CR123A cells can put 

out 1500 mA continuously, so I could easily get a few watts of heat as 

needed.  I wish metal core PCBs were a little cheaper - that might help 

spread the heat around better.



Scott

N1VG



Steve Noskowicz wrote:

> 

> 

> The sealed plastic pouch versions don't use air.  It is a reversible exothermic chemical reaction.  This is the ones with the metal popple disk.

> 

> I think they have a super saturated solution of an acetate salt, perhaps sodium acetate.  There's several YouTube videos showing the process - ad nausium...

> 

> at fractions of an inch of mercury the Iron compound versions will die.

> 

> 

> -- 73, Steve, K9DCI

> 

> 

> --- On Wed, 3/24/10, Scott Miller <scott at opentrac.org> wrote:

> 

>> About a dozen people have suggested

>> this, but I'm not convinced the oxygen level is

>> sufficient.  I do happen to have a vacuum chamber in

>> the shop, so once I get a functioning payload again I'll

>> have to throw a few of those in there and compare the heat

>> generated to a control at 1 atmosphere.

>> 

>> Scott

>> N1VG

>> 

>> AD4BL wrote:

>> > An alternative to keeping equipment warm on a balloon

>> flight is to use the hand warmers.   They

>> last about

>> > 8 hours and provide enough heat to keep equipment

>> operating in a cold environment.

>> > 

>> 

>> 

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> 

>       

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