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Re: Electronic components might survive lunar temperatures

Interesting and creative test method.  Definitely a gold start for 
effort .. ;-)

But .. the thermal cycle a device on the lunar surface is typically 
going to be looking at is about 2 weeks at +200 or thereabouts, 
followed by about 2 weeks at -200.  The temperature isn't the killer, 
it's the duration of exposure to each extreme.  And the fact that the 
components will be operating in a vacuum and will only be able to use 
conduction and radiation to get rid of internally generated heat.  I'm 
pretty sure most semiconductor components will tolerate an hour or two 
at 200 F, but a continuous soak of 14 days would probably kill just 
about anything on the market.  Hopefully I'm wrong.

It's possible that behind some sort of shield that would block direct 
sunlight the internal modules would not be heated nearly as much as the 
exterior of the package, but this would require extremely careful 
design .. over a 14 day heat soak even well isolated parts of the 
package would be heated pretty significantly.  Getting through the dark 
period would be somewhat easier IF there's some source of power that 
can keep it going "overnight" to generate heat.  That source of power, 
for obvious reasons, would have to be something other than PV, and I 
won't stir up the whole RTG hornet's nest again except to say that 
that's about all that works through the lunar night.

Basically, good work, but far more extreme engineering is going to be 
needed before this thing flies ..

> Today I did some tests with normal components expossing to 200C for a 
> period of 2hours (in mothers oven). I tested four BF968 PNP 
> transistors (I got many for free from a friend, so nothing to loose 
> :-) an 1206 metal-film SMD resistor, two crystals and a 1N4148 diode.
> Because I can not take my lab to the kitchen (where is the oven) I do 
> only test if the components survive a 200C temperure without 
> operation. The results were very good :-) After 2hours of 200C I 
> tested the baked components again and I could not find any difference. 
> This means that "normal components" might survive a 200C moon period 
> without operation. For a moon station it means that it can switch of 
> at to high temperatures and switch on again when the temperature is at 
> acceptable level to do operation. (some kind of none electronical 
> device like a bi-metal could do the job :-)
> Actually I expected the transistors to be internally damaged. Maybe 
> longer exposure will damage them as well, but thats for furter tests. 
> Now +200C might be possible, the next unknown is -200C :-(
> I'm still thinking out how to test this... its to cold for my refridge 
> unfortunatly.
> Maybe someone has more information about the "surviving of components 
> under extreem temperatures" ? (not operation but storage 
> temperatures!!)
> The components survived well but a bigger problem was the soldering.
> After a while some components became unsoldered, and I know that tin 
> gets brittle after many times changing from hot to cold. I'm also 
> looking for some way to overcome this problem, but I guess this is a 
> much bigger problem than the components.
> Somehow there will be a way to overcome all problems, and we will 
> finally have our lunar-sat :-)

Version: PGP 8.0


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