I think the idea was to have an air vent in the bottom so we lose our coolest air first going up. If we got a one way valve in there, it'll cause the mylar to get sucked up against stuff on the way down, which I consider not so much of a bad thing either. Vacuum packed! At the very least it'll prevent condensation. It should also keep quite a lot of heat in still, although it would circulate considerably less.<div>
<br></div><div>What would be the best method to seal it? Can we do a melted heat seam? Sew it a mylar sweater!<br><div><br></div><div>Christie<br clear="all">_______<br>"We also briefly discussed having officers replaced by very small shell scripts." -- Noisebridge meeting notes 2008-06-17<br>
<br>The outer bounds is only the beginning. <a href="http://www.flickr.com/photos/genriel/sets/72157623376093724/">http://www.flickr.com/photos/genriel/sets/72157623376093724/</a><br>
<br><br><div class="gmail_quote">On Wed, Mar 10, 2010 at 11:29 PM, Mikolaj Habryn <span dir="ltr"><<a href="mailto:dichro@rcpt.to">dichro@rcpt.to</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Will mylar hold much of a pressure differential? Or is the plan to<br>
line a foam cavity with mylar? I'm not sure we need to worry too much<br>
about heat loss through the foam, so I assume you're thinking of using<br>
the mylar to prevent convective heat loss through the cracks? Is there<br>
an easy way to prevent overheating as well?<br>
<br>
Tapping the radio battery triggers my recovery paranoia; if we have<br>
the weight budget to spare, I'd feel safer if we avoided tampering<br>
with the position reporting dependencies. For all the SMS stuff worked<br>
flawlessly last time, we'll be flying new software and if something<br>
goes wrong with it, the radio beacon will be the only way to find the<br>
payload.<br>
<font color="#888888"><br>
m.<br>
</font><div><div></div><div class="h5"><br>
On Wed, Mar 10, 2010 at 8:07 PM, Christie Dudley <<a href="mailto:longobord@gmail.com">longobord@gmail.com</a>> wrote:<br>
> While antifreeze sounds like a neat idea, vaporization is not the problem so<br>
> much as pressure/thinned atmosphere. Think pv=nrt sort of deal, keeping in<br>
> mind those phase charts from chemistry.<br>
> Christie<br>
> _______<br>
> "We also briefly discussed having officers replaced by very small shell<br>
> scripts." -- Noisebridge meeting notes 2008-06-17<br>
><br>
> The outer bounds is only the beginning.<br>
> <a href="http://www.flickr.com/photos/genriel/sets/72157623376093724/" target="_blank">http://www.flickr.com/photos/genriel/sets/72157623376093724/</a><br>
><br>
><br>
> On Wed, Mar 10, 2010 at 7:57 PM, Albert Alexander<br>
> <<a href="mailto:albert.alexander@gmail.com">albert.alexander@gmail.com</a>> wrote:<br>
>><br>
>> Dear mod(s): Please disregard prev. email, accidentally sent as<br>
>> non-member.<br>
>><br>
>> Here's what we did and thought about on Tuesday.<br>
>><br>
>><br>
>> THE FIGHT AGAINST CONDENSATION<br>
>><br>
>> The internals of the payload will be contained in a mylar envelope. This<br>
>> will provide a continuous thermal space that retains a LOT of heat (space<br>
>> blankets claim something like 90%). I'm still investigating the energy<br>
>> required to keep this space above dew point. That would prevent condensation<br>
>> (hopefully).<br>
>><br>
>> Still working on whether we should add a battery dedicated to warming. I'd<br>
>> much rather tap a camera or radio battery to avoid the extra mass. On first<br>
>> glance the radio battery looks like a prime candidate (low drain long life)<br>
>> and is least likely to automatically shut off if it gets hot.<br>
>><br>
>> Indium Tin Oxide film (ITO) is enroute courtesy of Bayview Optics. This<br>
>> will heat the lenses with a thermistor circuit. There is a cup in my freezer<br>
>> with antifreeze on it to test evaporation rate; this could be an acceptable<br>
>> passive substitute for lens heaters depending on the distortion (its kinda<br>
>> viscous).<br>
>><br>
>> Camera circuits will be sealed with a conformal coating. Silicone looks<br>
>> ideal. Hopefully will have some by Sunday for further testing.<br>
>><br>
>><br>
>> THE PAYLOAD<br>
>><br>
>> Styrofoam was cut and beveled with the classy new wire cutter. A camera<br>
>> port has been added. The payload looks fairly anthropomorphic now. It needs<br>
>> a name.<br>
>><br>
>><br>
>> COMLINK<br>
>><br>
>> Antenna was bound to carbon rods with thread.<br>
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>><br>
><br>
><br>
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</div></div></blockquote></div><br></div></div>