jamesh
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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 03, 2015 7:03 pm

Electronics in space require special cooling, the ISS for examples has a lot of cooling pipes etc. This is because there is no conductive cooling in space - so things get too hot as they cannot radiate away enough heat. Which is what the conversation above is about.

Look up the different sorts of cooling.
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iinnovations
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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 03, 2015 7:13 pm

MarkTF wrote:
TimG wrote:You cannot count on radiative cooling of electronics in a hard vacuum.

<snip>

As a back of the envelope estimate, one could do Stefan-Boltzmann using the area of the board and total power dissipation (say 0.004 m^2, 2 W, 0.85 emissivity) which gives 320 K for "average board temperature". Assuming the temperature gradients stay the same as in the linked thermal image, the SOC is about 10 C higher and the LAN chip is about 16 C higher. If I haven't bungled the calculation, that puts us remarkably close to normal room temperature operating conditions. That people have done high altitude work with the Pi gives some credence to this estimate.
I did not see this before my post, but this is pretty close to what I crudely estimated.
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afremont
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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 03, 2015 10:02 pm

If anyone is taking bets, my money is on it burning up in stock form when placed in a vacuum and operated at 100% CPU utilization. From what I learned hanging around the PICLIST and the old engineering news groups (anybody remember those things?) is that if it gets warm in air, it will likely be glowing in a vacuum.
"Experience: It's what you get when you were expecting something else"

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iinnovations
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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 03, 2015 10:37 pm

And that is why we don't intuit when doing science and engineering.

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afremont
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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 2:59 am

In case there was a misunderstanding, I wish to clarify that I was NOT slamming or slighting the Pi in any way. That said, I will be surprised if no modifications are necessary unless it was a design consideration from the start. I look forward to the test results. :)
"Experience: It's what you get when you were expecting something else"

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daveake
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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 5:39 pm

I've flown the Pi about 20 times so far, mostly at around 40km altitude (0.3% atmosphere), and no problems at all other than the SD card coming out of a model A when Babbage's 'chute opened and twisted his neck back!

Most flights have been 2-3 hours duration but some have been approx 20 hours.

So not conclusive proof of how the Pi would handle long term vacuum, but a strong indication that short term exposure is no problem at all.

Dave

Heater
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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 6:06 pm

daveake,

At last, the voice of experience. Thank you.

Do you happen to have any logs of board/SoC temperature during a flight to show us?

Certainly you have had the Pi up there long enough to put to bed this Pi cooling in a vacuum issue.

Well, except of course it's damn cold up there....
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3corey2
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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 6:37 pm

it does not work in a vacume, the top of our atmostphere is about -40 degrees CELSIUS, if a electronic gets tooooo cold the electricity cannot flow. my go pro froze when it reached the edge in a weather baloon, handwarmers didnt do the trick... but i did keep it in a air tight container.
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Heater
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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 9:01 pm

3corey2,

Be serious, -40C is a common low end spec. for industrial and automotive equipment. Heck it's a normal temperature in winter around here.

At 40Km up the temperature is said to be -20C. Mind you, you have to pass though a layer of about -60C at 20Km up !

Your GoPro could not handle it. That says nothing about electronics working in a vacuum or at altitude. It says a lot about Go Pro:)

Edit: And what is all this "if a electronic gets tooooo cold the electricity cannot flow"? You do realise that the resistivity of conductors generally goes down with decreasing temperature. Low temperatures may cause problems but it's not so simple as that.
Last edited by Heater on Thu Mar 05, 2015 4:48 am, edited 1 time in total.
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iinnovations
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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 9:27 pm

Heater wrote:3corey2,

You do realise that the conductivity of conductors generally goes down with decreasing temperature. Low temperatures may cause problems but it's not so simple as that.
I think you meant resistivity, but yes:

Image
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W. H. Heydt
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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 9:38 pm

3corey2 wrote:it does not work in a vacume, the top of our atmostphere is about -40 degrees CELSIUS, if a electronic gets tooooo cold the electricity cannot flow. my go pro froze when it reached the edge in a weather baloon, handwarmers didnt do the trick... but i did keep it in a air tight container.
Tell that to the team that used Pis to photograph penguins in Antarctica.

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Re: Does the Raspberry Pi work in a Vacuum?

Wed Mar 04, 2015 9:42 pm

daveake wrote:I've flown the Pi about 20 times so far, mostly at around 40km altitude (0.3% atmosphere), and no problems at all other than the SD card coming out of a model A when Babbage's 'chute opened and twisted his neck back!

Most flights have been 2-3 hours duration but some have been approx 20 hours.

So not conclusive proof of how the Pi would handle long term vacuum, but a strong indication that short term exposure is no problem at all.

Dave
There is a considerable difference between 0.3% of 1 atmosphere and a decent vacuum. Think of it this way...in an actual vacuum, a parachute doesn't work at all.

Meteors become incandescent at altitudes up to 100 Km, and that's well above where any of your balloons have gone, yet it's still enough air to heat a high-speed object.

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Re: Does the Raspberry Pi work in a Vacuum?

Thu Mar 05, 2015 4:44 am

@W. H. Heydt,
There is a considerable difference between 0.3% of 1 atmosphere and a decent vacuum
Yes and no. Depends what's important.

Experiment has shown the Pi can work very well at that 0.3%. As the balloon flights demonstrate. Taking away that last 0.3% of air is not going to significantly change the convective heat dissipation from the Pi. We have already removed nearly a 100% of it's effect.

If we were to be slamming the Pi into that air at ludicrous speed, like a meteorite, we may have an issue :)

@iinnovations

"conductivity", "resistivity", well spotted. I fixed it.
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rpiswag
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Re: Does the Raspberry Pi work in a Vacuum?

Thu Mar 05, 2015 11:20 am

What about for two weeks in near space?
A computer's power can't be just measured Gigahertz. It is the same thing with us humans.

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milkboy007
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Re: Does the Raspberry Pi work in a Vacuum?

Mon Mar 09, 2015 4:08 am

rpiswag wrote:What about for two weeks in near space?
Will it work in weather balloon near space/Stratosphere (~40km above sea), yes
With proper sheilding and other technical consideration & adjustment it will work (like keeping the soc & battery at working temp, thermal sheilding etc .....)
its extremely cold in in that region.
Image
from wikimedia

in lab vacuum with no modification, i wouldn't recommend it
here's the step if you want to try it out
1. ask university near you to let your RPi in their vacuum chamber
2. place RPi in vacuum chamber
3. ????
4. PROFIT!!!!
see http://en.wikipedia.org/wiki/Materials_ ... s_to_avoid

in space, there is the Van Allen radiation, solar storm, cosmicray, Micrometeorite, etc......
those stuff does wonders on RPi :roll:

Mennims
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Re: Does the Raspberry Pi work in a Vacuum?

Mon Mar 09, 2015 4:56 pm

Just a question on the cooling... Couldn't you use a heatsink and a peltier unit? Just out of interest.

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Re: Does the Raspberry Pi work in a Vacuum?

Mon Mar 09, 2015 6:41 pm

Mennims wrote:Just a question on the cooling... Couldn't you use a heatsink and a peltier unit? Just out of interest.
Oh joy, even more heat to get rid of....
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Re: Does the Raspberry Pi work in a Vacuum?

Mon Mar 09, 2015 7:14 pm

Mennims wrote:Just a question on the cooling... Couldn't you use a heatsink and a peltier unit? Just out of interest.
As pluggy indicates, there will be additional heat from the cooling system to get rid of. In space (ultimately) your only way to get rid of heat is radiation. You can move the heat around to a limited extent, but to get rid of it it has to be radiated away and everything that moves the heat around will generate heat on its own...leading to more heat to get rid of by radiation.

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Re: Does the Raspberry Pi work in a Vacuum?

Mon Mar 09, 2015 8:35 pm

Mennims wrote:Just a question on the cooling... Couldn't you use a heatsink and a peltier unit? Just out of interest.
The amount of power that can be radiated in free space goes as the 4th power of the radiator's temperature, so there might be some merit to using a Peltier unit in some application, even at the expense of having more net power to dissipate. That is, you could raise the temperature of the radiator without proportionately raising the temperature of the electronics. It could also give some control over the temperature of the electronics within some designated range by turning on/off the Peltier unit as necessary.

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Re: Does the Raspberry Pi work in a Vacuum?

Mon Mar 09, 2015 11:32 pm

Peltier units are hideously inefficient at cooling, they dramatically increase the overall amount of heat produced for only a small amount of extra cooling. Standard refrigeration technology (compressor - evaporator - condenser) is better by a factor of 4 or 5 over peltier. Their benefit is dubious where getting rid of heat isn't a problem. Turning them on and off is a non starter, if they aren't turned on they are very poor at transferring heat, if they're there they have to be on and working.
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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 10, 2015 7:57 am

Some options here, all of them are probably beyond any practical use for a Raspberry Pi in a vacuum, but useful to understand what options are actually used for cooling in space:

http://www.eng.ox.ac.uk/cryogenics/rese ... plications

Mennims
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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 10, 2015 9:00 am

Very interesting, so peltier is out of the question, so how would you guys recommend doing it? What setup would you use?

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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 10, 2015 10:11 am

I'd stick it in vacuum chamber as is, and keep an eye on the SOC temperature. Don't start working it hard until your monitoring is happy it isn't overheating. See how it goes. If it is getting too warm, stick a big passive heat sink on it to increase the radiation.

The trouble and expense of getting it into a vacuum chamber is going to far outrun the cost of a new Pi if you do happen to destroy it in the process. If it survives in a vacuum chamber at room temperature on he ground, in space where its much colder won't be a problem (for cooliing at least, but I suspect the other stuff going on up there is going to be a bigger problem).

If you don't need the horsepower of a Pi2 get hold of an A+ or a B+ as the amount of heat they can kick out is less. At idle there is little difference but the Pi2 has the capacity to work a lot harder and put out more heat.
Don't judge Linux by the Pi.......
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daveake
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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 10, 2015 1:28 pm

3corey2 wrote:it does not work in a vacume, the top of our atmostphere is about -40 degrees CELSIUS, if a electronic gets tooooo cold the electricity cannot flow. my go pro froze when it reached the edge in a weather baloon, handwarmers didnt do the trick... but i did keep it in a air tight container.
That's the GoPro batteries giving up, not the electronics. I've used GoPros on several flights and they do work, with enough insulation and with a second battery supply as the in-built battery will last no more than 1 hour, because of the cold.

I've never used handwarmers and don't see the need. Some of them don't work anyway at altitude since they rely on oxygen to work.

Also, you are confusing 2 things here - vacuum and cold. The Pi seems fine at 20 hours in 0.3% atmosphere which, pressure-wise, is pretty much a vacuum. A separate question is how cold it can get and still work. The coldest a high-altitude balloon gets to in daylight is -60C, and that happens at about 15km. Night-time at higher altitudes will be similar. I've yet to see a Pi failure in flight, and in a couple of cases there was precious little insulation. With insulation, and a short flight, the Pi won'y get much below zero. However on a longer flight the inside of the payload has much more time to cool, and with a Pi generating heat it will get to within about 20C of the outside temperature, so a minimum of -40C at night.

Dave

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Re: Does the Raspberry Pi work in a Vacuum?

Tue Mar 10, 2015 1:48 pm

Interesting.... What will be the biggest problem? Keeping it cool, or keeping it warm? :)
And, while we're talking space: No problems with radiation?

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