Author Topic: How to maintain operating temperature for outer space electronics ?  (Read 7711 times)

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Offline BravoV

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How those satellite engineers design the system that can maintain the electronic components within their safe operating temperature while at outer space ? Satellites for example, they work in both extreme temperatures, super hot when there is a sun or super cold when in the dark.  Or the outer space objects or probes that are constantly exposed to the sun ?

Are there other special techniques or something that is not commonly used ?

To be honest, its getting dizzier when it comes to think about temp co or the risk of too many extreme temperature cycling that may affect the temperature hysteresis and etc.
 

Offline Simon

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #1 on: January 26, 2014, 06:26:54 am »
hm thats interesting, never really thought about it. They could have put the electronics in a well insulated case and heat it to the right temperature
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Offline BravoV

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #2 on: January 26, 2014, 06:32:52 am »
They could have put the electronics in a well insulated case and heat it to the right temperature

Ok, what if its constantly exposed to the sun ? How to dissipate the heat or the "accumulated" heat ? Its not like on earth where we can use convective heat transfer like through the air in the atmosphere.

Remember, its vacuum out there, an almost perfect heat insulator.  >:D
« Last Edit: January 26, 2014, 06:34:48 am by BravoV »
 

Offline Simon

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #3 on: January 26, 2014, 06:35:05 am »
what about reflectors ? put the electronics behind the solar panel that is powering it, after all a vacuum is an insulator so as long as the suns rays do not beat on it all is well ?
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Offline BravoV

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #4 on: January 26, 2014, 06:39:54 am »
what about reflectors ? put the electronics behind the solar panel that is powering it, after all a vacuum is an insulator so as long as the suns rays do not beat on it all is well ?

Ok, lets say you have a 100% reflection (which I doubt it), but still, the electronics components still dissipate heat no matter how efficient it is (never 100% right ?), so how to "move the heat" out of the components so they stay within safe range ?
 

Online IanB

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #5 on: January 26, 2014, 06:40:52 am »
Thermal management in space is all about radiation. You point the things you want to cool down towards outer space, which is at a temperature of just a few Kelvin, and you protect the hot sun-facing side with reflective foil and insulation.

For a thought experiment: place the side with good insulating tiles towards the sun. Place the side with good heat conduction and radiation properties away from the sun. If you now look at the thermal profile, the side of the insulating tiles away from the sun will be quite cool.

Objects like satellites in space do not rotate and spin randomly. They always have their orientation precisely controlled, and they always have exactly the right side pointing towards the sun.
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Offline Greg Robinson

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #6 on: January 26, 2014, 06:41:19 am »
This documentary has some information on the subject.
 

Offline dfmischler

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #7 on: January 26, 2014, 10:03:22 am »
I remember when I found out that the first Mars rover (Sojourner) had a Warm Electronics Box heated with a plutonium isotope (Pu-238) to keep the electronics working.

Sojourner Mars Rover Thermal Performance paper
« Last Edit: January 26, 2014, 10:11:03 am by dfmischler »
 

Offline Rerouter

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #8 on: January 26, 2014, 10:10:40 am »
equally and they found this out with the voyager probes, the heat from the electronics does generate an incredibly tiny amount of thrust, causing the probes path to curve if more heat it expelled out one side than the other, it also means that by constantly cooling away from the sun you would eventually decelerate and start accelerating back towards the point of origin if the power source lasted a few centuries.
 

Offline wilfred

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #9 on: January 26, 2014, 10:31:24 am »
This documentary has some information on the subject.


The discussion on heat is at about 37:00. It also shows how to tilt a satellite properly. Some may recall a recent thread here where a satellite fell of the mount because it wasn't properly secured.
 

Offline Skimask

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #10 on: January 26, 2014, 10:33:31 am »
equally and they found this out with the voyager probes, the heat from the electronics does generate an incredibly tiny amount of thrust, causing the probes path to curve if more heat it expelled out one side than the other, it also means that by constantly cooling away from the sun you would eventually decelerate and start accelerating back towards the point of origin if the power source lasted a few centuries.
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I didn't take it apart.
I turned it on.

The only stupid question is, well, most of them...

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Online IanB

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #11 on: January 26, 2014, 10:52:41 am »
equally and they found this out with the voyager probes, the heat from the electronics does generate an incredibly tiny amount of thrust, causing the probes path to curve if more heat it expelled out one side than the other, it also means that by constantly cooling away from the sun you would eventually decelerate and start accelerating back towards the point of origin if the power source lasted a few centuries.

Conversely, the radiation from the sun hitting the space craft can impart a tiny amount of momentum in the other direction. This is the origin of the solar sails concept.
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Offline Rerouter

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #12 on: January 26, 2014, 11:02:41 am »
If you really wanted to get scifi, the concept of a neutrino sail would magnitudes more effective, just need to find out how to force them to react with matter at a much higher rate,
 

Offline NANDBlog

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #13 on: January 26, 2014, 11:51:02 am »
If you want well documented essays about the topic, read some "cubesat" documentation. It is a platform for universities to send a satellite not bigger than 100mm into orbit. Some of them are there for years. Since it is uni, it is well documented.
 

Offline Kohanbash

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #14 on: January 26, 2014, 11:52:24 am »
Hi
As IanB said one of the primary ways to control temperature is by controlling which surface is pointing to the sun and which surface is pointing to space (radiator panel). All of the thermally sensitive devices are directly heat piped (metal/carbon connections) to the radiator panel

On a past project we spent awhile working on a project that had solar panels on four sides. We loved the design since we could always get power from the sun and we could be in any orientation. Unfortunately one of our thermal engineers said it would not work since we would not be able to cool the system since the black (dark blue) solar cells would not radiate enough heat away. So we ended up making two sides (approximately) with solar panels and the other two sides white to help radiate the heat into space.

For the opposite extreme when it gets cold we also put heaters on certain (typically external) components such as the cameras, motors, and science payloads). We also use MLI (its the gold foil you see on satellites) to prevent heat loss via radiation.

Some systems that use a radioisotpes with an RTG can use the power produced to charge the batteries and then use the heat produced to keep the system warm. Depending on the RTG you can heat-pipe the heat to specific regions that need to be cool. The early lunokhod moon rovers had a lid that they would close at lunar night to stay warm and then open during the lunar day in order to not overheat.
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Offline G7PSK

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #15 on: January 27, 2014, 02:35:30 am »
There ought to be an EEVblog satellite It seems that they are very cheap to make now.  http://www.50dollarsat.info/
under $250 to make but they don't say what the launch cost is.
« Last Edit: January 27, 2014, 02:39:40 am by G7PSK »
 

Offline SeanB

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #16 on: January 27, 2014, 02:44:51 am »
Estimate at $10 000 per kilo, but if you can get space and fit in as a ballast mass on a launch ( they actually do add ballast mass to do compensation for uneven satellites or to trim to a specific launch vehicle charactaristics ) along with having something the launch operator thinks is cool, and are prepared to wait and not care much about orbit then it can be a lot cheaper, or even free. A lot of picosats and microsats go up that way as part of another paid for load. Less steel blocks to machine, and so long as you are not a bother and will not interfere with the main payload you are cheap to add. You might have to pay for the added mounting fixtures, testing and release mechanism to free you from the second stage booster before it is deliberately deorbited.
 

Offline Nerull

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #17 on: January 27, 2014, 03:41:14 am »
If you really wanted to get scifi, the concept of a neutrino sail would magnitudes more effective, just need to find out how to force them to react with matter at a much higher rate,

Sure, but that's essentially in the realm of 'magic' sci-fi, at least for now. Solar sails could be built today, if we really wanted to.
 

Offline BravoV

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #18 on: January 27, 2014, 04:07:50 am »
Thanks for all replies guys, much appreciated !   :clap:

Special thanks to Greg Robinson for that BBC video, it simply answers lots of my questions, and dfmischler for that Sojourner Mars Rover Thermal Performance document.  :-+

Just knew that those shiny heat protection golden foils are actually made from Kapton + aluminium foil.  :o

For geostationary orbit satellites, I guess the design and calculation for the ratio for the hot and cold sides area is really critical isn't it ? Apart from the daily routine that it must cycle through day (facing sun) and night (behind the earth) and extra occasions that will last for quite sometime like during total sun eclipse.

I'm imagining if there is a problem at one of those small rocket thrusters that are maintaining the satellite orbital position and the "orientation" went crazy, and ended up turn it up side down that made the cold side facing the sun while hot side facing outer space for long period, magic smoke ?  >:D
 

Offline SeanB

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #19 on: January 27, 2014, 04:17:55 am »
Rocket thrusters are there but are very rarely used, as they have a very finite fuel supply ( and you do not have an easy way to go put more in the tank either) so almost all orbiting satellites have reaction wheels to do orientation changes to point solar panels to the sun or aim antennas at a particular point. They work by storing up momentum in 3 flywheels that rotate the satellite around it's centre of mass to point in the right direction. Eventually you build up enough momentum that you have to dump it by using a series of thruster burns to counteract the change in wheel rotation and then you gradually build up again. Typically they only want to do this less than once a month to conserve fuel. As the fuel consumption is measured in grams per month and there is typically only 100 kg which is there for all manoeuvring including orbit changes and it has to last 15 years minimum and preferably 25 years using 3g a day will lead to a short life.
 

Offline BravoV

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #20 on: January 27, 2014, 04:24:50 am »
Fly wheel ? Don't see that in the BBC video ?  ???
 

Offline SeanB

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #21 on: January 27, 2014, 04:38:33 am »
There in the base unit as reaction control, placed pretty close to the middle of the platform. Right next to the 3 accelerometers and the ring gyros.
 

Offline DutchGert

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #22 on: January 27, 2014, 09:59:48 pm »
With CubeSats they use reflective shielding as a main protection against heat.

Another problem is the low-orbit they usually fly in which means there temperature cycles is  from -xx to +1xx a few times up to a couple of 10 times a (earth) day.... This means your PCB and components get heavvy stresses due t bending etc.
Therefore they generally don't use BGA's or QFN type packages because the soldering joints would just break. Using quad flat packages with leads and special solder technigues solves a lot of the reliablity problems in this area. 

And ofc, do not use an Electrolytic  in space...  >:D
 

Offline SeanB

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #23 on: January 28, 2014, 05:42:34 am »
You can use wet slug tantalum with no problems, just derate them a lot. They are the only high value capacitors available in a glass frit hermetic can. Biggest problem is getting heat out, as you only have conduction or direct radiation.
 

Offline DavidGoncalv

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Re: How to maintain operating temperature for outer space electronics ?
« Reply #24 on: January 29, 2014, 01:11:55 am »
I worked on a cubesat some time ago, and worked on making a small radar experiment for it with a bunch of local guys. It was a very cool opportunity. I worried a bit about the heat buildup from the power regulation our board needed, characterizing the frequency of the crystal at the range of operating temperatures, and including a temperature monitoring thermistor... but in the end the board was a tiny fraction of the power budget and the remaining electronics, batteries and charging circuits kept the inside of the cube at a fairly limited range of shirtsleeve temperatures. Lucky us!
 


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