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How to survive a lunar night?

Posted by: spaceratz - Fri Jan 28, 2011 4:14 pm
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How to survive a lunar night? 
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Post How to survive a lunar night?   Posted on: Fri Jan 28, 2011 4:14 pm
At the Google Lunar X- Prize there asking how to make a rover survive a lunar night.
http://www.googlelunarxprize.org/lunar/teams/part-time-scientists/blog/survival-of-the-fittest
I already submitted my suggestion but are uncertain if it would work. The basic idea is to have something that protects the rover at night like the lander that keeps it warm.
I think a lander should have sufficient power to heat the rover or even provide some isolated shelter.

The only problem i could see, would be you could not travel far away from the lander.


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Post Re: How to survive a lunar night?   Posted on: Sun Jan 30, 2011 8:01 pm
Why? Just make it robust enough to survive the lunar night in a dormant mode.


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Post Re: How to survive a lunar night?   Posted on: Mon Jan 31, 2011 4:44 pm
You would need to limit the amount of thermal energy emitted as black body radiation during the lunar night. Black body radiation can be reduced by minimizing the surface area and covering it with a material that has a low emissivity. I looked at this a few years ago, and determined that a cube that is 10cm on each side could be kept above the freezing point by wrapping it in aluminum foil and warming it with the equivalent of a D-cell battery powering the electronics for two weeks.


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Post Re: How to survive a lunar night?   Posted on: Wed Feb 02, 2011 2:23 pm
But at the same time it has to radiate lots and lots of heat away at daytime, because of the hot lunar day, these two designs do not work well together!! Therefore I think the most effective mode is, like JamesG says, "just" making it robust enough in the first place!


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Post Re: How to survive a lunar night?   Posted on: Wed Feb 02, 2011 3:28 pm
Cooling during the lunar day will require thermal radiators. The temperature range at the equator is -173 C at night to 117 C during the day. Many components will not survive at -173 C, such as electrolytic capacitors. The electronics needs to be designed to withstand a wide range of temperatures, but it would be difficult to design for a lower limit of -173 C. As I said, a small battery along with good thermal isolation should be enough to keep it above the minimum temperature throughout the lunar night.

Thermal cooling during the day would require a cooling systems. A fluid would be pumped through coils that would carry the excess heat to thermal radiators. The Apollo LEM used a sublimator for cooling, which depends on evaporating ice to carry away the heat. This would require carrying the extra weight of the ice to the moon, and it quits working after the ice is gone. However, if you land toward the end of the lunar day it may be a better trade-off than using large black-body radiators.


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Post Re: How to survive a lunar night?   Posted on: Wed Feb 02, 2011 5:15 pm
Yes insulation and a trickle heating current should be easily implemented and necessary if you want to use COTS components. Say you just have your rover remain immobile with its array oriented towards the horizon for the last 8 hours of the day.

But the highest efficiency (low mass/volume) is to "simply" not worry about it, and design it to tolerate the temperature range and then let it go dead during the night until the next day when the sun give enough charge to reboot the rover.

Day time temps are another can of worms and totally different that surviving the night. It would be nice if you could somehow store the excess heat of the day and then use it over the night, but that's not practical.


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Post Re: How to survive a lunar night?   Posted on: Sun Feb 20, 2011 6:46 am
The surface temperature at lunar night gets very low because regolity is a poor conductor so the surface can radiate heat and reach a low temperature at the very surface.

A short distance down (0.1 or 0.5 m?) the temperature will be the average for that lunar latitude. So if you could drill down a little, access to warmer material is possible. That and low emissivity covering might make it possible to keep temp in a lander above -30C or so. Still should avoid batteries, electolyic caps and other components that cannot easily take a cold soak.


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Post Re: How to survive a lunar night?   Posted on: Sun Feb 20, 2011 6:52 am
Forgot James' question re daytime temp. Easy to protect from that. Just shield from direct sunlight and most of the surrounding surface.

A parasol to shade from the sun and an upside down one for lunar surface will allow a radiator to "see" only dark space.

The surface for that maybe 5-10 m away will radiate little, so the bottom shield needs only to block that from near.


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Post Re: How to survive a lunar night?   Posted on: Mon Feb 21, 2011 4:24 pm
ckpooley wrote:
A short distance down (0.1 or 0.5 m?) the temperature will be the average for that lunar latitude. So if you could drill down a little, access to warmer material is possible. That and low emissivity covering might make it possible to keep temp in a lander above -30C or so. Still should avoid batteries, electolyic caps and other components that cannot easily take a cold soak.



That's a really good idea actually. Maybe have your rover dig itself a burrow at the end of each day? :lol:


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Post Re: How to survive a lunar night?   Posted on: Mon Feb 21, 2011 4:44 pm
Probably not have the rover dig it, but the lander, and have the rover come back to the lander to keep warm at end of each lunar day.

But engineering the landers and rovers to withstand the nightly cold soak may be easier.

If I can get Microlaunchers going, the 2nd size of launcher (ML-2, with 1-2 ton GLOW) would land multiple 1 kg landers, each with 2 or so 50 gram rovers.

It would be too difficult to keep that warm for lunar night, or drill any holes, so temp would be controlled as mention 2 of my posts ago, and have cold soak capability.

It appears I must forgo any chance at GLXP, but being able to do this will have the potential to earn much more. The rovers could be rented by the hour.
There would be hundreds of landing sites.


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Post Re: How to survive a lunar night?   Posted on: Sat Jun 25, 2011 11:41 am
I've just walked by mistake into this old thread here and read through the original post by the Part-Time Scientists and was eager to find out if they did some follow up already. Well, they did. Not just one but several blog posts and it looks like there could be some more coming.

They dug a bit deeper into the problem and explained the first two ideas. The first one is to "Dig a trench to avoid heat dissipation" and the second one is to "Focus a laser from earth to charge the rover battery remotely". But both ideas seem to have some problems.


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