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Lunar Soil Temperature



 
 
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  #1  
Old July 16th 03, 11:56 PM
Mike Miller
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Default Lunar Soil Temperature

The daytime lunar temperature swings between something like 400K and
100K. What is the average temperature several meters into the lunar
soil? Above or below 273K?
  #3  
Old July 17th 03, 12:30 PM
Dholmes
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Default Lunar Soil Temperature


"Mike Miller" wrote in message
om...
The daytime lunar temperature swings between something like 400K and
100K. What is the average temperature several meters into the lunar
soil? Above or below 273K?


The figures I have seen are -20 C at 2 meters.

I have found it almost imposible to find good figures.
The best estimate I can come up with is the temperature rises 1 degree every
200 to 400 meters or 273k occurs between 4 and 8 kilometers below the
surface of the moon.

  #4  
Old July 17th 03, 05:20 PM
Henry Spencer
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Default Lunar Soil Temperature

In article ,
Mike Miller wrote:
The daytime lunar temperature swings between something like 400K and
100K. What is the average temperature several meters into the lunar
soil? Above or below 273K?


Data is limited. At the Apollo 17 site, temperature 2m down was 256K,
rising about 1.3K/m. The Apollo 15 site was a few degrees colder, and may
have had a slightly higher gradient, but the deepest data we have there is
only 1.5m down so it's hard to be sure.

Day-night temperature swings are only a few degrees at 0.3m, and are
nonexistent at 1m. The lunar soil is an extremely good insulator. (Note,
this means that buried equipment or facilities will need to worry about
cooling, not heating. Only something that is generating no heat of its
own at all will cool to the ambient soil temperature.)

We don't have a good picture of either how much variation there is from
place to place, or what happens at much greater depths.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |
  #6  
Old July 21st 03, 01:05 PM
Mike Miller
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Default Lunar Soil Temperature

(Allen Thomson) wrote in message . com...

(*) Random thought that popped up while writing that: efficient
whitish-light LEDs/LED arrays for general lighting might actually be
significant in designing such habitats.


LEDs are more efficient than incandescent bulbs, but are still
significantly short of fluorescent bulbs.

http://www.eetimes.com/story/OEG20020718S0013

"White LEDs currently offer an efficiency of around 20 lumens (lm) per
watt, which is better than incandescent light bulbs, but not high
enough to compete with fluorescent lights that have an efficiency
rating of from 60 to 100 lm/W."

There are hopes to push white LEDs to low fluorescent efficiencies by
2004.

Mike Miller, Materials Engineer
  #7  
Old July 21st 03, 05:34 PM
Henry Spencer
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Default Lunar Soil Temperature

In article ,
Mike Miller wrote:
I've seen the thermal conductivities for dry sand (.35W/m*K, IIRC)
and soil (0.16), so I can imagine regolith to be a good insulator.


Lunar soil conductivity is estimated at 0.015-0.03 W/m-K at 1m depth.
Note that this is *very* well compacted, packed harder than could easily
be achieved with power machinery. The much fluffier top 1-2cm is around
0.0015 W/m-K. Regolith that was excavated and then loosely piled on top
of, say, a shelter would presumably be somewhere in between.

However, solid rock can have an order of magnitude higher...
So, would a habitat buried in a "big" (mountain-sized or more) cold
rock (200K, 1.5W/m*K) need supplementary cooling like a habitat
buried under lunar regolith?


My guess would be yes. If it's a substantial habitat, the rock in its
vicinity won't stay cold for very long.

Also, bear in mind that said rock will almost certainly be covered with
regolith. You don't generally find large masses of exposed rock on the
lunar surface.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |
 




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