Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Moon Poles: Which is better?

  1. Jan 11, 2018 #1

    Al_

    User Avatar

    North or South?
    Which is better for prospecting, mining, a site for a Moonbase and solar power.
    This could be quite a crucial question. The first solar array in permanent (ish) sunlight will stake a claim, because the next one will threaten to put it into shadow at certain times in the Lunar day.
     
  2. jcsd
  3. Jan 11, 2018 #2

    Drakkith

    User Avatar
    Staff Emeritus
    Science Advisor

    What?
     
  4. Jan 11, 2018 #3

    Al_

    User Avatar

    When someone puts a solar array on the top of one of the "Peaks of Eternal Light", then if there is another location on the same peak, or even another peak at at the same altitude nearby, and another array is placed there, the new array will shadow the first.
    This will cut off the power for the first lander, base or whatever. It will need batteries to carry it through the shadowed time. It may not have them.
     
  5. Jan 11, 2018 #4

    russ_watters

    User Avatar

    Staff: Mentor

    How small do you think the moon is?

    Anyway, the moon is tidally locked to Earth, so its rotation axis is the same as its orbit inclination. Just like Earth, it has seasons, so there isn't one pole always facing the sun.
     
  6. Jan 12, 2018 #5

    Al_

    User Avatar

  7. Jan 12, 2018 #6

    Al_

    User Avatar

    I get what you mean, I guess shadowing would only be significant if two arrays were placed on the same spot on the same peak, at the same height. Still, like you see clusters of telescopes on top of mountains, they will need to be aware of blocking each other.
     
  8. Jan 12, 2018 #7

    Al_

    User Avatar

    https://en.wikipedia.org/wiki/Peak_of_eternal_light
    There are peaks that have close to permanent illumination. Eg. "data from the SELENE spaceprobe determined that one peak at Peary Crater receives sunlight for 89% of a lunar year"
    That is at the North pole. And there seems to be more ice at the North pole too.
    https://nssdc.gsfc.nasa.gov/planetary/text/lp_pr_980305.txt

    However, a point at the South pole, on De Gerlache Crater Ridge has shortest period of darkness of only 6 days. This matters becasue the max period of darkness determines the mass of battery you need to lift up there.

    I looked into the Moons tilt but it's complex. It's not perfectly tidally locked, and there is a slight tilt of it's orbit around the Earth too.
     
  9. Jan 12, 2018 #8

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    The shadowing will work both ways - benefitting one at dawn and one at dusk. No need to fight about the available sunlight. But there may well be instances where despite the large area involved, certain sites may be worth fighting (negotiating) for.
     
  10. Jan 15, 2018 #9

    stefan r

    User Avatar
    Science Advisor
    Gold Member

    The poles are good places for telescopes. The gasses released from mining can ruin that.

    Best to be on the equator so you can build large solar farms. You want plains where you can run straight track for several hundred kilometers.
     
  11. Jan 15, 2018 #10

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    They wouldn't hang around long though. Cloud and plume formation is a thing that's due to an atmosphere. Those old pictures of Moon landings and takeoffs are very revealing.
    But isn't space the best place for a telescope? and no one can tinker about with them. Slamming doors and local machinery that are associated with humans are not good for telescope operation.
     
  12. Jan 15, 2018 #11

    davenn

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    not really ...... if you did astronomy, you would know that that would give you a very limited view of the sky
    Equatorial region is the best place
     
  13. Jan 16, 2018 #12

    Al_

    User Avatar

    Well, that would give a couple weeks of power, then nothing for a couple weeks. Why would that be useful?
    Or are you imagining huge battery storage? Even lithium batteries are heavy and they only last 1000 discharges.

    The poles have ice (some of it is in the form of pure crystals) and more constant light. That's why they are considered prime locations for mining and human residence.
     
  14. Jan 16, 2018 #13

    Drakkith

    User Avatar
    Staff Emeritus
    Science Advisor

    That's roughly 80+ years of useful power. Though I suppose that the lifetime would be even less due to degradation from sheer age.
     
  15. Jan 16, 2018 #14

    stefan r

    User Avatar
    Science Advisor
    Gold Member

    A "limited view" is a necessary thing if you want continuous coverage. A equatorial telescope would be off for 1/2 of each month and off of any one target for half of a year. A polar telescope could collect images of a target location at any time that likely to be interesting. It could also stare in one place for a long time and catch things that no one anticipated.

    Telescopes that see in the infra red need a cold location. Not sure how telescopes on the equator would compete with orbiting telescopes.

    If the goal is something like "fill x loads of liquid oxygen for rocket fuel" or "produce y tons of aluminum bars per year" the cycle is not much of a problem. Aluminum production on earth will cycle operations so that electricity costs are reduced.

    If you are looking for something specific and small scale, (perhaps you want just enough water to launch a rocket and prove that we can, or maybe He3 for fusion research) then the question becomes crater specific instead of pole. Does it make sense to compare the poles if there is no regional activity?

    The pole to equator distance is similar to the distance from Denver to Boston. It could be done with an off road solar vehicle. Lower gravity and no air drag make transportation much easier than Earth. On Earth we usually do not occupy long term residences at our mining sites.
     
  16. Jan 16, 2018 #15

    davenn

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    this is incorrect
    the poles are going to see sunlight for much longer periods so is going to screw up deep space observing
    consider on earth, the sun doesn't set for 6 months at a time
    and a polar located scope as I said has a limited sky view which severely limits the number of objects that can be seen and studied

    this is also incorrect ... IR telescopes just need to be looking through atmosphere that has little or no water vapor
    Hence why they are built on the tops of high mountains where they are above a high % 'age of the water vapor
    EG,
    https://en.wikipedia.org/wiki/NASA_Infrared_Telescope_Facility

    I have been there
    Orbiting scopes of any type are preferred, zero vapor, zero atmospheric distortion is offset by extremely high maintenance costs and shorter lifespans

    Now on the moon, with near zero vapor and zero atmospheric distortion, equatorial locations would be preferred because of the all sky coverage
     
  17. Jan 16, 2018 #16
    South pole is flatter landscape which has to be better for any schemes of extracting water and other useful stuff
     
  18. Jan 18, 2018 #17

    Al_

    User Avatar

    There are some challenges.
    Like any off-road vehicle, it's speed is limited.
    A tip over or a crash would be a big problem.
    Need to get there before dark, or carry big batteries.
    Highly abrasive ground and sticky dust getting into bearings.
    Temperature swings, overheating issues, cold.

    Unmanned:
    How to navigate without getting tipped or bogged.

    Manned:
    How to get there before dark, or carry big batteries to drive life support.
    How to recognise dangerous terrain, maybe like we've never seen before!
    How much life support gases and water to carry, don't want to be too heavy.
    Radiation shielding is heavy.

    I bet someone already wrote this sci-fi story!
     
  19. Jan 18, 2018 #18

    Al_

    User Avatar

    Radio astronomy from the far side of the Moon would be out of the noise from Earth - huge advantage.
    Both poles, of course, are on the edge of the far side.
     
  20. Jan 18, 2018 #19

    Al_

    User Avatar

    I just noticed in the previous link: https://phys.org/news/2018-01-lava-tube-skylights-north-pole.html

    "if ice is present inside the lava tubes – which is not yet known—it could be in the form of massive ice formations as often occur in cold lava tubes on Earth – instead of mixed-in within lunar grit"

    I hope they take a look soon!
     
  21. Jan 22, 2018 #20

    stefan r

    User Avatar
    Science Advisor
    Gold Member

    Drive from Denver to Boston in 14 days. Not a lot of speed needed. 2,727 straight kilometers. 185km per earth day 8.2 km/hr. 2.3 m/s average.

    Tractor/trailer suspension systems can be much larger b/c they only add 1/6 weight. Motors and propulsion can be smaller because it will haul lower weight vehicles. At highway speeds on earth air drag can be up to 70% of fuel loss. Motor losses (20%) will be lower in electric engines. Energy dissipation is limited to the wheels. Could make racing cars going several hundred meters per second.

    If you are transporting water and batteries the radiation shielding should be easy. Just position the tanks and battery as shield.

    A rail line would be nice. A cobble stone road could be slapped together faster. 30 km/hr is easy on gravel roads on earth.

    A 3 meter wide trail 3000 km is 9 km2 surface prep. The water mining operation will handle and process a much larger mass of regolith.

    I would worry about tires overheating.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted