I Optimizing Lunar Power: North vs. South Poles for Mining and Moonbase Sites

[Al_]

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.

 

[Drakkith]

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.

What?

 

[Al_]

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.

 

[russ_watters]

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.

 

[Al_]

The North pole seems to have a lava tube.
So a base could be built in there for protection and still have solar panels in permanent light, if there was a long power cable.
https://phys.org/news/2018-01-lava-tube-skylights-north-pole.html

 

[Al_]

How small do you think the moon is?

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.

 

[Al_]

there isn't one pole always facing the sun.

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.

 

[sophiecentaur]

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.

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.

 

[stefan r]

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.

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.

 

[sophiecentaur]

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.

 

[davenn]

The poles are good places for telescopes.

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

 

[Al_]

Best to be on the equator so you can build large solar farms.

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.

 

[Drakkith]

Even lithium batteries are heavy and they only last 1000 discharges.

That's roughly 80+ years of useful power. Though I suppose that the lifetime would be even less due to degradation from sheer age.

 

[stefan r]

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

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 anyone 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.

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.

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.

 

[davenn]

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 anyone 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.

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

Telescopes that see in the infra red need a cold location.

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

Not sure how telescopes on the equator would compete with orbiting telescopes.

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

 

[rootone]

South pole is flatter landscape which has to be better for any schemes of extracting water and other useful stuff

 

[Al_]

It could be done with an off road solar vehicle. Lower gravity and no air drag make transportation much easier than Earth.

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!

 

[Al_]

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.

 

[Al_]

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!

 

[stefan r]

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!

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.

 

[Al_]

I would worry about tires overheating.

I think the highly abrasive nature of the Lunar dust would prohibit the use of tyres.
Look at how the Mars rover's wheels were worn through, and Mars dust is thought to be less abrasive than Lunar.
I expect there will need to be extremely hard, thick coatings on the wheels. Tungsten carbide or some such. This itself limits the speed due to the need to keep impact forces within limits.
Electric motors have a unique problem in vacuum - cooling.
But yes, I expect 2.3 m/s is achievable.

But, I just don't see the use of being at the equator. Let's start at the poles where we know there is some useful stuff. Of course, prospecting is likely to change everything, if we discover a deposit of a mineral at the equator. But it makes sense to prospect around the poles first. Or just one pole, having decided which one.

 

[Al_]

the cycle is not much of a problem

Well it is a bit of a problem. Without constant power all the equipment has to go down to cryogenic temperatures at night. Why run into these issues if you don't have to? And why not keep running constantly?

 

[stefan r]

I think the highly abrasive nature of the Lunar dust would prohibit the use of tyres.
Look at how the Mars rover's wheels were worn through, and Mars dust is thought to be less abrasive than Lunar.
I expect there will need to be extremely hard, thick coatings on the wheels. Tungsten carbide or some such. This itself limits the speed due to the need to keep impact forces within limits.

I meant "wheels" made error. However, freedictionary.com has this definition for the noun "tire":

1. A covering for a wheel, usually made of rubber reinforced with cords of nylon, fiberglass, or other material and filled with compressed air.
2. A hoop of metal or rubber fitted around a wheel.

Tungsten carbide is frequently over rated. The key problem is that tensile strength (or any strength) is not the same as fracture toughness. Your window glass is probably "stronger" than steel sheets with the same thickness. One of my in-laws bought tungsten carbide wedding rings. It broke. One of those moments where I wanted to explain but kept quite instead. Bronze is tough if you want metal plates. You can pound on some types of bone for a few decades without breaking it.

Electric motors have a unique problem in vacuum - cooling.
But yes, I expect 2.3 m/s is achievable.

The electric motors only need to propel the vehicle an amount equal to the resistance. Basic electric motors get around 95% efficiency. Superconductor motors should get better than 98%. If we have a water hauling truck you can dump heat into the tank. The entire shell becomes the radiator.

On flat terrain (lunain?) almost all of the resistance comes from bending and flexing of the tires and the surface. The bearings and axle are inside relative to the wheel and become part of the same problem. Because the wheel is moving it is hard to pass a fluid without leaking. All of the tire heat has to radiate off the wheel either through the tire itself or sideways off of the hub.

If you have kilowatt power supply you would expect the electric motors to need to dump 50 watts. If the wheels and surface got equal energy you have to deal with 425 watts on flat terrain. Rolling down hill you could get more than a kilowatt in the wheels.

But, I just don't see the use of being at the equator. Let's start at the poles...

Well it is a bit of a problem. Without constant power all the equipment has to go down to cryogenic temperatures at night. Why run into these issues if you don't have to? And why not keep running constantly?

If cold temperatures are not good for your base then poles will be really bad for your base. Minimum temperature at the equator would still boil oxygen. Parts of the poles have He³ reserves. Rock has a high heat capacity. The buildings have to be air tight. They need a thick cover for radiation shielding. It might be underground. It will need an air circulation system for breathing and a water/waste recycling system. Stabalizing temperature is simple if you have a functioning water treatment plant and indoor greenhouse.

My impression was a combined nuclear and solar energy system. Plutonium can heat tents at 100% efficiency. Nuclear electric is much lower efficiency, somewhere between 5 and 25%. The other 75 to 95% could be used to keep the equipment sheds at sauna temperatures.

... Of course, prospecting is likely to change everything, if we discover a deposit of a mineral at the equator. But it makes sense to prospect around the poles first. Or just one pole, having decided which one.

Agreed prospecting would likely change some things. Functional cave systems might be valuable too. Also wide flat plains for landing. Your lava tube link might be convincing.

The earth-moon Lagrange point is directly over the equator. If an elevator gets deployed it should be fairly close to the tropics. Most of the solar system is in the ecliptic plane. I tend to assume that mass drivers, space stations, and rings will stay in the ecliptic too. That simplification is probably not correct.

Strip mines rarely become long term settlements. The programmers working in silicon valley (Google, Oracle, Facebook etc) could all live in Saskatchewan. That would put them conveniently close to the tar sands. Then there would be no need for pipelines from Canada to the USA. I think people will move to places where they could grow mangoes. People will spend most of there time in cubicles and cars but they are still willing to pay for the gardens. There needs to be a clear view of earth.

 

[Al_]

If cold temperatures are not good for your base then poles will be really bad for your base.

But, with constant power at the poles, sensitive equipment can be heated continuously.

 

[Al_]

If an elevator gets deployed it should be fairly close to the tropics.

Sure, but that is a long way ahead in time. Both poles will likely be explored and mined by that time, I guess. The OP is about considering which pole to focus on first, in the near term.

 

[Al_]

I think people will move to places where they could grow mangoes.

I get what you mean, people will move to where life is easiest. I think on the Moon that will be the poles.
It's close to known important resources - volatiles.
It has near-constant light without the need for nuclear plant and lightbulbs.
It has the capacity to keep things constantly cold or warm depending on where they are placed and how they are wired up.
A simple reflector on a pylon can direct light anywhere you like - even underground - no clouds to stop it working.

 

[Al_]

a combined nuclear and solar energy system. Plutonium can heat tents at 100% efficiency. Nuclear electric is much lower efficiency, somewhere between 5 and 25%.

It may be that nuclear power is getting compact and light enough to be realistic in the early stages of development.
But there is still the problem that it needs huge radiators.
Or - the type of isotope based power used in probes, but they have quite low power output.
For the first, smaller bases or robotic mining I think nuclear is just too heavy, too difficult to place there.

 

[stefan r]

It may be that nuclear power is getting compact and light enough to be realistic in the early stages of development.
But there is still the problem that it needs huge radiators.
Or - the type of isotope based power used in probes, but they have quite low power output.
For the first, smaller bases or robotic mining I think nuclear is just too heavy, too difficult to place there.

Casini used plutonium and the thermoelectric generators kicked out around 20 watts per kilogram(²³⁸Pu) of electricity. If your primary energy need is for heating then you already solved the radiator problem.

 

[dmac257]

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.

At the equator isn't the lunar day and night close to 15 days of total darkness??

I read someplace that at the south pole was two spots that were complementary with one or the other in sunlight all the time.

dmac257

 

[stefan r]

...I read someplace that at the south pole was two spots that were complementary with one or the other in sunlight all the time...

Opposite sides of a hill. On a perfect sphere with no seasons you could stick the panel on a vertical mast and rotate it.

Places that are receiving sunlight are not the same places that are most likely to have ³He.

At the equator isn't the lunar day and night close to 15 days of total darkness??
...

At the middle equator you could always see clearly with Earthshine. The terracycle would not include a new Earth at night. The new Earth would be above close to the noon sun. At sunset you have a quarter Earth waxing and at sunset you have a quarter Earth waning. A full Earth on Luna is brighter than a full moon on Earth.

 

[dmac257]

Opposite sides of a hill. On a perfect sphere with no seasons you could stick the panel on a vertical mast and rotate it.

Places that are receiving sunlight are not the same places that are most likely to have ³He. At the middle equator you could always see clearly with Earthshine. The terracycle would not include a new Earth at night. The new Earth would be above close to the noon sun. At sunset you have a quarter Earth waxing and at sunset you have a quarter Earth waning. A full Earth on Luna is brighter than a full moon on Earth.

So how much energy would be produced by a panel from "a full earth" on a lunar night compared to "lunar daylight". As for the vertical mast wouldn't it be fairly easy to erect a mast at a high point near one of the poles to keep a panel in sunlight all the time?

dmac257

 

[Al_]

Very little power from a panel in Earthshine. The albedo of the Earth is 0.37 (de Pater and Lissauer), and the Earth receives 1000W/m^2 from the Sun and appears as a disc covering 3 degrees seen from Moon. So, ballpark less than 1 Watt per square metre.
The mast would have to at least 100m high I estimate. Lunar gravity makes it a bit easier, but transport and construction... waaaaaay hard.

 

[stefan r]

So how much energy would be produced by a panel from "a full earth" on a lunar night compared to "lunar daylight".

The flux is lower by more than 10⁴. Not much energy but the view is impressive. NASA astronauts are effectively soldiers so the view will not matter. For a tourism industry a poor view can kill the project.

...As for the vertical mast wouldn't it be fairly easy to erect a mast at a high point near one of the poles to keep a panel in sunlight all the time?

dmac257

If you build a thriving steel industry you could build sky scrapers.

...
The mast would have to at least 100m high I estimate. Lunar gravity makes it a bit easier, but transport and construction... waaaaaay hard.

NASA has this article with nice topography pictures of Shackleton crater. The top of the rim on any side is less than a kilometer wide. Is much easier to lay a conductor line 1 km than to build a 100m tower.

The slope on all sides gets over 30% grade. You could use a cable or build roads with a lot of switchbacks. I suspect the cable is less effort unless you assume there is already an extensive road building infrastructure. The tow cable needs to haul loaded vehicles 7 to 8 kilometers. Presumably the solar panels are also providing power for vehicles working inside the crater which means we need to run 10+ km of conductive cable. You can use double the panels (place multiple locations) and have continuous coverage. A crew could also haul the panels from one side of the slope to the other if there was a demand for extra power. It is possible that the lower section of rim would be a better location because it cuts the the vertical ascent by half a kilometer.

You could also place moveable mirrors around the rim. Pillage the water in the basin and launch it out. If the primary goal is hydrogen fuel for inter-planetary missions that should work. Would be interesting to see how much fuel exhaust resettles back into the crater.

 

[Al_]

Thanks, nice article in the link.
Yes, a power cable running out to two panel sites makes more sense.
I think a vehicle can be built that can handle 30% grade, and initially it's much less mass than a long cable.
How about, thinking about a minimum mass solution, a steerable mirror on the rim that directs sunlight down to solar panels on the rover?