Digging the Moon

[farmerben]

 

Inspired by another thread, I had some ideas about burying habitats on the Moon or Mars.  What are the fastest, easiest ways to do it, and how to do other useful work at the same time.  

So the fastest easiest way to bury a habitat on the moon that I have come up with is to bury it with sand, using something like this.  

 

We could just leave one door at the top and bury everything else, that is a fast and easy way to do it.  The angle of repose for sand is about 33 degrees.  The side pressures involved allow plentiful tolerances.

 

How do we separate sand from fines and big rocks?  With a trommel like this.

 

 

 

Then we lay the bigger rocks back down where we found them turning the area around our base into a paved MacAdam surface which will support roads, launch pads, etc.  

 

 

The trommel isolates the fines from larger particles.  So we clean up the fines in key areas and pile it somewhere.  We don't want fines on our spacesuits and equipment, really on anything that might come inside the hab or anything that has parts subject to wear and tear.  

 

When we start mining, the piles of fines are ready to go.  In almost all mining operations the first step after crushing the ore is a density separation.  We could use air density separators like this.  The heaviest fines are going to be iron and nickel compounds along with other heavy metals.  The medium density ones are mostly silicon dioxide or aluminum oxide, and we can turn those into glass.  The low density stuff is mostly salt, so we pile that somewhere.  

 

 

Now that we have MacAdam surface around our base we can roll heavy furnaces around and 3-D print glass structures on it.  

[sevenperforce]

I am fond of laser sintering bricks and building around structures with robots, myself.

[Kerwood Floyd]

11 minutes ago, farmerben said:

The angle of repose for sand is about 33 degrees. 

Is that the angle of repose under one g or under the moon's gravity? Is the angle of repose even affected by gravity? If it is, and that figure is for 1 g, I imagine you could get steeper slopes on the moon.

[Nothalogh]

This is actually more pertinent to Mars, but yes, all the methods you lay out are absolutely going to be necessary.

 

Also, one other, mostly Mars specific, application that has always intrigued me would be for more G-force tolerant cargo to be landed via aerobrake followed by a controlled lithobrake on a skidway.

Kind of like a combination of a runway and a runaway truck ramp.

Each controlled crash landing would require the skidway to be regraded afterwards though.

5 minutes ago, sevenperforce said:

I am fond of laser sintering bricks and building around structures with robots, myself.

Seems needlessly complicated, slow, and unrobust.

Far simpler to just use heavy earthmoving equipment off the shelf from the mining industry.

[Thor Wotansen]

52 minutes ago, Nothalogh said:

Far simpler to just use heavy earthmoving equipment off the shelf from the mining industry.

You'd have to design new earth regolith-moving equipment anyways, to handle the unique environments on both Mars and the moon separately.  The moon has some pretty interesting requirements for cooling, since you're in a vacuum and those are known to be good insulators.  Also diesels don't work in either place.

[Nothalogh]

2 hours ago, Thor Wotansen said:

Also diesels don't work in either place.

Most mining equipment is diesel-electric, so conversion to another source of electricity is rather easy.

Cooling may be an issue.

Good thing there's a guy with an R&D farm company that makes big honkin batteries and electric motors.

[AngrybobH]

Cooling and electricity is easy for mining equipment as long as you don't mind being on a tether of sorts. Just sink a bunch of pipe in the ground, fill it with coolant, pump it to the vehicle and back to the ground. You can run the electrical from the base power supply with (or in) the coolant tether. And then you don't even need batteries or power generation on the equipment except for emergency systems. Of course you don't even need actual people on the equipment so no need for safety systems. They could be in the base with a VR headset and a direct wired connection. I imagine any kind of mining equipment is much lighter without a battery, power generation, or life support/cockpit so, actually sending it to the moon/mars/wherever would be easier.

7 hours ago, Nothalogh said:

Kind of like a combination of a runway and a runaway truck ramp.

I really like this idea.

[Nothalogh]

45 minutes ago, AngrybobH said:

They could be in the base with a VR headset and a direct wired connection. I imagine any kind of mining equipment is much lighter without a battery, power generation, or life support/cockpit so, actually sending it to the moon/mars/wherever would be easier.

Pretty much how the big boys do it already here on earth.

The Rio Tinto Mars operation is gonna be glorious.

[Nothalogh]

48 minutes ago, AngrybobH said:

I really like this idea.

It would be probably the most kerbal landing ever devised.

Horizontal Approach Lithobraking Trap

[Nuke]

probably sandbags would be the best approach. if the sandbags have a mylar inner layer between 2 layers of heavier fabric it could contain the finer particles, getting them out of the way without wasting them. given the lower gravity larger bags than what you would use on earth could be employed. having astronauts in space suits fill them with shovels might be more wear and tear on the suits than would be acceptable. some kind of bristle drum like what you see on a street cleaner mounted on a rover could kick up the dust into an auger which would transfer the material into bags which would be automatically sealed and dropped off the back of the rover. the whole thing could be automated so you could clear the landing site prior to a manned presence. while leaving plenty of sand bags for shielding the habitat. astronauts would just have to round them up and stack them. 

1 hour ago, AngrybobH said:

Cooling and electricity is easy for mining equipment as long as you don't mind being on a tether of sorts. Just sink a bunch of pipe in the ground, fill it with coolant, pump it to the vehicle and back to the ground. You can run the electrical from the base power supply with (or in) the coolant tether. And then you don't even need batteries or power generation on the equipment except for emergency systems. Of course you don't even need actual people on the equipment so no need for safety systems. They could be in the base with a VR headset and a direct wired connection. I imagine any kind of mining equipment is much lighter without a battery, power generation, or life support/cockpit so, actually sending it to the moon/mars/wherever would be easier.

I really like this idea.

i saw a paper on a lunar tunnel boring machine that got rid of its waste heat, by heating the resulting rubble, and physically removing it from the hole and dumping it on the surface taking the heat with it. 

[kerbiloid]

Also on Mars the simple plastic bags can be being manufactured by ISRU.

But the's a lot of ground to bag, so I would insist on first making a ground wall with a bulldozer, then cover it with sandbags.
Also plastic sandsausages to put on top of the modules to cover the upper part of module walls.

Edited October 9, 2019 by kerbiloid

[Thor Wotansen]

8 hours ago, AngrybobH said:

Cooling and electricity is easy for mining equipment as long as you don't mind being on a tether of sorts. Just sink a bunch of pipe in the ground, fill it with coolant, pump it to the vehicle and back to the ground. You can run the electrical from the base power supply with (or in) the coolant tether. And then you don't even need batteries or power generation on the equipment except for emergency systems. Of course you don't even need actual people on the equipment so no need for safety systems. They could be in the base with a VR headset and a direct wired connection. I imagine any kind of mining equipment is much lighter without a battery, power generation, or life support/cockpit so, actually sending it to the moon/mars/wherever would be easier.

I suspect the first machines to be somewhat similar to what Andy Weir describes in his book Artemis.  He's got some earth mover type machines picking up rocks for smelting in the base, and they dump their waste heat into a vat of wax with coolant lines running through it.  When the machine returns to base with a full load, it hooks up to an external dock and runs coolant through the wax heatsink from the base, while it recharges it's batteries and unloads.  The base will already have massive cooling needs, and will radiate the heat away with whatever it normally uses.

As far as building berms and earth structures with local regolith, laser sintering regolith into building blocks is a great option.  We already use that technology here on Earth to 3D print metal and plastic, and adapting it to work with fine regolith dust should be fairly straightforward.  A small device, maybe a meter cubed, could produce sintered bricks constantly, if at a slowish pace.  You could even make it work, on the moon at least, with sunlight and a lens to focus it, although you'd be limited by the daylight cycle.

[farmerben]

18 hours ago, Kerwood Floyd said:

Is that the angle of repose under one g or under the moon's gravity? Is the angle of repose even affected by gravity? If it is, and that figure is for 1 g, I imagine you could get steeper slopes on the moon.

The angle of repose is gravity independent.  The shape of the aggregate makes a difference.  On Earth and Mars 33 degree slopes of rounded sand are stable.  

Sharp edged Moon fines can stack a little bit steeper, but they will be vulnerable to avalanche.  

[Kerwood Floyd]

22 hours ago, farmerben said:

The angle of repose is gravity independent.  The shape of the aggregate makes a difference.  

Thanks for the further info.