Selective solar sintering

[Patchouli]

I think this new technology esp if scaled up could be extremely useful on the Moon,Mars, or asteroids.

It's a selective sintering machine that uses the sun to make 3d objects from sand.

I can see a large version literally printing buildings on the surface of the moon.

http://hackaday.com/2011/06/25/selective-solar-sintering-with-sand/

http://www.markuskayser.com/work/solar-sinter/

[A_M_Swallow]

Interesting energy saving technology.

The lunar version will probably need cooling radiators.

[Patchouli]

Interesting energy saving technology.

The lunar version will probably need cooling radiators.

Not really it's using the sun directly to melt the material.
Conduction with the lunar surface and radiation might be enough for the work piece to cool.

Scaled up it would be the machine moving vs the work piece which would be sitting on the lunar surface.

[A_M_Swallow]

Not really it's using the sun directly to melt the material.
Conduction with the lunar surface and radiation might be enough for the work piece to cool.

Scaled up it would be the machine moving vs the work piece which would be sitting on the lunar surface.

I am not convinced.  Heat does not go down hill well; particularly through both a powder and a vacuum.

[IsaacKuo]

I think you're missing the fact that minimal heat loss is a GOOD thing.  There is some inevitable heat loss due to radiation and conduction to the rest of the work piece.  The higher this heat loss, the greater the amount of power required to maintain the desired sintering temperature.  That implies a larger solar concentrator.

Conversely, the smaller the heat loss, the smaller the solar concentrator required to produce a working system.  This also concentrates the sunlight onto a smaller area, so higher resolution product pieces with thinner walls and finer details are possible.

Of course, a smaller solar concentrator with a smaller amount of power will also have a reduced production rate (by product mass).  However, the production rate can be increased simply by using more solar concentrators to work on more work pieces.  For example, if the required solar concentrator area is reduced by a factor of 4, simply make 4 solar concentrator systems to produce 4 work pieces at the same time.

[Bill White]

I suspect the sand being used in this video is relatively pure and carefully selected. The ability to replicate this process on the Moon will likely depend on the ability to quality control the purity and composition of the input materials.

= = =

That said, I believe concentrated solar will be very useful on the Moon.

Due to low shipping weight, mirrors made from ultra light Mylar might be more cost effective than using Fresnel lens, even if Mylar mirrors ended up being less efficient from a energy conversion perspective. Because the Moon is in vacuum, Mylar mirrors can be very light weight (with their shapes sewn on Earth) and mounted on ultra light scaffolding.

Uses include:

1.  Sintering (as here) 

2.  Volatiles extraction

3.  Energy production (Stirling cycle?)

Volatiles extraction and energy production might be combined by heating a working fluid via concentrated solar and then running pipes across the surface of those cold traps Warren Platts wishes to mine. Transfer the heat into the cold trap and use the fluid flow caused by convection to spin a turbine, producing electricity. 

[A_M_Swallow]

I think you're missing the fact that minimal heat loss is a GOOD thing.  There is some inevitable heat loss due to radiation and conduction to the rest of the work piece.  The higher this heat loss, the greater the amount of power required to maintain the desired sintering temperature.  That implies a larger solar concentrator.

Conversely, the smaller the heat loss, the smaller the solar concentrator required to produce a working system.  This also concentrates the sunlight onto a smaller area, so higher resolution product pieces with thinner walls and finer details are possible.

Of course, a smaller solar concentrator with a smaller amount of power will also have a reduced production rate (by product mass).  However, the production rate can be increased simply by using more solar concentrators to work on more work pieces.  For example, if the required solar concentrator area is reduced by a factor of 4, simply make 4 solar concentrator systems to produce 4 work pieces at the same time.

For a controlled shape the bit you want needs to be hot but the material next to it needs to be cold.  Keeping the unwanted material cool may need a cooling system, so will cooling the finished layer.

[baldusi]

Only if you want to make complex forms. You could do bricks. Or plates, and then sinter those plates together to make more complex forms. If you could have a "brick factory", and a bigger concentrator that fusions the bricks, you could do a big, airtight igloo, for example. Or make many small bricks and have a fixed concentrator and special gloves to make more complex tools manually.

[LegendCJS]

A simple modification to achieve finer shape control would be to inject granular sand only where you want solid material to end up, and not have a large bed of sand adjacent to the hot point.  Kind of like filament deposition 3d printing, deposit the sand into the hot point, moving around a small molten puddle that accepts the new sand.  You sacrifice the ability to do overhanging parts in this case, but fusing finished parts together to make overhangs should be easy enough.

[Crispy]

If you're making bricks, better to use molds and just heat those, rather than try to control the shape by moving the heat source.

[Hop_David]

Due to low shipping weight, mirrors made from ultra light Mylar might be more cost effective than using Fresnel lens, even if Mylar mirrors ended up being less efficient from a energy conversion perspective. Because the Moon is in vacuum, Mylar mirrors can be very light weight (with their shapes sewn on Earth) and mounted on ultra light scaffolding.

Would the mylar mirrors be vulnerable to the abrasive lunar dust?

[Bill White]

Due to low shipping weight, mirrors made from ultra light Mylar might be more cost effective than using Fresnel lens, even if Mylar mirrors ended up being less efficient from a energy conversion perspective. Because the Moon is in vacuum, Mylar mirrors can be very light weight (with their shapes sewn on Earth) and mounted on ultra light scaffolding.

Would the mylar mirrors be vulnerable to the abrasive lunar dust?

Almost certainly. Good procedure could be to protect those mirrors putting them behind terrain and at some distance from the operation of equipment and vehicles. 

Maybe microwave sinter the nearby surface to reduce the dust before deploying the mirrors.

UV degradation may be an issue, also.

However, it appears that ū mil Mylar film is about 20 gm/m^2 and with added layers of underside backing can come in at about 210 gm/m^2

Therefore, 1 kilogram of material could provide about 5 square meters of Mylar mirror, right?

But lets add margin and go with 1 kg per square meter of Mylar mirror (excluding support frames, etc . . . )

Deliver 2000 kg worth of Mylar fabric to the lunar surface and you will have 2000 square meters of mirrored surface available to deploy or 1.25 square miles of mirrored surface, right?

If any given Mylar panel is abraded by dust, it seems to me you can simply replace it.

[baldusi]

However, it appears that ū mil Mylar film is about 20 gm/m^2 and with added layers of underside backing can come in at about 210 gm/m^2

You mean grams per square meter? that would be g/mē

Therefore, 1 kilogram of material could provide about 5 square meters of Mylar mirror, right?

Yes

If you have 1kg to 5mē, then 2,000kg are 10,000mē. That's an hectare, or 0.01kmē (remember that this are square units). A kmē is 0.3861mileē. So it would be 0.003861mileē of surface area.
It's still close to two football fields (5,350mē x 2 = 10,700mē), to give you an idea of it's size in the very unusual units the you American like to use.

But lets add margin and go with 1 kg per square meter of Mylar mirror (excluding support frames, etc . . . )

Deliver 2000 kg worth of Mylar fabric to the lunar surface and you will have 2000 square meters of mirrored surface available to deploy or 1.25 square miles of mirrored surface, right?

Then you'd only get 2,000mē of surface, which is 0.002kmē. Yet, almost half a football field without the end zone.

[Bill White]

@baldusi

Corrections acknowledged. Thank you!