Our Friend, Moon Dust! (And Mars Dust!)

[Kibble]

Its In the Dirt!

Well making Al is a bit harder than I expected! But its no reason to give up - with some luck we will find an in situ source of cryolite! I have updated this post on 4 May to describe another crazy idea - making the other half of APCP!

Based on measurements by Phoenix and Curiosity, it's likely that Mars has a global distribution of perchlorates, likely in the form of Ca(ClO₄)₂. Wow! This is favorable, but still not useful...yet.

You just need to find some ordinary salt - NaCl. I may bee wrong, but I suspect this compound occurs naturally in extraterrestrial rock. Dissolve it into water, electrolyze it, and bake it in UV light and you make Hydrochloric acid. If you take your perchlorates and treat it with the shiny new batch of HCl, you get Perchloric acid and calcium chloride. Precious Perchloric acid, and excavated volatile Ammonia form that wonderful salt - Ammonia perchlorate!

Mix with your Aluminum, and you've got a modern, high-performance rocket fuel!

The data we've collected suggests that most small bodies have a fine layer of regolith, presumably including lithophile elements like there is on the Moon's surface. Among the compounds is a significant amount of Aluminium-Oxide. Hey, its modern rocketry's best friend - hi strength, lite weight Al! But how do you split it from those three pesky Oxygens? I have endeavoured to find the best way!

On Earth, we generally purify Al₂O₃ from a rock called bauxite, and sink it in a molten bath of a different rock called cryolite. I understand that this is because Al₂O₃ has an annoyingly high melting point, but when dissolved in cryolite it's halved. Unfortunately in space, we don't have world-wide industry scouring every corner of our unique planet for all the compounds and elements to produce useful things like cryolite. So its probably best to just buck up and go the whole 2000^o Celsius. A brief search shows it'll take 1.33 kiloWatt seconds to melt one gram. Sounds pretty high for one gram, but lets take it up a notch.¹

A potential configuration I found is a 22 kW solar array, basically equivalent to one of those big SAWs on Space Station, powering the smelter module. This can make 10 metric tonnes sheet aluminium in one week of sunlight. Of course, you'll also have to have rovers scooping buckets of regolith, geological probes scouting for rich areas, and geologists or probes sorting the good stuff from the junk. In my opinion, it's unlikely that this can bee done with out at least a teleoperated human presence.

But with 10 mT sheet Al and some proper machine tooling, you are on your way to a nice-sized rocket - manufactured in situ! The smelter, excavation rovers, and tooling modules can probably come in the form of 20 mT pieces landed at a piloted extraterrestrial base. For some synergy, the rovers, having scooped up a load of dirt, can hook up to a crane (a basic construction tool) and boost its stability and rated load, while keeping the crane itself lightweight!

^{1: No its not. According to the astoundingly knowledgable Kryten, that high temperature it will melt the catalyst for electrolysis.}

I am no expert, so please point out any inaccuracies in the proposed architectures.

Woof!

Edited May 5, 2015 by Kibble

[ComradeWolfe]

I don't know about making spacecraft, but for in-situ construction you don't need to refine the moon dust. You'd just do something like what this guy did with sand:

[Kryten]

If you just stick regolith into a smelter, all you'll get out the other end is a solid lump of regolith. That's not how any kind of refining process works.

[Ethanadams]

And isn't moon dust poisoness

[Robotengineer]

And isn't moon dust poisoness

Considering Buzz Aldrin is still alive, and other Apollo Moon walkers, I think not.

[Newt]

And isn't moon dust poisoness

If you breath it it is rather dangerous, yes.

Considering Buzz Aldrin is still alive, and other Apollo Moon walkers, I think not.

Well, that just means it it not as bad as it could be. The astronauts breathed some Lunar dust, defenitly, but it was over just a few days, in limited amounts. If you lived on the Moon, for months or years, always walking into the main base habitat area with your dusty suit and boots right by where you sleep, more problems might manifest.

This however, is talking about melting it. Part of the danger is from the extremely fine particles, when melted the stuff should be pretty safe.

[tater]

Some guys I had as profs were working on a "subselene" at Los Alamos. It looked somewhat like a drill head for tunnels, but was nuclear powered, and it used the thermal energy from the reactor to melt lunar regolith (a simulant in testing) to make glass. As the drill moves forward, the regolith is melted, and seeps into the surrounding soils. What is left is a tube in the side of a hill (crater, whatever) that is lined with glass. Cap the outside end, and you have a habitat.

[mrfox]

http://en.m.wikipedia.org/wiki/Lunarcrete

[Kryten]

To be more specific, cryolite is used not to safe energy, but because the aluminum has to be extracted through electrolysis; the temperatures required for doing this with pure alumina would melt any practical electrolysis cell. Even that won't get you anywhere without sufficiently pure alumina to start with; you can't just shove bauxite into an electrolysis cell, and certainly not regolith.

[AngelLestat]

you can do that for sure.. but what is the point?

To make a rocket you still need thousands of other parts and materials, some as complex like electronics.

But well, lets said that you build your rocket.. whats next?

What benefics you get? You cant live on the moon or have children there, or train people to space missions..

Your explorers or scientist will still come from earth.

And you are wasting the same fuel doing it this way..

Maybe for unmanned missions could work. But you need a perfect 3d printing machine on the moon able to do anything, which reminds me the von neumann probes, something that we are very far to accomplish.

In the case we can accomplish that then leave the earth will be so easy that it will be not benefic for a moon factory.

Edited May 4, 2015 by AngelLestat

[PakledHostage]

Even that won't get you anywhere without sufficiently pure alumina to start with; you can't just shove bauxite into an electrolysis cell, and certainly not regolith.

Not to mention that pure aluminium isn't good for much in aerospace structures (except maybe cladding). You've got to alloy it with other elements to make a useful raw material such as 2024 aluminium alloy, 7075 aluminium alloy, etc. People need to remember that there is more to materials science than just sending a few dwarves into a cave with pick axes.

[shynung]

There's a kind of vehicle in hard sci-fi circles called a 'scooter', which is basically a rocket engine attached to the bottom of a truss/girder, to which astronauts strapped themselves to, and take off. In a lunar base with some basic manufacturing capacity, making a scooter using 90% lunar material is possible. Aluminium tubes is made into the truss, sheets for seats/racks, covering electronics/engine components, propellant tanks, and using Al/LOX from smelted aluminium as propellant for a hybrid rocket. The only Earth-made things needed would be electronic control/navigation systems, and probably combustion chamber/nozzle parts, as I'm not sure if a pure aluminium nozzle is enough to withstand the heat, and I can't imagine using LOX as regenerative cooling fluid; that thing is ridiculously corrosive at the temperatures in which rocket engines operate.

[Kibble]

To be more specific, cryolite is used not to safe energy, but because the aluminum has to be extracted through electrolysis; the temperatures required for doing this with pure alumina would melt any practical electrolysis cell. Even that won't get you anywhere without sufficiently pure alumina to start with; you can't just shove bauxite into an electrolysis cell, and certainly not regolith.

Thanks! This is exactly the kind of response I wanted.

Although i did imagine the alumina would bee sorted from the rest of the dirt by hand (if that's practical). You don't happen to know if cryolite is found on extraterrestrial bodies, do you? I cannot find any figures for the frequency of trace elements and compounds on anywhere but Earth!

[Nuke]

Some guys I had as profs were working on a "subselene" at Los Alamos. It looked somewhat like a drill head for tunnels, but was nuclear powered, and it used the thermal energy from the reactor to melt lunar regolith (a simulant in testing) to make glass. As the drill moves forward, the regolith is melted, and seeps into the surrounding soils. What is left is a tube in the side of a hill (crater, whatever) that is lined with glass. Cap the outside end, and you have a habitat.

i read the paper on that i think. it was pretty impressive. i liked the way they plan to cool the reactor, by heating the rocks and then simply dumping them outside.

[Kibble]

Some guys I had as profs were working on a "subselene" at Los Alamos. It looked somewhat like a drill head for tunnels, but was nuclear powered, and it used the thermal energy from the reactor to melt lunar regolith (a simulant in testing) to make glass. As the drill moves forward, the regolith is melted, and seeps into the surrounding soils. What is left is a tube in the side of a hill (crater, whatever) that is lined with glass. Cap the outside end, and you have a habitat.

That sounds like a wonderful idea! After talking with my dad (he's an estimator) he thinks a sensibly 4m diameter tunnel boring machine could bee a nice 20 mT. Compact and simple!

Also, I updated the OP with some more junk.