Lunar materials - habitat sealant

[webtaz99]

I have seen evidence of researchers having produced oxygen, iron, aluminum, glass, fiberglass, "concrete"-like building materials, and even solar cells from Lunar regolith (powdery surface material).<br /><br />Has there been any research into a sealant for habitats? It would have to remain flexible and retain atmosphere even after long exposure to vacuum, and be made almost entirely of lunar materials. It should be easy to apply in large quantities, and fairly strong.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[webtaz99]

This is an example of things we need in order to "live on the Moon". Too many people mistakenly think we have all the technology we need to build a "Moon base". <br /><br />Sure, we can set up a tin can with a CO2 scrubber and some canned food. But in order to truly make use of the Moon, we have to build shelters almost entirely from Lunar materials. <div class="Discussion_UserSignature"> </div>

 

[chriscdc]

We had a discussion about this sort of thing ages ago but thanks for bringing it up again.<br /><br />There are methods of generating glasses out of lunar material, but you would likely have to filter out the materials that you need so that glass for a habitat is of decent quality.<br /><br />We had a massive argument over nuke vs solar, so can we agree at the start of this thread that we will only discuss using in situ resources to generate power.<br />Many solar cell production methods use hard vacuum deposition methods. You can use CVD but this requires extra chemicals which you would no doubt lose in the space environment.<br />I advocated an 'overkill' approach whereby you rip the atoms out of the mined material. These ions are then filtered due to mass to charge ratio (like a simplified mass spectrometer) into collecting vessels. <br />The silicon removed by this method is then deposited to make amorphous silicon (amorphous is better than crystalline, if you know anything about solid state physics then this is a real puzzler, similar to why glass is transparent). <br /><br />The problem with the above system is trying to get the ions to the same energy easily. Perhaps it would simply be better to accelerate them to high speeds whereby the original binding energy is insignificant but this has it's own problems.<br /><br />There is a massive revolution occuring in the world of catalysts that should allow easy processing which should make most discussions at this point obsolete by the time a moon base is built. But it's fun to speculate anyway.<br /><br />All these ideas can be easily tested on earth and using cheap rovers on the moon before any people set foot on the moon.

 

[webtaz99]

My intent was not to create (or resurrect) a thread about general Lunar living. I just got the impression from my findings that multiple ways exist for making habitat spaces from Lunar materials. (Tunnels would be the obvious choice, but the "moonquake" data says that may not be such a hot idea.) It seems that all manner of bricks, panels, trusses and joints could be made, and even silicon-based "rubber" compounds. But any Lunar-built habitat will have to be sealed to hold atmosphere, and unless you've ever worked with HARD vacuum (I have) you can't really appreciate how tough that can be, especially over large areas. And Lunar vacuum, unlike the pitiful little spots we create, never stops "sucking". (Technically, "vacuum" doesn't suck - pressure pushes.) <br /><br />It just seems odd to me to see so much research on making oxygen and other materials out of Lunar regolith, and so much talk about making habitats from those materials, yet not thing about sealing them in. It's not a trivial thing, unless you want to wake up dead. And we certainly can't bring enough with us. <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

Iron dust can be separated from regolith with a simple electromagnet, a vibration hopper could also separate particles of regolith by density similar to how gold panning works. <br /><br />Once you've got relatively pure metal, you could weld with it by by melting and squirting it into the weld. Being a vacuum, space is the perfect place to weld things because the metal won't oxidize. A light robotic arm with a welder could build any shape part by simply layering beads of weld on top of eachother in the manner that a swallow builds a nest with spit. A little finish machining of the areas that need to attach to things, maybe a stress relief anneal, and it'd be done. <br /><br />This little robot could built the frame and shell of an entire habitat if given enough time, feedstock and power. Then it could go on to build anything else out of metal that is fairly large and crude, as well as feedstock that could be machined into smaller precision parts such as fasteners. <br /><br />The problems with vacuum in space are the opposite of the problems with vacuum on earth. It's much easier to hold pressure in than keep it out.

 

[webtaz99]

Experiements have produced "Lunacrete", but it would require fiberglass or other filler for strength. There is no doubt we could produce the gross parts for a habitat (walls, floors, ceilings, etc.) but it's the myriad seams and cracks between them that need sealing. Obviously, tiny leaks can be tolerated, but every gram of "air" that leaks must be replaced, and keeping it inside in the first place is better in the long run. Enough will be lost through airlocks and the like.<br /><br />In the long run, habitats will probably be built underground, for the obvious benefits. But in light of the Lunar seismic activity, they will built along the lines of NORAD, with habitats joined to larger volumes by springs (or other vibration-damping means).<br /> <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Iron sorted out can be turned into rebar "Lunabar(TM)" to produce reinforcement.<br /><br />Just what is the level of lunar seismic activity? Are we talking shakin and quakin, or merely your garden variety rumble?

 

[josh_simonson]

That's why I was suggesting to weld everything. Build the plates and beams, then weld it all. That way you get 100% metal seams and no leaks. <br /><br />You can also get an airtight seal that's vacuum hardy by squishing a gasket of soft metal, such as copper, lead, aluminum or magnesium between two harder fittings. Vacuum chambers used in microelectronic fabrication often utilize copper gaskets. Some type of solder is another possibility. I could even picture an airlock that solders itself sealed with every use, that'd be pretty dust-resistant.<br /><br />

 

[webtaz99]

From what I've been able to gather, serious quakes are rare, and large asteroid strikes as well. But there appear to be large numbers of Richter 1-2. This is admittedly rather minor, but any habitat would need to be flexible enough to withstand such tremors on a routine basis. And even tiny cracks will slowly get bigger. It's not so much a "threat" as a "design consideration". And when you make the (necessary) assumption of using plentiful Lunar materials, designing a habitat to withstand a serious (Richter 5) quake should not be difficult, and neglected at peril.<br /><br />While iron is plentiful on the Moon, some alloy would be needed for more strength. Raw iron is too brittle for structural use. Also, Lunar habitats will need to be modular in nature, for various reasons. So making one solid-piece habitat is not practical. The good news is that for the things iron can be used for on the Lunar surface, there's plenty of it, and it won't rust. <div class="Discussion_UserSignature"> </div>

 

[inventorwannabe]

Well I'm a bold one!<br /><br />When I'm going to build my base I will start to drill caves in to a suiting lunar hill or mountain. When I have got a large enough cave I will mix some easily bought chemical glues used to seal tunnels on earth from groundwather and put a none-yet-decided thickness off it on the walls and floor. Then I would put a rubber film on the "glue" and then start to pressurize the cavity! Easy isn't it, just keep the mixture slow burning so it will be sucked and pushed into the lunar rock. It will be elastic too so safety from lunar quakes might be disminished! An idea from the self healing hulls idea would be that you have extra layers of non mixed glue components separated by an membrane which will broke when the seal is broken! <br /><br />After a first cave there is no stop on how big the cavesystem could grow! The excavated material is to be processed to whatever one wants to get out of it!<br /><br />Start with 100 cubic meters and it will easily grow to whatever volume you want... Remember - energy out there is practically free for 14day periods!<br /><br />My 10c / IW<br /> <br />Hmmm bold was it... 100 cu meters... Thats for ants - I meant of course 1000000 cu meters. Thats 100m*100*100m. With the right light I could grow trees in there Trees? I ment a small forrest of course!<br /><br />I noticed that there were some parallell threads on this issue and I won't build my base of any inflexible material... So revert!<br /><br />Brgds / IW<br />

 

[josh_simonson]

Aluminum can be welded too, it's just a bit harder get it in it's metallic form.

 

[arobie]

Steve, Lol, I knew you would come in the thread and talk about solar energy density. You are persistant. So we all are apparently. Other than to say that, I don't have much to say on that topic. It's already been argued in detail and in length. I'm not up for a debate on it.<br /><br />I wanted to bring up an article about Moonquakes since this topic was mentioned here. Space.com ran this article last month. <br /><br />Moonquake Concerns: Bases Might Need Special Construction<br /><br />The seismometers placed by the Apollo missions gather data on Moonquakes until they were switched off in 1977. The date shows there to be four kinds of Moonquakes:<br /><font color="yellow"><br /> * Deep moonquakes (~700 km below the surface, probably caused by tidal in origin)<br /> * Meteorites impact vibrations<br /> * Thermal quakes (the frigid lunar crust expands sunlight returns after the two week lunar night)<br /> * Shallow moonquakes (20 or 30 kilometers below the surface) </font><br /><br />The first three are mild while the last one is the most intense, registering up to 5.5 on the Richter scale. Between 1972 and 1977 twenty-eight shallow quakes were observed by the seismometers placed by the Apollo missions which only covered a small portion of the Moons surface.<br /><br />To me that data shows them to be frequent and strong enough to require attention.