Why Isn't Concrete Used On Space Stations Or Space Craft

[andytak3740]

Hello everyone, 

 

A friend of mine has asked me a question that I was too stumped to answer. "Why isn't concrete used in space stations and in space craft? In both real life or in science fiction." This question stumped me and I still haven't figured out a response. What do y'all think. I thought concrete could possibly be used in space stations or installations. Though, I am not entirely sure on the matter.

 

 

[GAHD]

Too expensive to fly it up there. Everything in space has to be as light as possible just because of the massive amount of money it takes to get it up there. I think it works out to around $10 000 per pound? Somewhere in that ballpark.

A really great business model might be to get something up into LEO that can "catch" the smaller debris and lump it all up to be moved around and make "space concrete" out of it. Save money on all the aggrigates and what not and just need an epoxy binder or some kind of solar welding to make a shell out of the bits. That or mine some of the near-earth asteroids and shift that stuff around to use it. Those kind of situations would be a little more likely to get used.

Space concrete IS part of some science fictions, but the "rule of cool" generally has things made out of more..."cool" things than plain old silica+binder. Troy Rising has some use of it, if I remember correctly. They quickly move on to Nanotube Carbon Fiber, artificial sapphire, and other "high performance" buzzwordium though.

So, that's it really: Things Cost Money. Concrete is expensive to get up there. Aluminium, Cromoly, Steel, Titanium, Carbon Fiber, Kevlar, and Plastics just get the job done a few thousand dollars per pound cheaper than silicon and lime.

[andytak3740]

Thanks for the reply and the informative answer. It really helped. So, unless we can mine the materials required from objects with minimal gravity, it is just to costly to use. That makes sense. Once again thanks.  

[exchemist]

If you are thinking of mining cement on the moon with its lower gravity or finding it on an asteroid, Cement is made from calcite fossilized shells and corals.

 

Our moon and asteroids have no "life as we know it" :). and no cement

You would also need either water or CO2 (for hydraulic and non-hydraulic cements respectively) as setting agents. 

[exchemist]

UMMMM    water might be found in ice at the poles of the moon, there are comets full of ice. https://en.wikipedia.org/wiki/Lunar_water Water might be available in frozen form. http://enacademic.com/dic.nsf/enwiki/11764572 and there might be a lot of it.

Sure. I was just thinking of how you would mix liquid water into something, in a vacuum.....

 

But the whole thing is daft anyway, for the reason you originally gave - no CaCO3 type minerals in the first place. 

[exchemist]

:hihi: I wonder , since brexit might happen and the UK might leave EuropE, if we try looking further afield for CaCO3 and water, for another EuropA,  :hihi: just maybe life under the oceans of Europa might turn into cement. Clearly this is not a concrete idea, but it might work     and the tidal forces of Jupiter could arrghh do the mixing of this less than concrete idea.    

 

https://solarsystem.nasa.gov/moons/jupiter-moons/europa/in-depth/  

Yes, well, the UK can't stop being part of Europe, whatever the Moggatollah thinks. All we can do is leave the EU - if we are nuts enough....... :)

[andytak3740]

If we were to gather the required raw materials from moons, asteroids, and comets couldn't we synthetically make our own? All we would need are sources of carbon, water, oxygen, calcium and probably a few other resources. It seems that the only thing hindering concrete would be how to make, pour, or use it properly. I thought that it would be useful in quickly making cast forms through injection molding. For example you could have a facility that mines a moon, processes the materials, mixes the ingredients, inject the mixture into a mold, heat the cast, and then release the cast item to be used. Wouldn't a machine of this sorts be useful in rapid construction of a structure on the moon. What do y'all think? Makes sense?

[exchemist]

If we were to gather the required raw materials from moons, asteroids, and comets couldn't we synthetically make our own? All we would need are sources of carbon, water, oxygen, calcium and probably a few other resources. It seems that the only thing hindering concrete would be how to make, pour, or use it properly. I thought that it would be useful in quickly making cast forms through injection molding. For example you could have a facility that mines a moon, processes the materials, mixes the ingredients, inject the mixture into a mold, heat the cast, and then release the cast item to be used. Wouldn't a machine of this sorts be useful in rapid construction of a structure on the moon. What do y'all think? Makes sense?

No. Far too complicated and at the end of it you would have a heavy material, with no tensile strength, that was porous. Not good for sealing in the air one would need for habitation. If you are going to all that trouble you'd be better off mining for aluminium (plenty in silicate minerals) and reducing that using solar electricity, I would think. 

Edited January 24, 2019 by exchemist

[GAHD]

No. Far too complicated and at the end of it you would have a heavy material, with no tensile strength, that was porous. Not good for sealing in the air one would need for habitation. If you are going to all that trouble you'd be better off mining for aluminium (plenty in silicate minerals) and reducing that using solar electricity, I would think. 

I'm not very up-and-up on the Al content of moon dust, but I'm going to say I think you're wrong about the useful properties of concrete-like materials in space or on the moon. For one, sealing could be easily accomplished with a VERY thin layer (or two or three because redundancy) of any non-permeable material on the inside of any such building. For another, aggrigate-in-binder construction(concrete/cement in a very broad view) is a very useful way to "fill out" a shortage of whatever the binder is without sacrificing overall strength; sometimes the end properties of the resultant materiel are quite superior to it's component parts after all.

 

I seem to recall in-place construction like that being a big part of several NASA proposals for a moonbase I've seen in the past. I'll see if I can find them when I have time to really dig.

 

The prevalence of Fe in untrafine particles in moondust would probably mean that some kind of Vapor-deposition laser-welding(printing) of solid iron could be a good option as well, but even just using that dust in an unrefined state as an aggrigate would yield some very useful properties to a "space concrete".

 

[exchemist]

I'm not very up-and-up on the Al content of moon dust, but I'm going to say I think you're wrong about the useful properties of concrete-like materials in space or on the moon. For one, sealing could be easily accomplished with a VERY thin layer (or two or three because redundancy) of any non-permeable material on the inside of any such building. For another, aggrigate-in-binder construction(concrete/cement in a very broad view) is a very useful way to "fill out" a shortage of whatever the binder is without sacrificing overall strength; sometimes the end properties of the resultant materiel are quite superior to it's component parts after all.

 

I seem to recall in-place construction like that being a big part of several NASA proposals for a moonbase I've seen in the past. I'll see if I can find them when I have time to really dig.

 

The prevalence of Fe in untrafine particles in moondust would probably mean that some kind of Vapor-deposition laser-welding(printing) of solid iron could be a good option as well, but even just using that dust in an unrefined state as an aggrigate would yield some very useful properties to a "space concrete".

 

Yes, on reflection you are clearly right of course about the porosity issue. I'd be interested in what you can dig up about ideas for building materials on the moon. 

 

The reason I mentioned Al is that this is a prevalent element, in feldspars, which seem to be a common rock type on the moon: https://en.wikipedia.org/wiki/Moon_rock#Composition

 

Regarding iron, is there much elemental Fe on the surface? If so I would agree it seems an obvious material to use, as it would not need chemical reduction, which would need to be done electrolytically due to the absence of carbon or other reducing agents and would take a lot of energy. 

[exchemist]

In the early days of human development on earth, people lived in caves. If you are going to the trouble of mining rocks on the moon, why not dig a hole and live under the surface of the moon in a cavern. 

 

 

 

The melting temperature of aluminium is around 600 C other metals have different temperatures https://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html . 

 

It might be possible to reach these temperatures using solar mirrors. https://en.wikipedia.org/wiki/Concentrated_solar_power .

 

Is raw aluminium found on the moon as bauxite, or due to the lack of air would it be found in purer form requiring less processing than on earth. https://www.chemguide.co.uk/inorganic/extraction/aluminium.html

 

I think this exercise might be cost prohibitive, the accountants might use a bigger rocket and blast a pre fabricated house into space in stages, and maybe just maybe be able to construct a space station, oops its been done already. https://en.wikipedia.org/wiki/Space_station

I agree it is speculative, but there is plenty of Al in feldspars. If one has solar energy one has electricity. Al is normally reduced from its ore by electrolysis. Admittedly this is Al2O3 on Earth rather than an aluminosilicate rock, but it ought to be feasible in principle. I don't pretend the economics would be great though. 

 

As for digging holes etc, the question I have is what is one trying to protect oneself from, on the moon, and is a hole the best way to do it?  It's not the weather, or wild animals.

Edited January 25, 2019 by exchemist

[GAHD]

I agree it is speculative, but there is plenty of Al in feldspars. If one has solar energy one has electricity. Al is normally reduced from its ore by electrolysis. Admittedly this is Al2O3 on Earth rather than an aluminosilicate rock, but it ought to be feasible in principle. I don't pretend the economics would be great though. 

 

As for digging holes etc, the question I have is what is one trying to protect oneself from, on the moon, and is a hole the best way to do it?  It's not the weather, or wild animals.

Yeah from what I've looked at the average of the apollo samples seems to be around ~60% oxy, ~12% aluminum, ~12-16% silicon, the rest a mix of iron, titanium, Chromium, Calcium, Phosphorus, etc... In responce to your previous post: Not too sure how much of the iron and iron-group are found elemental, I just remembered that the seals and bearings of the rover's wheels got chewed up because the electric motors attracted the iron dust while they were going on their jaunts. So, appreciable amount of it pure enough to be ferromagnetic and thus easily collected by exploiting that property along with mesh-sifting.

 

So really, using some electrical method to separate the finer dust would yield useful materials. Converting into an ionic plasma and magnetically separating that plasma could be an analog industrial method(upscale the standard practice). Energy intensive, but with enough solar power...feasible? Depending on how it's done, re-condensing the pure oxy would be a nice side benefit. (Or just let it gass-off into space.) That's a bit outside the purview of thread topic, but still an interesting digression.

 

Micrometeorite strikes is the first thing I can think of. No atmos to slow them down or burn them up. The moon IS the earth's big shield after-all. Energetic rays and accelerated ionic hydrogen being another couple of things a good and thick wall would be useful against. Really, some method of heat-fusion into bricks would probably be a good thing to focus on. Could have a purpose-built autonomous rover that just sweeps up dust and drops bricks in it's wake for future assembly by either a human mission or another purpose built machine. Maybe a semi-mobile Solar-sinter.  Again, slightly offtopic from OP, but useful digression.

 

Based on those elements, what do you think could be a viable binding agent? Lot of oxy and decent alum seems to say extruded sapphire might be a good choice, but for simplicity sake and to make a viable production:energy I do think some kind of binder padded-out with loose soils for volume would be a good idea.

 

 

 

[fahrquad]

Concrete is too porous to hold air to be a practical material and too heavy (and expensive) to launch in to space, not to mention the problem of getting it to cure in a frigid vacuum.  Building in space with metal would be easier since there is plenty of it whizzing by in the form of meteors, asteroids, and derelict satellites.  I am not sure how much though has been given to the idea of building with ice.  A thin membrane could be deployed, then inflated with a small amount of gas, then sprayed from the inside with liquid water to freeze on the frigid membrane.  Successive layers of ice could be added to attain the desired thickness.  Sealing punctures would be a simple process from the inside.  Ice is fairly abundant in comets, asteroids, and some moons.  If sublimation becomes an issue, a reflective coating could be applied to the surface facing the sun.   

[fahrquad]

Oh heck, why don't we just build a giant ring around the sun using all of the material in the solar system like Larry Niven's novel "Ringworld".

 

https://en.wikipedia.org/wiki/Ringworld_series

 

There are no new ideas, jut new people to think them up.  --Me

[GAHD]

Concrete is too porous to hold air to be a practical material and too heavy (and expensive) to launch in to space, not to mention the problem of getting it to cure in a frigid vacuum.  Building in space with metal would be easier since there is plenty of it whizzing by in the form of meteors, asteroids, and derelict satellites.  I am not sure how much though has been given to the idea of building with ice.  A thin membrane could be deployed, then inflated with a small amount of gas, then sprayed from the inside with liquid water to freeze on the frigid membrane.  Successive layers of ice could be added to attain the desired thickness.  Sealing punctures would be a simple process from the inside.  Ice is fairly abundant in comets, asteroids, and some moons.  If sublimation becomes an issue, a reflective coating could be applied to the surface facing the sun.   

Vacuum is not frigid. Vacuum stops heat transfer because there's no air to drag it away, the only heat loss is black-body radiation, this is why satellites can easily overheat. Just saying.

 

[fahrquad]

Sorry, but I was assuming construction would be in the shadow of a body to prevent exposure of construction personnel to solar radiation.

[GAHD]

Sorry, but I was assuming construction would be in the shadow of a body to prevent exposure of construction personnel to solar radiation.

Don't be sorry, just take it as an opportunity to learn and think. Now that you mention it it brings up an interesting point: Chemical reactions, like say binder-hardening of cements, could easily lead to runaway overheating. That's a valid concern. There's no atmos to pull the excess heat away after all.

 

Space being "cold" is a rather interesting misconception a lot of people have. I mean, there IS an absence of heat energy, but that doesn't lead to "cold" the same way it does down on this rock. Edit: you gotta think of free space as a giant thermos tube to really get a grasp on it I guess. The soup inside stays hot longer.