# Effects of Low gravity - On construction



## Moonbat (Feb 26, 2014)

I was thinking about this earlier and wonder what the effects of low gravity - say that of the moon - would be on the construction industry.


If, for instance, someone was building a structure on the moon, what kind of advantageous or detrimental effects would the low gravity have?


I think, though I may be wrong, that any machinery or human would be able to lift about 6 times as much weight (I know that it should probably be mass here - or should it?) as it/they could on earth.


Also, as things fall more slowly, is this with less force, would they need hard hats? I expect if the thing falling was more than 6 times heavier/more massing than a brick on Earth than it would still cause a head injury - but I'm wondering if I'm right.


How would it affect things like cranes and digging machines?


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## Parson (Feb 26, 2014)

Well, firstly the engines would have a hard time running on vacuum.


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## chrispenycate (Feb 26, 2014)

Yes, it should be mass. You can lift the same weight. 

And you can build structures much higher, less massive because there is less weight per mass. This goes for the buildings themselves, and cranes and the like. Bulldozers are going to look much the same, despite having electric motors and solar cells, if they're working outside.

Most plans for Luna colonies involve digging underground, both for radiation screening and temperature stabilisation (with the big transparent domes beloved by early SF the fortnight of day would have your heat pumps running flat out to stop you cooking, then the fortnight of dark would reverse this trying to freeze everything to minus two hundred degrees (umm, sorry. You used the moon as an example, not a rotation standard. But any low gravity environment's likely to have very little atmosphere, which is part of the problem. Underground has considerable advantages, not the least of which is you can seal it off and pressurise it; much easier to work without total environment suits.

And remember, a breeze block might have one sixth its Earth weight, but it still has exactly the same inertia, and you've got a fraction of the friction to control it. Your reflexes will take months to adapt, during which time I seriously suggest you keep the hard hats - remember, a brick hitting you on the head from just a few inches can be quite unpleasant (I've had stiches to remind me), and a lot of the time it'll be the head hitting other things as physics doesn't react as your body thinks it ought to.

If you do have atmosphere dust is going to take roughly forever to settle, so breathing masks and antistatic goggles.

Fractional friction – when you lean against a drill or block you're pushing in your feet slide away unless you've chocked them. Same when you swing a hammer. You have to fall from quite a height to get enough speed to kill yourself, but remember that on Earth you can sprain an ankle with as little as a couple of centimetres, a step that isn't there. Carelessness with the apparently benevolent lower gravity and the body's millennia incorporated reactions will fill fracture wards. Use robots whenever suitable; more expensive, but programmable to conditions.

Poured concrete will always have to be vibrated into place; it'll take too long for all the air bubbles and impurities to surface on their own.


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## mosaix (Feb 26, 2014)

My brother-in-law trained to be a civil engineer. 

He was once asked by a lecturer "What stops buildings falling down?"

The answer: "Gravity!"

Gravity plays an important part in holding the structure of a building together.


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## jastius (Feb 26, 2014)

there are physical effects upon the human body as well.


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## Moonbat (Feb 26, 2014)

Thanks for the responses.


I guess the machines would have to be in a pressurised dome with air to run on normal fumes, but then the exhaust would need to be dealt with, Solar seems better, but what about the 14days of  night. Makes for an interesting shift rota.


As for the domes, do they have to be transparent, can they not be covered with solar panels and use the heat?


Dust is interesting, and so is the concrete, and drilling. 


What would happen with a hammer hitting a nail, would I (the builder in a pressurised dome building a wooden hut, be able to bang a nail in normally, or would I need to be tether tightly to the ground? Could I generate enough force with a down swing?


So as far as the structures are concerned they could be larger with engineering stresses being less, so fewer beams required. Also, would about a rollercoaster? Would larger loops be possible or not? Would it be able to pull faster turns and yet not inflect as many G (should that be lowercase? g) 's on the people riding it?


Thanks again for the responses.


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## chrispenycate (Feb 27, 2014)

A gravity powered roller coaster (as on Earth) would be pretty unimpressive, with one sixth the acceleration. If you did a linear accelerator style you could turn it upside down with less physiological stress, and free fall sections, which can last seconds on a one gee ride, could be extended considerably (with strategic paper bags). However, if anyone has travelled there from Earth presumably they've experienced enough free fall that it will no longer impress.

Knocking a nail in will be a little like doing the same under water - you'll need to attach yourself solidly, hooking your toes under something so you're not thrown backwards with each hit. I recommend a nail gun, with anti recoil (we didn't have one under water; I don't know if one existed back then). Most of these problems can be prepared for in a swimming pool cheaply, and specialist tools can be developed – we did it, NASA did it.

Yeah, you can put solar panels on the dome; you're still going to get very hot in daytime, and they're not going going to slow night time cooling much. And since you're not able to see the stars (or Earth) with an opaque dome, why not bury it a few metres into the regolith? You can put a high enough ceiling that you can build small skyscrapers – well, roofscrapers – and project clouds or stars onto it; it doesn't have to be claustrophobic. And ghost trains should be very impressive (helter skelter's out, though).


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## Mirannan (Feb 27, 2014)

Another interesting point about low gravity construction is that security measures on upper floors of buildings inside domes might have to be a bit better than they are on Earth. Why? Two reasons at least. First, cat burglars would have an easier time of it; climbing drainpipes or whatever would be easier and less dangerous. The other reason is a bit more exotic. In 1 bar pressure and under lunar gravity, it would be possible (just) to fly using strap-on wings. Batman's antics in the comics might actually be practical...


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