Engineering question

"Spanfeller is a twat" (theaspiringengineer) 08/15/2019 at 15:02 • Filed to: None

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An architecture student approached me yesterday to ask me a very complicated question. How could he design a water pumping system in the moon. for a homework assignment I guess.

I’m not very confident in my engineering skills, after warning him I told him that I could only imagine a solution to the problem.

Water cannot exist as a liquid in the moon, because the atmosphere is nonexistent, so this water pumping system would need to include an inert gas. He could use a pump to introduce more gas into the tank and push the water out on the bottom, since the moon does have gravity this could work.

If this system was made for a moon station, it could even use air as the gas.

maybe ya’ll have a better solution.

Edit:

Thanks for pitching in!

Highlander-Datsuns are Forever > Spanfeller is a twat 08/15/2019 at 15:07

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PV=n RT

Michael > Spanfeller is a twat 08/15/2019 at 15:12

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Check out a well pump system.  Put some inert gas in the tank.

gmporschenut also a fan of hondas > Spanfeller is a twat 08/15/2019 at 15:13

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Sunny side or dark side?

One is 127c and the other -173c

MasterMario - Keeper of the V8s > Spanfeller is a twat 08/15/2019 at 15:14

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If it’s a closed system then it doesn’t matter what the lunar atmosphere is. The water itself will become the gas within the system wherever pressure is low enough. 

3point8isgreat > Spanfeller is a twat 08/15/2019 at 15:14

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Pretty sure it’s work fine as long as it is a closed system. Then the water isn’t able expand to basically infinite volume.

If the water were added to the system after the system we’re built in the vacuum, you’d just be able to better fill it completely and not hav e bubbles. And unfilled volume would get filled with water vapor up to whatever vapor pressure water can make at that temperature.

Snuze: Needs another Swede > Spanfeller is a twat 08/15/2019 at 15:14

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Where is he trying to pump the water to? Is it just to circulate it in a habitat or something? Or is it going to be pumped across long distances, like a pipeline? Also, you’re right, liquid water cannot exist out in the open, but in a closed piping system it could work.

Below is the phase diagram of water.  The triple point exists at 611 Pa and 0.0098*C.  In other words you can have liquid water at very low pressures and relatively low temperatures, so the lack of atmosphere isn’t actually as big a problem as you’d think. In fact if you pressureize the system sufficiently you can keep the water liquid even below 0*C.  

MKULTRA1982(ConCrustyBrick) > Spanfeller is a twat 08/15/2019 at 15:16

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I’m no geologist, but wouldn’t you be able to move the water as a gas, and then convert (probably easier said than done) when it is needed? Maybe the Tang could just be added into the water when it is a vapor to save a step? 

Spanfeller is a twat > Highlander-Datsuns are Forever 08/15/2019 at 15:17

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yes.

Spanfeller is a twat > gmporschenut also a fan of hondas 08/15/2019 at 15:18

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I do subscribe to Pink Floyd’s lunar illumination theory.

Kidding aside, I guess it would have to be in the most habitable zone.

jminer > Spanfeller is a twat 08/15/2019 at 15:19

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You would only need to handle it as a gas in a vacuum. If we assume this is built around a pressure and temperature controlled environment like would exist if we needed water on the moon it gets much easier. The only real thing is you have to account for the essentially zero gravity.

Spanfeller is a twat > MasterMario - Keeper of the V8s 08/15/2019 at 15:20

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Yep, since water loses energy as it boils.

random001 > Spanfeller is a twat 08/15/2019 at 15:20

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It’s the moon.  Two words: conveyor belt.

Spanfeller is a twat > jminer 08/15/2019 at 15:21

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For the gravity part I had two solutions, either add an inert gas as a pressurizer, or a heating element to form water vapor, again, as a pressurizer.

TheTurbochargedSquirrel > Spanfeller is a twat 08/15/2019 at 15:30

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What are we trying to do here? Plumbing to a moon base? If that’s all we are trying to do you just need to fly water to the moon, put it in a storage tank pressurised by the atmospheric pressure you maintain inside your moon base, and then either use a standard water pump to pump it where it needs to be or put your storage tank up high and let the moons gravity make your water pressure for you. Your only concerns being on the moon is that a leak in the system outside the pressurised area of the moon base will cause the water to boil off.  That and the fact that getting water to the moon is a PITA. Water is surprisingly heavy.

MrDakka > random001 08/15/2019 at 15:32

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Put your back into it. The ice ain't gonna mine itself

Spanfeller is a twat > Snuze: Needs another Swede 08/15/2019 at 15:33

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In the end it was a closed system, admittedly he didn’t give much detail originally.

Spanfeller is a twat > TheTurbochargedSquirrel 08/15/2019 at 15:36

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Yeah, I did warn him that any leaks would be very problematic. Then I guess that using the most dense gas possible as the inert gas would be preferable (but then again, you’d need to store that inert gas somewhere when you don’t need it, and that’s less practical compared to compressing the tank using the base’s air)

TheTurbochargedSquirrel > Spanfeller is a twat 08/15/2019 at 15:49

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Pressurizing it using the base’s atmosphere is the simplest way to do it. No need to use the pressure to actually move the water, you still have gravity and water pumps.

jminer > Spanfeller is a twat 08/15/2019 at 16:46

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But the pressurizer wouldn’t work that well without extensive use of check valves otherwise the water coul d go back out the in. It's an interesting thought experiment for sure.