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tahanson43206

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Registered: 2018-04-27

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Re: Air locks

Louis created this topic, and I note that in 2017, JoshNH4H described the habitat atmosphere in terms that match up reasonably well with the consensus that has emerged since then.  The consensus boils down to the 3-5-8 rule, that every Mars child must learn from the earliest possible age. 

I looked for a topic with the words "air" and 'lock" because in early 2025, Calliban reminded us of the practical solution for a non-mechanical air lock.

A U shaped reservoir of water could serve as an air lock on Mars.  Such an air lock would need an evaporation cap at the surface, and it might need something similar inside the habitat.

There are two advantages that I see for using such an air lock...

First, there is no need to maintain a seal around the door, which would be required on every other air lock on Mars.

Second, the water would automatically collect Mars dust as residents move from outside through the tunnel to the habitat.

Calliban pointed out that Mars suits that travel through the water passage would collect water on the surface, which would evaporate on Mars. Thus, there would be a need to replenish the water in the lock.

Everything has tradeoffs.  I expect that only the very wealthy will have air locks of this type.

This topic is probably worth a read from the top.

(th)

Void

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Registered: 2011-12-29

Posts: 8,307

Re: Air locks

A Barometric Airlock.  I have been into that sort of thing for some time.

Search "Barometric".

I would suggest that you might look at what that could fetch.

If you had a shed on top of a lake which was covered in ice, then you might have a hatch that covers a hole in the ice.
If the shed can be pressurized to lets say 50 mbar of Martian atmosphere, then you could open that hatch and boiling would not be so much of a problem.

If you had a Hoist in the shed above the hatch, you would bring large items in and out of the lake.

https://endmemo.com/chem/vaporpressurewater.php
Actually  23.2977 mbar is enough for 20 deg C water.  So, you could probably go down to 12 mbar or so as the maximum pressure the shed would have to hold.  That would almost deal with 10 degree C water.

The Shed, would have horizontal doors like a barn, for instance that would need to be capable of holding up to 12 to 24 mbar of pressure.  When the shed was pressurized those doors would be closed, and the hatch could be opened in the floor leading into the lake a load could be transferred Lake<>Shed.

Then the hatch could be closed, and the "Barn Doors" could be opened and the loads transferred Mars Surface<>Shed.

While humans in suits could move though this method(s), it would be much more sensible to be more safely and efficiently remotely teleoperating robots from a safe spot at the bottom of the lake for instance.

Ending Pending

Search Barometric: https://newmars.com/forums/search.php?s … d=78699263

Last edited by Void (2025-02-03 10:39:20)

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Void

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Registered: 2011-12-29

Posts: 8,307

Re: Air locks

You arguments have some merit, but as you have suggested mine might have a place as well: https://newmars.com/forums/viewtopic.ph … 74#p229574
Quote:

tahanson43206
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For Void re #124

Thanks for your reminder that water exists on Mars.

This is a situation where we both can be right.

I stated that only an obscenely wealthy individual could afford to pay for the water that may exist on Mars to fill a lake.

The fact that water exists on Mars does not mean it is affordable to average persons.

On Earth, it is possible to buy a one liter bottle of water for $1.50 at a convenience store.  Apparently one liter can be purchased for as little as 50 cents.

On Mars, in 2025, the price of that bottle of water is infinite.

When the first liter of water lands with the first humans to drop in on the planet, that liter will cost about 80 billion dollars, give or take.

After many many decades, and possibly centuries, the price of a liter of water may fall to the equivalent of 50 cents.

I conclude that in this conversation, it is possible for us both to be right.

All we have to do is to select the epoch we are talking about.

(th)

We still don't have the ground truth the extent that I think Dr. Johnson would be comfortable with.

But the ISS already can tightly recycle water.  So, a little water would go a long way.  The bulk of water will be wanted to make propellants.  Nuclear power would be a good choice for the surface of Mars, I think that most people now believe.

We will want large ice bodies for fuel.  But for Make-Up water for people:
https://www.extremetech.com/extreme/167 … of%20water.
Quote:

If you heat up a cubic foot of Mars soil, you can harvest around two pints (one liter) of water. According to new data returned by NASA's Curiosity rover, this isn't just a one-off lucky find, either: It seems that most of the dirt on Mars harbors large amounts of water.

If you have electrical power either nuclear or solar, then you could likely get that water sufficiently to make it on Mars.
But of course that may be more trouble than extracting large amounts from an ice body.

If you want to use nuclear reactors, you will want to have radiators.  A pond or lake can be such a radiator, and an airlock, and a farm.

A Lake with an inflatable dome over it might be covered in ice.  It may not even need to be a transparent dome, just to serve as a vapor barrier and a radiator.  With nuclear you may become less dependent on solar.

So, if you want gardens you can have them in chambers under water, or in vaults dug in the rock under a body of water.
Much of the agriculture might be precision fermentation type, so you don't even need lights for it.  You just need electricity to crack water into Hydrogen and Oxygen.  The Oxygen you can breath or use as propellants.  The Hydrogen of course can be used in precision fermentation along with CO2.

If you have a lake with a low pressure dome over it, then you can play with day/night temperature fluctuations.  At night frost will move from the ice to the interior surface of the dome.  During the day that frost will evaporate as sunlight warms the dome.  You can then compress the humid air inside the dome to produce distilled water.

So, you see the whole setup might serve rather well.

Then if you want greenhouses on the surface to grow vegetables you can do that as an independent function.

Much food can be stored indefinitely on Mars using freezing and drying.  So, your solar dependent economy could tolerate interruptions like dust storms or winters.  But your nuclear process will make sure that you have Oxygen to breath and water to drink, and even food from precision fermentation and mushrooms and stored frozen and dried foodstuffs.

Large amounts of water near Candor Chaos, the size of the Netherlands: https://www.newscientist.com/article/23 … e-equator/

It has to be evaluated how deep that water goes and if it is brine or ice or a combination.

A landing by SpaceX with robots might be able to give information on that.

Ending Pending

Last edited by Void (2025-02-03 12:50:36)

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tahanson43206

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Registered: 2018-04-27

Posts: 21,086

Re: Air locks

The subject of airlocks came up again in the context of Martian dust, and specifically the need to clean off the dust before entering a habitat on Mars from a trip outside.

There seems to be some misunderstanding of how a water lock on Mars would work, so I'll try to make a sketch to show what's involved.

The key concept to understand is that the air pressure inside the habitat must exactly balance the water column.  The generally accepted habitat pressure is 1/2 bar.

This means that the water column must provide exactly that pressure so that the contents of the water lock do not enter the habitat, or blow out into the Mars landscape.

Google came up with a height of 13.437 meters for a water column able to exert a pressure of 1/2 bar (50,000 Pascal).

What this means is that a J (jay) shaped pipe has the low end of the J inside the habitat, where pressure is 1/2 bar of air.

The tall section of the J must rise 13.437 meters above the surface inside the habitat.

The net effect is that a home owner or business owner has the option of building a standard air lock with features to remove dust from the Mars suits of visitors, or of building a water lock.  The water lock has the distinct advantage that no time is wasted pumping habitat air into the air lock, or dealing with all the dust that the visitor's Mars suit will be carrying. On the ** other ** hand, the visitor will have to enter the water at the top of the J and climb (or swim?) down and through the inverted arch of the J, to rise in the habitat wearing a wet but dust free suit.

I'll try to create a drawing to show what this might look like.

In various posts scattered throughtout the archive, Void has pubished suggestions for removing dust and other debris from water.

For the record: JoshNH4H posted about a water lock: http://newmars.com/forums/viewtopic.php … 04#p142104

The system described by JoshNH4H would involve the person donning a bag and filling the airlock with water.

Note: The "dust door" at the top of the J tube has a more important function than keeping dust out of the opening. It is there to prevent evaporation. While the door is open for passage of a resident, evaporation will occur.  A supply of replacement water will be needed.

(th)

tahanson43206

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Registered: 2018-04-27

Posts: 21,086

Re: Air locks

This is a follow up to post #54...

The hand drawn sketch in post #54 is a bit too random for a public exhibition like this, so i looked for tools to try to improve the straight lines, and to some extent to improve the curved ones. 

Image here:

Update: Per feedback from GW Johnson, the label over the top of the J tube will be changed from "dust cover" to "evaporation cover"

In addition, the entrance will be set on the crater wall and the habitat moved inside.

In addition, the bend of the J tube will be compressed to the extent practical.

In addition, the surface of the J tube inside the habitat needs to be secured with a cover.

The interior cover would have a number of uses, but controlling access to the interior of the habitat is one that most home owners might appreciate.  Prevention of evaporation inside the habitat is another use that might be valued. Prevention of accidental dropping of tools or household items into the opening of the J tube is another.

(th)

GW Johnson

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Registered: 2011-12-04

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Re: Air locks

The water column height that makes this work is not the top to bottom height of the J-tube.  Is is the difference in elevations between the outside entrance surface and the habitat floor level surface inside.  There does not need to be a deep bend. 

Put the habitat instead just under the crater floor,  and the entrance instead 13.5 m (less the hab floor burial depth) higher up the adjacent crater wall,  and you do not even need the ladder!

Biggest problem will be the water freezing,  or the water evaporating at a high rate from the exposed water surface at the entrance.  I'm not sure which will dominate. 

But the local atmospheric pressure on Mars is 6 to 7 mbar generally.  That's not enough to stop violent boiling away of the water.  Even if it is a bit higher in some areas so that the violent boiling didn't occur,  you would still have a very high evaporation rate! 

The only thing that stops the (non-violent-boiling) high evaporation rate is when the vapor pressure of the water in the local air,  not just the local air pressure,  exceeds the equilibrium vapor pressure of just-at-freezepoint water.  Warm the water and that vapor pressure requirement is even higher.

What you really need for such an application is a liquid with almost no vapor pressure at all to slow its evaporation rate,  a much lower freezepoint to limit freezing effects,  and preferably a much higher density.  The higher density would lower the height difference between the exposed liquid surfaces,  making the design far easier to implement.

Mercury immediately comes to mind,  but with all the toxicity problems it brings.

GW

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GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

tahanson43206

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Registered: 2018-04-27

Posts: 21,086

Re: Air locks

Thanks to GW Johnson for feedback in Post #56

Here is a revised drawing incorporating several suggestions:

Additional feedback is welcome!   It is likely only the very wealthy Mars residents will be able to afford the fresh water to fill this system.

Everyone else will need a double door lock system with dust removal systems of some kind.

As we move closer to actual residence on Mars, the designs for living there will evolve from hand waving to architectural drawings.

There will be an entire industry devoted to air locks, with multiple competitors.

(th)