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#1 2017-11-18 06:10:32

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,792

Air locks

Do people have any views on air lock chamber design for habs on Mars?

My view is that human EVAs shouldn't be very frequent or necessary.  Mostly, the Mars pioneers can get around in pressurised vehicles - mini-vehicles, similar to a golf buggy, for going from A to B on the base with larger rovers being reserved for exploration missions, mining and so on.

Do we need a double air lock to minimise dust entry into habs?  There could be two chambers: the first is where the dust is showered off the vehicle.  Humans could then leave the vehicle by a rear connection to chamber number two, not coming into contact with the dust covered vehicle.

Other approaches could included pressurised inflatable corridors used to create pressurised walkways between habs, so minimising use of vehicles to connect. 

Explorer rovers used for EVAs should have integral shower cubicles for washing dust off EVA suits and then for humans to shower. The use of disposable overalls might be considered. It might make dust management if overalls were discarded on re-entry to the Rover.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#2 2017-11-18 08:37:18

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,565

Re: Air locks

Problem 1:
moon-bfr.jpg

Just getting to the ground since the craft will not be designed with any exit at its bottom....

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#3 2017-11-18 10:19:34

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Air locks

The base's ability to interact with its surroundings is going to be vital, and therefore I expect that there will be a lot of different ways to get in and out. 

As far as people and things are concerned, you're going to have airlocks of various different sizes, from person-sized up through vehicle-sized (and also airlocks to pressurize raw materials that have been mined and depressurize construction materials).

I think vehicles in general will not be in pressurized garages but will connect to larger habitats through mated airlocks, maybe with some kind of "jetway" style connection.  Density may end up being the name of the game in Martian cities, and I think individual habitat buildings will tend to be tall (maybe 10 stories?) and clustered fairly close together.  When the settlements get big enough you might see some kind of streetcar used for indoor transportation between buildings.

Keeping dust out of the habitable parts of the settlement will be important, but some amount of dust is always going to get through and there's pretty much nothing that can be done about it.  Hopefully it's not too toxic.  I'd look towards an anti-dust coating on the outerwear, a pretty aggressive blow-down during pressurization (think something like those new, high-powered hand-dryers across your entire body), and maybe wiping down with water to keep the dust from getting into the air.

Lockers for storage will probably be located just inside the airlock to prevent unnecessary contamination of other parts of the settlement.

Speed will be the name of the game for airlock transitions.  The faster you can depressurize and get out/in, the better.


-Josh

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#4 2017-11-18 11:23:51

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
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Re: Air locks

Dear Louis: Any Mars base will probably be built with pressurized tunnels connecting everything except things that have to be kept at a distance, like launch pads. Control areas will probably be in the main part of the base, not scattered about in separate, isolated pressurized structures. This is a safety issue; every pressured structure needs at least one, if not two, escape routes. I would be sure to connect pressurized units together in a complex network with lots of directions one can go in an emergency.

I would not try to "wash off" vehicles and space suits because if they have been outside any length of time they will be way below the freezing temperature and would quickly get encased in ice. I would use high pressure bursts of air. There may be ways to electrostatically charge the air slightly so dust particles are attracted off of surfaces. There may be ways to combine soft brushes with air bursts as well.

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#5 2017-11-18 13:26:37

louis
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From: UK
Registered: 2008-03-24
Posts: 5,792

Re: Air locks

Yes, looks like a crane is the preferred solution.  Another solution might be something like the chutes composed of plastic cut of cones that builders use for getting waste out of higher floors to ground level. Something like that which slows the descent of the goods might be working. Or maybe an inflatable chute. A crane seems a rather slow method of offloading.

SpaceNut wrote:

Problem 1:
http://www.spacex.com/sites/all/themes/ … on-bfr.jpg

Just getting to the ground since the craft will not be designed with any exit at its bottom....


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#6 2017-11-18 13:29:52

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,792

Re: Air locks

Yes tunnels make more sense, so as not to create barriers to vehicular traffic.

Yes, I like the idea of multiple escape exits. We definitely need many pressurised zones rather than just one as a single pressurised zone could mean total disaster for a mission.

As for suits, I am veering more towards disposable overalls as the quickest and most effective method.

RobS wrote:

Dear Louis: Any Mars base will probably be built with pressurized tunnels connecting everything except things that have to be kept at a distance, like launch pads. Control areas will probably be in the main part of the base, not scattered about in separate, isolated pressurized structures. This is a safety issue; every pressured structure needs at least one, if not two, escape routes. I would be sure to connect pressurized units together in a complex network with lots of directions one can go in an emergency.

I would not try to "wash off" vehicles and space suits because if they have been outside any length of time they will be way below the freezing temperature and would quickly get encased in ice. I would use high pressure bursts of air. There may be ways to electrostatically charge the air slightly so dust particles are attracted off of surfaces. There may be ways to combine soft brushes with air bursts as well.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#7 2017-11-18 15:01:27

IanM
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From: Chicago
Registered: 2015-12-14
Posts: 276

Re: Air locks

I think this might be a model, though on Mars it will probably be underground: https://en.wikipedia.org/wiki/Minneapolis_Skyway_System


The Earth is the cradle of the mind, but one cannot live in a cradle forever. -Paraphrased from Tsiolkovsky

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#8 2017-11-18 16:57:00

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: Air locks

Pressurized connectors and suit ports are probably better than multi-stage airlocks from a general utility standpoint.  The suit ports could greatly inhibit dust ingress.  The abrasive volcanic lunar regolith is more of a problem than the Martian regolith.  Anything that survives a couple years on the moon should have no issues on Mars.

Battery powered electrostatic brushes for vacuum and vacuums for pressurized areas could remove the regolith that still makes it into the vehicles or modules.  If you go off road your, then your vehicle simply gets dirty and there's no stopping that.  The astronauts also need basic hand tools like a foxtail (I forget the civilian term for it, but it's just a type of hand brush with a handle on it) to remove excessive dust from their vehicles, robots, and experiments.  I think that's the best you can realistically do.

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#9 2017-11-18 18:05:51

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Air locks

Something else you can do is to design the layout of the settlement in such a way as to make ingress/egress points as far as possible from the living quarters, ideally on the other side of farm modules (which should clean the air and trap dust somewhat)


-Josh

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#10 2017-11-18 18:36:48

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,565

Re: Air locks

From what I can tell the opening in the image is the unpressurized section simular to the Dragon truck location at approximately 50 meters from what I can tell by the scale of people to the overall size but then again it could be even higher.
For permanent life on the ground we would make a temporary means to get from that location via the crane as it would be to dangerous to climb or to ride a chute that distance.

Fox tail aka dust broom..

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#11 2017-11-19 14:02:20

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: Air locks

Electrified matting outside the ingress/egress points can also use static electricity to repel dust.  It may not be practical for use with vehicles, but could definitely keep the airlocks a bit cleaner, provided that someone is using brooms to clean off excessive regolith buildup.  It's done wonders for the rover solar panels, so why not base entry points?

SpaceNut,

I guess what I'm talking about would be a kind of "hand broom".  It has a short handle and you squat down rather than stand up to use it.  It's often accompanied by a small dust pan.  I jut Googled it and apparently it's actually called a "foxtail" by some companies and a "hand broom" or "counter broom" or "bench broom" or "beaver tail brush" or "finish brush" by various others.  I just remember asking my father for a foxtail to clean up awhile back and he looked at me like I asked him for a purple unicorn.  He's been Mr. Cleanup and Mr. Handyman at his church for quite some time now and they do use these things there, so I figured there must be other names for it.

In any event, this is what I'm talking about:

Counter Duster Foxtail Bench Brush (White Bristle, Case of 12)

Basically, every mission needs a case of these things for cleanup.  I would wager that special plastics may be required to prevent outgassing, reduce flammability, etc.  NASA has been talking about daily EVA's.  It's unlikely that explorers or even settlers are just going to stay in their base 24/7.

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#12 2017-11-19 15:28:58

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,565

Re: Air locks

Thats one big dome if the settlers can stay inside 24/7 and we sure will need to keep the dirt down from each eva or we will have problems as it gets into many different places and cause things to stick or not function all the time or intermitently.
Simple hand wipes and a swipper mop will also come in handy for such clean ups as well.
I have a feeling that the first ship will serve as the habitat so we will need to have a payload that accomplishes the purpose of keeping the dirt at ground level as much as possible with it having some sort of garage door for the large rover to be able to enter so disembarking is controlled.

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#13 2017-11-19 16:35:30

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: Air locks

Another possibility is using compressed CO2 like shop air to "blow down" astronauts and rovers.  If you had a system like that, then you could also use air tools on Mars.  Generally speaking, air tools are more powerful than battery tools, can be disassembled for maintenance using hand tools, and contain no microelectronics that could malfunction from the radiation environment.  Using a CO2 pump in a ship or a base module to fill portable CO2 cylinders, you can then take air cylinders and air tools with you in the rover around the base.  Any time something requires maintenance, you blow down the affected components to minimize dust ingress and take the affected components inside for repair.  The air tools would also assist with construction, maintenance of components with bolts or screws, and assembly of cargo.

If we accept that shop air is a requirement for construction and cleaning, then the number and volume of hand tools could be greatly reduced.  That presumes a high reliability CO2 compression system and high reliability air tools, but these systems already work quite well in dusty construction environments.  NASA or SpaceX would inevitably develop some sort of over-engineered system to assure reliability, but it can still be done and probably already has been done for industry.

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#14 2017-11-19 16:54:02

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 18,565

Re: Air locks

What little that would be used from the normal Co2 capture for making methane will not even be noticed with in the garage.

Agreed that it would be a good addition to the garage for the rover and crews to exit into on the surface before going up to the top of the lander to have a meal, exercise, write reports, examine samples, ect....

While I am not sure that Space X will get it right on the first try it does look like they can once they analyze any failures as they have done on all the others before.....

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#15 2017-11-19 20:18:51

kbd512
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Posts: 3,452

Re: Air locks

I really don't know what can or can't be done on the "first try", but this endeavor is so expensive that there might not be a "second try" if the entire ship is lost.  We're talking about a billion dollars or more, per mission, for the type of hardware set that SpaceX wants to send to Mars.

The unnecessary complications only hurt the mission timeline, thus all the past cancellations, and never seem to help in any material way.

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#16 2017-11-22 07:57:25

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Air locks

Just thinking about this a little bit more:

Given the choice of completely evacuating the airlock of ambient martian air and allowing the martian air to remain but mixing it with the hab air, I see no reason why it shouldn't be allowed to remain.  The composition of Mars's atmosphere is roughly as follows:

96% CO2
1.9% Ar
1.9% N2
0.1% O2
55 ppm CO
And various others (does not sum to 100.0% due to rounding)

Of these gases, CO2 and CO have the potential to be hazardous*.  In general on these forums we talk about hab pressures around 50 kPa, as compared to 0.03 kPa-1.2 kPa (depending on location) on Mars's surface.  Assuming a limit case of an external pressure of 1.2 kPa and an internal hab pressure of 50 kPa, after pressure equalization external gases will constitute up to 2.4% of the air in the lock.  Roughly speaking, external CO2 will increase the partial pressure of CO2 by 1.1 kPa over the levels in the hab, which is considerable but probably fine for a short period, and will dilute to lower levels when the air mixes with the rest of the habitat (although this is probably another good reason to put the airlock near the farms).

I'm a little more concerned about CO.  If the atmospheric level is 55 ppm, the level after pressurization will be up to 1.3 ppm (above ambient hab levels).  According to wiki the average CO level in a home is 0.5-5 ppm, so this also is probably fine.  However, because CO is at such a low concentration in the Martian atmosphere there could be substantial variation from place to place.

*For those among us who like to split hairs, while any gas technically can be hazardous depending on its pressure the pressures involved here are simply too small to put the other ones anywhere near the limit.


-Josh

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#17 2017-11-22 08:48:45

elderflower
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Registered: 2016-06-19
Posts: 1,219

Re: Air locks

CO is highly toxic but can be oxidised quite easily using a catalyst. Resulting CO2 would be a tiny quantity compared to the CO2 brought in from the atmosphere. I don't know, though, how long it would take to deal with the CO from an airlock full of Mars atmosphere. It might be done within the airlock to avoid releasing it into the hab if this process can be fast enough.

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#18 2017-11-22 10:10:15

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Air locks

Something that gets mentioned from time to time on these boards is the water lock. I think it's actually a pretty good idea for Mars.

The way it would work is as follows:

Egress:

Settler puts on suit and enters a bag.  The bag should be airtight (or alternatively, should have a one-way valve that only lets air out).  This bag is pretty much like a bigger version of those "as seen on TV" storage bags that you vacuum the air out of to compress clothes.

Settler enters the lock chamber in the bag, currently full of air at hab pressure (50 kPa, as above).

Lock chamber is sealed and fills with water.

Water is pumped out without replacement.  Chamber fills with water vapor at vapor pressure. The appropriate water temperature for Mars atmospheric pressure is 0-10 C.  Vapor pressure at 0 C is 0.6 kPa, which is roughly the pressure at the datum.  At altitudes above this you could open a bleed valve before exiting the lock and the vapor will precipitate out as snow.  Use of saltwater can reduce this pressure somewhat but will also tend to make the water much more corrosive.

The pressure is equalized and you can exit the bag and open the door.

For ingress, simply allow the lock chamber to fill with ambient  hab air and open the inner door, as discussed above.


-Josh

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#19 2017-11-22 10:12:34

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Air locks

elderflower wrote:

CO is highly toxic but can be oxidised quite easily using a catalyst. Resulting CO2 would be a tiny quantity compared to the CO2 brought in from the atmosphere. I don't know, though, how long it would take to deal with the CO from an airlock full of Mars atmosphere. It might be done within the airlock to avoid releasing it into the hab if this process can be fast enough.

This is definitely something that could be done but it seems like a lot of trouble if we don't have to.  Based on the calculations above, even on the highest-pressure place on Mars even the air in the lock chamber wouldn't have negative health effects so I think we're probably fine unless the CO concentration is found to be extremely variable.


-Josh

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#20 2017-11-22 15:37:05

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 3,272
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Re: Air locks

How big does the airlock have to be? The smaller it is, the less Martian air gets mixed into the hab. In extremis, it could be the size of a coffin - step in one side, equalise pressure, and step out the other side.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#21 2017-11-22 18:04:28

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Air locks

If it were up to me I might make it something like a "standing coffin", especially for ingress.  It might be a tube with an inner diameter of under a meter whose bottom end was maybe 2 meters off the ground.  When finishing an EVA, someone could climb up into the tube, shut the door, press the button, and be inside within a minute or two (I'm not sure how the body would react to rapid pressurization like this, and I'm assuming people are using MCP suits with a helmet)

Any settlement is definitely going to have locks in many different sizes for the different sizes of things that need to enter and leave the habitats.


-Josh

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#22 2017-11-22 19:23:15

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,792

Re: Air locks

Standardisation is better surely in terms of cost and efficiency.  You have a standard air lock...for something like an on-based small pressurised vehicle (golf buggy style). If you need to scale up to a bigger explorer rover you go to a special hab and transfer from the golf buggy to the big rover in a pressurised environment.  If you need to do an EVA (a rare event), the likelihood is you will need to be transported to a particular location, probably in the larger explorer rover.

JoshNH4H wrote:

If it were up to me I might make it something like a "standing coffin", especially for ingress.  It might be a tube with an inner diameter of under a meter whose bottom end was maybe 2 meters off the ground.  When finishing an EVA, someone could climb up into the tube, shut the door, press the button, and be inside within a minute or two (I'm not sure how the body would react to rapid pressurization like this, and I'm assuming people are using MCP suits with a helmet)

Any settlement is definitely going to have locks in many different sizes for the different sizes of things that need to enter and leave the habitats.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#23 2017-11-22 21:50:19

JoshNH4H
Member
From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Air locks

I definitely agree that you'd want to have a few standardized lock sizes and shapes for various common functions.  A direct, movable connection between two pressurized spaces will be an important one (although arguably is not an airlock, since the term is derived from the water lock and implies a difference in pressure).

We disagree on how much can be done with robots and how often EVA will be required (or desired), but I think we probably agree that it will have to happen sometimes, and therefore that it ought to be as simple, fast, and non-wasteful as possible.


-Josh

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#24 2017-11-22 23:13:57

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,452

Re: Air locks

I still think a blow down system would do wonders for keeping regolith out of the habitat modules and you need the CO2 for oxygen, but a tube that you stand in would minimize the volume of atmosphere lost while not requiring the complication of a perfect seal that a suit port mandates, to say nothing of the requirement for complete mobility to use a suit port.

A broken leg could be tantamount to a death sentence unless two other suited astronauts can pin you to the suit port and then they might have to further injure you to remove you from the suit.  The process could take hours.  The tube concept would enable the use of MCP suits and blow down systems.  If you're injured, you can be suspended in the tube by your legs or arms to avoid moving the injured limb or put on a board, splints can be applied, and your suit can be cut off using a pair of shears.  If you require an IV from dehydration, plasma for blood loss, or an anticonvulsant for controlling convulsions following a depressurization accident, a split gauntlet would enable someone with a little medical knowledge to start an IV.  I think it's generally accepted that MCP suits are eminently more suitable for exploration than current gas bag suits are.  There are certainly valid medical reasons to use them where injuries are more likely.

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#25 2017-11-23 03:40:12

elderflower
Member
Registered: 2016-06-19
Posts: 1,219

Re: Air locks

Part of existing clean room/ hazard control technology is the use of air showers to remove the great majority of dry contaminants from a suited person. This would be done using humidified compressed mars atmosphere before entering an airlock, so minimizing the dust ingress problem.

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