Airlock Design for Mars

tahanson43206 · 2021-10-13 12:02:41

For SpaceNut ... there was no topic in Life Support Systems for airlock design

This new topic is offered for those NewMars members who would like to describe existing airlock designs that might work on Mars, or to reveal totally new designs that are (possibly) unique to Mars.

The opening design is from work done by Void in mid-to-late 2021 on Earth ...

His design (as I understand it (which is not necessarily the same as his design)) features a liquid, such as water.

A habitat designed to use this airlock design would NOT have to worry about mechanical seals or double door entry ways.

The principle of operation is that a column of water on Mars of 50 feet or (approximately) 15 meters will balance a habitat pressure of 8 psi / 500 mBar.

This pressure is close to the pressure recommended by RobertDyck at multiple places in the forum archive.
Rule of thumb: 3-5-8 (3 parts Oxygen, 5 parts inert gas, 8 parts total)

A person inside the habitat would don an EVA suit, including air supply, and enter the surface of the liquid opening into the habitat.

The person would then swim through a U shaped bend of pipe, and then up 50 feet of liquid to reach the surface.

At the surface, there would be a small cabln to protect the opening to the airlock from Mars dust and whatever else might fall into the opening.

The pressure inside the cabin would be Mars atmosphere, since the cabin would not be sealed except to keep dust out.

The Mars dweller would shake off any liquid remaining after egress from the passage, open a standard door, and proceed to the surface of Mars.

(th)

kbd512 · 2021-10-13 16:45:12

tahanson43206,

I don't think a water column is a like-kind replacement for a standard mechanical airlock.

1. At 6mb atmospheric pressure, water will boil at any temperature above its freezing point on the surface of Mars, so it would either freeze or evaporate rather quickly.
2. Atmospheric gases would pass through the water and leak out of the habitat. This is how O2 / CO2 / CH4 gases become entrained in the sea water back here on Earth. Additionally, a water column does nothing to reduce pre-breathe (N2 flushing) times.
3. If there were an accidental loss of pressurization, then you have a 50 foot column of water flowing back into the habitatable area, which is probably not an additional emergency that you'd want to contend with during a loss of pressurization scenario.
4. This assumes that anybody injured outside will be able to swim back into the habitat module after an EVA. What if someone breaks their leg or arm on the surface? Do we then need at least two crew to propel them through the water column?
5. Does it take more time and energy to replenish gases released during airlock operation, or both gases and water lost using water airlocks?

The dust is not a show stopper problem if every airlock is equipped with a CO2 blown-down station. A fixed steel spray bar surrounding the entrance is sufficient to blow all dust off the suited person and away from the airlock entrance. That's little different from a car wash or car drying system. The dust is an annoyance, but fine bone dry dust can be easily removed with a blast of CO2 gas. If you turn the dust into mud by swimming through a water airlock, that's much harder to clean off. Eventually, you have to take all equipment and personnel inside, whereupon you'll track-in mud / dust contamination anyway, no matter which solution is used. Although I initially was intrigued with the idea, upon closer examination, I think this is a solution in search of a problem- fun to contemplate, but brimming with practical problems.

SpaceNut · 2021-10-13 17:35:17

Make the air lock a double chamber unit for being able to have a sort of mud room and then the exit side. When you come in the first is to decontaminate and remove as much dust as possible while the second allows for the suits to be removed and retained away from the remaining habitat.

tahanson43206 · 2021-10-13 18:05:46

Thanks to kbd512 and to SpaceNut for contributions to this new topic.

There is plenty of room in the creative department right now, because there are ** no ** airlocks of ** any ** kind on Mars.

However, for kbd512

It is not possible for anyone to read ** everything ** that's been published in the forum over 20+ years.

It is quite possible I am the only person (besides RobertDyck) who has read every post by RobertDyck in the Large Ship topic.

Along the way, RobertDyck explained how he arrived at his specifications for habitat pressure and gas mixture.

There is NO need for pre-breathing, using the specifications which RobertDyck has published.

***
I have addressed the issue of exposure of the top of the water column to the atmosphere of Mars.

In addition, I pointed out that only very wealthy individuals, or large groups such as corporations or cities would be able to afford the liquid air lock.

A double room design a suggested by SpaceNut seems to me to make sense as a basic design, a step or two above the Apollo Moon Lander design, which was a door that seals and replace the air every time you do an EVA.

I would call that design Level 0 airlock, and a design with a mudroom (like the ISS design) Level 1

SpaceNut's double mudroom design is definitely a step above Level 1.

(th)

Void · 2021-10-13 19:00:23

First, thanks for your time and attention, all of you.

tahanson43206,
I don't think a water column is a like-kind replacement for a standard mechanical airlock.

I get to have mechanical airlocks in my city/terraform plan also, where they are more useful. In fact I would
not think it likely that the beginning on Mars would use a fluid airlock. Only later for various purposes.

It's like "What's in the tool box?" Answer I only have hammers. Of course your want other kinds of tools,
for various purposes.

1. At 6mb atmospheric pressure, water will boil at any temperature above its freezing point on the surface of Mars, so it would either freeze or evaporate rather quickly.

I definitely stated that, and intended to use means to not expose fresh water directly to the atmosphere.
However, brine at -13 degC is likely to do much better. I also provided for a two chamber mechanical airlock to impose
a few extra mBar of pressure on that water. However, I think that with chilled brine, that may not always be needed.
I have also provided a very large source of "Make-Up" water. As for the 2 chambered airlock, I guess the question might be
"You still have a mechanical airlock?", Yes, but it may be just doors and pumps that only cycle perhaps 10-20 mBar extra
pressure range, using Martian atmosphere.

2. Atmospheric gases would pass through the water and leak out of the habitat. This is how O2 / CO2 / CH4 gases become entrained in the sea water back here on Earth. Additionally, a water column does nothing to reduce pre-breathe (N2 flushing) times.

That is subject to "Henry's Laws". I have taken some time with parts of that. In many cases that can be an advantage.
But I think I can assert that a mechanical airlock will leak "Cabin Air" also, and with wear, more over time. And also
in useing a mechanical airlock you have to do something extra to not discharge habitat air with each cycle. Can do, but
it is not free. The low pressure mechanical airlock I am thinking of may have simple doors, not finely machined parts.
You would very likely just vent the chambers and then repressurize them as needed. A much smaller amount of gasses, and
after all only Martian atmopshere, and yes perhaps a bit of fizz gas from the water column. The top of the water column
can have a weighted plate put on top of it when not in use. Teflon coatinng may stop it from freezing solid, and incidently
moisture freezing would seal it better. In this case though, I don't think we would care much, as this polder will have
Martian atmopsheric gasses dissolved in it, and also Hydrogen gass added to it and we will hope that Methanogens will
create Methane. If it had a 69 foot layer of ice with a tube above it, most of the action of Henry's Law sill be the
pressure imposed on the water. Of course a pathway would exist to

But, I mentioned multiple polders, and in this case, I might try to explain a possible industrial process. Very likely
for industrial processes on Mars, we are not going to want to expose humans to toxic things such as gasses, so, in my
mind very likely humans wear a suit like a SpaceX flight suit, possibly for pressurization at times, but in this case
usually to be PPE against toxins.

Lets say this factory process involved making Urea Bricks. You need to get Nitrogen for the Urea, and of course do things
to produce the Urea. So, to get the the makings for it we can do an Oxydizing method or a Fuel method. This is a reason
to have many polders. They are after all canisters primarily made of water contained in Ice a regolith. It is better not
to mix Oxygen and Fuel, until you desire to.

The raw materials for this will be Martian atmosphere, water, and Photons. There are many ways, we can go into that later,
if you desire, but some ways may.

As I have said, there can be multiple polders for specialized conditions and purposes.

In one case, the ice could be 69 feet thick like that of like Vida. ~(69 * .9 = 62.1 feet of water equivalent).
So, for the most part the surface pressure on the water would be ~621 mBar. In the case where we are extracting Nitrogen
and Argon from Martian atmosphere we may not have a liquid airlock at all, but we could then convert CO2 into Oxygen,
organic Matter and Methane. Keep in mind these would likely be done in seperate polders. So, if we have the Nitrogen
we then can perhaps make Urea. And have rocket propellants and organic matter(s) of various sorts. So, with a 621
mBar pressure equivlent, we don't worry about outgassing to the surface much.

So, we presume that we have Urea and water.

Regolith is a raw material that contains various types of salts. We want the regolith itself for the bricks, and the
berms, and we want the salts, of various kinds for various reasons. So, we want a washing process(s). Dump regolith
down a shaft in a polder specialized for that. Wash it, leaving the salts in the water. We probably do not want
to encourage biological processes with a fuel added to the water, as we may want to extract the Perchlorates. This will
be a toxic polder but very useful.

After washing(s) which could use fresh water at the end, Then you have regolith purged of most salts.

You may make Pee-Bricks (Urea-Bricks in a factory chamber. You would have various forms for them to match a desire.

Your factory floor may well be inside a brick chamber inside of a berm, the berm would also define the bounds of
a polder. The water/Ice table would merge with the berm, so that over your chamber would be mud, and then permafrost.

3. If there were an accidental loss of pressurization, then you have a 50 foot column of water flowing back into the habitable area, which is probably not an additional emergency that you'd want to contend with during a loss of pressurization scenario.

In this case, this would be a factory setting, People would wear suits, and the probability of an air leak should be minimal.
Even then it is better to be immersed in water than to breath 5.5 mBar.

4. This assumes that anybody injured outside will be able to swim back into the habitat module after an EVA. What if someone breaks their leg or arm on the surface? Do we then need at least two crew to propel them through the water column?
As I have said, this is not for first habitations. It is for developed industrial abilities. And yes you would have rescue
methods. Also you may have an resource method at the bottom of the lake. Air, drinking water, temporary shelter, etc.

5. Does it take more time and energy to replenish gases released during airlock operation, or both gases and water lost using water airlocks?
It depends on your process. And in some cases you might want to purge something out of the airlock.

The dust is not a show stopper problem if every airlock is equipped with a CO2 blown-down station. A fixed steel spray bar surrounding the entrance is sufficient to blow all dust off the suited person and away from the airlock entrance. That's little different from a car wash or car drying system. The dust is an annoyance, but fine bone dry dust can be easily removed with a blast of CO2 gas. If you turn the dust into mud by swimming through a water airlock, that's much harder to clean off. Eventually, you have to take all equipment and personnel inside, whereupon you'll track-in mud / dust contamination anyway, no matter which solution is used. Although I initially was intrigued with the idea, upon closer examination, I think this is a solution in search of a problem- fun to contemplate, but brimming with practical problems.
I did provide for coveralls, then compressed air to blow the dust off, then a cold shower of brine, then go jump in a lake...

I really do appreaciate your attention.

Keep in mind that some polders can be very clean, and rather safe, and so then you might be under decent pressurization, with
breathable atmosphere in the polder. Now I will admit that I need solutions for how styrofoam can get soggy, and how it
may outgass toxins. So, some work need there, for sure.

However if you make diving bells out of, (Something resembling Syrofoam, where those problems are reasonably addressed),

You can have an entire ceiling of them where the sytrofoam bells are interposed between the ice above, and the water below.

Then add lighting and plants, and you have a place to swim. You would of course set the water temperature.

So, there could be polders like that as well.

Not every brick buildin under a polder would be factory. Some may be housing, and some may be artificial lighting greenhouses.

Done for now.

Spacenut,

Pretty OK, as I have said there will be an enormos number of ways to set up a polder, for various purposes. Keep in mind that
it will be possible to have brick buildings/passages, under the walls of the polders. Of course as in any case toxic situations
have to be handled/isolated from doing harm to humans. Your proposed setup is an option for one or more polders.

(th),

Only by having industry and factories and agriculture, can people have wealth at all on Mars, I would say.

And as I have explained, this would very probably not be the original settlement method for Mars, but the sooner, the
better in my opinion.

Done for now. Rather tired. Did some spell correction but not all. Sorry....

Last edited by Void (2021-10-13 19:08:53)

louis · 2021-10-13 19:07:19

There have certainly been plenty of discussions over the years probably under general headings.

Manufacturing airlocks on Mars or importing them from Earth are both big demands on resources.

One proposal I had was using ice as the gas barrier. So when you want to open the airlock you melt the ice and when you want to recreate the barrier, you freeze water to make ice. This approach could be achieved in various ways.

Another proposal I had was to use cut basalt as the air lock door.

tahanson43206 wrote:

For SpaceNut ... there was no topic in Life Support Systems for airlock design
This new topic is offered for those NewMars members who would like to describe existing airlock designs that might work on Mars, or to reveal totally new designs that are (possibly) unique to Mars.
The opening design is from work done by Void in mid-to-late 2021 on Earth ...
His design (as I understand it (which is not necessarily the same as his design)) features a liquid, such as water.
A habitat designed to use this airlock design would NOT have to worry about mechanical seals or double door entry ways.
The principle of operation is that a column of water on Mars of 50 feet or (approximately) 15 meters will balance a habitat pressure of 8 psi / 500 mBar.
This pressure is close to the pressure recommended by RobertDyck at multiple places in the forum archive.
Rule of thumb: 3-5-8 (3 parts Oxygen, 5 parts inert gas, 8 parts total)
A person inside the habitat would don an EVA suit, including air supply, and enter the surface of the liquid opening into the habitat.
The person would then swim through a U shaped bend of pipe, and then up 50 feet of liquid to reach the surface.
At the surface, there would be a small cabln to protect the opening to the airlock from Mars dust and whatever else might fall into the opening.
The pressure inside the cabin would be Mars atmosphere, since the cabin would not be sealed except to keep dust out.
The Mars dweller would shake off any liquid remaining after egress from the passage, open a standard door, and proceed to the surface of Mars.
(th)

Void · 2021-10-13 19:10:46

It is good to have options Louis.

For instance I have a notion for getting Make-Up water, as I expect that it will be needed, on a continuing basis. It is to use an under ice laser to vaporize ice and suck up the moisture into a pressurization method to condense it to liquid.

After that is done the tunnels might indeed have a use for what you have suggested.

Done.

kbd512 · 2021-10-13 22:10:31

tahanson43206,

If the atmosphere is breathable, long-term, then you will need to pre-breathe pure Oxygen to flush any accumulated Nitrogen from your body, or run space suits at the same partial pressure as the habit modules. If you don't, then the Nitrogen will boil out of your blood and you'll be seriously injured or killed. So, unless we're running a pure O2 atmosphere, which is not particularly healthy, if still survivable at partial pressure, then this is impractical, if not unacceptably dangerous in practice. There must be some reason why ISS is run at 1 atmosphere of pressure with a normal mix of O2 and N2 gases. I could see work crews that will do EVA work for a certain period of time, maybe a week or two at a time, living in a pure O2 environment, to negate the pre-breathing requirement. However, normal civilian colonists will need to live and work in an Earth-like atmosphere for best results.

tahanson43206 · 2021-10-14 07:26:35

For kbd512 re #8

It is good to see a restatement of the principles of atmosphere design for Mars or a spacecraft.

RobertDyck has invested a great deal of time and thought covering the subject.

I regret that the design of the forum software precludes easy reference to the material he has posted, so we don't have to keep refreshing our collective memory.

There ** is ** a "Sticky" feature of the software, that ** could ** be used to put the principles of atmosphere design at the top of one of the Indexes.

However, to this point, no one has chosen to use that tool to put principles of design of Large Ship where they can be found easily.

As a reminder for all forum readers .... RobertDyck will be presenting on Large Ship this Saturday in the Mars conference. Hopefully he will take a moment to explain atmosphere design for the cabins and for EVA.

(th)

kbd512 · 2021-10-14 23:35:24

Void,

If you need to purge / blow dust out of / away from the airlock, then compressed CO2 is your friend. We use compressed air here on Earth, because that's what's most readily available. Compressed gas would easily clean off the exterior of a space suit.

At a temperature of -13C / 8.6F, a person not protected by a dry suit, which definitely does not describe a MCP suit, in which the user is meant to perspire through the fabric of the suit, means a wet airlock is best suited to gas and liquid impermeable fabrics, or traditional space suits. Immediately upon exiting the airlock, any brine left on the suit will either freeze or sublime, dependent upon the outside temperature, which restricts the time of day / seasons / locales that such an airlock could be used. Any metal components such as steel or Aluminum would corrode rather quickly if left inside the habitat module, especially in a pure O2 atmosphere, if not immediately washed down with fresh water and blown dry. Obtaining potable / fresh water from a high-salinity brine is an energy-intensive process. Even stainless will corrode rather quickly in a high salinity brine, and pretty much any Aluminum alloy would be pitted in short order, probably less than a year. All those articulating joints in the space suits would have to be made from UHMWPE, rather than Aluminum or steel, and the life support backpack would also have to be water-tight. All of the life support equipment uses Aluminum / steel / brass lines and fittings.

Have you ever swam in an arctic or antarctic ocean or a lake up north?

It's so cold that you can get muscle cramps upon entering the water. Can a strong, healthy person do it? Yes, but several times per day would wear on you rather quickly. From personal experience, constantly being cold and wet is pretty miserable. Plus, swimming down and then up through a 50 foot column of water, even at bath water temperatures, much less water that's colder than any ice cube in your freezer, will definitely not be an easy feat of strength. That's like swimming under the keel of an aircraft carrier in the arctic ocean, so I hope the person doing it is in excellent physical condition and the suit is not damaged in any way.

I can see how this might be useful for working in a greenhouse where cleanliness is not required and people would need to enter / exit many times per day to take care of the crops, where perhaps repeated pressure cycling would be unacceptable.

An industrial area? Maybe, but again, the issues associated with using the airlock makes it more trouble than it's worth.

We have large Silicone rubber seals on the air-tight (air-tight dogs on one side, water-tight dogs on all sides) doors of the ships I served on, and yes, we had lots of grit (dust / rust / paint chips from the constant work done on the ship) in the seals, but they still seal, and were only replaced after years of operation. We wiped them off periodically, maybe once per week, and that keeps the structure air-tight. That might have to be done every time someone enters / exits on Mars, but that only takes seconds to accomplish.

What about personal equipment like hand tools and whatnot? Won't you need dry bags to store that stuff?

The bottom line is that while abrasive dust is a real problem on Mars, an abrasive mud loaded with salts is an even bigger problem.

Calliban · 2021-10-15 01:51:11

A water filled U-bend type airlock is an intriguing idea. The question is not so much if it can be made to work, but whether it is an optimal use of resources. It has the advantage of design simplicity. It has the disadvantage of requiring a lot of water. This water must be heated if people are passing through it. And it adds the requirement that spacesuit design must be waterproof. Otherwise, people will freeze to death. To suppress evapouration, the LP side of the airlock at the top of the stairwell, would need to be pressurised with Martian CO2 using a high dp fan. A single door would lead outside and you would equalise pressure before opening. Dust isn't really a problem. Mud would collect at the bottom of the bend and could be sucked out into a tank during periodic cleaning.

The question is around optimal use of resources. We have a design function that we are trying to meet in allowing astronauts to safely and easily traverse between pressurised areas and the outside, as quickly as possible. A fluid airlock has design simplicity, but requires us to build a deep U-bend arrangement and fill it with water. Is that going to be the cost optimum solution? Remember that water on Mars will have an energy cost per unit mass comparable to concrete on Earth.

tahanson43206 · 2021-10-15 06:12:02

For Calliban re #11

Thank you for your support of Void's idea! Heating the airlock liquid is a nice refinement.

As a follow up, it seems to me the need for any pressure on either side of the airlock is questionable.

The habitat provides pressure on the lower entrance.

A simple piece of solid material could (and would) provide all the "pressure" needed on the LP side.

The goal at the top entrance is (a) to keep Mars dirt out and (b) to keep clean water molecules in.

A simple lid of solid material would be more than sufficient for that purpose.

SearchTerm:Heated liquid for liquid airlock
SearchTerm:Airlock liquid heated

I like your analysis of use of resources.

A refinement is that any underground burrow on Earth (or at least ** many **) has two entrances.

Thus, an air lock made of liquid would necessarily be backed up by one done in the traditional way.

Earlier, a NewMars member observed that if pressure is lost inside the habitat, then the liquid would enter the habitat, pulled by gravity.

A solution to that (quite reasonable) observation is to make the liquid design a true U shape, even in both sides.

I bring ** this ** up as worth consideration for one of the many habitat designs that would occupy volume in the wall of bluffs.

When air pressure inside the habitat is normal, the surface of the liquid would be well below the top of the U.

If air pressure should be lost, the liquid would rise to balance on both sides, but nothing would reach the habitat.

(th)

Void · 2021-10-15 11:25:31

OK, this is representative of many options. By no means all of them. I am also
concerned about cascade failures in some fault modes. However, it can be delt with,
I think, and curiously results in an expansion of possible options.

The concern I have with this one, is that if water did flow into the airspace, inside
of the berm, the ice block being massive might displace the berm and the buildings
inside of it.

My new solution is to have thiner ice so that it would yield, (Break/distort) rather
than crushing the berm/buildings. Other methods may work, but just now I am thinking
about floors in a lake. That is if you can have a durable materials to partition the
water with several floors, then you can have water of different types of salts and
temperatures. This opens up a lot.

However having floors in a lake/polder, may give better results, but also requires
materials suitable. At this time I am thinking Hemp/resin panels.

------

A, B, C, and D represent various pressurization and interface options.

A is an additive Pyramid with brick building option. It is also the berm(s) that surround each poled of ice/water. An oval near the apex
represents an airlock, mechanical.
B is a Lollipop airlock. Has a viewing room on top. This is more for sanity than for productive activities. See the stars? See the sun?
However it could also have a thermal receiver for heliostats. An oval lower down represents an airlock, mechanical.
C represents a combinational airlock, in which most or all of the pressure change is in fluid. I would usually expect 2 chambers on the
top, but as Calliban has indicated one might do, and if you are using a very cold fluid perhaps none. However I would at least expect
a shed, as you probably want a hoist.
D represents subtraction structure. You dug a chamber or tunnel.

I have not shown all the possible connections or options. This is just some of the possible things.

This relies on the notion that their really are very large ice slabs in the Mid lattitudes.

I am still working on this. I will try to add some more specific replies to the
other members next.

Not Done.......

Well, I am not done but I am going to get a sauna, and a workout.

I may do more later today or tomorrow.

Done for now.

Last edited by Void (2021-10-16 17:51:05)

kbd512 · 2021-10-15 15:32:05

Void,

What's the "killer app" is for this liquid airlock technology?

Is it a very large greenhouse?

A massive swimming pool / man-made "lake under ice"?

A place to bring marine life from Earth to replicate that part of Earth's biosphere on Mars?

Void · 2021-10-15 17:31:58

KBD512,

Thanks for the query(s). I have a little time before my next thing to do.

I don't know that there is a "Killer App", but a collection of potentials.

First I have concluded that for a berm with buildings in it, where it is going
to provide family and other sensitive housing, perhaps it should be specialized
for that and the polder inside the polygon berm, should contain no liquid water.

Otherwise, if berm/polder setups are constructed with good sense, then trickier
things could be tried such as liquid water with ice above. Tunnels and doors should
allow egress to safety where some mishap did occur.

Yes, to your question, however you have to handle control of how much and what
is dissolved in a "Bioreactor". Henry's Law must be satisfied to the needs of the
biology being fostered.

Lighting or chemicals would drive the biology.

Lighting would either come from the sun, using certain tricks, or from artificial lighting. I am open to fission nuclear and solar, and if it is possible geothermal, and perhaps eventually fusion.

Handling a polder might require compatible devices.

It is possible (Maybe) to have a polder where the bottom water just might be
up to 170 to 180 degF. The top water would be cold. This could be an energy
storage device. The upper cooler layer(s) could support life, by various means.

Even though you would have hot water down below, you might have pressurized
bags where you could grow aquatic plants. Lighting needed. In this particular
body of water, you might degas all the water to discourage pest organisms from
growing on the bag(s), but since the bags would be pressurized, you could dissolve
all the gasses into them that they could hold.

For this one I would not promote a liquid airlock. I would fear a geyser event.

-----

Less fussy might be the mimic of certain Antarctic Dry Valley Lakes.

Similar tricks possible, but bottom water ~73 degF. Upper water much colder.

So, the bags could be brought down from the light source to humans on the bottom of the lake, to plant or harvest.

These lakes maintain that temperature year around, I believe. It is solar powered,
but also melt water goes into the lake(s) about 2 weeks a year.

-----

A little different could be fresh water. In this case freezing ice water on the top
just under the ice. Down on the bottom 39 degF.

In this case you may actually warm up the contents of a plastic bag. Light source
not defined yet. This could make a radiator for a nuclear reactor, perhaps.

------

My feelings are that the buildings inside of the berms, could also be artificially lighted for a pleasant garden place(s), where people could walk in shirt sleeves.

------

There are other possible options involving plankton and Mushrooms, or brine shrimp/fish.

------

I really think that special suits for being in cold water could be made. Based
on Oil Rig technology perhaps.

------

No particular killer app.

Done.

Last edited by Void (2021-10-16 17:50:21)

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Airlock Design for Mars

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