Airlocks for Mars Colony

[Paul451]

Regarding the "outside area" I think it doesn't really need to be outside the hill-side. Just let it be the first big room in the tunnel system and then have the airlock a bit further inside the hill. That way it won't be necessary to build a hall outside and expend invaluable material on unnecessary walls.

Being unpressurised and without significant loading from wind, the walls can the flimsy and the frame can be light. Or it can be made of sintered bricks (which are horribly porous and structurally weak), arched or domed. (Finally a dome makes sense on Mars.)

I suspect that it would use up fewer resources than "digging a sodding great hole in the rock" just for an unpressurised box. But if you are digging deep into rock for the habitat, and need to dig in a certain way before you reach suitable structural rock, then yes you might use that entry volume for the airlock extension. Although you'd still need support walls, which will be stronger (therefore more resource demanding) than a structure that's not holding up semi-consolidated regolith or weak fractured rock.

(I need a better name. Porch/veranda/etc doesn't really capture that it's enclosed. Shed/carport doesn't specify that it's attached. And then, of course, I'm suggesting another inside area which is pressurised, and that needs another name.)

A problem that may happen with the external structure is that it will itself become dirty and contaminated

The only source of permanent contamination are fluids in the vehicles and equipment. And that would affect any maintenance area.

Everything else is just regolith dust and CO₂, which are obviously present in an unenclosed area.

and might create a local atmosphere that is worse than the outdoors.

How? It's not meant to be airtight, by definition. And without wind, the air won't hold any significant quantities of dust.

It's a "shed". Except that by being on Mars, it doesn't have to handle significant winds, so it can be a very light structure. It's just a way to keep the wind-borne dust out, provide a stable floor to work on, protect against sun, provide consistent work lighting, and allow you to run conduit around the walls with at least power to vehicle recharge stations and power tools (and maybe air & water lines too). Given such an area, it also seems like the logical spot to also service equipment from outside that needs to be repaired, which gives you a protected area to do fiddly work without losing parts or getting them full of dust. And that also suggests it as an area for the storage of bulk items used outside. Like spools of steel/fibre cable, power cables, large structural elements, spare vehicle parts, down to nuts and bolts and connectors. Or anything unloaded from the incoming ships, but still waiting to be assembled/deployed.

(OTOH, IMO there's no real advantage to having stand-alone roofed area, far from the airlocks, as your main vehicle storage area. You need another vehicle or an EVA to get from the habitat airlock to the vehicle shed, and when you're done for the day, you need another vehicle or EVA to get back to the habitat again. If you want to recharge the air and water supply, or drain the waste-water, you need to transport the fluids to/from the habitat or have a secondary fluid/gas processing plant at the shed. Similarly you can't easily share power with the hab. And what does it gain?

Exception: You might have a simple sun-shade at a common off-site area that needs a lot of maintenance - such as the ISRU plant, the launch/landing pads, etc. Solar panels as the roof to allow recharging the vehicle while the crew are off EVAing. But that's only when you are using vehicles to travel to an area each day, then exiting for on-foot EVA. The vehicles return to the habitat at the end of each shift.)

[Paul451]

Should this thread be moved from the SpaceX Mars section back to the general Missions To Mars (HSF) section?


Feeling a bit guilty for hijacking the thread.

So here's another airlock concept that was discussed in other threads.

The Wetlock or Moon-pool.



Image courtesy of MeekGee. (KelvinZero is another strong proponent.)

MeekGee suggests an ice-layer at the end (kept thin enough to walk or drive through, but which reduces evaporation). KelvinZero has wondered about using another liquid with a very low evaporation, or having a low-evaporation layer floating on the water. I've suggested a low pressure airlock at the outer-end, just enough pressure to reduce boil-off at the target temperature, and high enough humidity to eliminate further evaporation.

And many of us have mentioned the complication of buoyancy.

[Lar]

Should this thread be moved from the SpaceX Mars section back to the general Missions To Mars (HSF) section?

Moved. Doing a report to mod is another good way to ask for same, actually better... (2 years from now when someone's coming up to speed, they won't care about this housekeeping stuff)

If there is another one that should have moved (I forget now) report to mod or PM me...

[Ionmars]

For the outdoor foyer to the airlock:
Maybe there is finally a practical use for an iRobot Roomba.
Or would it even work in very low air pressure? Maybe a rotary dust brush like a Bissel Sweeper, electrified.
(I know my proper role in the Earthly Martian household!)

[Jim]

(The airlock-proper is the larger disc-shaped section, called the "equipment lock". The unpressurised extension is the long, narrow cylinder sticking out, called the "crew lock". Which seems backwards to me.)

Wrong.  The long, narrow cylinder is the "airlock".  It is the part where the crew (two of them at the same time) enters and exits the station.  It is the only part that is depressurized and repressurised, hence crew lock.   The "equipment lock" is where the EVA suits and tools are stored and maintained.  It is where the crew does there pre breathe campout.

There is no "unpressurised but enclosed room".  There is no "umbilical to extend PLSS lifespan" on the exterior.  Just like the shuttle (in fact the crew lock is based on the shuttle airlock), the crew is on umbilical until the airlock is depressurized and goes back on umbilical while the airlock is depressurized.

Two crew in the crew lock (who else would have taken the photo of one of the crew)

[lamontagne]

This is a spin-off thread from the Amazing Martina habitats thread.

The existing docking and berthing ports may not be adequate for use on the surface of Mars.  The docking ports are very small, and the berthing cargo port, although wide, is not very high.

A number of mock-ups have been part of various Mars base and and martian vehicles over the years, there does not seem to have been any serious design effort done yet. 

- What is the correct name for 'it' ?  An airlock, a port, a pressure door?
- Should it open in, open ot, or dilate like a SF movie door?
- What is the best way to signify 'open' and 'closed'? 
- Can the port do some of the connecting work, or is it all done by the vehicle?
- How high off the ground should it be?  If it is high up how do 'walkers' reach it?
- Should it be used in space as well?
- Should it have a doorknob? 
- What are the visual signals required for operating it safely?
- Must it have a manual override?

To kick things off, here is the design I have been using lately, with a few images of its use.  It's a rectangular door with rounded edges, latches for strong connections, a flexible neck for angular corrections and a seal with mainly lateral forces.

[grythumn]

This is a spin-off thread from the Amazing Martina habitats thread.

The existing docking and berthing ports may not be adequate for use on the surface of Mars.  The docking ports are very small, and the berthing cargo port, although wide, is not very high.

A number of mock-ups have been part of various Mars base and and martian vehicles over the years, there does not seem to have been any serious design effort done yet. 

- What is the correct name for 'it' ?  An airlock, a port, a pressure door?

The picture seems to portray a single port or pressure door.

Airlock implies a two-doored chamber that can depressurize independently from the connected habitable space.

- Should it open in, open ot, or dilate like a SF movie door?

Open in is the usual concept, so if there is a large pressure gradient between the hab and outside the door, it cannot be opened and depressurize the hab space, as a safety measure.

[lamontagne]

This is a spin-off thread from the Amazing Martina habitats thread.

The existing docking and berthing ports may not be adequate for use on the surface of Mars.  The docking ports are very small, and the berthing cargo port, although wide, is not very high.

A number of mock-ups have been part of various Mars base and and martian vehicles over the years, there does not seem to have been any serious design effort done yet. 

- What is the correct name for 'it' ?  An airlock, a port, a pressure door?

The picture seems to portray a single port or pressure door.

Airlock implies a two-doored chamber that can depressurize independently from the connected habitable space.

- Should it open in, open ot, or dilate like a SF movie door?

Open in is the usual concept, so if there is a large pressure gradient between the hab and outside the door, it cannot be opened and depressurize the hab space, as a safety measure.

Yes, would need two doors to make an airlock.  Should the system be systematically configured as an airlock, or can it vary from single doors to double doors (airlocks)?  Or be designed to be able to offer both configurations?
How often are airlocks required, if they are mostly used for connection between pressurized elements?  Or is the safety of an airlock an essential design element?

[lamontagne]

How important/useful are alignment guides?

Will an airlock/port be operated using artificial intelligence controls to provide docking adjustments?  Just how possible are docking maneuvers between vehicles and habitats in the real world?

[Lar]

An airlock can use two of the doors shown, or perhaps since the outer door has to cope with both sides depress (just before opening or closing) maybe it's different?

The door shown for sure has to handle pressure on one side and vacuum on the other. Does that mean it's asymmetric (the always pressure side is different than the sometimes vacuum side) ?

[lamontagne]

Oups!  Just found a pre-existing thread from RocketmanUS  (the search function on the website is not very good BTW :-)  I even posted to it 

Perhaps we can merge the two?

https://forum.nasaspaceflight.com/index.php?topic=42098.0

That was more for whole vehicle airlocks, rather than the smaller doors/hatches I'm illustrating here, but still.

[Lar]

Oups!  Just found a pre-existing thread from RocketmanUS  (the search function on the website is not very good BTW :-)  I even posted to it 

Perhaps we can merge the two?

https://forum.nasaspaceflight.com/index.php?topic=42098.0

That was more for whole vehicle airlocks, rather than the smaller doors/hatches I'm illustrating here, but still.

Sure. But now I have to ponder which thread is in the right place, LOL.

[Lar]

back on track, what are some of the design considerations here? does it matter which side or sides will be exposed to vacuum? What about gas composition, if a greenhouse is much higher C02, does that matter (I think not)

[lamontagne]

I see three functions:

Habitat connector.
Vehicle connector.
Airlock hatch.

Habitat connectors, if they have a door at all, will be safety features.  So the pressure can be on either side and the function is to keep the pressure on the non depressurized side.  These can be male/female connectors, but this limits configurations and means everything needs to be planned.  If they are rigid, then the habitats need rigid foundations, because you want to reduce strain on these connecting elements.

Vehicle connectors are vacuum outside, pressure inside.  They become part of an airlock if the vehicle cannot be exposed to vacuum and if they also serve as exit ports for space suited crew members.  Vehicle connectors would need to be androgynous, or else they would need to be two per vehicle.  A vehicle could have a vehicle connector and a separate airlock, or suitports.

An airlock hatch has no connector function, so the male/female question is not a problem.  The outer door and the inner door are probably vacuum outside, pressure inside.  This would probably be the same design for a pressurized hab, low pressure greenhouse arrangement.

Specs:
Operating pressure: 15 psi (101 kPa)
Dimensions: 1000mm x 2200mm
Alignment requirements :TBD
Angular motion: TBD

Can a single connector/hatch/port serve all these purposes?  Or is that a road to overdesign?

[lamontagne]

Here is a nice NASA presentation on inflatable airlocks.

They are aiming for 15 psi.
They favor some kind of internal structure.
They don't seem to have though of these as vehicle ports?  Not sure about that.

[Lar]

Vehicle real estate is at a premium so it may be worth it to have your docking door and your airlock door be the same door...  when independent you go through an inner door, airlock operates, and then through the outer to get outside. When at base, you go through an inner door, there may be a brief pressure equalization (or not) then through the outer to get to the base.

So the inner has to be able to handle pressure/pressure and pressure/vacuum while the outer has to be able to handle pressure/pressure (while docked) pressure/vacuum (while airlock is pressurised) and vacuum/vacuum (while airlock is depress, just before opening).

Note I use vacuum to also stand in for "Mars Ambient"

[lamontagne]

Vehicle real estate is at a premium so it may be worth it to have your docking door and your airlock door be the same door...  when independent you go through an inner door, airlock operates, and then through the outer to get outside. When at base, you go through an inner door, there may be a brief pressure equalization (or not) then through the outer to get to the base.

So the inner has to be able to handle pressure/pressure and pressure/vacuum while the outer has to be able to handle pressure/pressure (while docked) pressure/vacuum (while airlock is pressurised) and vacuum/vacuum (while airlock is depress, just before opening).

Note I use vacuum to also stand in for "Mars Ambient"

Seems correct.  Adding vacuum vacuum to the concept.

And here is another paper, a bit old, that seems to bemoan the point that there isn't really that much going on in hatch and airlock design.  Interestingly, it adds another type of airlock, the sample airlock for exploration vehicles.  I guess we could add the whole vehicle airlock, and therefore have up to five type of airlocks for a martian base.  Although the whole vehicle airlock is for a big base :-)

[lamontagne]

An airlock can use two of the doors shown, or perhaps since the outer door has to cope with both sides depress (just before opening or closing) maybe it's different?

The door shown for sure has to handle pressure on one side and vacuum on the other. Does that mean it's asymmetric (the always pressure side is different than the sometimes vacuum side) ?

I would expect the door to be asymmetrical.  The inverted operation of the safety door between two habitats seems like the main case where a door would need to function in Pressure/vacuum in two directions.  That might best be served by a symmetrical door?

[RonM]

An airlock can use two of the doors shown, or perhaps since the outer door has to cope with both sides depress (just before opening or closing) maybe it's different?

The door shown for sure has to handle pressure on one side and vacuum on the other. Does that mean it's asymmetric (the always pressure side is different than the sometimes vacuum side) ?

I would expect the door to be asymmetrical.  The inverted operation of the safety door between two habitats seems like the main case where a door would need to function in Pressure/vacuum in two directions.  That might best be served by a symmetrical door?

There's no need for an asymmetrical hatch design. Each habitat module should have its own hatch for safety, so when two modules are connected there are two doors. As long as you leave enough room in the design, by default you get a one-person airlock when you connect two hatch assemblies.

[lamontagne]

An airlock can use two of the doors shown, or perhaps since the outer door has to cope with both sides depress (just before opening or closing) maybe it's different?

The door shown for sure has to handle pressure on one side and vacuum on the other. Does that mean it's asymmetric (the always pressure side is different than the sometimes vacuum side) ?

I would expect the door to be asymmetrical.  The inverted operation of the safety door between two habitats seems like the main case where a door would need to function in Pressure/vacuum in two directions.  That might best be served by a symmetrical door?

There's no need for an asymmetrical hatch design. Each habitat module should have its own hatch for safety, so when two modules are connected there are two doors. As long as you leave enough room in the design, by default you get a one-person airlock when you connect two hatch assemblies.

Indeed.  Most buried inflatables will need to be connected by corridors anyway, and I expect there would be nodes with multiple doors serving the purpose of airlocks.  The only time a door might be used with vacuum on either side might be in a large colony, when modules would be so large that airlocks might no longer be practical.  And in such a case there will be specific designs. 
So one option less; we can have all the doors similar, opening the same way, and designed to hold pressure on the side the door opens, with the door pressed against a seal.