Airlocks for Mars Colony

[RocketmanUS]

This thread is for airlocks for a Mars colony. The air locks are for people, trucks and or equipment. They can be for one person or many people. They can be for small, big trucks, or multiple trucks.

The air pressure on the ISS is at Earth sea level. You can use what ever pressure you like for your airlock concepts. The air mixture in the colony is expected to be primarily nitrogen and oxygen.

Issues on Mars with airlocks-
Lose of some air when door is opened to Mars outside of the airlock.
Dust from Mars getting into colony habitable space.
CO2 getting into habitable area when people or equipment reenter.
How much energy is needed for egress.

Splinter thread from-
Envisioning Amazing Martian Habitats
https://forum.nasaspaceflight.com/index.php?topic=41427.0

[Jim]

And?

[RocketmanUS]

Air pressure in airlock A is at habitat air pressure. Air pressure in airlock B is at Mars atmospheric pressure for that location.
A is ready for people or equipment to enter from hab. B is ready for people or equipment returning from outside.

Person enters airlock A and door closes. Valve opens to airlock B and air flows to B until both have the same pressure ( no energy needed except to open and close valve ).  Valve in A opens and air is pumped into air tank till A is near a vacuum ( saves N2 and O2 ). Valve in A is opened to Mars outside letting in air ( CO2 ) till A has same pressure as out side, valve is closed and door to outside is opened and persons walks out.

When person is ready to reenter A is ready. Person enters and door is closed. Valve is opened and pump takes the air pressure down to near vacuum sending the CO2 back to the outside ( helps keep CO2 out of A and hab ). Valve between A and B is opened and air flows back from B to A till they have the same pressure. Valve is closed and another valve is opened using using a vacuum pump to send the rest of the air from B back to A  ( B is then near vacuum ), valve closes and pump turn off. Then air ( hab air N2/O2 from air tank ) is let back in till it has the same air pressure as hab. A vacuum hose and attachment like from a shop vac is used to vacuum the dust off the persons suit and inside airlock A helping keep dust out of the hab. Door is opened in A to hab and person returns to prep area.

Using two airlocks only half the air pressure is pumped when exiting, the rest is done by high pressure to low pressure flow between the two airlocks. When entering back only half of what is in B needs to be pumped back to A as half air pressure would flow fro high pressure to low , B to A.

[Paul451]

Using two airlocks only half the air pressure is pumped when exiting, the rest is done by high pressure to low pressure flow between the two airlocks. When entering back only half of what is in B needs to be pumped back to A as half air pressure would flow fro high pressure to low , B to A.

As I said in the other thread, you aren't saving any energy, there's no free lunch.

[Bob Shaw]

I'm not at all sure why you'd need to worry about CO2 from outside getting into the air inside. The mass of any incoming Martian air is minimal compared to the habitat air, and if required then the airlock procedures could simply employ a partial flush cycle to blow away the CO2 as the entry volume is initially pressurised.

[Ionmars]

We don't usually think this way, but co2 above 1 pct is toxic to humans. The long term occupational health level is set to 0.5 pct in the US. So whether or not the co2 in an airlock is a problem will depend on specific circumstances.

First, is the airlock volum significant compared with the indoor space the person will enter. One function of the ECLSS system for the indoor space is to remove co2 from breathable air. So if the indoor volume is 100 times the volume of the airlock, I wouldn't worr about it. But if the indoor space is small, say a small garage for 1 or 2 vehicles then we may have a concern. If the airlock contains Martian air at 96 pct co2 but the pressure is raised 20 times to match the inside air then when the interior door is opened, the amount of co2 entering may be signicant. If the indoor volume were say 10 times airlock volume then it might not take too many airlock openings to reach 1pct.

We can't be sure of operating conditions at all times, so it might be good practice to pump out as much outdoor air as we can before refilling the airlock with indoor air, not co2.

If we are employing  a double lock system as suggested here, we would be using indoor air from airlock 1 to refill airlock 2, etc. This would be a good way to conserve indoor air, which is expensive to create on Mars.

[RocketmanUS]

Using two airlocks only half the air pressure is pumped when exiting, the rest is done by high pressure to low pressure flow between the two airlocks. When entering back only half of what is in B needs to be pumped back to A as half air pressure would flow fro high pressure to low , B to A.

As I said in the other thread, you aren't saving any energy, there's no free lunch.

Have two identical containers connected at their base with a valve in between the two. Have one on the left filled to its top with water. The one on the right is empty. Open the valve, the water will flow to the other container till the water is at the same level in both, no pumping needed. Now if you want the rest of the water in the right side container to be in the left side container then a pump is needed. We don't need to pump all the water from one side to the other , just half of it. It should be the same for the two airlocks except we are dealing with air pressure.

So how does this not save energy in not having to pump all the air out of airlock A into B as some of it will flow to B until the two airlocks have the same pressure?

[john smith 19]

Using two airlocks only half the air pressure is pumped when exiting, the rest is done by high pressure to low pressure flow between the two airlocks. When entering back only half of what is in B needs to be pumped back to A as half air pressure would flow fro high pressure to low , B to A.

You do realize that using B to pressurize A on the return leg will pressurize it not to (Phab-Pmars/2) but ((Phab-Pmars/2)/2) IE 1/4 of hab pressure, not 1/2 of hab pressure right? That leaves you with 3/4 of the Phab pressure to make up from the gas you pumped out of the lock on exit and storage or by pumping it back into A from B and the rest from storage.

At best you can schedule some of the pumping energy needed to pressurize and de pressurize the locks. You also have a lowish pressure differential (but high volume) air pump between chambers.
It's easy to depreussurize a lock on Mars, you just vent it. However given Mars Patm is 1/160 of Earth conserving that atmosphere on a long term basis is likely to be important.

Likewise it's easy to pressurize a chamber if you have a much higher pressure storage tank.

The benefits of a low pressure differential pump are cancelled by the high volume it's going to pump. You will still need a high pressure pump to keep the main habitat reserve tanks pressurized in any case.

[Ionmars]

You do realize that using B to pressurize A on the return leg will pressurize it not to (Phab-Pmars/2) but ((Phab-Pmars/2)/2) IE 1/4 of hab pressure, not 1/2 of hab pressure right? That leaves you with 3/4 of the Phab pressure to make up from the gas you pumped out of the lock on exit and storage or by pumping it back into A from B and the rest from storage.

At best you can schedule some of the pumping energy needed to pressurize and de pressurize the locks. You also have a lowish pressure differential (but high volume) air pump between chambers.
It's easy to depreussurize a lock on Mars, you just vent it. However given Mars Patm is 1/160 of Earth conserving that atmosphere on a long term basis is likely to be important.

Likewise it's easy to pressurize a chamber if you have a much higher pressure storage tank.

The benefits of a low pressure differential pump are cancelled by the high volume it's going to pump. You will still need a high pressure pump to keep the main habitat reserve tanks pressurized in any case.

Very good reminder of basic principles. We'll need high pressure pumps somewhere in the system. And if we can save a little energy here and there it will add up over many uses of the airlock(s).

[darkenfast]

Regarding dust: how about a liquid "car-wash" type sprayer to get the dust off after the pressure is sufficiently high.  The liquid would be filtered and recycled.  Followed by a drying cycle, prior to cracking seals or rings.  Some of the Apollo suits were filthy after use on the Moon, and I'm not sure how healthy Martian dust is.   Obviously, the suits would have to be designed for this from the beginning.  The liquid doesn't have to be water, of course, but I have no idea what might be better.   

[AncientU]

Dust removal should be done before entering the airlock, say in an anteroom, preferably by robotically articulated arm CO2 sprayers (like Co2 fire extinguishers held by robots). We clean observatory mirrors with such a 'snow' blast and solids instantly dissipate... Almost free as only a multi-stage compressor is needed using unprocessed Mars atmosphere -- and robots, of course.  Robots should have capability to determine size and position of objects/people in the anteroom and should do a thorough top-down spray cleaning and finish with soles/wheels as objects/people move into airlock.  Anteroom will be cleaned of accumulated dust and debris by robots as needed.

Hand held vacuums won't work in low (Martian atmosphere) pressure; they are too slow and inefficient even in Earth conditions with an assistant doing the vacuuming.  Impossible to self-clean those hard to reach areas.

[Paul451]

Dust removal should be done before entering the airlock, say in an anteroom, preferably by robotically articulated arm CO2 sprayers [...]
Hand held vacuums won't work in low (Martian atmosphere) pressure; they are too slow and inefficient even in Earth conditions with an assistant doing the vacuuming.  Impossible to self-clean those hard to reach areas.

There's a big gap between "handheld vacuums" and "robotic arms spraying CO₂ snow".

Hand-held pressurised CO₂ "air"-hoses, fixed frame CO₂ "air curtains"/"air blades", hand-held brush-hose combinations (such as you use to clean your car, but with CO₂ instead of water), etc.

Regarding dust: how about a liquid "car-wash" type sprayer to get the dust off after the pressure is sufficiently high.  The liquid would be filtered and recycled.

I don't think you would use water for cleaning, since you then have to design every component to be water-proof. (Not just pressure vessels (which should be okay, obviously) but every support system around the pressure vessel.)

And if you're going to that much trouble, you might as well go all the way to a wet-lock and get rid of the airlock entirely

[AncientU]

Dust removal should be done before entering the airlock, say in an anteroom, preferably by robotically articulated arm CO2 sprayers [...]
Hand held vacuums won't work in low (Martian atmosphere) pressure; they are too slow and inefficient even in Earth conditions with an assistant doing the vacuuming.  Impossible to self-clean those hard to reach areas.

There's a big gap between "handheld vacuums" and "robotic arms spraying CO₂ snow".

Hand-held pressurised CO₂ "air"-hoses, fixed frame CO₂ "air curtains"/"air blades", hand-held brush-hose combinations (such as you use to clean your car, but with CO₂ instead of water), etc.

Robotics will be a fact of life on Mars. 
 -- Mass delivered to Mars is order of magnitude same for person or robot
 -- Consumables needed for robot near zero
 -- Stay time in Martian atmosphere, radiation environment essentially unlimited for robot
 -- Intelligence/speed for single, repetitive functions much superior for robots (assembly line type operations such as at auto assembly plant)

Unique situation analyses are human strengths... human time wasted doing routine tasks (vacuuming, manually spraying, etc.) will need to be minimized.

Robots will outnumber people, possibly permanently...

Remember, this is a Silicon Valley mindset, not evenly vaguely similar to Beltway behavior.  Compare ITS and its timeline and ultimate goals versus SLS/Orion, their timeline, and ultimate goals (if any can be discerned)

Here's an article on robots in the Gigafactory... gives an idea of the possibilities.
https://electrek.co/2016/07/31/tesla-gigafactory-robots-machines-battery-factory/

[JazzFan]

Maybe the airlock can serve an additional purpose than on orbital stations, such as ISS.  The use of an outer window on the airlock could be an additional observation vantage and control point for Mars surface operations.  Kind of like flight control stations on naval vessels for air operations. 

[Robotbeat]

If you count cars, trucks, lawn mowers, vacuum cleaners, drones, CNC machines, and 3D printers as robots, robots outnumber humans in the US, too.

[Coastal Ron]

The goal here, for daily use, is to move humans between surface suits and inside living/working areas.  Maintenance can be handled differently.

NASA already has surface suit concepts where humans will access the suit through a hatch on the back of the suit.  Which means the amount of area that needs to be cleaned for human-transfer operations is just the hatch on the back, which likely won't be as dirty as the feet and hands of the suit.  Also there could be a cover on the "hatch" so that it stays clean during surface operations, also reducing the amount of cleaning required when "docking".

But if you want to reduce the amount of air lost when leaving a station, then one way would be to have a "balloon" inflate inside the airlock to force out as much station air as possible, then retract when suited worker is ready to leave the lock.  That should require less energy than trying to evacuate the entire lock.

[Robotbeat]

I bet suit ports as we have now will not be the most common type of suit used. Too cumbersome.

[Ionmars]

I bet suit ports as we have now will not be the most common type of suit used. Too cumbersome.

A suitport is not really a type of suit, but an alternative to an airlock. Here is Wikipedisa's definition: "A suitport or suitlock is an alternative technology to an airlock, designed for use in hazardous environments and in human spaceflight, especially planetary surface exploration. Suitports present advantages over traditional airlocks in terms of mass, volume, and ability to mitigate contamination by—and of—the local environment." See diagram.

[Coastal Ron]

I bet suit ports as we have now will not be the most common type of suit used. Too cumbersome.

Certainly we don't know why humans will be venturing out onto the surface of Mars to do, so everything is pretty speculative at this point.  So I think suitports could be what is initially used until the requirements for EVA suits are better understood.

[Robotbeat]

I bet the opposite. We'll use the suits SpaceX is developing for Mars first. SpaceX is not developing a suit port.