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.
Quote from: RocketmanUS on 01/21/2017 06:37 amUsing 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.
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.
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.
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.
Quote from: AncientU on 01/22/2017 10:51 amDust 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.
I bet suit ports as we have now will not be the most common type of suit used. Too cumbersome.
I bet the opposite. We'll use the suits SpaceX is developing for Mars first. SpaceX is not developing a suit port.
Quote from: AncientU on 01/22/2017 10:51 amDust 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.Quote from: darkenfast on 01/22/2017 10:05 amRegarding 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
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.
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.
Robots will outnumber people, possibly permanently...
Quote from: Robotbeat on 01/22/2017 05:28 pmI bet the opposite. We'll use the suits SpaceX is developing for Mars first. SpaceX is not developing a suit port.SpaceX is not developing a suit port for travel to ISS.We don't know what are they developing for Mars.IMHO suit port is much better than airlock for Mars.
Someone above mentioned 'no free lunch'... how do you retract without pumping? Suggest you save the balloon for something more useful.
Quote from: AncientU on 01/22/2017 06:48 pmSomeone above mentioned 'no free lunch'... how do you retract without pumping? Suggest you save the balloon for something more useful.I'm figuring that air loss is more important than power, but no doubt there is a balance to be struck.
Even if suitports are used for most EVAs, there still needs to be an airlock to bring suits and equipment inside for maintenance.
I expect workshops for maintenance of suits and vehicles completely separate from the living quarters. Maybe with a pressurized path but separated by their own airlocks. That would reduce contamination significantly.
Remember that Mars dust has a high concentration of perchlorate salts, which are highly toxic. Fighting perchlorate contamination will be one of the toughest tasks a Mars expedition is going to be faced with.I can see only two ways of prevent Martian dust from contaminating the atmosphere of the hab:- Either an extensive washdown of anything coming inside, which will consume a lot of water.- Or suit ports.Even if suitports are used for most EVAs, there still needs to be an airlock to bring suits and equipment inside for maintenance.
The idea that you have an outside, unpressurised by enclosed area you can do things like brush or blow dust off of vehicles, and which has a floor that is not regolith & dust.
Quote from: Paul451 on 01/23/2017 11:05 amThe idea that you have an outside, unpressurised by enclosed area you can do things like brush or blow dust off of vehicles, and which has a floor that is not regolith & dust.I like the whole scheme for incremental regions. But for the outer, unpressurized area, would it be helpful to have filtered and (slightly) pressurized ambient Martian air flow into that area, so that it would help keep any new dust from coming in?
Quote from: pobermanns on 01/23/2017 09:42 pmQuote from: Paul451 on 01/23/2017 11:05 amThe idea that you have an outside, unpressurised by enclosed area you can do things like brush or blow dust off of vehicles, and which has a floor that is not regolith & dust.I like the whole scheme for incremental regions. But for the outer, unpressurized area, would it be helpful to have filtered and (slightly) pressurized ambient Martian air flow into that area, so that it would help keep any new dust from coming in?Then you either need another airlock, or continuous over-pressure. Which seems a waste. The outside area is just about creating a stable, protected prep and storage area. Based on the similar unpressurised structure on the ISS "Quest" airlock. But scaled up, in this case, for vehicles.
Are we talking a very large Hab that we've buried with regolith, or an actual "we've tunneled our way into a hillside" kind of idea? I just need some context.
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.
A problem that may happen with the external structure is that it will itself become dirty and contaminated
and might create a local atmosphere that is worse than the outdoors.
Should this thread be moved from the SpaceX Mars section back to the general Missions To Mars (HSF) section?
(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.)
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?
Quote from: lamontagne on 08/23/2019 12:39 pmThis 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.Quote- 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.
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=42098.0That was more for whole vehicle airlocks, rather than the smaller doors/hatches I'm illustrating here, but still.
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"
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) ?
Quote from: Lar on 08/23/2019 03:43 pmAn 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?
Quote from: lamontagne on 08/23/2019 05:47 pmQuote from: Lar on 08/23/2019 03:43 pmAn 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.
(KelvinZero is another strong proponent.)...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.
Quote from: Coastal Ron on 01/22/2017 03:35 pmThe 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.Someone above mentioned 'no free lunch'... how do you retract without pumping? Suggest you save the balloon for something more useful.
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.[...]- Should it open in, open [out],
or dilate like a SF movie door?
- What is the best way to signify 'open' and 'closed'?
- Should it have a doorknob?
Quote from: AncientU on 01/22/2017 06:48 pmQuote from: Coastal Ron on 01/22/2017 03:35 pmBut 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.Someone above mentioned 'no free lunch'... how do you retract without pumping? Suggest you save the balloon for something more useful.The thing is that there are lots of ways to compress a balloon without pumping. It generally comes down to some sort of piston operation.
Quote from: Coastal Ron on 01/22/2017 03:35 pmBut 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.Someone above mentioned 'no free lunch'... how do you retract without pumping? Suggest you save the balloon for something more useful.
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.
Alternatives to a balloon could be a child's ball pit (with slightly squishy balls that flatten together)
or one of those pin-impression toys.
Quote from: lamontagne on 08/23/2019 05:47 pmQuote from: Lar on 08/23/2019 03:43 pmAn 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.
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.
Most buried inflatables will need to be connected by corridors anyway
Quote from: lamontagne on 08/23/2019 07:05 pmMost buried inflatables will need to be connected by corridors anywayWhy?
The interesting question, to me, is whether the vehicle docking adaptor should also be the same as the inter-module berthing adaptor. Or are the vehicle docking adaptors a removable assembly attached to one of the hab's berthing adaptor (as they will be for commercial-crew on ISS.) Or are the vehicle docks different than berthing adaptors, but are fixed features only on particular modules, in place of berthing adaptors at that location (as on the Soyuz/Progress docking ports on ISS.)Likewise the EVA hatches. Is there a dedicated airlock module, attached to any berthing adaptor on a regular module (as with ISS), with the outer hatch being a dedicated EVA hatch. Or is the outer EVA hatch on the airlock module also the standard berthing adaptor.
Quote from: RonM on 08/23/2019 06:28 pmEach 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.No. One of the hatches in that configuration is opening in the wrong direction, it won't be usable as an airlock even if all the other requirements for an airlock were met.
A piston is a pump. The only difference is whether the airlock itself is being used as the inside of the pump or the pump is a separate thing connected to the airlock. The energy is the same.
The airlock requires a lot of space in a vehicle, due to the door opening inwards. Seems unavoidable though.
A very badly aligned connection; 10 degrees. Would the connector compensate, as shown here, or would the vehicle compensate using active suspension?
Would it be useful to have a few degrees of freedom in the connector, or should we expect the construction to be aligned?
[pistons and pins and balls (oh my)]
A few details.
A more complete hatch.
Quote from: lamontagne on 08/25/2019 07:23 pmA more complete hatch.I always feel bitchy criticising someone who has actually put in the effort, but... I think you're focusing too much on the "hatch", the door. The critical part of any docking system is the docking collar and surrounds. The hatch itself is, in a way, an afterthought.How do the two sides connect? How do they align? How do they make an airtight seal? How do they do all that while leaving an unobstructed hole in the middle for people to move through? What utilities need to pass through the collar, in addition to the opening/tunnel for people? Do the utilities need to be inside the pressurise (airtight) part, or outside (but still connected by the process of docking), and how do those connections align? How tolerant is the seal to dirt/dust, to wear, even to collision?Once you've solved that, you can stick a hatch at the back of the hole.[Edit: This complexity might mean that an EVA airlock must be different from a vehicle docking port. Which means, if you're focused on the airlock, you can ignore the docking part, as long as you realise it probably can't be tacked on afterwards. It also means that a vehicle that is used for EVAs needs two hatches, the EVA side and the vehicle-to-hab docking side; both of which take up space and structure, but skip either one and you limit the use of the vehicles.]
The connection is through the four cam and rod attachments, one at each corner.The alignment must be pretty precise. The cam and rods should be able to make final adjustments.
Quote from: lamontagne on 08/26/2019 12:51 pmThe connection is through the four cam and rod attachments, one at each corner.The alignment must be pretty precise. The cam and rods should be able to make final adjustments.So that's a female half of a male/female pair? Ie, an asymmetric system. Which means the vehicles fitted with the male half of this collar can't dock with each other.[Edit: Also, re: utilities. You've put them all outside the collar's seal (assuming the yellow is meant to represent however the collars create an airtight seal against each other). That means they are, in effect, outside the pressure vessels on both the habitat and vehicles. So strictly EVA for maintenance.]
Quote from: Paul451 on 08/24/2019 12:27 pmQuote from: lamontagne on 08/23/2019 07:05 pmMost buried inflatables will need to be connected by corridors anywayWhy?Because of the slope of the regolith on top of them. They can connect to one another underground, but they need at least a small corridor to the outside.Attachment:
Wouldn't a reinforced earth retaining wall ("reinforced mars" sounds weird) be an alternative here?
Quote from: Twark_Main on 12/01/2019 10:44 pmWouldn't a reinforced earth retaining wall ("reinforced mars" sounds weird) be an alternative here?Or, bury the entire complex and have the rovers drive down into a tunnel. Because the vehicles will need to be protected too when they are not on the surface.Not sure I've stumbled across this topic before, but I'm glad I did because what is designed and defined here might be applicable to rotating space stations.One thought I've had for first generation rotating space stations is that we could use the Common Berthing Mechanism (CBM), though with a much quicker way of latching and unlatching. And yes this is a passive port, not meant for docking, and that is because I envision it truly will be more like berthing than docking.Which brings up the question for this thread, is there is need for "docking" vs "berthing". I'm thinking that there will be some version of an "active berthing mechanism", but otherwise the docking hardware needed for spacecraft today will be overkill for mating two habitable objects on Mars.What do you think?
Quote from: Coastal Ron on 12/02/2019 12:42 amQuote from: Twark_Main on 12/01/2019 10:44 pmWouldn't a reinforced earth retaining wall ("reinforced mars" sounds weird) be an alternative here?Or, bury the entire complex and have the rovers drive down into a tunnel. Because the vehicles will need to be protected too when they are not on the surface.Not sure I've stumbled across this topic before, but I'm glad I did because what is designed and defined here might be applicable to rotating space stations.One thought I've had for first generation rotating space stations is that we could use the Common Berthing Mechanism (CBM), though with a much quicker way of latching and unlatching. And yes this is a passive port, not meant for docking, and that is because I envision it truly will be more like berthing than docking.Which brings up the question for this thread, is there is need for "docking" vs "berthing". I'm thinking that there will be some version of an "active berthing mechanism", but otherwise the docking hardware needed for spacecraft today will be overkill for mating two habitable objects on Mars.What do you think?I think that the vehicles with adaptive suspension can do some of the docking/berthing work, and that bellows on the airlock can help as well. The airlock I propose has four cam attachments at the corners that pull in the two facing plates one against the other. As far as bolting building components together, large flanges with gaskets are indeed probably enough. But it might make sense to size these so that they can have a complete docking mechanism, eventually an airlock, attached to them.I usually imagine the vehicles as going to park themselves in an infra red heated surface enclosure.
Quote from: lamontagne on 12/02/2019 01:37 amQuote from: Coastal Ron on 12/02/2019 12:42 amQuote from: Twark_Main on 12/01/2019 10:44 pmWouldn't a reinforced earth retaining wall ("reinforced mars" sounds weird) be an alternative here?Or, bury the entire complex and have the rovers drive down into a tunnel. Because the vehicles will need to be protected too when they are not on the surface.Not sure I've stumbled across this topic before, but I'm glad I did because what is designed and defined here might be applicable to rotating space stations.One thought I've had for first generation rotating space stations is that we could use the Common Berthing Mechanism (CBM), though with a much quicker way of latching and unlatching. And yes this is a passive port, not meant for docking, and that is because I envision it truly will be more like berthing than docking.Which brings up the question for this thread, is there is need for "docking" vs "berthing". I'm thinking that there will be some version of an "active berthing mechanism", but otherwise the docking hardware needed for spacecraft today will be overkill for mating two habitable objects on Mars.What do you think?I think that the vehicles with adaptive suspension can do some of the docking/berthing work, and that bellows on the airlock can help as well. The airlock I propose has four cam attachments at the corners that pull in the two facing plates one against the other. As far as bolting building components together, large flanges with gaskets are indeed probably enough. But it might make sense to size these so that they can have a complete docking mechanism, eventually an airlock, attached to them.I usually imagine the vehicles as going to park themselves in an infra red heated surface enclosure.Makes sense to me. I like the autonomous parking particularly.This is really getting down into the weeds, but what do you think about having six cam attachments instead of four? It seems that you'd want each attachment to hold roughly the same structural loads, otherwise some of them are over/under-built. The "span" of the door's top and bottom sill is half that of the sides, so it seems that each side would do better with two cam attachment points instead of one.In general the more attachment points the lighter the door, since the frame can be less overbuilt. To take an extreme example, imagine using just one or two attachment points, vs using dozens.And besides all that right brain logical reasoning, when I draw it on paper that layout just "feels" more "right," not just structurally but aesthetically speaking (at least to me). Would you agree?
Looking at the model again, I actually placed the four cam attachments symmetrically and almost equidistant from one another. They are in a 1,42 and 1,43 m rectangle. Don't know if this is good or bad, really, since the rigidity of the frame comes from an angled shaped structure and not that much from the cams.
Quote from: lamontagne on 12/19/2019 10:11 pmLooking at the model again, I actually placed the four cam attachments symmetrically and almost equidistant from one another. They are in a 1,42 and 1,43 m rectangle. Don't know if this is good or bad, really, since the rigidity of the frame comes from an angled shaped structure and not that much from the cams.The cams are resisting the enormous pressure forces pushing the frames apart. Keeping the cams at the same spacing interval minimizes the structural mass required to avoid unacceptable deflection of the frame.
Which brings up the question for this thread, is there is need for "docking" vs "berthing". I'm thinking that there will be some version of an "active berthing mechanism", but otherwise the docking hardware needed for spacecraft today will be overkill for mating two habitable objects on Mars.What do you think?
Here is a different design for a docking airlock. Not nearly as prettydrawings as those by Lamontagne but they should illustrate the general idea.It is bellows walled tube (doors not shown) which is moved into position with 6 blue actuators acting as a Stewart platform. These motions would be carried out with the pressure in the tube equal to the outside pressure so there would be no large forces involved.The rectangular opening can be moved in three directions and tilted in two. The bellows will prevent rotation of the doorway around the axis of the tube so a rotary seal was added between the outer ring and the green doorway frame. Once the tube is in position the doorway can be locked in place with with latches like the International docking system.In principal the actuators could also be used to resist the force from the air pressure and since they would be in tension buckling would not be a worry. However these large forces would likely require very heavy actuators so I added 12 1/2" dia red Dyneema rope lines to resist the air pressure. Each line has a 21,500 lb breaking strength. They are attached to winches which need to be able to apply enough tension to keep the ropes orderly during motions and to lock in position before the air pressure is applied. The rope will stretch about 1% as the load is applied.One comment about running service lines through the door frame. Can we move the waste water lines to the floor level? If I was working on a waste line I would want it as far as possible from any potable water lines. All of the lines should probably be purged and vented before disconnection so they don't boil out all over the doorway.
Quote from: Coastal Ron on 12/02/2019 12:42 amWhich brings up the question for this thread, is there is need for "docking" vs "berthing". I'm thinking that there will be some version of an "active berthing mechanism", but otherwise the docking hardware needed for spacecraft today will be overkill for mating two habitable objects on Mars.What do you think?Related to that thought is the need for docking/berthing seal maintenance. IMHO, the seals for a docking port will need to be easily serviceable and cheap to replace owing to the wear and tear they will experience on a daily, if not hourly basis. However, they may not need to be as effective as a less-often-used berthing seal. A slight positive pressure (e.g. air leaks) to force contaminants out of the airlock and also the seal may not be a bad thing.A frequently used airlock in my mind would consist of a docking door with seals that are replaced as much as monthly, then a surface exposure decontamination hallway to remove soils and perchlorates, then a higher-level seal and door behind it. A berthing airlock would have sets of doors that are rarely cycled, whose seals will last for months or years between replacements, and no decontamination hallway.
Airlock designs I've seen for the Moon have exactly that, a dust room, after the airlock, for decontamination. I've also seen some pretty severe criticism of back entry suits, so perhaps the ailocks might be used more often than I expected for entry with 'conventional' suits. Perhaps I'm making a mistake by trying to use a port designed for connecting vehicles as an airlock design; I should perhaps work the other way around: Define the airlock requirements, and then deduce the port that can satisfy them.
Quote from: lamontagne on 01/03/2020 04:11 pmAirlock designs I've seen for the Moon have exactly that, a dust room, after the airlock, for decontamination. I've also seen some pretty severe criticism of back entry suits, so perhaps the ailocks might be used more often than I expected for entry with 'conventional' suits. Perhaps I'm making a mistake by trying to use a port designed for connecting vehicles as an airlock design; I should perhaps work the other way around: Define the airlock requirements, and then deduce the port that can satisfy them."First Principles" are always the correct place to start a problem solving exercise. A coupling system differs in requirements from an airlock system.An airlock system must:1) Keep the inside environment in and the outside environment out2) Prevent contamination of people, air, and equipment inside the habitat3) Allow for repeated entry and exit- but not necessarily in both directions for the same system.After that, and I think we are moving away from first principles and into feature sets.Any more?
If by berthing you mean a permanent connection between prefabricated habitat sections I agree that a simple seal, rather like a giant version of a pipe flanged assembly, will probably be sufficient.
Define the airlock requirements, and then deduce the port that can satisfy them.
I guess the seals on the existing berting ports are already specified for difficult temperature environments, but dust is perhaps a new design issue, as Coastal Ron mentions.
Quote from: lamontagne on 01/04/2020 03:41 pmI guess the seals on the existing berting ports are already specified for difficult temperature environments, but dust is perhaps a new design issue, as Coastal Ron mentions.It's not the dust, it's the abrasiveness of the dust. And the corrosiveness of the perchlorates that will be the problem.You need something super cheap and easily replaceable for a door seal that is used often in that environment. Also, a door seal doesn't have to be one compound. You could use several materials to achieve the required results and be cheap.Think of oven doors. Woven asbestos or fiberglass fiber covering a silicon tubing core would make very abrasion and temperature resistant seals that are extremely flexible so that a nice seal may be achieved with mechanical pressure applied from both sides. And unlike orbital seals, a little leak while the airlock chamber is in use wouldn't be horrible because you have a source of replenishment gas.A 99% sealed system may be just fine for an outside door that is used all the time if the inner airlock door has a better seal that doesn't see radiation, thermal expansion or the same level of abrasive dust and corrosive perchlorates, and so its seal is replaced less often.I'm sure there are dozens of other combinations that would make nice door seals.
Quote from: Kenm on 12/31/2019 10:31 pmHere is a different design for a docking airlock. Not nearly as prettydrawings as those by Lamontagne but they should illustrate the general idea.It is bellows walled tube (doors not shown) which is moved into position with 6 blue actuators acting as a Stewart platform. These motions would be carried out with the pressure in the tube equal to the outside pressure so there would be no large forces involved.The rectangular opening can be moved in three directions and tilted in two. The bellows will prevent rotation of the doorway around the axis of the tube so a rotary seal was added between the outer ring and the green doorway frame. Once the tube is in position the doorway can be locked in place with with latches like the International docking system.In principal the actuators could also be used to resist the force from the air pressure and since they would be in tension buckling would not be a worry. However these large forces would likely require very heavy actuators so I added 12 1/2" dia red Dyneema rope lines to resist the air pressure. Each line has a 21,500 lb breaking strength. They are attached to winches which need to be able to apply enough tension to keep the ropes orderly during motions and to lock in position before the air pressure is applied. The rope will stretch about 1% as the load is applied.One comment about running service lines through the door frame. Can we move the waste water lines to the floor level? If I was working on a waste line I would want it as far as possible from any potable water lines. All of the lines should probably be purged and vented before disconnection so they don't boil out all over the doorway.-Very interesting design. Offers a lot more interior space than my proposal, and since there are a lot of recommendations out there on using a buddy system for airlock use it might be a basic design requirement to have more space.-Regarding the water lines on my design, I would expect the waste water line to be pumped, so there could/would be a 'wash cycle' before the line was connected or disconnected. There is a valve in the design, right behind the outer wall, for all the lines to reduce waste to the minimum and risk of leakage. There is a mechanical attachment below the floor, so not really much space there.-It might be a good idea to have purge valves to empty out the small space between the two valves. Would need to use some air for the purging, in particular in 0g.-Why so much built-in travel? -With the door closed, the pressure will be taken up on the actuators and the reels. Are there fail safe mechanisms that ensure that the system is operational without power? Is that even a requirement?-Is rotational misalignment a possibility? Or does the docking system automatically put the doors in the proper orientation? Trying to avoid the rotating seal. -Have you tried mating this to vehicles? As my design started as a vehicle airlock, it needed to be compact. But it's probably overdesing as a permanent connection.
Here is another try at an airlock design. This one needs the rover to bring the two airlocks into contact and uses inflatable sealsto avoid having to pull the seal faces together. In this design there are no actuators which need to resist the air pressure. Each airlock has a gimbal located near the body of the rover which is used to bring the ports into alignment before contact. A bellows would seal the joint within the gimbal which is not shown.This design has eight tang and clevis sets to hold against the air pressure. When the tang bottoms out in the clevis the holes will be lined up so the pin can be inserted. Since the inflatable seals can compensate for a gap the pins can be a loose fit in the holes so as to avoid problems with dust. The hole in the tangs are elongated to allow for a slight rotational misalignment around the axis of the airlock.
Quote from: Kenm on 01/12/2020 08:50 pmHere is another try at an airlock design. This one needs the rover to bring the two airlocks into contact and uses inflatable sealsto avoid having to pull the seal faces together. In this design there are no actuators which need to resist the air pressure. Each airlock has a gimbal located near the body of the rover which is used to bring the ports into alignment before contact. A bellows would seal the joint within the gimbal which is not shown.This design has eight tang and clevis sets to hold against the air pressure. When the tang bottoms out in the clevis the holes will be lined up so the pin can be inserted. Since the inflatable seals can compensate for a gap the pins can be a loose fit in the holes so as to avoid problems with dust. The hole in the tangs are elongated to allow for a slight rotational misalignment around the axis of the airlock.Does the rover really need an airlock? Might it be better off with a suitport(s) and a docking port, while the movable and flexible airlock was on the base only?I think the gimbal is perhaps a bit too much flexibility? Would really love to see two vehicles really doing the matching up manoeuver.I've joined a paper on the NASA Athlete vehicle for some docking details. There's also an interesting youtube video.The rover might just have a rigid docking port first shirtsleeve transfer
Here is another try at an airlock design. This one needs the rover to bring the two airlocks into contact and uses inflatable sealsto avoid having to pull the seal faces together. In this design there are no actuators which need to resist the air pressure. Without an airlock there is no way to move anything in or out of the rover.If you need a tool or want to work on something without gloves on you have to head back to base. This suggests that at least a small equipment airlock would be useful.Another question is how can we transfer crew if one of the rovers is disabledand unable to connect to a docking port. Having spare empty suitports on the roverswould allow the crew to move in their suits to the rescue rover. Of course if you are not using suitports an airlock would be available on each rover.
How about a movable and agile airlock? If instead of depending on an agile rover, what if the airlock was itself on an agile platform, like a smaller version of the Athlete platform? You could carry it around like a limpet, and it could move out and move around if required. Connecting to any number of rovers in different attitudes like a local shuttle service. No need to pump out as well. Longer term installations would connect port to port. A bit like these flatbed trailers used for deliveries.
Quote from: lamontagne on 01/14/2020 12:31 pmHow about a movable and agile airlock? If instead of depending on an agile rover, what if the airlock was itself on an agile platform, like a smaller version of the Athlete platform? You could carry it around like a limpet, and it could move out and move around if required. Connecting to any number of rovers in different attitudes like a local shuttle service. No need to pump out as well. Longer term installations would connect port to port. A bit like these flatbed trailers used for deliveries.I love it! I was thinking more along these lines, however. Why reinvent the wheel?
How tightly can you pack a spacesuit?
Quote from: lamontagne on 01/14/2020 10:20 pmHow tightly can you pack a spacesuit?Is a Personal Rescue Enclosure a spacesuit?You'd probably want a cylinder rather than a sphere for easier handling in gravity.A fabric airlock designed to connect to a standard or emergency hatch would also be useful. With an inner door it could do double duty for emergency transport. If it's big enough for a person in a space suit it's not a big stretch to holding a patient and a medic in shirt sleeves.
Quote from: Kenm on 12/31/2019 10:31 pmHere is a different design for a docking airlock. Not nearly as prettydrawings as those by Lamontagne but they should illustrate the general idea.Those flexible bellows would have to withstand the hoop stress of the internal atmosphere when pressurized. What would they be made out of?
Here is a different design for a docking airlock. Not nearly as prettydrawings as those by Lamontagne but they should illustrate the general idea.
Quote from: Twark_Main on 02/03/2020 02:09 amQuote from: Kenm on 12/31/2019 10:31 pmHere is a different design for a docking airlock. Not nearly as prettydrawings as those by Lamontagne but they should illustrate the general idea.Those flexible bellows would have to withstand the hoop stress of the internal atmosphere when pressurized. What would they be made out of?Probably fairly thin stainless steel. Kevlar cloth should also work for a more rounded look, but might be sensitive to the cold.
Quote from: Barley on 01/15/2020 01:42 amQuote from: lamontagne on 01/14/2020 10:20 pmHow tightly can you pack a spacesuit?Is a Personal Rescue Enclosure a spacesuit?You'd probably want a cylinder rather than a sphere for easier handling in gravity.A fabric airlock designed to connect to a standard or emergency hatch would also be useful. With an inner door it could do double duty for emergency transport. If it's big enough for a person in a space suit it's not a big stretch to holding a patient and a medic in shirt sleeves.Thanks, I knew these existed but couldn't find their name!This raises the question, could you have some kind of fabric tube with a frame and hatch mated to a suit port? Don't see why not. As an emergency device, you can be 'poured' into it, rather than need to move yourself inside? Even add a set of wheels if need be....Or just have a strong fabric tube with two light frames that match up with two docking ports. They would have to be handleable by a single astronaut. Stretch from one vehicle to the next and pressurise. No need for an airlock or precise matching of positions The docking ports supply the rigidity and structural strength required. But again, as an emergency device rather than a fixed connection. Hard to keep clean and rather bulky....
also discussed in the Martian dust storm topictrouble with Solar with events 100 sols long'Should Astronauts Be Worried About Mars Dust?'https://www.universetoday.com/articles/should-astronauts-be-worried-about-mars-dust
Quote from: JulesVerneATV on 03/07/2025 12:00 pmalso discussed in the Martian dust storm topictrouble with Solar with events 100 sols long'Should Astronauts Be Worried About Mars Dust?'https://www.universetoday.com/articles/should-astronauts-be-worried-about-mars-dustThere is still quite a lot of diffuse sunlight during a 100 day storm.
Those vertical panels on the moon will be situated at the South Pole. Early Mars settlements will be much closer to the equator thereby requiring a more angled orientation to catch the most sunlight possible.
A low tech airlock especially suitable for people living in lava tubes, could be made with a simple liquid filled sump. If an airlock needs to be built on Mars this is probably the way to do it with low technology and locally sourced equipment.
I think a layer of suitable oil on top of the volatile liquid (water or other) might prevent the evaporation /boiling off.I was not thinking about for early missions but for a future when Mars might have to survive independently from Earth.You do not want the whole of humanity to go extinct because there is no way to make/repair an airlock.
Quote from: colbourne on 03/14/2025 03:29 amI think a layer of suitable oil on top of the volatile liquid (water or other) might prevent the evaporation /boiling off.I was not thinking about for early missions but for a future when Mars might have to survive independently from Earth.You do not want the whole of humanity to go extinct because there is no way to make/repair an airlock.No need for oil, just have an external door on the far side with a basic plastic seal capable of maintaining a very small pressure difference. That should be enough to prevent boil off as the conditions on Mars are close to the water triple point.
Partial terraforming is probably cheaper than building an entire Mars city. On the order of $100B (meaning $30B-300B) is probably enough for an orbital mirror array large enough to reach comfortably above the Armstrong limit at low altitudes.
Partial terraforming is probably cheaper than building an entire Mars city.
Airlocks then don’t need to be fully pressure capable, just more or less airtight.
Quote from: Robotbeat on 03/14/2025 12:07 pmPartial terraforming is probably cheaper than building an entire Mars city.Maybe, but then you'd have to wait, what, 100 years or more for the terraforming to be done? No one is going to wait that long.And of course there is the question of who will pay for it? Which no one knows for sending humans to Mars as quickly as possible, but at least you get people on Mars - regardless how long they may live while there. In other words, the urgency is getting people to Mars, not terraforming Mars. That is secondary.QuoteAirlocks then don’t need to be fully pressure capable, just more or less airtight.Airlocks are important, but we can't forget that anyone going outside for a walk will accumulate Mars regolith on them, which is toxic due to the high concentrations of chlorine. So while you need airlocks, you also need decontamination systems as part of the airlock systems.
Quote from: Slarty1080 on 03/14/2025 12:10 pmNo need for oil, just have an external door on the far side with a basic plastic seal capable of maintaining a very small pressure difference. That should be enough to prevent boil off as the conditions on Mars are close to the water triple point.Indoor pool problem. Humidiry is going to condense on all your (cold) surfaces.
No need for oil, just have an external door on the far side with a basic plastic seal capable of maintaining a very small pressure difference. That should be enough to prevent boil off as the conditions on Mars are close to the water triple point.
Now instead of losing air (at least, the air that can't be pumped out) every cycle, you're losing 100% water vapor every cycle.
Quote from: Twark_Main on 03/14/2025 12:55 pmQuote from: Slarty1080 on 03/14/2025 12:10 pmNo need for oil, just have an external door on the far side with a basic plastic seal capable of maintaining a very small pressure difference. That should be enough to prevent boil off as the conditions on Mars are close to the water triple point.Indoor pool problem. Humidiry is going to condense on all your (cold) surfaces."Indoor", in this case is the outer entrance. It drains back into the pool. Don't invent fake problems.Quote from: Twark_Main on 03/14/2025 12:55 pmNow instead of losing air (at least, the air that can't be pumped out) every cycle, you're losing 100% water vapor every cycle.Now you are pretending that the losses from a 100,000Pa/600Pa airlock and a 650pa/600pa door are somehow the same.An airlock is not a "medieval", not if you want it to be useful and reliable. They are complex and precise, and the inevitable dust/grit around the seal will cause them to leak continuously. There's a minimum time required to cycle a full pressure airlock if you don't want to lose large amounts of air, given a certain number of people/equipment needing to be cycled through each day (or each shift), that sets a minimum number of airlocks. Plus a reserve for maintenance, plus a reserve for emergencies.You can't avoid conventional airlocks when you have a small scale settlement, but once you have sufficient people that you are constantly cycling workers in/out during the day, airlocks become enough of a chokepoint that you are going to be looking for alternatives.One alternative is to, essentially, ban EVAs. That adds its own demands, since tele-op systems are not "free". But moreso, IMO, it is an anti-solution, "solving" a problem by avoidance rather than robustness. You aren't settling the planet, you are hiding from it.The advantage of a water-lock is that it is bi-directional and continuous, enabling a vastly greater flow-through per lock. Even if you have a very-low-pressure outer hatch to reduce evaporation at the outer water surface, your cycle times are vastly reduced and flow-through increased. I suspect that even without an outer hatch, the rate of water loss won't exceed the rate of air loss from a set of air-locks large enough to get the same net flow-through when operating continuously. Add in the vastly reduced maintenance cost/time of a water-lock and it becomes even more valuable.There are many problems to solve (as with any system used on Mars, including airlocks), but once your settlement is starting to scale up, the advantages over traditional airlocks might make it worth the effort.A settlement will need to remove excess heat, so available waste heat can be used to prevent freezing (although some others have suggested that allowing a thin ice layer at the outer entrance is actually desirable/useful.) You need to waterproof all suits and vehicles that pass through it, but it will also act as a dust barrier, not only massively reducing the ingress of regolith into your settlement, but also washing suits/vehicles/equipment before they come back inside. You need water, duh, but then any large settlement will have a large emergency surplus of water, so "here it is". Buoyancy is going to be an annoyance, especially if using a "wet tunnel" system, but it's an easily solvable one.And yes, it also has a certain elegance. Especially because it only makes sense on Mars, due to the atmospheric pressure being so close to the triple-point pressure of water. Using the properties of the planet to solve half the problem, and simple water to solve the other half.
Quote from: Twark_Main on 03/14/2025 12:55 pmQuote from: Slarty1080 on 03/14/2025 12:10 pmNo need for oil, just have an external door on the far side with a basic plastic seal capable of maintaining a very small pressure difference. That should be enough to prevent boil off as the conditions on Mars are close to the water triple point.Indoor pool problem. Humidiry is going to condense on all your (cold) surfaces."Indoor", in this case is the outer entrance. It drains back into the pool. Don't invent fake problems.
Quote from: Twark_Main on 03/14/2025 12:55 pmNow instead of losing air (at least, the air that can't be pumped out) every cycle, you're losing 100% water vapor every cycle.Now you are pretending that the losses from a 100,000Pa/600Pa airlock and a 650pa/600pa door are somehow the same.
An airlock is not a "medieval", not if you want it to be useful and reliable. They are complex and precise, and the inevitable dust/grit around the seal will cause them to leak continuously. There's a minimum time required to cycle a full pressure airlock if you don't want to lose large amounts of air, given a certain number of people/equipment needing to be cycled through each day (or each shift), that sets a minimum number of airlocks. Plus a reserve for maintenance, plus a reserve for emergencies.
You can't avoid conventional airlocks when you have a small scale settlement, but once you have sufficient people that you are constantly cycling workers in/out during the day, airlocks become enough of a chokepoint that you are going to be looking for alternatives.
One alternative is to, essentially, ban EVAs. That adds its own demands, since tele-op systems are not "free". But moreso, IMO, it is an anti-solution, "solving" a problem by avoidance rather than robustness. You aren't settling the planet, you are hiding from it.
The advantage of a water-lock is that it is bi-directional and continuous, enabling a vastly greater flow-through per lock. Even if you have a very-low-pressure outer hatch to reduce evaporation at the outer water surface, your cycle times are vastly reduced and flow-through increased. I suspect that even without an outer hatch, the rate of water loss won't exceed the rate of air loss from a set of air-locks large enough to get the same net flow-through when operating continuously.
Add in the vastly reduced maintenance cost/time of a water-lock and it becomes even more valuable.
There are many problems to solve (as with any system used on Mars, including airlocks), but once your settlement is starting to scale up, the advantages over traditional airlocks might make it worth the effort.A settlement will need to remove excess heat, so available waste heat can be used to prevent freezing (although some others have suggested that allowing a thin ice layer at the outer entrance is actually desirable/useful.)
You need to waterproof all suits and vehicles that pass through it, but it will also act as a dust barrier, not only massively reducing the ingress of regolith into your settlement, but also washing suits/vehicles/equipment before they come back inside.
You need water, duh, but then any large settlement will have a large emergency surplus of water, so "here it is".
Buoyancy is going to be an annoyance, especially if using a "wet tunnel" system, but it's an easily solvable one.
And yes, it also has a certain elegance. Especially because it only makes sense on Mars, due to the atmospheric pressure being so close to the triple-point pressure of water. Using the properties of the planet to solve half the problem, and simple water to solve the other half.
I really should't answer forTwain, but...
I really should't answer forTwain, but an indoor pool is a source of humidity. Especially if it is large. So to avoid interior condensation your airlock walls need to be well insulated, and there is probably a door between the airlock and the habitat.
But really, what is the practicality of a 30m drop form one side of the airlock to the other? How can it be traversed in a useful way that doesn't invole a whole host of mechanical elements that will eventually be just as costly as a well build airlock door? [...] You'd have to go down and then up and likely tie down the wheel to a kind of moving system.
By the way, did we ever get any solid answer on whether the triple-point think is a coincidence or not?? It seems like an areogeochemical equilibrium is being maintained here...
Now suddenly the airlock is freezing
[airlocks are] Nothing that can't be done with medieval technologies! At most you might need an 18th century lathe and metalworking shop.
big underwater elevator [...] and elevator grease [...] there's a reason nobody's job is "underwater SCUBA elevator repairman"
Humidity is no more a concern than the agricultural spaces that will
The outer end is "outside" and will be colder. But there won't be much condensation due to the low pressure.
Whereas if the pump fails on a conventional airlock, you're either not using the airlock, or venting bulk atmosphere. Likewise if the seals fail.
Quote from: Twark_Main on 03/14/2025 08:10 pmBy the way, did we ever get any solid answer on whether the triple-point think is a coincidence or not?? It seems like an areogeochemical equilibrium is being maintained here...I've suspected that. Moreso, I suspect that water close to the surface is accumulated from frozen vapour rising from deeper reserves (aquifers/etc), rather than just-barely-drained from historical surface sources. Hence if you warm the surface, you will not release surface water, you will lose your near-surface sources as they drain back to deeper reserves. But I have no way of proving it.
Quote from: Twark_Main on 03/14/2025 08:10 pmNow suddenly the airlock is freezingWater has significant heat capacity. A large pool of water doesn't freeze "suddenly". ... A water-lock acts as a thermal buffer for the habitat.
It will take hours to get a crust of ice on the outer surface, which will then insulate the outer pool for days, and take weeks to freeze solid.
Quote from: Twark_Main on 03/14/2025 08:10 pm[airlocks are] Nothing that can't be done with medieval technologies! At most you might need an 18th century lathe and metalworking shop.And a water-lock is a tunnel and a pool of water, prehistoric technologies.
Quote from: lamontagne on 03/14/2025 07:54 pmBut really, what is the practicality of a 30m drop form one side of the airlock to the other? How can it be traversed in a useful way that doesn't invole a whole host of mechanical elements that will eventually be just as costly as a well build airlock door? [...] You'd have to go down and then up and likely tie down the wheel to a kind of moving system.You can use weight. You might add simple mechanical elements, if and only if they are more convenient. But you don't have to. Hence a failure of those optional elements doesn't prevent you from using the water-lock....Quote from: Twark_Main on 03/14/2025 08:10 pmbig underwater elevator [...] and elevator grease [...] there's a reason nobody's job is "underwater SCUBA elevator repairman"Because no-one uses an "elevator" to raise/lower equipment in water. Rope, hook, winch. Or just weight. But the fact that you keep repeating it, waiting for me to bite, suggests you aren't being genuine in this, or any of your arguments.
this thread is a hoot. just use 2 doors with silicone gaskets. bring extra gaskets and some grease. am i missing something?
Quote from: BN on 03/24/2025 01:12 pmthis thread is a hoot. just use 2 doors with silicone gaskets. bring extra gaskets and some grease. am i missing something?There is two parts to this thread.1) Early days while contact and supply from Earth is possible, when simple airlock doors are available,2) The future when Mars has to survive with no re-supply from Earth. Then airlocks have to be manufactured on Mars from available materials with available equipment. Depending upon how advanced the base is, how many airlocks are needed (maybe multiple bases, as the colony grows) and whether there is ample metal from meteors and scraped spaceships available. In this case water sumps might be the best solution.I predict that a Mars base will be quite primitive when it has to fend for itself, with low energy availability, and little manufacturing capability. It might be the case that plant materials will be used , and with future genetic engineering, it might be possible to grow airlocks
Quote from: BN on 03/24/2025 01:12 pmthis thread is a hoot. just use 2 doors with silicone gaskets. bring extra gaskets and some grease. am i missing something?There is two parts to this thread.1) Early days while contact and supply from Earth is possible, when simple airlock doors are available,2) The future when Mars has to survive with no re-supply from Earth.
Mars better be able to machine the surfaces of an airlock. If a mars city doesn’t have like a field machinist on site, they’re ngmi regardless of resupply shipments.
What’s the difference between these naval doors and airlock doors ? Is there any ? Does there need to be any, apart from materials ?
Quote from: MickQ on 04/01/2025 02:08 amWhat’s the difference between these naval doors and airlock doors ? Is there any ? Does there need to be any, apart from materials ?Leak rate. The naval doors are super heavy. They probably don't use vacuum-rated grease, etc, so it'd be kind of messy if used in a vacuum. Temperature capability.
We produce hatch seals from solid rubber, sponge rubber and a composite material (sponge core with a solid rubber skin)....Our customers regularly use our composite seals on; Naval Ships, Cruise Ships, Ferry Lines and Oil, Gas & Chemical Tankers.
Quote from: Robotbeat on 04/01/2025 03:50 amQuote from: MickQ on 04/01/2025 02:08 amWhats the difference between these naval doors and airlock doors ? Is there any ? Does there need to be any, apart from materials ?Leak rate. The naval doors are super heavy. They probably don't use vacuum-rated grease, etc, so it'd be kind of messy if used in a vacuum. Temperature capability.Grease? On seals?
Quote from: MickQ on 04/01/2025 02:08 amWhats the difference between these naval doors and airlock doors ? Is there any ? Does there need to be any, apart from materials ?Leak rate. The naval doors are super heavy. They probably don't use vacuum-rated grease, etc, so it'd be kind of messy if used in a vacuum. Temperature capability.
Whats the difference between these naval doors and airlock doors ? Is there any ? Does there need to be any, apart from materials ?
Quote from: Coastal Ron on 04/01/2025 05:31 amQuote from: Robotbeat on 04/01/2025 03:50 amQuote from: MickQ on 04/01/2025 02:08 amWhats the difference between these naval doors and airlock doors ? Is there any ? Does there need to be any, apart from materials ?Leak rate. The naval doors are super heavy. They probably don't use vacuum-rated grease, etc, so it'd be kind of messy if used in a vacuum. Temperature capability.Grease? On seals?I expect grease is for the main door movement (hinges and/or sliding rails), and for the moving parts of the latch mechanism.For this a low-vapor pressure, high vacuum grease would be used such as MOLYKOTE or Krytox.
What do/did they use for the SARJ TB lubrication on ISS?
Quote from: Robotbeat on 04/01/2025 03:50 amQuote from: MickQ on 04/01/2025 02:08 amWhat’s the difference between these naval doors and airlock doors ? Is there any ? Does there need to be any, apart from materials ?Leak rate. The naval doors are super heavy. They probably don't use vacuum-rated grease, etc, so it'd be kind of messy if used in a vacuum. Temperature capability.Grease? On seals? I doubt that is used for doors that are frequently used. Plus, it would collect dust very easily, which on Mars can't be good.I did a quick Google search and came up with a manufacturer of seals for ships - The Rubber Company. From their website:QuoteWe produce hatch seals from solid rubber, sponge rubber and a composite material (sponge core with a solid rubber skin)....Our customers regularly use our composite seals on; Naval Ships, Cruise Ships, Ferry Lines and Oil, Gas & Chemical Tankers.That is for water of course, and other liquids. For gases in an environment with harsh chemicals I would imagine other materials would be used, like silicone.
If we’re talking about making a gasket in a pinch, ABS plastic (which can be 3D printed and solvent welded together into larger parts and then solvent smoothed to make it airtight) with a little acetone absorbed in it is elastomeric, although it smells awful, would be messy and potentially cause other issues, and wouldn’t last long. But ABS parts have been 3D printed on ISS already and probably we’ll bring this stuff to Mars. (Although I’m not sure anyone has brought a bottle of acetone to ISS… you’d only ever want to use it in a glove box if you’re in a small space habitat for a TON of reasons, although ISS’s life support system can remove acetone vapors from the atmosphere…)
Quote from: Robotbeat on 04/01/2025 01:31 pmIf we’re talking about making a gasket in a pinch, ABS plastic (which can be 3D printed and solvent welded together into larger parts and then solvent smoothed to make it airtight) with a little acetone absorbed in it is elastomeric, although it smells awful, would be messy and potentially cause other issues, and wouldn’t last long. But ABS parts have been 3D printed on ISS already and probably we’ll bring this stuff to Mars. (Although I’m not sure anyone has brought a bottle of acetone to ISS… you’d only ever want to use it in a glove box if you’re in a small space habitat for a TON of reasons, although ISS’s life support system can remove acetone vapors from the atmosphere…)ABS+acetone is an existing technology as you say. However, I think we should be discussing the requirement and ways to solve it instead of existing suboptimal solutions. If silicone gaskets are a better solution, then figure out how to make them on Mars, starting from whatever processes we know will be needed on Mars anyway, e.g. propellant production. My guess: Mars will need an entire small-scale industrial polymer industry with multiple products. Input will be mostly methane and oxygen from the propellant factory. Major products will be polymer films, sheets, and fibers. Some of the intermediates will also be intermediates for silicone and other elastomers. Design the entire integrated system, not just a silicone production system.
No doubt the real process is more complex.
Quote from: lamontagne on 04/01/2025 04:05 pmNo doubt the real process is more complex.Occasionally I watch NileRed videos on YouTube, and it's amazing how many "simple" reactions turn out to be like the kids story "the old woman who swallowed a fly". You add a thing to undo the last thing you added, then add another thing to remove that thing, then another... "...Then we add a strong acid to dissolve the powder, then filtrate to remove the undissolved impurites, then add a strong base to neutralise the acid, then filtrate to remove the impurities, then add a weak acid to neutralise the unreacted base, then filtrate to remove the impurities, then we add (obscure reactant) to precipitate the powder again, then filtrate to capture the product, washing the powder in excess water to remove the soluble impurities, then we wash again in alcohol to remove the water, then heat to remove the alcohol. Now... we have our first ingredient prepared and can move on to our second step."[His experiments usually have a ridiculous purpose, just for the sake of seeing if he can, but it so often demonstrates how a simple, single-step reaction on paper is a dense tangle of micro-steps in reality, involving a dozen chemicals that aren't actually involved in the reaction.]Smelting and working metals goes back millennia, but even "simple" plastics required the industrial revolution plus a century.
Quote from: Paul451 on 04/01/2025 05:55 pmQuote from: lamontagne on 04/01/2025 04:05 pmNo doubt the real process is more complex.Occasionally I watch NileRed videos on YouTube, and it's amazing how many "simple" reactions turn out to be like the kids story "the old woman who swallowed a fly". You add a thing to undo the last thing you added, then add another thing to remove that thing, then another... "...Then we add a strong acid to dissolve the powder, then filtrate to remove the undissolved impurites, then add a strong base to neutralise the acid, then filtrate to remove the impurities, then add a weak acid to neutralise the unreacted base, then filtrate to remove the impurities, then we add (obscure reactant) to precipitate the powder again, then filtrate to capture the product, washing the powder in excess water to remove the soluble impurities, then we wash again in alcohol to remove the water, then heat to remove the alcohol. Now... we have our first ingredient prepared and can move on to our second step."[His experiments usually have a ridiculous purpose, just for the sake of seeing if he can, but it so often demonstrates how a simple, single-step reaction on paper is a dense tangle of micro-steps in reality, involving a dozen chemicals that aren't actually involved in the reaction.]Smelting and working metals goes back millennia, but even "simple" plastics required the industrial revolution plus a century.Of course, but it's nice to have at least an understanding of the process. As far as steel goes, I expect entirely new alloys will be required to optimise according to what is available on Mars. Chrome, for example, might be hard to come by.
Would, or could there be airtight doors on Starship that could be fitted with easy removal in mind so they could be salvaged specifically for use on Mars ??
I am not sure why the talk of winches with the water sump.With vehicles you drive down the angled underwater tunnel and then up the other side. Very efficient.For people on foot you would have a vertical shaft and simply use buoyancy control as used by scuba divers.Evaporation should not be a problem as a thin layer of oil will prevent this. It might be necessary to have heaters to prevent ice build up when this becomes a problem, but the ice may be useful to prevent water loss when no one is using the passage.
I am not sure why the talk of winches with the water sump.With vehicles you drive down the angled underwater tunnel and then up the other side. Very efficient.
Evaporation should not be a problem as a thin layer of oil will prevent this. It might be necessary to have heaters to prevent ice build up when this becomes a problem, but the ice may be useful to prevent water loss when no one is using the passage.
Quote from: colbourne on 03/23/2025 08:46 amI am not sure why the talk of winches with the water sump.With vehicles you drive down the angled underwater tunnel and then up the other side. Very efficient.Not efficient in terms of the quantity of fluid, or in general the overall physical size. Bigger things cost more.Quote from: colbourne on 03/23/2025 08:46 amEvaporation should not be a problem as a thin layer of oil will prevent this. It might be necessary to have heaters to prevent ice build up when this becomes a problem, but the ice may be useful to prevent water loss when no one is using the passage.It should be easy to verify the (in)feasibility of this idea using an inexpensive vacuum pump and some pipe. This is one experiment we can do on Earth, and in a home setting no less!My expectation: the water will boil near the surface, everywhere above the equipressure surface where the water column pressure drops below the boiling point. It doesn't matter if a thin film means the water can't "see" the vacuum, all that matters is the pressure. The roiling surface will break up whatever oil or ice layer anyway.On Mars the goal is to bring precious water inside, not the opposite. If you thought the water conservation rules implemented in Phoenix were bad, you ain't seen nuthin' yet...
Most oils have a fairly low vapour pressure; most vacuum pump oils should be fine especially as it decreases with temperature anyway. Just pile on sufficient oil to increase the pressure at the top of the water column to above say the Armstrong Limit. That's about 0.6m of Earth water, 1.6m of Mars water so call it 1.8m of oil on Mars. (Vegetable oil seems to boil and emulsifies with water, great for making salad dressings I guess)PFPE "oils" are used in vacuum pumps, spacecraft etc. Only trouble is their 1.8g/cc density so you can't float it over some water. But you could make an Archimedes lock of water connect to a secondary lock (entrance above the Armstrong limit) of PFPE. PFPE can also be a ferrofluid carrier.
You don't need oil on the water to reduce evaporation/boiling, you'd have an unpressurised outer chamber that is saturated with water vapour.
Why even bother with the water? Just have it be turtles PFPE oils the whole way down.This also reduces the height of your shaft or ramp by 1 - 1.0/1.8 = 44%. If the large construction is only half the size (actually even better, because you can eliminate the Archimedes lock), it could be worth it to use more expensive oil instead of water.
You don't need oil on the water to reduce evaporation/boiling, you'd have an unpressurised outer chamber that is saturated with water vapour. An outer door (not hatch) reduces mixing with the outer atmosphere. (For vehicle size water-locks, you might get away with air-curtain type barriers, avoiding the need for an outer door at all.)
Perhaps just use something like the simple fabric airlocks on inflatable structures on Earth, just inflated with local atmosphere. The pressure differential normally used with those things is like 2-3kPa which is not fantastic; not enough to get even to 0°C boiling limit above Mars pressure.
Speaking of reading the phase diagram wrong, I just googled for an online phase calculator for water, to double check myself, and, of course, google's AI helpfully worked it out for me... yay! ...telling me the 3 kPa boiling point was 69.1° C. So there! AI saves the day!
If you want the right answer, Wolfram|Alpha can do that.https://www.wolframalpha.com/input?i=boiling+point+of+water+at+3+kPa
Quote from: Paul451 on 05/30/2025 09:13 pmI just googled for an online phase calculator for water, to double check myselfIf you want the right answer, Wolfram|Alpha can do that.https://www.wolframalpha.com/input?i=boiling+point+of+water+at+3+kPaWeird, that gets it wrong too.[Edit: I mean, assuming we're using R = 8.315 J/mol*K, Hvap for water = 40.657 kJ/mol, and a baseline of 100°C at 101.325kPa, and the standard Clausius-Clapeyron equation.]
I just googled for an online phase calculator for water, to double check myself
Quote from: Paul451 on 05/31/2025 04:22 amQuote from: Twark_Main on 05/30/2025 09:48 pmIf you want the right answer, Wolfram|Alpha can do that.Weird, that gets it wrong too.[Edit: I mean, assuming we're using R = 8.315 J/mol*K, ΔHvap for water = 40.657 kJ/mol, and a baseline of 100°C at 101.325kPa, and the standard Clausius-Clapeyron equation.]I expect it's using a more exact (non-ideal) model of water.You're trying to "double check yourself," but if you're assuming your answer is right and anything else is wrong then... what are you double-checking exactly?
Quote from: Twark_Main on 05/30/2025 09:48 pmIf you want the right answer, Wolfram|Alpha can do that.Weird, that gets it wrong too.[Edit: I mean, assuming we're using R = 8.315 J/mol*K, ΔHvap for water = 40.657 kJ/mol, and a baseline of 100°C at 101.325kPa, and the standard Clausius-Clapeyron equation.]
If you want the right answer, Wolfram|Alpha can do that.
Is it just that you doubt your own arithmetic?
assuming we're using [...] ΔHvap for water = 40.657 kJ/mol
Quote from: Twark_Main on 05/31/2025 03:12 pmQuote from: Paul451 on 05/31/2025 04:22 amQuote from: Twark_Main on 05/30/2025 09:48 pmIf you want the right answer, Wolfram|Alpha can do that.Weird, that gets it wrong too.[Edit: I mean, assuming we're using R = 8.315 J/mol*K, ΔHvap for water = 40.657 kJ/mol, and a baseline of 100°C at 101.325kPa, and the standard Clausius-Clapeyron equation.]I expect it's using a more exact (non-ideal) model of water.You're trying to "double check yourself," but if you're assuming your answer is right and anything else is wrong then... what are you double-checking exactly?I was double checking my eyeballing a phase change chart against a calculated result by an online tool. Then I checked those results by hand using the CC equation, noting that most online tools get the same result that I do, but Wolfram-Alpha doesn't (nor does Google AI, by a much wilder and more amusingly random margin.)Quote from: Twark_Main on 05/31/2025 03:12 pmIs it just that you doubt your own arithmetic?No, I doubted the claim by Lampyridae that 3 kPa over Mars ambient isn't enough to push the boiling point of water above 0°C. Then I doubted my ability to draw two converging lines on a chart. Then I doubted the online tools. Then I doubted Wolfram Alpha.And it turns out my arithmetic was fine. But...Quote from: Paul451 on 05/31/2025 04:22 amassuming we're using [...] ΔHvap for water = 40.657 kJ/mol No, we are not. It varies with temperature. That's annoying. It's better to use ~44 kJ/mol for temps between 0 and 30°C. (Used a different online tool. Good old Engineering Toolbox. Dumb as a box of hammers, but also as reliable.)The whole thing makes using any equation that uses ΔHvap pretty useless for calculating boiling points, since you need to calculate ΔHvap for the temperature that you are trying to find. Very circular. Curious what the best equation would be. Can't figure out a question-phrasing that gets WA to tell me what equation it's using. (And google is still worthless.)[Also noted that while WA quotes the same ΔHvap figure for near-100°C as everyone else (although it struggles with converting to J/mol), it must be hard coded (or hard data'd?) to use a different figure when actually calculating boiling point. But I can't get it to show what. That hard coded data might be right, but I have no way to check its work.]
