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....