Mars landing starship airlock configuration

[Slarty1080]

There are a number of possible configurations for airlocks for a Starship Mars mission. These could have a significant impact on the rest of the ships layout. I am interested to discover which option(s) are most likely to be used and what benefits and constraints each would provide. For example:

The whole ship could be pressurized with external access provided by a large airlock on the cargo deck through which all cargo and crew EVA would pass. This would enable the greatest volume of pressurized space and a minimum of additional pressure bulkheads. But the large airlock would take up a considerable volume and mass and could present issues with sealing, cycling and redundancy.

The cargo deck could be unpressurised with external access via a large unpressurized door. A small crew only airlock could be built into the floor above the cargo deck allowing suited crew to descend into the cargo deck via a ladder or a lift. Or a pressurized access tube could be provided from the deck above the cargo deck into an EVA prep area and crew only airlock on the cargo deck. This avoids the large airlock issues of the first option but requires extra space and mass to enable a pressure bulkhead between the cargo deck and the rest of the ship.

Then there are other possibilities such as the need for multiple airlocks for redundancy and potentially small airlocks for sample entry and examination inside the ship.

   

[Twark_Main]

A sensible "belt and suspenders" approach seems to be to have 1-2 dedicated airlocks for nominal operation (as seen on the Artemis mock-ups), while leaving the option to use the main cargo door as a contingency / emergency operation mode, which pressurizes / depressurizes the entire cargo bay.

Having an outer door that seals is probably a "given" anyway, since it leaves you the ability to pressurize the cargo area during flight which rigidizes the Starship fuselage.

[Slarty1080]

A sensible "belt and suspenders" approach seems to be to have 1-2 dedicated airlocks for nominal operation (as seen on the Artemis mock-ups), while leaving the option to use the main cargo door as a contingency / emergency operation mode, which pressurizes / depressurizes the entire cargo bay.

Having an outer door that seals is probably a "given" anyway, since it leaves you the ability to pressurize the cargo area during flight which rigidizes the Starship fuselage.

Having the contingency of using the main cargo deck as a backup option and two smaller airlocks would be very useful, but would come at a high cost in mass and volume since there would have to be a robust curved pressure bulkhead above for nominal operation and a very large (3m?) and heavy airlock door for the cargo bay. Although I suppose it would only have to take one atmosphere pressure. Would the Starship cargo bay need pressure stabilization during launch? If so how much pressure about 1atm?

[Twark_Main]

A sensible "belt and suspenders" approach seems to be to have 1-2 dedicated airlocks for nominal operation (as seen on the Artemis mock-ups), while leaving the option to use the main cargo door as a contingency / emergency operation mode, which pressurizes / depressurizes the entire cargo bay.

Having an outer door that seals is probably a "given" anyway, since it leaves you the ability to pressurize the cargo area during flight which rigidizes the Starship fuselage.

Having the contingency of using the main cargo deck as a backup option and two smaller airlocks would be very useful, but would come at a high cost in mass and volume since there would have to be a robust curved pressure bulkhead above for nominal operation and a very large (3m?) and heavy airlock door for the cargo bay. Although I suppose it would only have to take one atmosphere pressure. Would the Starship cargo bay need pressure stabilization during launch? If so how much pressure about 1atm?

SpaceX has said the highest stress portion of flight is reentry, not launch. The center of the Starship will be subject to large bending loads, and these are much easier to handle if the fuselage is pressurized.

Then again, relying on internal pressurization introduces a bunch of cascading failure modes if the pressure seal is broken. Probably best for reliability to not rely solely on internal pressure.

I think the cost in mass is greatly compensated for by the improvement in operational cost, since maintenance and logistical activities in the cargo bay can be performed in bunny suits instead of EVA suits.

[TheRadicalModerate]

First question is whether you're talking about an "exploration" variant or  "liner" variant. 

The exploration variant needs to be able to land on unimproved sites, and seems like it could be modeled pretty closely on the HLS variant:  redundant airlocks on a garage deck, with a fairly small crew module above, with a way to climb down into the airlocks.  The rest of the garage would be unpressurized (at least after landing).

The liner variant has port facilities, or at least tender vehicles.  It still probably needs an emergency airlock, but the way to get passengers on and off at scale is to dock a tender vehicle, equalize pressure, and get everybody on or off.

There's an open question about how much cargo a liner variant would hold.  Optimizing the safety and comfort of large groups of people would seem to militate for a very large crew module, but a fairly low payload mass, so that landing delta-v and acceleration margins can be fairly sloppy.  That would imply that heavy cargo came on another variant.

[Slarty1080]

First question is whether you're talking about an "exploration" variant or  "liner" variant. 

The exploration variant needs to be able to land on unimproved sites, and seems like it could be modeled pretty closely on the HLS variant:  redundant airlocks on a garage deck, with a fairly small crew module above, with a way to climb down into the airlocks.  The rest of the garage would be unpressurized (at least after landing).

The liner variant has port facilities, or at least tender vehicles.  It still probably needs an emergency airlock, but the way to get passengers on and off at scale is to dock a tender vehicle, equalize pressure, and get everybody on or off.

There's an open question about how much cargo a liner variant would hold.  Optimizing the safety and comfort of large groups of people would seem to militate for a very large crew module, but a fairly low payload mass, so that landing delta-v and acceleration margins can be fairly sloppy.  That would imply that heavy cargo came on another variant.

Good point, my primary interest is in the exploration variant (the liner variant is a long way off). I do wonder if there would be sufficient payload mass for a single ship to carry all of the solar panels, ISRU equipment, vehicles and still have room for 4-8 crew, food, supplies, ECLSS, decks, and other paraphernalia? If not and they need a cargo ship as well then that could impact the design of the airlocks. I also wonder how heavy a 2-3m airlock hatch would have to be?

[TheRadicalModerate]

Good point, my primary interest is in the exploration variant (the liner variant is a long way off). I do wonder if there would be sufficient payload mass for a single ship to carry all of the solar panels, ISRU equipment, vehicles and still have room for 4-8 crew, food, supplies, ECLSS, decks, and other paraphernalia? If not and they need a cargo ship as well then that could impact the design of the airlocks. I also wonder how heavy a 2-3m airlock hatch would have to be?

I think it's highly unlikely that an exploration crew vehicle will carry heavy payload, for two main reasons:

1) Landing a crew without confidence that ISRU is sufficient to get them back to Earth simply isn't going to happen.  I know this is a topic of some controversy, but it just seems to be the height of irresponsibility not to land ISRU equipment in a previous synod, deploy it, and make the propellant before sending the crew.

2) When I've simulated this, the flip-and-burn landing for heavy Starships on Mars is pretty hair-raising.  It's hard to do for a reasonable delta-v budget at less than 5 gees, which is pretty hard on a crew that's just spent 4-6 months in microgravity.  If you reduce the payload, things get considerably better.

I can't think of a case where you'd have a 2-3m airlock hatch.  You have an unpressurized garage deck, with redundant airlocks opening onto the deck.  Then you have a fairly flimsy hatch that gets you outside the Starship fairing.  That's the hatch from which the elevator deploys.

Other than the structural issues associated with Mars EDL, I can't think of a reason for deviating much from the likely architecture to be used by the HLS.  The cargo load-out for the crewed mission will be pretty modest, and mostly pressurized cargo (e.g. consumables).  I'd guess they'd want a rover and some miscellaneous unpressurized stuff, but that's about it.  Everything else should be pre-positioned.

[Slarty1080]

Good point, my primary interest is in the exploration variant (the liner variant is a long way off). I do wonder if there would be sufficient payload mass for a single ship to carry all of the solar panels, ISRU equipment, vehicles and still have room for 4-8 crew, food, supplies, ECLSS, decks, and other paraphernalia? If not and they need a cargo ship as well then that could impact the design of the airlocks. I also wonder how heavy a 2-3m airlock hatch would have to be?

I think it's highly unlikely that an exploration crew vehicle will carry heavy payload, for two main reasons:

1) Landing a crew without confidence that ISRU is sufficient to get them back to Earth simply isn't going to happen.  I know this is a topic of some controversy, but it just seems to be the height of irresponsibility not to land ISRU equipment in a previous synod, deploy it, and make the propellant before sending the crew.

2) When I've simulated this, the flip-and-burn landing for heavy Starships on Mars is pretty hair-raising.  It's hard to do for a reasonable delta-v budget at less than 5 gees, which is pretty hard on a crew that's just spent 4-6 months in microgravity.  If you reduce the payload, things get considerably better.

I can't think of a case where you'd have a 2-3m airlock hatch.  You have an unpressurized garage deck, with redundant airlocks opening onto the deck.  Then you have a fairly flimsy hatch that gets you outside the Starship fairing.  That's the hatch from which the elevator deploys.

Other than the structural issues associated with Mars EDL, I can't think of a reason for deviating much from the likely architecture to be used by the HLS.  The cargo load-out for the crewed mission will be pretty modest, and mostly pressurized cargo (e.g. consumables).  I'd guess they'd want a rover and some miscellaneous unpressurized stuff, but that's about it.  Everything else should be pre-positioned.

Yes that makes sense, although raises another issue. There would then presumably have to be 3 different ships. One cargo variant to land and deploy all of the solar power and machinery required to extract water plus the compressors chillers and sabatier equipment, etc. Another ship to land the crew and a third that gets filled on the surface to take them home. But there could be issues.

The two ships could not land that close to each other for fear of rocket plume debri damage. So the water or cryogenic propellants would need to be carried or piped over which doesn't sound practical. Second thoughts put the chillers and compressor on the return ship and pipe in oxygen and methane gas and liquify them there. That just leaves the food for the return journey that will be rather ancient by the time it's needed...

Apart from that it seems there would be two versions. The cargo version would have no airlocks at all and no  pressure vessel, just bracing, a crane and racks of equipment. The crewed version would have redundant airlocks perhaps located on the garage deck to make better use of the space and aid in supporting /bracing the pressure vessel above. Both versions would use the low or no pressure 2-3m flimsy aerodynamic hatch.

[TheRadicalModerate]

Yes that makes sense, although raises another issue. There would then presumably have to be 3 different ships. One cargo variant to land and deploy all of the solar power and machinery required to extract water plus the compressors chillers and sabatier equipment, etc. Another ship to land the crew and a third that gets filled on the surface to take them home. But there could be issues.

It's probably a good idea to have a fresh ship for return, but there's nothing that says that the crew's landing ship can't be refueled.

I don't want to drift too far into ISRU and pre-landing cargo load-outs, because they're covered elsewhere, but I'd think that you'd have at least five cargo landers of various payload flavors in the previous synod, if for no other reason than you need the landing data.  Might as well double up on electrolysis/Sabatier/RWGS/whatever ships and water extraction ships, and you probably want at least one extra return ship, just in case.

The two ships could not land that close to each other for fear of rocket plume debris damage. So the water or cryogenic propellants would need to be carried or piped over which doesn't sound practical. Second thoughts put the chillers and compressor on the return ship and pipe in oxygen and methane gas and liquify them there. That just leaves the food for the return journey that will be rather ancient by the time it's needed...

Depends on whether you're landing Starships on Mars with waist thrusters, a la HLS Starship, or with Raptors.

This is another reason why you may want to keep crewed ships as lightly loaded as possible.  You may land cargo ships on Raptors, because you're willing to take the risk that they fall into their own plume craters, but you definitely don't want to do that with the crew.  If the crew lands on waist thrusters, the ejecta problem will be dramatically reduced, especially in (admittedly very thin) atmosphere.  That might allow the crewed ship to land in the middle of several widely dispersed cargo ships, with not a huge amount of distance between the crew ship and each cargo ship.

I don't think that a universal tank on a rover is particularly far-fetched, either for water or finished propellant transport.  Venting the tank to the atmosphere will cause everything to evaporate/sublime almost instantly, so a single tank can be used for water, LCH4, and LOX.  You could put a water line on the existing QD and have the rover/tank combo plug into that for transfer operations.

[Eka]

Transporting water is easy. Put it into easily dropped off and picked up tanks. Load those tanks with robotic forklifts onto robotic transports. Thinking of things more, Mars is freezing. Forget the tanks. Just freeze the water into huge ice blocks with legs so they can be easily picked up and moved by the robotic forklifts. So having separate water extraction and propellant production ships is viable, and even some distance between them is also viable. For propellant moving, just use tanks. Robotic forklifts and transports are possible now. One just needs to make Mars adapted ones.

Fresh ship??? Somebody gonna ship a Starship manufacturing plant to Mars? All ships sent to Mars will have gone through atmospheric reentry at least once. I can see subtle design differences in crewed ships meant to stay versus ones that are planned to return to Earth. All personnel carrying ships will go to Mars fully crewed. Some may return with only skeleton crews of those who wish to return to Earth, or even empty. They are robotic.

Airlocks... I think the main LOX and Methane tanks are designed for 6 bar operational pressures for the Raptor engine propellant intakes. .5 to 1 bar pressure in the cargo hold is nothing for containing. Put good seals on the outer doors, and the pressure will stay in. That bulkhead of the propellant tank under the cargo floor won't be dented by 1 bar when it is pushing back with 6 bar.

Airlocks between the crew area and the cargo hold will be in at least duplicated small few crew number size, and larger cargo doors that require the full cargo hold to be pressurized to use. I don't see cargo airlocks due to their excessive size.

[Slarty1080]

Transporting water is easy. Put it into easily dropped off and picked up tanks. Load those tanks with robotic forklifts onto robotic transports. Thinking of things more, Mars is freezing. Forget the tanks. Just freeze the water into huge ice blocks with legs so they can be easily picked up and moved by the robotic forklifts. So having separate water extraction and propellant production ships is viable, and even some distance between them is also viable. For propellant moving, just use tanks. Robotic forklifts and transports are possible now. One just needs to make Mars adapted ones.

Fresh ship??? Somebody gonna ship a Starship manufacturing plant to Mars? All ships sent to Mars will have gone through atmospheric reentry at least once. I can see subtle design differences in crewed ships meant to stay versus ones that are planned to return to Earth. All personnel carrying ships will go to Mars fully crewed. Some may return with only skeleton crews of those who wish to return to Earth, or even empty. They are robotic.

Airlocks... I think the main LOX and Methane tanks are designed for 6 bar operational pressures for the Raptor engine propellant intakes. .5 to 1 bar pressure in the cargo hold is nothing for containing. Put good seals on the outer doors, and the pressure will stay in. That bulkhead of the propellant tank under the cargo floor won't be dented by 1 bar when it is pushing back with 6 bar.

Airlocks between the crew area and the cargo hold will be in at least duplicated small few crew number size, and larger cargo doors that require the full cargo hold to be pressurized to use. I don't see cargo airlocks due to their excessive size.

I'm sure that some sort of bowser transfer could be arranged, but it's not very convenient, probably easier just to run some sort of pipe for gaseous oxygen or methane. But the devil is in the details and assumptions made of course.

"Fresh ship" I think means different from the one the crew arrives in and yes they will all be coming from Earth. On the first few crews at the very least I think all the crews will be coming home.

No problem with vacuum or 1 bar in the cargo hold, but I doubt they will pressurise the cargo deck on the earliest missions as working in shirt sleeves in there would up the contamination levels in both directions. 

[Twark_Main]

working in shirt sleeves in there would up the contamination levels in both directions.

...hence my

maintenance and logistical activities in the cargo bay can be performed in bunny suits instead of EVA suits.

"Shirt sleeves" are indeed inadvisable.

[Eka]

working in shirt sleeves in there would up the contamination levels in both directions.

...hence my

maintenance and logistical activities in the cargo bay can be performed in bunny suits instead of EVA suits.

"Shirt sleeves" are indeed inadvisable.

I'm not sure if many people realize Mars is already very well seeded by Earth bacteria, and has been for billions of years. Bacteria is known to get lofted high into Earth's atmosphere by the ionosphere lift phenomenon, and some gets drawn off into space by the solar wind. That solar wind sweeps across Mars often enough to transplant Earth bacteria there. Also read up on the extremophiles bacteria on Earth, MIR, and ISS.

[Slarty1080]

working in shirt sleeves in there would up the contamination levels in both directions.

...hence my

maintenance and logistical activities in the cargo bay can be performed in bunny suits instead of EVA suits.

"Shirt sleeves" are indeed inadvisable.

I'm not sure if many people realize Mars is already very well seeded by Earth bacteria, and has been for billions of years. Bacteria is known to get lofted high into Earth's atmosphere by the ionosphere lift phenomenon, and some gets drawn off into space by the solar wind. That solar wind sweeps across Mars often enough to transplant Earth bacteria there. Also read up on the extremophiles bacteria on Earth, MIR, and ISS.

I'm sure many people are not aware. I would have thought that the (COSPAR) Panel on Planetary Protection would have been aware, but who knows? They appear to be ultra cautious over contamination of Mars. Hopefully that will eventually change, but it does make things more complicated. So yes bunny suits would help, perhaps shirt sleeves...in the fullness of time...

[Eka]

working in shirt sleeves in there would up the contamination levels in both directions.

...hence my

maintenance and logistical activities in the cargo bay can be performed in bunny suits instead of EVA suits.

"Shirt sleeves" are indeed inadvisable.

I'm not sure if many people realize Mars is already very well seeded by Earth bacteria, and has been for billions of years. Bacteria is known to get lofted high into Earth's atmosphere by the ionosphere lift phenomenon, and some gets drawn off into space by the solar wind. That solar wind sweeps across Mars often enough to transplant Earth bacteria there. Also read up on the extremophiles bacteria on Earth, MIR, and ISS.

I'm sure many people are not aware. I would have thought that the (COSPAR) Panel on Planetary Protection would have been aware, but who knows? They appear to be ultra cautious over contamination of Mars. Hopefully that will eventually change, but it does make things more complicated. So yes bunny suits would help, perhaps shirt sleeves...in the fullness of time...

Just because Earth seeded Mars, it does not follow that Mars is only populated by Earth sourced microorganisms. Those seeded microorganisms will have evolved their own survival techniques specially for Mars. There can also be unique Mars lifeforms that originated up on Mars. Even organisms that evolved elsewhere. So, yeah we can contaminate Mars.

I predict that the microbiome we live with and depend on will be one of the biggest issues with our branching out as a space faring civilization. The thing is we can only figure out what the issues are by going out and doing space exploration and colonization. We can predict thousands of possible issues and never see any of them, and have our asses handed to us by a totally unanticipated one. Life is extremely complex.

There is a reason I say "We are all part of this biological entity called Earth." and "Life finds a way."

[TheRadicalModerate]

I'm not sure if many people realize Mars is already very well seeded by Earth bacteria, and has been for billions of years. Bacteria is known to get lofted high into Earth's atmosphere by the ionosphere lift phenomenon, and some gets drawn off into space by the solar wind. That solar wind sweeps across Mars often enough to transplant Earth bacteria there. Also read up on the extremophiles bacteria on Earth, MIR, and ISS.

Off-topic.  If you must, try here.

[sghill]

I'm sure many people are not aware. I would have thought that the (COSPAR) Panel on Planetary Protection would have been aware, but who knows? They appear to be ultra cautious over contamination of Mars. Hopefully that will eventually change, but it does make things more complicated. So yes bunny suits would help, perhaps shirt sleeves...in the fullness of time...

As has been pointed out ad nauseum on this forum. Once humans land on Mars, planetary protection is done and over.

Fortunately, many of the potential contaminants won't live very long on Mars, and won't spread wide and fast.

[Slarty1080]

I'm sure many people are not aware. I would have thought that the (COSPAR) Panel on Planetary Protection would have been aware, but who knows? They appear to be ultra cautious over contamination of Mars. Hopefully that will eventually change, but it does make things more complicated. So yes bunny suits would help, perhaps shirt sleeves...in the fullness of time...

As has been pointed out ad nauseum on this forum. Once humans land on Mars, planetary protection is done and over.

Fortunately, many of the potential contaminants won't live very long on Mars, and won't spread wide and fast.

Is it? Once the first humans land on Mars are all restrictions then removed allowing the crew to go where they please and drill own to any arbitrary depth? I understand the point that once humans arrive on Mars, Mars will be contaminated with bacteria from Earth to some extent, but that should be localized around the landing site and on the surface. What am I missing? 

[Twark_Main]

I'm sure many people are not aware. I would have thought that the (COSPAR) Panel on Planetary Protection would have been aware, but who knows? They appear to be ultra cautious over contamination of Mars. Hopefully that will eventually change, but it does make things more complicated. So yes bunny suits would help, perhaps shirt sleeves...in the fullness of time...

As has been pointed out ad nauseum on this forum. Once humans land on Mars, planetary protection is done and over.

Fortunately, many of the potential contaminants won't live very long on Mars, and won't spread wide and fast.

Is it? Once the first humans land on Mars are all restrictions then removed allowing the crew to go where they please and drill own to any arbitrary depth? I understand the point that once humans arrive on Mars, Mars will be contaminated with bacteria from Earth to some extent, but that should be localized around the landing site and on the surface. What am I missing?

You're missing (or not) that sghill is using something called "wishful thinking," because they don't want to deal with planetary protection. 

Anyway, let's take that tangent to the appropriate thread: https://forum.nasaspaceflight.com/index.php?topic=47049.0