Author Topic: What would it take to do "Mars Direct," let alone MCT?  (Read 73636 times)

Offline Burninate

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on the OP's query:
The largest challenge seems to be volume for living space,  people are going to need several cubic meters each for such a long journey.  If there is an in-space propulsion vehicles then it would have no trouble accommodating the volume need through inflatables, while the lander can easily accommodate people at air-liner like densities for the brief launch and landing periods, as well as house the ECLSS and consumables.

Let's put a simple, arbitrary, *conservative* curve on living space.  Not precise at all, but there's no real way to be precise without testing astronauts to failure at high N.  Evidence is all about what people felt was appropriate in the past subjectively.  Numbers are in pressurized volume.  Everyone seems to agree that there is a curve, and it has some relationship to time and crew size, though the shape varies.

Hours: 1m3 survivable minimum, 3m3 comfortable, 10m3 plausible maximum benefit
Days: 3m3 survivable minimum, 10m3 comfortable, 30m3 plausible maximum benefit
Months: 10m3 survivable minimum, 30m3 comfortable, 100m3 plausible maximum benefit
Years: 30m3 survivable minimum, 100m3 comfortable, 300m3 plausible maximum benefit

Several of the studies max out at 6 months (~= indefinite), but this has not been demonstrated or falsified.  The last one I checked said something about 16m3 demonstrated need, 25m3 assumed margin for indefinite stay.  At some point you have to factor in long-term things like the aforementioned laundry / spare clothes, and a host of other subtle things that you would find you miss only if kept in solitary confinement.  Remember that this also needs to include space for spacesuits, backup spacesuits, tools, clothing, food, repair equipment, samples, sample-collecting tools, emergency gas and liquids canisters... everything.

Designing to the 100m3 mark for an interim exploration mission of 25 people, and the ~25m3 mark for the eventual 100 person colony mission, is what I lean towards.
I also showed that one of our best models for extended spaceflight, the ballistic missile submarine, has at least 22m3 pressurized volume (and according to a serviceman, the real number is higher than that) per person when you take into account living space and operations space that's not devoted directly to SSBN hardware.  Pressurized volume is not air space, but may be filled with gear and food - everyone apparently has their own definition of 'habitable volume'.

~1.27m3 is Gemini grade accommodations.  ~10.6m3 is Shuttle grade accommodations, ~120m3 is Skylab grade accommodations.  The Allure of the Seas cruise ship provides around 73m3 per person internal volume  at maximum occupancy, but has open decks, no ECLSS and minimal ventilation issues, and makes frequent resupply and port calls.

Going another power of 3 down relative to these 'survivable minimum' spans may be borderline technically possible, but leaves no spare space for any kind of activity (the vast majority would not be air volume, but gear/food), and goes beyond the threshold for what we could expect the most stable people to tolerate - you would expect a certain amount of damaged goods on the other end of such a trip.  Gemini 7 went 2 weeks and Gemini 5 went 1 week with 1.27m3 per person, to demonstrate that it was survivable... and based on what I've read of their experiences, if you put a hundred carefully screened people through that not all of them are going to come out the other end.
« Last Edit: 06/09/2015 05:28 pm by Burninate »

Offline Vultur

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What was the volume per person in early 20th century Antarctic winter quarters? They didn't even have modern entertainment...

Offline Patchouli

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I also showed that one of our best models for extended spaceflight, the ballistic missile submarine, has at least 22m3 pressurized volume (and according to a serviceman, the real number is higher than that) per person when you take into account living space and operations space that's not devoted directly to SSBN hardware.  Pressurized volume is not air space, but may be filled with gear and food - everyone apparently has their own definition of 'habitable volume'.

~1.27m3 is Gemini grade accommodations.  ~10.6m3 is Shuttle grade accommodations, ~120m3 is Skylab grade accommodations.  The Allure of the Seas cruise ship provides around 73m3 per person internal volume  at maximum occupancy, but has open decks, no ECLSS and minimal ventilation issues, and makes frequent resupply and port calls.

Going another power of 3 down relative to these 'survivable minimum' spans may be borderline technically possible, but leaves no spare space for any kind of activity (the vast majority would not be air volume, but gear/food), and goes beyond the threshold for what we could expect the most stable people to tolerate - you would expect a certain amount of damaged goods on the other end of such a trip.  Gemini 7 went 2 weeks and Gemini 5 went 1 week with 1.27m3 per person, to demonstrate that it was survivable... and based on what I've read of their experiences, if you put a hundred carefully screened people through that not all of them are going to come out the other end.

The realistic minimum is probably what you'd find on a ballistic missile sub or 22m3 per person as the Navy does carefully screen people for those missions.
Though for conjunction class missions with a long Mars stay I'd double or triple that number for the surface hab.
Maybe even go to Skylab class accommodations since an inflatable surface hab can be lighter per cubic meter then a typical Bigelow module as it doesn't need as much MMOD shielding since the Martian atmosphere offers some protection and there's plenty of soil and water ice that can be used for radiation protection.
« Last Edit: 06/11/2015 04:25 am by Patchouli »

Offline Robotbeat

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Except in early 1900s and earlier, the "economy class" accommodations on ships were only 5 m^3 per passenger (including hospital, etc). That is clearly possible as it was standard accommodations. I don't see why we'd pick a minimum more than that.

Also keep in mind ballistic missiles are working vessels, not passenger ships. This a large portion of that per person volume is space devoted to their task, like the sonar room, etc.
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Offline laszlo

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Except in early 1900s and earlier, the "economy class" accommodations on ships were only 5 m^3 per passenger (including hospital, etc). That is clearly possible as it was standard accommodations. I don't see why we'd pick a minimum more than that.

Also keep in mind ballistic missiles are working vessels, not passenger ships. This a large portion of that per person volume is space devoted to their task, like the sonar room, etc.

Those economy class passengers could go up on deck where they had unlimited volume in the upward direction, the entire deck area, albeit shared and class-restricted, and unlimited "visual" volume in their upper hemisphere. That's a lot different than being packed into the below decks space.

A good modern indicator might be how much time the ISS crews spend in the cupola with the shutters open.

Offline Burninate

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Except in early 1900s and earlier, the "economy class" accommodations on ships were only 5 m^3 per passenger (including hospital, etc). That is clearly possible as it was standard accommodations. I don't see why we'd pick a minimum more than that.

Also keep in mind ballistic missiles are working vessels, not passenger ships. This a large portion of that per person volume is space devoted to their task, like the sonar room, etc.
The Cunard and White Star line descriptions emphasize how unlike their competitors, they believed in comfort for the third class passengers as well, and provided them with extensive accommodations, like supplied food, dining areas, and recreation areas.  Their competitors are less well-documented.  I can't help but think this probably added up to more than 5m^3: A 1m x 2m x 1m berth accounts for 2m3, and room access to the 4 berths accounts for 1-2m3 more per person;  These people had hallways and recreation areas and dining areas even if you shut them out of the upper decks.    Do you have a citation for 5m3 of volume per passenger?  Even a sailing ship a hundred years prior, the USS Constitution, amounts to 10m3 per passenger without counting the open deck.
« Last Edit: 06/12/2015 12:02 pm by Burninate »

Offline Robotbeat

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BTW, I don't think departure from LEO is a good assumption. If you assume departure from LEO, ~100 day transits are likely to not be terribly practical. Depart from a high orbit, though, with propellant possibly delivered with SEP, and ~100 day trajectories become feasible.
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Offline Burninate

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Do you have a citation for 5m3 of volume per passenger?

BTW, I don't think departure from LEO is a good assumption. If you assume departure from LEO, ~100 day transits are likely to not be terribly practical. Depart from a high orbit, though, with propellant possibly delivered with SEP, and ~100 day trajectories become feasible.

For the longest time I wanted to loft *everything* to high Earth orbit or high Mars orbit with SEP before adding humans to the mix (skipping the Van Allen belts) with a small crew capsule.  This would have saved a *lot* of IMLEO.  Unfortunately, I can't discount the possibility it would give unmanned electronics problems to spend so much time in the Van Allen belts, so you revert to the much smaller bonus of lofting propellant to high orbit with SEP and sending the ~200-500T spacecraft there with chemical propulsion to refuel.
« Last Edit: 06/13/2015 04:22 pm by Burninate »

Offline Impaler

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Van Allen radiation is frequently experienced by military satellites on elliptical orbits, while bad for people their seems to be no problem in keeping electronics from frying when in it.

Offline A_M_Swallow

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For the longest time I wanted to loft *everything* to high Earth orbit or high Mars orbit with SEP before adding humans to the mix (skipping the Van Allen belts) with a small crew capsule.  This would have saved a *lot* of IMLEO.  Unfortunately, I can't discount the possibility it would give unmanned electronics problems to spend so much time in the Van Allen belts, so you revert to the much smaller bonus of lofting propellant to high orbit with SEP and sending the ~200-500T spacecraft there with chemical propulsion to refuel.

Simply powering down electronics makes it much more resistant to radiation. Most of the SEP's own electronics need to be powered up when passing through the Van Allen belts but can the cargo be powered off?

The transfer vehicle's part could be powered down until it is inside the transfer vehicle in high orbit. The Mars base's avionics may be off until sfter it has landed on Mars. Temperature controls may still be needed.

Offline kato

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Regarding habitable volume in the broadest sense - i.e. including storage etc - for a long-term full-autonomous mission in which you simply can't run into some port for the next 6-8 months : You might want to look at some of the Antarctic Stations.

Concordia Station at Dome C is actually used by ESA for long-term training in this regard. 200 m³ per person. On a very rough scale 20 m³ individual cabin space, 45 m³ common-use incl. radio room, hospital and immediately connecting corridors, 60 m³ additional workspace (laboratories, workshops etc), 45 m³ other corridors and technical rooms, 30 m³ storage, mostly for experiments. At -50 to -80°C temperatures for six months in the winter no just going out on deck to enjoy the free space either.

Offline RonM

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5 m3 seems too small, being less than half the volume of a US prison cell. 10 m3 would probably work considering the sleeping quarters for a crewman in microgravity can be the size of a small closet. Most of the volume would be for common areas.

For those used to playing wargames or RPGs, 5 m3 is about the same size as a single square with a 2.1 m ceiling (5' x 5' x 7').

The previously quoted 22 m3 on submarines is sounding better.

Offline KelvinZero

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Just wanted to insert one of my hobby horses of a really good expansive VR game combined with treadmill ..or maybe something even more elaborate to reproduce anything up to rock climbing exercise. I imagine just some sort of resistance arm for each limb. If you can reach out and not touch anything that should be big enough for anyone.

My estimate is about 10 m^3 for such a contraption that allows you to reach in all directions and not touch anything, assuming your back is strapped in place. If you spend a third of each day (eg 8 hours) in this machine (averaging 3.3 m^3 per person), then perhaps eating, reading and sleeping could all be done in just a couch along walls with a shared corridor, eg 2 m^3 per person. You could still have smaller vr headsets to isolate yourself from neighbours.

That totals 5.3 m^3. The VR areas could also be folded away for large open spaces for special occasions. Maybe you could arrange the 2 m^3 couch areas like stadium seats around this central volume so it can be used for talks etc.

(That 10 meters is probably a significant over estimate, it assumes 2x2x2.5m whereas I can only reach about 200x180x230cm, and not into all the corners of that region)
« Last Edit: 06/14/2015 02:52 am by KelvinZero »

Offline MATTBLAK

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The pressurized volume of the Shuttle's Flight Deck, Mid Deck and Airlock combined was about 76 cubic meters - around 2,700 cubic feet. With a crew of about 7, this was deemed adequate for missions lasting up to two weeks. But I guess You'd have to be motivated even so! A similar volume for a crew of three - my recommendation for the first Mars crew, for what that's worth - should be quite adequate. You will of course have to round that figure up a bit to accommodate all the supplies; say between 3200 and 3500 cubic feet (even with a crew of 4) so using that as your baseline for Mars Direct (or other) Habitat architecture, I say have at it and design your craft accordingly.

Also, as a relevant analogue; I once interviewed Dr Shannon Lucid and asked if a Shuttle with Spacelab or Double SpaceHab module attached as example would be enough volume for a crew of 7 Astronauts on a long mission to Mars. She said; "Oh sure! As long as the toilet kept working and there was plenty of food".

There I believe is a more than adequate example ;)
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Offline rayleighscatter

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To give a striking example of how little is too little space is the 18th century slaver, Brookes
Each person had 1.8-2.0m^3 not counting storage. Even a little more than doubling that to 5.0m^3 still shows just how little space that is.

Offline Robotbeat

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Do you have a citation for 5m3 of volume per passenger?

BTW, I don't think departure from LEO is a good assumption. If you assume departure from LEO, ~100 day transits are likely to not be terribly practical. Depart from a high orbit, though, with propellant possibly delivered with SEP, and ~100 day trajectories become feasible.

For the longest time I wanted to loft *everything* to high Earth orbit or high Mars orbit with SEP before adding humans to the mix (skipping the Van Allen belts) with a small crew capsule.  This would have saved a *lot* of IMLEO.  Unfortunately, I can't discount the possibility it would give unmanned electronics problems to spend so much time in the Van Allen belts, so you revert to the much smaller bonus of lofting propellant to high orbit with SEP and sending the ~200-500T spacecraft there with chemical propulsion to refuel.
Musk said the volume of an SUV per person. http://www.edmunds.com/ford/explorer/2015/features-specs/ The Ford Explorer SUV has an internal volume of 5 m^3 (and this is the per-person accomodations of steamships turn of the century for steerage class, including facilities like hospitals, etc... I  believe I have this citation at some point, but it was likely ignored). So I generally give a range of 5-10m^3 for Musk's figure. Musk also said 50-100 people on the MCT, not straight up 100 people. So a total volume of 500m^3 seems realistic, whether 50 people and 10m^3 or 100 people and 5m3. Remember, the greater volume you assume, the less chance Musk has of making this ever work at the price he mentioned. (And we can make better use of volume in microgravity than in gravity.)

And I was using high orbit in a generic sense. EML1 or EML2 are energetically basically the same as a highly elliptical Earth orbit.
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Offline Vultur

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I actually have trouble seeing it as that small (500m^3). If the rocket core is 10m, then the MCT will probably be 10-15m.

10m = 5m radius. 3.14 * 5m^2 = 78.5 m^2. So even if it's only 10m diameter, the habitable part would only be (500/78.5) = ~6.37 m tall.

That seems odd to me.

I think the SUV thing likely refers to individual cabin volume (excluding communal spaces) not total habitable volume divided by number of passengers.

Offline Robotbeat

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The whole thing will be larger than the habitable section. And it is going to be cone or ogive, won't be just a cylinder.
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Offline Burninate

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Do you have a citation for 5m3 of volume per passenger?

BTW, I don't think departure from LEO is a good assumption. If you assume departure from LEO, ~100 day transits are likely to not be terribly practical. Depart from a high orbit, though, with propellant possibly delivered with SEP, and ~100 day trajectories become feasible.

For the longest time I wanted to loft *everything* to high Earth orbit or high Mars orbit with SEP before adding humans to the mix (skipping the Van Allen belts) with a small crew capsule.  This would have saved a *lot* of IMLEO.  Unfortunately, I can't discount the possibility it would give unmanned electronics problems to spend so much time in the Van Allen belts, so you revert to the much smaller bonus of lofting propellant to high orbit with SEP and sending the ~200-500T spacecraft there with chemical propulsion to refuel.
Musk said the volume of an SUV per person. http://www.edmunds.com/ford/explorer/2015/features-specs/ The Ford Explorer SUV has an internal volume of 5 m^3 (and this is the per-person accomodations of steamships turn of the century for steerage class, including facilities like hospitals, etc... I  believe I have this citation at some point, but it was likely ignored). So I generally give a range of 5-10m^3 for Musk's figure. Musk also said 50-100 people on the MCT, not straight up 100 people. So a total volume of 500m^3 seems realistic, whether 50 people and 10m^3 or 100 people and 5m3. Remember, the greater volume you assume, the less chance Musk has of making this ever work at the price he mentioned. (And we can make better use of volume in microgravity than in gravity.)

And I was using high orbit in a generic sense. EML1 or EML2 are energetically basically the same as a highly elliptical Earth orbit.
Right.  I was asking if you could give us the citation on 5m^3 per person in the third class of passenger ships in 1900.

Offline Hanelyp

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For an individual sleeping cell 2m^3 seems enough to me.  This of course does not include storage and the various shared facilities and common areas.

A major consideration on available volume is the option to isolate yourself, at least for a time, from other individuals you have a personality conflict with.  One hardship I see on an old slave transport is being stuck in the same place, next to the same people, all day every day for the duration of the voyage.  Having some private personal space and common areas you can move about would make the voyage much more livable.  Designing the major common area so it can be opened up or subdivided for smaller groups according to activities and mood would be nice.

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