Quote from: Darkseraph on 01/08/2017 05:46 pmIt might be better to rely on a cheaper prexisting Tunnel Boring Machine, The Universe, that has already created tunnels on Mars for us! Caves and Lavatubes likely already exist on the surface and a survey of these and their extent with human and robotic assets would be a better starting off goal. Most of these lava tubes are probably not ideal for habitation or not close to useful resources but a few probably are and with an extensive enough survey, these could be discovered. I recently visited a lava tube, on Lanzarote Island (part of the Canary Islands). I'm not a geologist, so this was all-new for me. In case y'all have never seen one, here's my report on that.The tunnel starts from near sea level on the east side of the island, and goes uphill about 7 KM toward the summit of "La Corona". Our tour only went a about half a KM into it, starting at "Cueva de los Verdes", but I've seen a cross-section map that shows that it's continuous for most of the way. As shown on the JPG, another attraction, "Jameos del Agua", was a non-continuous but additional section, right on the Atlantic.The graphics that I've seen some members here post, about having multiple, half-cylinder pressure habitats within a lava tube, wouldn't have worked in the one that I visited. It wasn't wide or high enough. I didn't take any measurements, but I'd estimate that the widest point that I saw was 50-60 feet, and the highest about 40 feet. And at that widest point, the ceiling was only 20 feet. Many sections were much tighter, including places where we had to stoop to pass thru, although I'm sure that with explosives or other equipment these could have been expanded. There was one section where there were actually two levels, so perhaps such an area could have supported a structure of 100 foot in height. Some areas had strangely smooth walls, but most of the ceilings were very jagged. In many places the floor was relatively flat, but still with fist-sized or bowling-ball-sized rocks all over. Rock in-falls were common, but again, I'm sure that these could be cleared with time and effort. I would estimate that we were about 100 feet underground for most of the tour.Again, I'm no expert on this, so I defer to any of you who are.
It might be better to rely on a cheaper prexisting Tunnel Boring Machine, The Universe, that has already created tunnels on Mars for us! Caves and Lavatubes likely already exist on the surface and a survey of these and their extent with human and robotic assets would be a better starting off goal. Most of these lava tubes are probably not ideal for habitation or not close to useful resources but a few probably are and with an extensive enough survey, these could be discovered.
Quote from: pobermanns on 01/25/2017 08:15 pmQuote from: Darkseraph on 01/08/2017 05:46 pmIt might be better to rely on a cheaper prexisting Tunnel Boring Machine, The Universe, that has already created tunnels on Mars for us! Caves and Lavatubes likely already exist on the surface and a survey of these and their extent with human and robotic assets would be a better starting off goal. Most of these lava tubes are probably not ideal for habitation or not close to useful resources but a few probably are and with an extensive enough survey, these could be discovered. I recently visited a lava tube, on Lanzarote Island (part of the Canary Islands). I'm not a geologist, so this was all-new for me. In case y'all have never seen one, here's my report on that.The tunnel starts from near sea level on the east side of the island, and goes uphill about 7 KM toward the summit of "La Corona". Our tour only went a about half a KM into it, starting at "Cueva de los Verdes", but I've seen a cross-section map that shows that it's continuous for most of the way. As shown on the JPG, another attraction, "Jameos del Agua", was a non-continuous but additional section, right on the Atlantic.The graphics that I've seen some members here post, about having multiple, half-cylinder pressure habitats within a lava tube, wouldn't have worked in the one that I visited. It wasn't wide or high enough. I didn't take any measurements, but I'd estimate that the widest point that I saw was 50-60 feet, and the highest about 40 feet. And at that widest point, the ceiling was only 20 feet. Many sections were much tighter, including places where we had to stoop to pass thru, although I'm sure that with explosives or other equipment these could have been expanded. There was one section where there were actually two levels, so perhaps such an area could have supported a structure of 100 foot in height. Some areas had strangely smooth walls, but most of the ceilings were very jagged. In many places the floor was relatively flat, but still with fist-sized or bowling-ball-sized rocks all over. Rock in-falls were common, but again, I'm sure that these could be cleared with time and effort. I would estimate that we were about 100 feet underground for most of the tour.Again, I'm no expert on this, so I defer to any of you who are.40 feet wide and 20 feet high for several kilometers could house a pretty significant base. You don't need a blowup structure inside except to start off with. Seal the ends then pressurize.
You want a glassified tunnel surface to prevent zillions of small air leaks and act as its own pressure vessel. Glass forced into cracks also acts as anchors to provide mechanical support for the walls and ceilings
I would think that a better idea would be to have a whole bunch of relatively small modules, which could be linked together, ad hoc. That would allow the arriving astronauts to set things up as the physical dimension limits allowed, and yet still use the lava tube for protection.
Quote from: pobermanns on 01/26/2017 08:50 pmQuote from: sghill on 01/26/2017 01:17 pmYou want a glassified tunnel surface to prevent zillions of small air leaks and act as its own pressure vessel. Glass forced into cracks also acts as anchors to provide mechanical support for the walls and ceilingsI'm uploading a few pix from my trip to the two sites on Lanzarote. Perhaps you all will find these instructive. The first 6 are from the long tube, which extends most of the way to the summit. The last one is from the place on the Atlantic, which is non-continuous with the rest of the lava tube. It is has cave-ins on both ends, with a shallow pond of collected rainwater inside of it.Gorgeous photos. They illustrate perfectly why lava tubes won't be used IMHO. You'd have no idea about the mechanical strength and stability of the tube, and their wildly varying shapes and ragged edges would force you to tunnel through the tunnel to get some sort of standardized diameter- which you would then have to reinforce.All of this would be done in a hard vacuum over months or years with materials brought from Earth, and they'd be small tools too because of shipping constraints.So much safer, cheaper, and easier to use an electric TBM or welding subterrene and make a new tunnel, then only ship an airlock door, which you mount to the sealed walls. You're already going to have to send up a huge powerplant, so it's not your limiting constraint. The ITS diameter and mass to Mars is your limiting constraint.And I haven't even broached the subject of longevity. A glassified tunnel would exist for eons. Anything less will not. If we're serious about colonizing Mars with anything less than complete terraforming, then we need to think on the time scales of civilizations, not decades.
Quote from: sghill on 01/26/2017 01:17 pmYou want a glassified tunnel surface to prevent zillions of small air leaks and act as its own pressure vessel. Glass forced into cracks also acts as anchors to provide mechanical support for the walls and ceilingsI'm uploading a few pix from my trip to the two sites on Lanzarote. Perhaps you all will find these instructive. The first 6 are from the long tube, which extends most of the way to the summit. The last one is from the place on the Atlantic, which is non-continuous with the rest of the lava tube. It is has cave-ins on both ends, with a shallow pond of collected rainwater inside of it.
I think trying to make them air tight might not be worth it. Probably just using it as extra shelter from radiation and temperature swings. Maybe if you find a big one that is strong, you can pressurize it to 1-2psi with outside air (in case it's leaky) as a double layer of safety for the habs. That'd mean a positive-pressure oxygen mask and/or helmet would work but you could have far better dexterity since the limbs wouldn't need to be pressurized.
Were you using pure oxygen in your positive pressure device?The Apollo suits were 3.5psi, without positive pressure breathing. They used pure O2.Some people climb Everest without oxygen. That's a partial pressure of just 1psi oxygen. Twice that is adaptable for pure oxygen, and if you add another 1psi of positive pressure (or some other method like blood doping), I think performance should be more than acceptable.
Except you adapt fairly quickly to higher altitudes, but it still takes weeks or months, you shouldn't compare your experience of just going from sea level to low pressure in minutes or hours. People who live at high altitudes have adapted to this. On Mars, you'll likely have lower pressures, so it'll be like living in Breckenridge or Aspen at 10000ft, then going hiking or skiing at 13000-14000ft.
So is .2 atm @ 100% o2 the same as 1 atm @ 20% o2?
It's not perfect adaption. As you go higher and higher, it's harder and harder. But this is the reason why people who attempt Mount Everest stay at the base camp for a while before starting the real climb. You have to give your body time to adapt. And you don't have to be born some place to take advantage of it. Merely living there a while can do it.Over the longer term, many generations, you get actual genetic adaptations. The Tibetans are a classic example, who adapted to the high altitudes (15000 ft... The average altitude of the whole country is higher than any peak in Colorado) after splitting off from their low altitude cousins just 2750 years ago. Gene therapy can probably accelerate this and help regular people adapt, too. And so there's a long-term reason to make your habs low-pressure: to develop adaptations (natural and artificial) to prepare Martians for the early days of terraforming when pressures will be very low.I can tell a lot of people have misconceptions about high altitudes. Maybe we have people who live in Denver (Lockheed, etc) design the habs so we don't get this low lander bias in the design.
Quote from: rsdavis9 on 01/27/2017 06:30 pmSo is .2 atm @ 100% o2 the same as 1 atm @ 20% o2?Referencing the Navy Flight Surgeons Manual ( http://www.med.navy.mil/sites/nmotc/nami/academics/Documents/FlightSurgeonsManual.pdf), 33,700 feet MSL yields the same blood O2 saturation level, when on 100% O2, as when breathing normally at sea level. That's about 4 psis. I don't know what the partial pressure of oxygen would be at .2 ATM, nor that the equivalent altitude would be, but I'm sure that a full-pressure suit would be mandatory.