Author Topic: SpaceX's Martian Underground  (Read 18551 times)

Offline sanman

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SpaceX's Martian Underground
« on: 01/08/2017 07:47 AM »
I know people didn't like my thread on Elon's idea for a tunnel boring machine, feeling it wasn't SpaceX-related. But as I continue to read further about the idea, I was wondering if there's a possibility that a tunnel-boring machine could be the start of a path to more substantive ISRU on Mars (or Moon) than just making fuel by Sabatier, electrolysis, etc.

Could a tunnel-boring machine evolve into a mining machine? Could it eventually be turned into something very useful for ISRU?

http://www.fool.com/investing/2016/12/25/will-elon-musk-really-build-tunnel-boring-company.aspx

Quote

TUNNEL BORING MACHINES ARE MASSIVE PIECES OF EQUIPMENT -- TRAIN-SIZED MOBILE FACTORIES DESIGNED
TO DIG INTO THE EARTH. COINCIDENTALLY, THEY'RE ALMOST PERFECTLY SHAPED TO FIT ABOARD A ROCKET TO
MARS.


Musk knows ISRU is fundamental to the survival of any Mars colony, and obviously extraction of raw materials from the ground is a major challenge and necessity. What better way to gain experience in developing technology in this area than by going into the tunneling business? And perhaps as a way of not too overtly tipping his hand, "tunnel-boring" becomes the initial launch concept rather than "mining".

Let's also remember that Mars is very areologically stable - as a smaller planet farther out from the Sun, it has cooled faster and has a crust thickness comparable to Earth's despite its smaller size. Furthermore, the Martian interior could also serve as an additional source of power, via areothermal heating.

If reusable rockets, solar panels, and electric vehicles can each have their vital niche in enabling the Mars vision, can tunnel-boring technology prove to be another useful undertaking that would help sustain a Mars colonization effort?

Offline gospacex

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Re: SpaceX's Martian Underground
« Reply #1 on: 01/08/2017 10:36 AM »
Full-scale TBM is way too heavy for the initial colony. Even on Earth, TBMs make economic sense only if you need to bore multi-kilometer long tunnels.

I imagine much smaller machines will be used to build first Mars underground habitats. Perhaps these machines will be more versatile, not specialized only for tunneling work.

Offline Oersted

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Re: SpaceX's Martian Underground
« Reply #2 on: 01/08/2017 11:01 AM »
We are already discussing tunnelling in the Amazing Habitats thread. I think the contents of this thread fit very well in that one.

Offline sanman

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Re: SpaceX's Martian Underground
« Reply #3 on: 01/08/2017 11:58 AM »
Well, I was thinking there was the mining/ISRU aspect to this as well. Perhaps a tunneling machine would eventually evolve into a mining machine, which could extract ore and maybe even feed it into a smelter.


The article shows a large-sized machine as the current state of the art, but there's no reason that a smaller machine couldn't be used to bore large tunnels, if it had the right technology. I was thinking that microwave boring machine could be small enough and light-weight enough to be transportable to Mars, where it could be used to bore much larger cavities - although using the microwave approach for extracting ore might take some re-thinking (maybe with microwaves you could somehow bore and smelt at the same time?)


And at the same time, a microwave-based approach might offer the chance to disrupt the marketplace and take business from the higher-cost established players.

Online guckyfan

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Re: SpaceX's Martian Underground
« Reply #4 on: 01/08/2017 12:13 PM »
Whatever he has in mind, I am sure it is significantly different to present day technology. Or else he would not get into it.

Offline meekGee

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Re: SpaceX's Martian Underground
« Reply #5 on: 01/08/2017 01:55 PM »
Full-scale TBM is way too heavy for the initial colony. Even on Earth, TBMs make economic sense only if you need to bore multi-kilometer long tunnels.

I imagine much smaller machines will be used to build first Mars underground habitats. Perhaps these machines will be more versatile, not specialized only for tunneling work.
And tunnels are not ideal living spaces.  You want to build an open space, so create a room and pillar space.

Road headers are more flexible, don't require the kind of support infrastructure that TBMs do, and you can have several of them working at once.

Even on Earth, operation and maintaining a TBM is tricky. A RH, OTOH, is just a simple tractor-like vehicle.
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Offline llanitedave

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Re: SpaceX's Martian Underground
« Reply #6 on: 01/08/2017 05:05 PM »
Full-scale TBM is way too heavy for the initial colony. Even on Earth, TBMs make economic sense only if you need to bore multi-kilometer long tunnels.

I imagine much smaller machines will be used to build first Mars underground habitats. Perhaps these machines will be more versatile, not specialized only for tunneling work.

The cutting head alone is extremely massive.  A 4.5m cutterhead assembly can easily weigh 130 tons.

They also use huge amounts of power.  I don't think you gain much by trying to build a TBM on earth and transport it to Mars.  Wait until your Martian industrial capacity can support it, and build it there out of local materials.
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Offline Darkseraph

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Re: SpaceX's Martian Underground
« Reply #7 on: 01/08/2017 05:46 PM »
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. The hardware to do such a survey would individually be quite a lot lighter than a TBM.

Perhaps you would use aerial drones to photograph large swathes of the landscape in more detail than is possible with orbital satellites, to look for entracnes and sky lights on lava tubes and follow up candidates with a more detailed survey using rovers, ground penetrating radar, lidar and so on.

Eventually it may be desirable to use a TBM for construction on Mars but I don't expect this to be the case until there is an extensive human presense on the surface with tons of ISRU! Knowing what kind of rock you are boring into would be a very important step before using any such machine which will require a lot of surveying work to be done first.
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Offline Rocket Science

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Re: SpaceX's Martian Underground
« Reply #8 on: 01/08/2017 05:49 PM »
Drill and blast might work...
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Offline Patchouli

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Re: SpaceX's Martian Underground
« Reply #9 on: 01/08/2017 06:03 PM »
Something like a roadheader would be more ideal for use on Mars then a TBM since it's much simpler and lighter and you would have more flexibility in the shape of the chambers that can be created.
« Last Edit: 01/08/2017 06:04 PM by Patchouli »

Offline sanman

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Re: SpaceX's Martian Underground
« Reply #10 on: 01/09/2017 08:21 AM »
Something like a roadheader would be more ideal for use on Mars then a TBM since it's much simpler and lighter and you would have more flexibility in the shape of the chambers that can be created.

So that's interesting - could a roadheader like that one be used for mining purposes, for raw material extraction?
Can this thing be used for more than just tunneling?

Offline docmordrid

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Re: SpaceX's Martian Underground
« Reply #11 on: 01/12/2017 08:40 AM »
Something like a roadheader would be more ideal for use on Mars then a TBM since it's much simpler and lighter and you would have more flexibility in the shape of the chambers that can be created.

So that's interesting - could a roadheader like that one be used for mining purposes, for raw material extraction?
Can this thing be used for more than just tunneling?

Roadheaders were initially used for coal mining, so hell-yeah. Tunnels for the O-Train in Ottawa were done using three 135 ton roadheaders, and they were used for parts of the Big Dig..
« Last Edit: 01/12/2017 08:48 AM by docmordrid »
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Offline sanman

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Re: SpaceX's Martian Underground
« Reply #12 on: 01/12/2017 05:27 PM »
Roadheaders were initially used for coal mining, so hell-yeah. Tunnels for the O-Train in Ottawa were done using three 135 ton roadheaders, and they were used for parts of the Big Dig..

Wow, that's a lot of mass to send to the Moon or Mars.
I wonder if the thing could be redesigned to shave weight off it?

Additionally, making it all-electric power supply would also be required, as well as robotic/tele-operated/semi-autonomous.

And for the lunar environment, there's that pesky angular dust which always messes things up.

If you had something that big, and were using it all the time, you'd probably be able to expand your interior living space pretty rapidly from tunneling/burrowing.

I wonder what the ideal layout would be for a burrow?

Offline docmordrid

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Re: SpaceX's Martian Underground
« Reply #13 on: 01/12/2017 05:56 PM »
The cutter above is often used to cut an arched tunnel, like a quonset hut, but there are other heads used for profile cutting such as squaring off.  There are vertical versions for boring shafts.

The head motors are hydraulic, so power can be whatever you can run the pump with; electric, or an IC using ISRU methalox. Possibly alcohol + GOX using a different ISRU process.
« Last Edit: 01/12/2017 06:07 PM by docmordrid »
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Online TrueBlueWitt

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Re: SpaceX's Martian Underground
« Reply #14 on: 01/12/2017 06:13 PM »
The cutter above is often used to cut an arched tunnel, like a quonset hut, but there are other heads used for profile cutting such as squaring off.  There are vertical versions for boring shafts.

The head motors are hydraulic, so power can be whatever you can run the pump with; electric, or an IC using ISRU methalox. Possibly alcohol + GOX using a different ISRU process.

Cutters work well enough, as long as whatever you're boring through is solid enough to be self supporting..

Otherwise you may need a boring machine with shield and have to erect  support ribs/marscrete behind you.  At least not too much water to deal with.. depending on where you're going..

Offline Rocket Science

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Re: SpaceX's Martian Underground
« Reply #15 on: 01/12/2017 06:16 PM »
I like these cutters, even better if they can be made to work with existing vehicles with a PTO so that a dedicated vehicle need not to be sent the planet...
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Online philw1776

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Re: SpaceX's Martian Underground
« Reply #16 on: 01/12/2017 07:17 PM »


Roadheaders were initially used for coal mining, so hell-yeah. Tunnels for the O-Train in Ottawa were done using three 135 ton roadheaders, and they were used for parts of the Big Dig..

So, now we know why Elon greatly upped the mass to LEO and landed on Mars from a paltry 100 tonnes
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Online Robotbeat

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Re: SpaceX's Martian Underground
« Reply #17 on: 01/12/2017 07:53 PM »
Roadheaders were initially used for coal mining, so hell-yeah. Tunnels for the O-Train in Ottawa were done using three 135 ton roadheaders, and they were used for parts of the Big Dig..

Wow, that's a lot of mass to send to the Moon or Mars.
I wonder if the thing could be redesigned to shave weight off it?

Additionally, making it all-electric power supply would also be required, as well as robotic/tele-operated/semi-autonomous.

And for the lunar environment, there's that pesky angular dust which always messes things up.

If you had something that big, and were using it all the time, you'd probably be able to expand your interior living space pretty rapidly from tunneling/burrowing.

I wonder what the ideal layout would be for a burrow?
Usually underground mining equipment like that is already electric. They use a lot of power, and electricity is cheaper, but more importantly they don't require oxygen and don't have exhaust, which helps a LOT.

The first road header I saw on Google was electrically powered.
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Online Robotbeat

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Re: SpaceX's Martian Underground
« Reply #18 on: 01/12/2017 07:56 PM »
The cutter above is often used to cut an arched tunnel, like a quonset hut, but there are other heads used for profile cutting such as squaring off.  There are vertical versions for boring shafts.

The head motors are hydraulic, so power can be whatever you can run the pump with; electric, or an IC using ISRU methalox. Possibly alcohol + GOX using a different ISRU process.
Gah, combustible fuels in an engine are just TERRIBLE if you're doing ISRU. They use about an order of magnitude more power (wasting like 90% of the energy) than electric, and since you have to bring along oxygen (and usually want to reclaim the water in the exhaust), usually don't even end up lighter even compared to battery power.

I wish that idea would just die.
« Last Edit: 01/12/2017 08:00 PM by Robotbeat »
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Offline docmordrid

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Re: SpaceX's Martian Underground
« Reply #19 on: 01/12/2017 08:04 PM »
Just stating the options. I agree with electric, unless you're boring some distance from high power generation. You're not going to carry a reactor or 200 m^2 of panels around. Solid oxide fuel cells maybe...
« Last Edit: 01/12/2017 08:06 PM by docmordrid »
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Offline envy887

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Re: SpaceX's Martian Underground
« Reply #20 on: 01/12/2017 08:05 PM »
The cutter above is often used to cut an arched tunnel, like a quonset hut, but there are other heads used for profile cutting such as squaring off.  There are vertical versions for boring shafts.

The head motors are hydraulic, so power can be whatever you can run the pump with; electric, or an IC using ISRU methalox. Possibly alcohol + GOX using a different ISRU process.
Gah, combustible fuels in an engine are just TERRIBLE if you're doing ISRU. They use about an order of magnitude more power (wasting like 90% of the energy) than electric, and since you have to bring along oxygen (and usually want to reclaim the water in the exhaust), usually don't even end up lighter even compared to battery power.

I wish that idea would just die.

Particularly for mining equipment that's not moving fast or far. All it needs is an extension cord.  ;D

Online Robotbeat

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Re: SpaceX's Martian Underground
« Reply #21 on: 01/12/2017 08:27 PM »
Just stating the options. I agree with electric, unless you're boring some distance from high power generation. You're not going to carry a reactor or 200 m^2 of panels around. Solid oxide fuel cells maybe...
A good lithium ion battery actually trades very well when you have to carry the oxygen with you.

And actually, solar panels are easy to place remotely.
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Offline sanman

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Re: SpaceX's Martian Underground
« Reply #22 on: 01/14/2017 05:36 AM »
Cutters work well enough, as long as whatever you're boring through is solid enough to be self supporting..

Otherwise you may need a boring machine with shield and have to erect  support ribs/marscrete behind you.  At least not too much water to deal with.. depending on where you're going..

If Musk were to use some kind of microwave drill thing to bore tunnels with, perhaps it could also microwave-sinter together the material forming the walls of the tunnel, to make it more self-supporting.

Online guckyfan

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Re: SpaceX's Martian Underground
« Reply #23 on: 01/14/2017 07:01 AM »
If Musk were to use some kind of microwave drill thing to bore tunnels with, perhaps it could also microwave-sinter together the material forming the walls of the tunnel, to make it more self-supporting.

When Elon Musk goes into tunneling, as he is claiming, then I expect some novel method used. I strongly doubt that he would start a company using conventional boring heads. On earth those heads or at least the cutting implements are exchanged very frequently for wear. It would be very advantageous to have a method that reduces need of maintenance. On earth and much more so on Mars.

Offline sanman

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Re: SpaceX's Martian Underground
« Reply #24 on: 01/14/2017 10:49 AM »
When Elon Musk goes into tunneling, as he is claiming, then I expect some novel method used. I strongly doubt that he would start a company using conventional boring heads. On earth those heads or at least the cutting implements are exchanged very frequently for wear. It would be very advantageous to have a method that reduces need of maintenance. On earth and much more so on Mars.

I agree he'd probably have some disruptive technological approach in mind. I'm thinking Microwave Drilling could be a candidate, because it could work well for off-world usage too. Microwave Drilling doesn't need heavy hundred-ton rotorheads, which would suffer wear and tear, and need replacement. It would be lighter in mass, and would work on fungible energy supply, and save on the need for replacement parts from Earth.

It would also be a logical progression for colonization technology, after developing the big transport rocket.

But just regarding the idea of microwave-sintering your tunnel walls/roof right there in-situ, is that something that might be feasible/worthwhile?

Offline Bob Shaw

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Re: SpaceX's Martian Underground
« Reply #25 on: 01/14/2017 12:11 PM »
I think Musk may consider developing drilling using rocket technology (also a possibility for power generation using MHD). There are already torpedoes which 'drill' through water using forward-facing rocket motors.

Offline Rocket Science

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Re: SpaceX's Martian Underground
« Reply #26 on: 01/14/2017 12:51 PM »
Explosives are "crude but  effective"... ;) Plus it provides a form of entertainment while Elon is perhaps building the first Martian Movie Multiplex.. ;D.
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Offline TripD

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Re: SpaceX's Martian Underground
« Reply #27 on: 01/14/2017 11:21 PM »
Explosives work well, but drilling those holes would imo require manpower vs. automation.  Drills get frequently stuck badly in holes and can require a frustrated artistry to remove.

Offline lamontagne

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Re: SpaceX's Martian Underground
« Reply #28 on: 01/14/2017 11:53 PM »
Well, I was thinking there was the mining/ISRU aspect to this as well. Perhaps a tunneling machine would eventually evolve into a mining machine, which could extract ore and maybe even feed it into a smelter.


The article shows a large-sized machine as the current state of the art, but there's no reason that a smaller machine couldn't be used to bore large tunnels, if it had the right technology. I was thinking that microwave boring machine could be small enough and light-weight enough to be transportable to Mars, where it could be used to bore much larger cavities - although using the microwave approach for extracting ore might take some re-thinking (maybe with microwaves you could somehow bore and smelt at the same time?)


And at the same time, a microwave-based approach might offer the chance to disrupt the marketplace and take business from the higher-cost established players.

We've been going over this on the Amazing martian habitat thread.  You might want to check out the discussion.

Here is a visual of what I think might be an underground colony made with roadheaders adapted to Mars.  It is largely based on personal experience with mining garages in the Canadian north.

Hope you enjoy!

As far as microwave sintering goes, it may not go deep enough.  There appears to be calcium carbonate on Mars, so my proposal is to put the base near to a deposit and use it to make concrete to line the walls.
« Last Edit: 01/14/2017 11:55 PM by lamontagne »

Offline lamontagne

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Re: SpaceX's Martian Underground
« Reply #29 on: 01/14/2017 11:57 PM »
Explosives work well, but drilling those holes would imo require manpower vs. automation.  Drills get frequently stuck badly in holes and can require a frustrated artistry to remove.

Explosives are just a form of energy.  On Mars they would probably need to be made from atmospheric nitrogen, and in some sense eventually come from solar energy.  So might as well use the solar energy directly to drive equipment.  Bringing the explosives from Earth would likely be too expensive.

Online Robotbeat

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Re: SpaceX's Martian Underground
« Reply #30 on: 01/15/2017 02:13 AM »
No way. Just mix liquid carbon monoxide (or, if you want it closer to oxyliquit as used on Earth, reduce the CO/CO2 all the way to carbon) and liquid oxygen.

We used to use it for mining on Earth all the time, and has already been used for Mars exploration (well, in FICTION :) ).
https://en.wikipedia.org/wiki/Oxyliquit

No water required, no fancy chemistry. In fact, we're sending a CO/O2 ISRU device to Mars for testing on the 2020 rover, so the chemistry will be demonstrated very soon.
« Last Edit: 01/15/2017 02:14 AM by Robotbeat »
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Offline TripD

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Re: SpaceX's Martian Underground
« Reply #31 on: 01/15/2017 03:27 AM »
Explosives work well, but drilling those holes would imo require manpower vs. automation.  Drills get frequently stuck badly in holes and can require a frustrated artistry to remove.

Explosives are just a form of energy.  On Mars they would probably need to be made from atmospheric nitrogen, and in some sense eventually come from solar energy.  So might as well use the solar energy directly to drive equipment.  Bringing the explosives from Earth would likely be too expensive.

I was not promoting bringing explosives from earth.  I was bringing up the issue of having to drill many holes for any type of explosive.  Rocks chip and pin the bit quite frequently.  You literally have to outsmart the bit from time to time to retrieve it because shear torque will not work.

Offline KelvinZero

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Re: SpaceX's Martian Underground
« Reply #32 on: 01/15/2017 09:01 AM »
I was wondering if laser boring for the holes to place oxyliquit within might be a good trade on mars where using more power and simplicity of operation might be preferable to having to replace more parts that would be cheap on earth but dominated by cost/kg on mars, and also cost of labour

I did find one possibly legitimate hit on the topic. It was hard for me to tell how legitimate it was.
http://www.mining.com/web/lasers-the-future-of-mining/

Offline sanman

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Re: SpaceX's Martian Underground
« Reply #33 on: 01/15/2017 10:41 AM »
Is there a safety/risk issue in manufacturing and using explosives on Mars for mining purposes? Or would that all be done by robots anyway? (including placement of explosives)

By contrast, controllable machinery like a road-header or its laser/microwave equivalent might seem a little safer and less risky.




Offline gurucr7.fc

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Re: SpaceX's Martian Underground
« Reply #34 on: 01/15/2017 10:52 AM »
Too much exiting

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Offline Lumina

Re: SpaceX's Martian Underground
« Reply #35 on: 01/15/2017 11:18 AM »
A NASA report I read argues that the optimal source of ISRU water is granular surface regolith which has a 1% to 3% water content almost everywhere on Mars between latitudes 0-50N.

If this is how water production will go, then there is synergy in processing the 97% to 99% regolith already in hand to isolate minerals and metals.

If tunnels are excavated to produce habitats then the tailings from the excavation could also be processed for ISRU of water and minerals in the same system that processes the loose surface regolith.

So based on the above, it might not be worth the time and maintenance effort to excavate tunnels just for ISRU mining. The tunnels would also have to serve a habitat purpose to make economic sense.

Offline TripD

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Re: SpaceX's Martian Underground
« Reply #36 on: 01/15/2017 05:10 PM »
A system set up to process fine grains would have a tough time dealing with  chunks of rocks from mine tailings.  I just remembered the simplicity of those old stamp mills.  They could turn those rocks into powder.  ;)

Offline lamontagne

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Re: SpaceX's Martian Underground
« Reply #37 on: 01/16/2017 12:13 AM »
Explosives work well, but drilling those holes would imo require manpower vs. automation.  Drills get frequently stuck badly in holes and can require a frustrated artistry to remove.

Explosives are just a form of energy.  On Mars they would probably need to be made from atmospheric nitrogen, and in some sense eventually come from solar energy.  So might as well use the solar energy directly to drive equipment.  Bringing the explosives from Earth would likely be too expensive.

I was not promoting bringing explosives from earth.  I was bringing up the issue of having to drill many holes for any type of explosive.  Rocks chip and pin the bit quite frequently.  You literally have to outsmart the bit from time to time to retrieve it because shear torque will not work.
I was just agreeing that it was not a good idea to bring them from Earth.  I'm curious as to what is more cost effective, creating in-situ explosives, using solar power, probably solar electricity, or mechanical mining using electricity.

Offline sanman

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Re: SpaceX's Martian Underground
« Reply #38 on: 01/17/2017 01:05 AM »
There are some places like Hellas Basin where the Martian crust is supposed to be much thinner (10km), and deeper lying rock strata have been exposed.

What kind of depth would have to be tunneled to, in order to support liquid water?

Offline Rocket Science

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Re: SpaceX's Martian Underground
« Reply #39 on: 01/17/2017 01:15 AM »
With a 3D Solar Sinter you could print your own shelter and possible avoid the need for tunneling out a shelter...

"The laws of physics are unforgiving"

Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #40 on: 01/25/2017 08:15 PM »
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.

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.

« Last Edit: 01/25/2017 08:32 PM by pobermanns »

Offline Darkseraph

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Re: SpaceX's Martian Underground
« Reply #41 on: 01/25/2017 08:30 PM »
I couldn't claim to be an expert on this, but from what I've heard, it's expected that much larger lava tubes are possible on the Moon and Mars due to lower gravity. And that due to lack of seismic activity or significant weather, these structures are likely to be reasonably stable.  That could turn out to be wrong, that there are no suitable sized accessible caves or that those that exist are dangerous for habitation. We'd have to do an extensive geographic survey to find out first. Japan is aiming to land a robot (SLIM )in or near such a lava tube in 2019 and I'm looking forward to what is discovered.

https://en.wikipedia.org/wiki/Smart_Lander_for_Investigating_Moon
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Re: SpaceX's Martian Underground
« Reply #42 on: 01/25/2017 08:40 PM »
Mars has significant weather.

It sucks that lava tubes tend to be at high altitude where the air is thinner (harder EDL, greater temperature extremes, worse surface radiation, etc etc) and there's less water.
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Re: SpaceX's Martian Underground
« Reply #43 on: 01/25/2017 08:40 PM »
Personally, I'd doubt that the Moon has any lava tubes. From the theory of Late Heavy Bombardment which I've heard, the "Mare" areas are all due to impact heating and lava flooding, and not due to volcanic activity.

However, your suggestion about the lower gravity on Mars might make the necessary difference. Frankly, I can't see how even expert volcanologists can predict this one. Any rock-hounds out there?

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Re: SpaceX's Martian Underground
« Reply #44 on: 01/25/2017 08:43 PM »
Mars has significant weather.

It sucks that lava tubes tend to be at high altitude where the air is thinner (harder EDL, greater temperature extremes, worse surface radiation, etc etc) and there's less water.

Agree with most of the disadvantages, but why is worse surface radiation a problem if you're under 100' of rock?

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Re: SpaceX's Martian Underground
« Reply #45 on: 01/25/2017 08:52 PM »
Mars has significant weather.

It sucks that lava tubes tend to be at high altitude where the air is thinner (harder EDL, greater temperature extremes, worse surface radiation, etc etc) and there's less water.

Agree with most of the disadvantages, but why is worse surface radiation a problem if you're under 100' of rock?
Because you're not always inside and not always under the rock. It'd be nice to see the surface, and practically, people will need to venture outside in vehicles and spacesuits.
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Re: SpaceX's Martian Underground
« Reply #46 on: 01/25/2017 08:52 PM »
You got to go out and clean your solar panels, unload delivery rockets, etc.
bob

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Re: SpaceX's Martian Underground
« Reply #47 on: 01/25/2017 08:53 PM »
What if... Radiation just ends up not being a big issue? Then there's not as much reason to be in a lava tube.
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Re: SpaceX's Martian Underground
« Reply #48 on: 01/25/2017 08:59 PM »
"Personally, I'd doubt that the Moon has any lava tubes. From the theory of Late Heavy Bombardment which I've heard, the "Mare" areas are all due to impact heating and lava flooding, and not due to volcanic activity."

I'm sorry but this is completely false.  The idea that the maria were caused by impact heating was promoted by Harold Urey in the 1950s and 1960s, and even he accepted the alternative view promoted by Gene Shoemaker and confirmed by Apollo samples, that the maria are true volcanic lavas.  Dating mare basalts shows that volcanism extended at least a billion years after the large basins were formed, and Shoemaker's observation of post-basin but pre-mare craters (Sinus Iridum, Archimedes, Cassini etc.) showed a substantial time gap between impact and lava.  Check out Don Wilhelms' book 'To a Rocky Moon' for details.

Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #49 on: 01/25/2017 09:12 PM »
"Personally, I'd doubt that the Moon has any lava tubes. From the theory of Late Heavy Bombardment which I've heard, the "Mare" areas are all due to impact heating and lava flooding, and not due to volcanic activity."

I'm sorry but this is completely false.  The idea that the maria were caused by impact heating was promoted by Harold Urey in the 1950s and 1960s, and even he accepted the alternative view promoted by Gene Shoemaker and confirmed by Apollo samples, that the maria are true volcanic lavas.  Dating mare basalts shows that volcanism extended at least a billion years after the large basins were formed, and Shoemaker's observation of post-basin but pre-mare craters (Sinus Iridum, Archimedes, Cassini etc.) showed a substantial time gap between impact and lava.  Check out Don Wilhelms' book 'To a Rocky Moon' for details.

Well, if that's all true, then I tip my hat to an expert - which I personally ain't.

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Re: SpaceX's Martian Underground
« Reply #50 on: 01/25/2017 09:22 PM »
What if... Radiation just ends up not being a big issue? Then there's not as much reason to be in a lava tube.

On in the Moon in particular, to avoid some of the downsides of huge temperature swings. That effects Mars too, but much less.
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Re: SpaceX's Martian Underground
« Reply #51 on: 01/25/2017 09:47 PM »
Agreed. If you had a lava tube handy, it'd be utilized.
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Offline jimvela

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Re: SpaceX's Martian Underground
« Reply #52 on: 01/25/2017 11:29 PM »
Personally, I'd doubt that the Moon has any lava tubes. From the theory of Late Heavy Bombardment which I've heard, the "Mare" areas are all due to impact heating and lava flooding, and not due to volcanic activity.

Take a look at this:

https://sservi.nasa.gov/articles/lava-tube-lunar-base/

or if you prefer

http://phenomena.nationalgeographic.com/2016/03/25/scientists-may-have-spotted-buried-lava-tubes-on-the-moon/

That sure looks like a good candidate for a lava tube to me...

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Re: SpaceX's Martian Underground
« Reply #53 on: 01/25/2017 11:45 PM »
Personally, I'd doubt that the Moon has any lava tubes. From the theory of Late Heavy Bombardment which I've heard, the "Mare" areas are all due to impact heating and lava flooding, and not due to volcanic activity.

That sure looks like a good candidate for a lava tube to me...

"That sure looks like a good candidate for a lava tube to me..."

Not to me. Seems like wishful thinking. And while I hope that GPR will help in guiding us to clear understanding of the presence or absence of subterranean cavities, I'm afraid that on-site exploration by humans or human-operated-robots will be needed to resolve this question. I'd really like for this to be true, but not being in a vacuum, I won't hold my breath.
« Last Edit: 01/25/2017 11:48 PM by pobermanns »

Offline Torbjorn Larsson, OM

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Re: SpaceX's Martian Underground
« Reply #54 on: 01/26/2017 01:31 AM »
Personally, I'd doubt that the Moon has any lava tubes. From the theory of Late Heavy Bombardment which I've heard, the "Mare" areas are all due to impact heating and lava flooding, and not due to volcanic activity.

However, your suggestion about the lower gravity on Mars might make the necessary difference. Frankly, I can't see how even expert volcanologists can predict this one. Any rock-hounds out there?

We know there lava tubes on Mars [ https://en.wikipedia.org/wiki/Martian_lava_tube ] but that is due to indigenous volcanism [ https://en.wikipedia.org/wiki/Tharsis_Montes ].

Frankly, I would not put too much credence into suggestions of a late bombardment* seeing how the idea is caused by a statistical error [ http://www.pnas.org/content/113/39/10802 ], and further is not consistent with basic planetary physics and especially chemistry of the Tellus-Theia collision [ ]. And not surprisingly then it just doesn't fit with our biological record [ibid]. An extraordinary hypothesis needs extraordinary evidence, and in retrospect this hypothesis lacks that. (It would not be the first time... ::)

* If you want to satisfy the generic Nice model there are many observations that place the equivalent mechanisms in the natural early bombardment. Which planetary orbit changes is consistent with what we see in other systems.

Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #55 on: 01/26/2017 09:52 AM »
Frankly, I would not put too much credence into suggestions of a late bombardment* seeing how the idea is caused by a statistical error [ http://www.pnas.org/content/113/39/10802 ], and further is not consistent with basic planetary physics and especially chemistry of the Tellus-Theia collision

So, are you saying that the LHB theory is incorrect? If so, is this now the prevailing opinion among planetary scientists?

And not surprisingly then it just doesn't fit with our biological record [ibid]. An extraordinary hypothesis needs extraordinary evidence, and in retrospect this hypothesis lacks that. (It would not be the first time... ::)

* If you want to satisfy the generic Nice model there are many observations that place the equivalent mechanisms in the natural early bombardment. Which planetary orbit changes is consistent with what we see in other systems.

Agree that "An extraordinary hypothesis needs extraordinary evidence", but I really don't understand what you're saying here. Maybe translate it for a non-scientist?
« Last Edit: 01/26/2017 09:52 AM by pobermanns »

Offline sghill

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Re: SpaceX's Martian Underground
« Reply #56 on: 01/26/2017 01:17 PM »
On Mars, you don't want a mechanical TBM.  Too many parts to break down.  The logical path is to utilize things you will be able to make on site up there- power and fuel.

That means a TBM that uses a flame drill or heated subterrene, which have no rotating drill head to contact with tunnel surfaces.  They melt their way through- thus eliminating wear parts a 33 million miles from a supply store.  Hook them up to the colony's power supply and light the burner with methane you're already making up there.

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

This:

http://www.freepatentsonline.com/4073351.html

And This:
http://forum.nasaspaceflight.com/index.php?topic=34667.msg1362562#msg1362562
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Re: SpaceX's Martian Underground
« Reply #57 on: 01/26/2017 01:20 PM »
WAYYYY too energy-intensive.
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Re: SpaceX's Martian Underground
« Reply #58 on: 01/26/2017 03:10 PM »
Yeah, it matters. Repairing stuff on-site is lower mass than the Gigawatt of power this would reaquire. That energy production equipment has to come all the way from Earth, too.
« Last Edit: 01/26/2017 03:18 PM by Robotbeat »
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Re: SpaceX's Martian Underground
« Reply #59 on: 01/26/2017 07:16 PM »
"Personally, I'd doubt that the Moon has any lava tubes. From the theory of Late Heavy Bombardment which I've heard, the "Mare" areas are all due to impact heating and lava flooding, and not due to volcanic activity."

I'm sorry but this is completely false.  The idea that the maria were caused by impact heating was promoted by Harold Urey in the 1950s and 1960s, and even he accepted the alternative view promoted by Gene Shoemaker and confirmed by Apollo samples, that the maria are true volcanic lavas.  Dating mare basalts shows that volcanism extended at least a billion years after the large basins were formed, and Shoemaker's observation of post-basin but pre-mare craters (Sinus Iridum, Archimedes, Cassini etc.) showed a substantial time gap between impact and lava.  Check out Don Wilhelms' book 'To a Rocky Moon' for details.

Well, if that's all true, then I tip my hat to an expert - which I personally ain't.


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Offline clongton

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Re: SpaceX's Martian Underground
« Reply #60 on: 01/26/2017 07:32 PM »
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.

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.
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Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #62 on: 01/26/2017 08:50 PM »
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.

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.

Totally agree! However . . .

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.

If you really could seal the the whole tube, as you suggest, that would be outstanding, but perhaps we should plan for something less ambitious at the beginning.

I'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.

« Last Edit: 01/26/2017 09:40 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #63 on: 01/27/2017 09:37 AM »
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.

In that case the lava tube would only provide radiation shielding. The habitats would still need to withstand the full habitat pressure. Not needing structural strength in habitats because the cave provides it is the main advantage over manufactured habitats.

Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #64 on: 01/27/2017 03:43 PM »
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'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.

I'm not going to venture an opinion on drilling methods, 'cause I know less than zero about such things.

I also don't know how to judge the stability of caves, tunnels or lava tubes, but I will mention that this tube has been there for about 4000 years, so perhaps it's already done whatever collapsing that it was going to do. From what I've read, the volcanos on Mars are much older, so I would also guess that they're stabilized.

Fun fact: in centuries past, the inhabitants used to hide in this tunnel when pirates showed up, seeking people to abduct and sell in North Africa as slaves.

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Re: SpaceX's Martian Underground
« Reply #65 on: 01/27/2017 04:02 PM »
We do know these lava tubes exist, because some have caved in and we can look into them through the holes.

Using them may well be a good idea long term. But I would want geologists do very thorough surveys. It will also be a major undertaking. I understand the ones we know of are huge and making them airtight will be a huge undertaking. Worth it if we want to build a city with plenty of space for a million people, but not something we can do early. Unless we find much smaller ones.

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Re: SpaceX's Martian Underground
« Reply #66 on: 01/27/2017 04:16 PM »
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.
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Re: SpaceX's Martian Underground
« Reply #67 on: 01/27/2017 04:43 PM »
Something else that I've been wondering about, for a lava tube or a drilled tunnel, would be heating. If we used a separate habitat inside of such a cave, it would be easier to keep the temperature inside the hab comfortable. If we just sealed the whole thing, it would take quite a while before the surrounding rock warmed up enough so that it wasn't a cold sink. I've never been any good at thermo calculations, but perhaps someone else knows how to model this problem.

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Re: SpaceX's Martian Underground
« Reply #68 on: 01/27/2017 05:53 PM »
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.

I've been think exactly the same thing about having a double-pressure vessel. However, I'd really want much higher ambient pressure in the cave. I've personally used a version of positive-pressure breathing on a few flights in Navy jet aircraft - and that was only with about 4 psia @ 30,000 feet, and it was fatiguing. True positive-pressure breathing - at 50,000 feet and above - is known to be highly conducive to hyperventilation and hypoxia, followed by unconsciousness. If it were possible to get up to about 7-8 psi, that would be a good thing.

As you say, having a double pressure system could also be a safety feature. If somehow a habitat breached, those inside could scramble to grab an emergency O2 mask, just like all airline pax have available. And this could also mean that the habitat would have less stringent construction specs.

And your points about this resulting in less restrictive suits sound really good.
« Last Edit: 01/27/2017 06:07 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #69 on: 01/27/2017 06:06 PM »
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.
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Re: SpaceX's Martian Underground
« Reply #70 on: 01/27/2017 06:25 PM »
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.

Yes, it was 100% O2, derived from an onboard LOX converter. It has to be, so as to keep your blood-oxygen level above 90% at the lower ambient pressures.

Note that all of the Apollo guys were former Navy/Air Force jet pilots, and thus very used to this regimen. I was mostly a helicopter guy, so although I'd been thru the pressure chamber multiple times for qualification, flying with my friends in the back seat was my only experience with this.

The problem with positive-pressure breathing is that it inverts the normal breathing cycle that people use. Normally, we use muscles to inhale, but exhalation happens by simply relaxing. With PP breathing, the system pushes air into your lungs, so that's easy, but you have to push to exhale. Your exhalation muscles aren't as strong as those you use to inhale. This means that your next breath will come immediately after you stop pushing out, which is how you can get into the spiral of hyperventilation. This can quickly lead to hypocapnia - too low CO2. Quoting Wikipedia,

"Because the brain stem regulates breathing by monitoring the level of blood CO2, hypocapnia can suppress breathing to the point of blackout from cerebral hypoxia."

As for the point about mountain climbers, it is also the case that most people are not so adapted, and would suffer altitude sickness from it. When I personally went thru the pressure chamber - at a simulated altitude of 30,000 feet - I lost consciousness after about 30 seconds. So, I guess that I'll never climb Mt. Everest - or go to Mars. The fact that I'm now 66 might also have something to do with that.
« Last Edit: 01/27/2017 06:30 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #71 on: 01/27/2017 06:28 PM »
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 Leadville at 10000ft, then going hiking or skiing at 13000-14000ft.
« Last Edit: 01/27/2017 06:33 PM by Robotbeat »
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Re: SpaceX's Martian Underground
« Reply #72 on: 01/27/2017 06:30 PM »
So is .2 atm @ 100% o2 the same as 1 atm @ 20% o2.
1. The same for fire propagation?
2. It should be the same for human breathing and health?
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Re: SpaceX's Martian Underground
« Reply #73 on: 01/27/2017 06:36 PM »
No to the first.

You need buffer gas in a hab to help reduce fire risk (to carry away heat from a fire).

But in a spacesuit, you don't have many ignition sources, and you can control the environment easier. So pure O2 isn't a problem for a suit or mask.
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Re: SpaceX's Martian Underground
« Reply #74 on: 01/27/2017 06:38 PM »
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.

Well, I'd have to hear a medical professional verify that before I believe the "fairly quickly" part of this. And if it were true, why is true that people who are real mountain climbers suffer from "altitude sickness"? Personally, I do not believe this.

Obviously, people who are born in Bolivia or Colorado develop tolerance to this. So does this mean that we would only recruit people for Mars who were born at high altitudes?

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Re: SpaceX's Martian Underground
« Reply #75 on: 01/27/2017 06:48 PM »
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. :)

« Last Edit: 01/27/2017 06:56 PM by Robotbeat »
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Re: SpaceX's Martian Underground
« Reply #76 on: 01/27/2017 07:14 PM »
So 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 psia.

I don't know what the partial pressure of oxygen would be at .2 ATM, nor what the equivalent altitude would be, but I'm sure that a full-pressure suit would be mandatory.
« Last Edit: 01/27/2017 07:29 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #77 on: 01/27/2017 07:26 PM »
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. :)

I have respected your opinions on many previous posts, but in this case I think that you are wrong. Personal experience tells me that these are dangerous assumptions.

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Re: SpaceX's Martian Underground
« Reply #78 on: 01/27/2017 07:31 PM »
I think we've had this discussion before. More than once. Some intrepid reader pointing to threads where this happened might reduce how stale this seems.
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Re: SpaceX's Martian Underground
« Reply #79 on: 01/27/2017 07:38 PM »
So 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.

0.2 atm is 20 kPa or 2.9 psi. It's the standard air pressure at 41,000 feet, and a full pressure suit is not critical, according to page 1-21 of that manual.

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Re: SpaceX's Martian Underground
« Reply #80 on: 01/27/2017 08:23 PM »
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. :)

I have respected your opinions on many previous posts, but in this case I think that you are wrong. Personal experience tells me that these are dangerous assumptions.
It would not be the first time I've been wrong. :)
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Re: SpaceX's Martian Underground
« Reply #81 on: 01/27/2017 08:32 PM »
It would not be the first time I've been wrong. :)

Sadly, for all of us, that is the human condition.

I hope that I did not give any offense with my comments.

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Re: SpaceX's Martian Underground
« Reply #82 on: 01/27/2017 08:38 PM »
So 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.

0.2 atm is 20 kPa or 2.9 psi. It's the standard air pressure at 41,000 feet, and a full pressure suit is not critical, according to page 1-21 of that manual.

Thanks for finding that. And you're quite right. I guess that laziness prevented me from seeing the same thing. Or, since it's 10:30 PM here and I'm already thru a few great German Biers, I'm a little distracted.

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Re: SpaceX's Martian Underground
« Reply #83 on: 01/27/2017 08:44 PM »
So 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.

0.2 atm is 20 kPa or 2.9 psi. It's the standard air pressure at 41,000 feet, and a full pressure suit is not critical, according to page 1-21 of that manual.

Thanks for finding that. And you're quite right. I guess that laziness prevented me from seeing the same thing. Or, since it's 10:30 PM here and I'm already thru a few great German Biers, I'm a little distracted.

HEY wait a second. We have MUCH better beer here in NH.  :)
bob

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Re: SpaceX's Martian Underground
« Reply #84 on: 01/27/2017 08:55 PM »
So 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.

0.2 atm is 20 kPa or 2.9 psi. It's the standard air pressure at 41,000 feet, and a full pressure suit is not critical, according to page 1-21 of that manual.

Thanks for finding that. And you're quite right. I guess that laziness prevented me from seeing the same thing. Or, since it's 10:30 PM here and I'm already thru a few great German Biers, I'm a little distracted.

HEY wait a second. We have MUCH better beer here in NH.  :)

Es tut mir leid, aber die deutsche Biere sind die Beste der Welt! Mein Großvater war ein Deutscher, und das hat er mir als Kind erzählt!

Although, I haven't ever had any beer from NH. Maybe the next time that I visit my daughter in Boston, I'll cruise up to your beautiful state for a couple. Kraft beers?

@guckyfan - maybe you can double-check my German? Thanks.
« Last Edit: 01/27/2017 10:01 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #85 on: 01/28/2017 06:44 AM »
Once ITS goes thru TMI there will be 3+ months for pressure and O2 levels to be adjusted from Earth norm to
Mars norm, whatever that turns out to be.  Should be time enough to adapt.

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Re: SpaceX's Martian Underground
« Reply #86 on: 01/28/2017 10:40 AM »
Es tut mir leid, aber die deutsche Biere sind die Beste der Welt! Mein Großvater war ein Deutscher, und das hat er mir als Kind erzählt!

............

@guckyfan - maybe you can double-check my German? Thanks.

It is very good. "die besten", otherwise perfect.  :)

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Re: SpaceX's Martian Underground
« Reply #87 on: 01/28/2017 05:19 PM »
Once ITS goes thru TMI there will be 3+ months for pressure and O2 levels to be adjusted from Earth norm to
Mars norm, whatever that turns out to be.  Should be time enough to adapt.

That's of course true. It's just that I doubt how low we can adjust O2 levels. Plus, unless we want to have a 100% oxygen atmosphere in the ITS or in the habitat, we'll need some buffer gas, too. In that case, we'd create a higher total pressure, because it'll be the partial pressure of O2 that must have a lower limit.

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Re: SpaceX's Martian Underground
« Reply #88 on: 01/28/2017 06:18 PM »
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. :)

When I visit my relatives in Denver it takes me 1 to 1-1/2 days before my high altitude headaches go away, but I remain short of breath for a good week or more. They tell me that it took them almost a full year after they moved there before they were fully comfortable with the lower pressure and able to always breath easy like they used to in Connecticut before the move without shortness of breath.
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Re: SpaceX's Martian Underground
« Reply #89 on: 01/28/2017 07:10 PM »
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. :)

When I visit my relatives in Denver it takes me 1 to 1-1/2 days before my high altitude headaches go away, but I remain short of breath for a good week or more. They tell me that it took them almost a full year after they moved there before they were fully comfortable with the lower pressure and able to always breath easy like they used to in Connecticut before the move without shortness of breath.

I think low pressure acclimation here on Earth for altitude changes is something that is not completely understood, or at least not predictable without actually experiencing it.

For instance, I've done a lot of backcountry backpacking, mostly at altitudes between 7-12,000 feet, and once even to 14,000.  I live along the coast (but you knew that) and I've never had altitude sickness.  At most we would acclimate for one night before doing our backpacking trips.  And this is while humping 50 lb loads on our backs while climbing sometimes aggressively vertical trails.

But one of my backpacking buddies was concerned about altitude sickness, and his doctor prescribed him something for our 14,000 foot trip - which apparently helped (or at least didn't hurt).

So maybe one way to know ahead of time if someone is going to being able to acclimate quickly or not is to send them to a high altitude camp for a couple of weeks of strenuous work?  Cheaper than taking the trip to Mars and finding out that low pressure is an issue.

NASA is incorporating that into their HI-SEAS (Hawai’i Space Exploration Analog and Simulation) Mars simulation on Hawaii's Mauna Loa, located at an altitude of only 8,200 feet.
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Re: SpaceX's Martian Underground
« Reply #90 on: 01/28/2017 07:17 PM »
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. :)

When I visit my relatives in Denver it takes me 1 to 1-1/2 days before my high altitude headaches go away, but I remain short of breath for a good week or more. They tell me that it took them almost a full year after they moved there before they were fully comfortable with the lower pressure and able to always breath easy like they used to in Connecticut before the move without shortness of breath.

And Denver is only about 5000 feet. For most pilots, that's peanuts  :-\. Even the ski spots around there are only about 9-11 K. Your reaction and those of your relatives to this relatively low altitude point out the problems that ordinary people, especially those who are not young and perhaps not in super-physical condition like military pilots - just like most accomplished scientists would be -  would experience on Mars with low p.p. of O2.

The FAA's rule for altitude limitations is that you cannot fly above 12,500 feet without supplemental oxygen, at least for the flight crew. I've piloted an unpressurized helicopter to that altitude, and I had no problems.

But when you get into the 20's and 30's, you're going to run into serious problems. I've experienced hypoxia - all of us did. That's the whole purpose of training in a pressure chamber - to experience your personal symptoms from it, so that you will recognize it when it starts happening to you. Blurred vision, tunnel vision, coordination problems, foggy thinking, and most of all, black-out. It's insidious, it kills and is not to be trifled with!
« Last Edit: 01/28/2017 07:19 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #91 on: 01/28/2017 07:34 PM »
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 Leadville at 10000ft, then going hiking or skiing at 13000-14000ft.


When I visit my relatives in Denver it takes me 1 to 1-1/2 days before my high altitude headaches go away, but I remain short of breath for a good week or more. They tell me that it took them almost a full year after they moved there before they were fully comfortable with the lower pressure and able to always breath easy like they used to in Connecticut before the move without shortness of breath.

I think low pressure acclimation here on Earth for altitude changes is something that is not completely understood, or at least not predictable without actually experiencing it.

-----------------------------------

So maybe one way to know ahead of time if someone is going to being able to acclimate quickly or not is to send them to a high altitude camp for a couple of weeks of strenuous work?  Cheaper than taking the trip to Mars and finding out that low pressure is an issue.

I think that this is the central problem. How to know who could successfully adapt. When you go to live at an altitude - even 5000' - you experience an oxygen debt over time. It's not sufficient to say that some people can handle that; we'd have to be really sure that those we send to Mars will be able to handle it.

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Re: SpaceX's Martian Underground
« Reply #92 on: 01/28/2017 07:38 PM »
Why?
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Re: SpaceX's Martian Underground
« Reply #93 on: 01/28/2017 07:46 PM »
Why?

Assuming that you are asking why we'd test future Martians for their tolerance to low-O2 levels - would you send these people without testing them for this attribute?

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Re: SpaceX's Martian Underground
« Reply #94 on: 01/28/2017 07:55 PM »
People go to high altitudes without such preselection. Also, there are countermeasures available for those who'd want to stay.
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Re: SpaceX's Martian Underground
« Reply #95 on: 01/28/2017 08:01 PM »
People go to high altitudes without such preselection.

Sure, but they're not 30+ million miles from benign conditions - Earth - so they can evacuate themselves if it doesn't work out.

Also, there are countermeasures available for those who'd want to stay.

Right. For one whole synod, they're going to survive on blood doping and O2 masks? This would violate the Principal of the Six P's: "Proper Planning Prevents Pxxx-Poor Performance".

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Re: SpaceX's Martian Underground
« Reply #96 on: 01/28/2017 08:43 PM »
No, simpler ones. Anyway, basically everyone who doesn't have a profound health problem can adapt to high altitude.

Again, this is the bias of ignorance of people who have not spent much time at high altitudes, manifesting in fear.
« Last Edit: 01/28/2017 08:52 PM by Robotbeat »
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Re: SpaceX's Martian Underground
« Reply #97 on: 01/28/2017 09:25 PM »
No, simpler ones. Anyway, basically everyone who doesn't have a profound health problem can adapt to high altitude.

Again, this is the bias of ignorance of people who have not spent much time at high altitudes, manifesting in fear.

Well, I guess that that settles it, since you obviously are either a doctor or someone who is similarly trained in high altitude medical issues.

I cannot argue against your "alternate facts", so you win. I stand corrected. And I'm done with this topic. >:(
« Last Edit: 01/28/2017 09:50 PM by pobermanns »

Offline RonM

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Re: SpaceX's Martian Underground
« Reply #98 on: 01/28/2017 10:30 PM »
How about looking at some numbers?

Sea level pressure is 14.7 psi with 21% O2. That yields an O2 partial pressure of 3.1 psi.

Airliner cabins are pressurized at levels between 6000 ft and 8000 ft. This effective altitude is used because almost everyone can handle it without medical issues.

Using the high end of 8000 ft, air pressure is 76% of sea level, resulting in an O2 partial pressure of 2.4 psi.

NASA is incorporating that into their HI-SEAS (Hawai’i Space Exploration Analog and Simulation) Mars simulation on Hawaii's Mauna Loa, located at an altitude of only 8,200 feet.

So, NASA is already thinking about this, having the test at 8200 ft.

When I visit my relatives in Denver it takes me 1 to 1-1/2 days before my high altitude headaches go away, but I remain short of breath for a good week or more. They tell me that it took them almost a full year after they moved there before they were fully comfortable with the lower pressure and able to always breath easy like they used to in Connecticut before the move without shortness of breath.

Adaption can take awhile. . .

Once ITS goes thru TMI there will be 3+ months for pressure and O2 levels to be adjusted from Earth norm to
Mars norm, whatever that turns out to be.  Should be time enough to adapt.

That will be enough time for most people. Others may need to stay at an 8000 ft facility before launch.

Now remember that 2.4 psi O2 partial pressure I was talking about? In an 8 psi habitat that would be 30% O2. Slight increase in fire risk, so hab designers need to take that into consideration. An advantage of 8 psi with 30% O2 is someone can go straight to a spacesuit without prebreathing. Good for anyone who needs to work outside.

Speaking about spacesuits, they are at 4.7 psi with 100% O2 for a good reason. You don't really want to go lower pressure than that because you need to work, not be fatigued and just getting by.

Now how does this relate to the actual topic of this thread? Well, habs can be at 8 psi with 30% O2, the interior of the lava tube or tunnel can be at 4.7 psi with 100% inert gas (no fire risk at all) and anyone having to work exposed in the pressurized lava tube will only need an oxygen mask.

If everybody isn't comfortable at 8 psi, then the main habs can be at a more Earth-like atmosphere and only work areas with airlocks can be at 8 psi.

Check out www.altitude.org for information on going above 8000 ft.

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Re: SpaceX's Martian Underground
« Reply #99 on: 01/28/2017 10:49 PM »
FWIW there are ways to minimize the impact on altitude disruption. When going to high altitude, one can increase red meat consumption to allow for greater red blood cell demand to carry oxygen. Conversely, when losing the adaptation, one steers clear of iron bearing items in ones diet to allow for the liver to absorb the load of too much hemoglobin breaking down.

When I've been at extreme altitudes, primary concern is hypoxia - it sneaks up on you in peculiar ways. To train you for it, you're conditioned in a hyperbaric chamber for considerable time with a few others in somewhat humorous circumstance. Even then, when returning from a mission almost landed on the road next to the runway instead of the runway. The adjacent power/telephone poles were a dead giveaway ...

Many have nitrogen bubbles in bones/cartilage, so at altitude you get strange aches in weird places. A particular favorite is quite literally a pain in the tailbone (coccyx). I have decades old shrapnel wounds that have had trapped gas pockets that took awhile to find and "pop", would reliably give "charlie horse" in a muscle above 50,000 ft.

There are many who have vision problems at altitude, and it may take a day or two before they show up. Have to chase that one down, but I think it has something to do with vitreous humor pressure.

And, decades back, watched many fall out of the AF academy because of sinus problems/allergies and altitude. They did not want to do be at the bottom of a silo or fly a desk.

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Re: SpaceX's Martian Underground
« Reply #100 on: 01/28/2017 10:50 PM »
How about looking at some numbers?

Sea level pressure is 14.7 psi with 21% O2. That yields an O2 partial pressure of 3.1 psi.

Airliner cabins are pressurized at levels between 6000 ft and 8000 ft. This effective altitude is used because almost everyone can handle it without medical issues.

Using the high end of 8000 ft, air pressure is 76% of sea level, resulting in an O2 partial pressure of 2.4 psi.

NASA is incorporating that into their HI-SEAS (Hawai’i Space Exploration Analog and Simulation) Mars simulation on Hawaii's Mauna Loa, located at an altitude of only 8,200 feet.

So, NASA is already thinking about this, having the test at 8200 ft.

When I visit my relatives in Denver it takes me 1 to 1-1/2 days before my high altitude headaches go away, but I remain short of breath for a good week or more. They tell me that it took them almost a full year after they moved there before they were fully comfortable with the lower pressure and able to always breath easy like they used to in Connecticut before the move without shortness of breath.

Adaption can take awhile. . .

Once ITS goes thru TMI there will be 3+ months for pressure and O2 levels to be adjusted from Earth norm to
Mars norm, whatever that turns out to be.  Should be time enough to adapt.

That will be enough time for most people. Others may need to stay at an 8000 ft facility before launch.

Now remember that 2.4 psi O2 partial pressure I was talking about? In an 8 psi habitat that would be 30% O2. Slight increase in fire risk, so hab designers need to take that into consideration. An advantage of 8 psi with 30% O2 is someone can go straight to a spacesuit without prebreathing. Good for anyone who needs to work outside.

Speaking about spacesuits, they are at 4.7 psi with 100% O2 for a good reason. You don't really want to go lower pressure than that because you need to work, not be fatigued and just getting by.

Now how does this relate to the actual topic of this thread? Well, habs can be at 8 psi with 30% O2, the interior of the lava tube or tunnel can be at 4.7 psi with 100% inert gas (no fire risk at all) and anyone having to work exposed in the pressurized lava tube will only need an oxygen mask.

If everybody isn't comfortable at 8 psi, then the main habs can be at a more Earth-like atmosphere and only work areas with airlocks can be at 8 psi.

Check out www.altitude.org for information on going above 8000 ft.

Thanks -  for bringing some sanity to this discussion!
« Last Edit: 01/28/2017 11:11 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #101 on: 01/28/2017 11:07 PM »
FWIW there are ways to minimize the impact on altitude disruption. When going to high altitude, one can increase red meat consumption to allow for greater red blood cell demand to carry oxygen. Conversely, when losing the adaptation, one steers clear of iron bearing items in ones diet to allow for the liver to absorb the load of too much hemoglobin breaking down.

Curious! But don't understand the last part about avoiding iron-bearing foods. Why?

When I've been at extreme altitudes, primary concern is hypoxia - it sneaks up on you in peculiar ways. To train you for it, you're conditioned in a hyperbaric chamber for considerable time with a few others in somewhat humorous circumstance. Even then, when returning from a mission almost landed on the road next to the runway instead of the runway. The adjacent power/telephone poles were a dead giveaway …


Ok, that last part sounds pretty bad!

Many have nitrogen bubbles in bones/cartilage, so at altitude you get strange aches in weird places. A particular favorite is quite literally a pain in the tailbone (coccyx). I have decades old shrapnel wounds that have had trapped gas pockets that took awhile to find and "pop", would reliably give "charlie horse" in a muscle above 50,000 ft.

Where the h*** were you flying, that you got such wounds? And, my respects to you for your service!

There are many who have vision problems at altitude, and it may take a day or two before they show up. Have to chase that one down, but I think it has something to do with vitreous humor pressure.

And, decades back, watched many fall out of the AF academy because of sinus problems/allergies and altitude. They did not want to do be at the bottom of a silo or fly a desk.

Yes, of course, on both the sinus probs and the career probs! For our guys, the equivalent would have been driving a ship, but your point is well taken.
« Last Edit: 01/28/2017 11:19 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #102 on: 01/28/2017 11:30 PM »
Guys, be excellent to each other.

Meanwhile I suggest dueling studies instead of dueling assertions. What does the data say?
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Re: SpaceX's Martian Underground
« Reply #103 on: 01/29/2017 12:02 AM »
Well the highest inhabited village in Europe is Ushguli at about 2100m (7000'). Populations live higher than that, and in large numbers, but they are genetically adapted to the altitude.

If you are thinking of having permanent populations of physiologically adapted I'd suggest that as an upper limit for now.

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Re: SpaceX's Martian Underground
« Reply #104 on: 01/29/2017 12:03 AM »
Curious! But don't understand the last part about avoiding iron-bearing foods. Why?

I interpreted it as trying to reduce the load on the liver, while it's removing excess haemoglobin.



Now remember that 2.4 psi O2 partial pressure I was talking about? In an 8 psi habitat that would be 30% O2. Slight increase in fire risk, so hab designers need to take that into consideration.

No. You can't expect a whole colony to be like a vehicle/lander. You have to assume that you can't control the materials that closely. Hence, any increased fire risk is unacceptable.

IMO, even the baseline fire risk of Earth at sea-level is unacceptable in a closed atmosphere. That's why I've suggested higher total pressure (right back to 14-15psi) but the lowest O₂ levels we can get away with, without making people lethargic/clumsy when doing heavy work or complex mental tasks, say 2-2.25psi. Keep the oxygen fraction below 15%. Reduce the fire risk, not debate how much we can increase it.

Remember, you're going to be doing stuff that would never be allowed in a more conventional NASA moon/Mars mission. Welding, grinding, fabbing, moulding, lubing, etc. Fumes and sparks and hydrocarbons and random materials and machinery. And those are precisely the areas where the workers themselves will need the most oxygen for breathing (coz they're working). And if you aren't running the workshop/machine-room/repair areas at reduced pressure, what's the point of doing it through the rest of the hab?

the interior of the lava tube or tunnel can be at 4.7 psi with 100% inert gas (no fire risk at all) and anyone having to work exposed in the pressurized lava tube will only need an oxygen mask.

Although it's worth remembering that even with nitrogen, the effects of losing oxygen are quick and deceptive. (Faster than holding your breath. Biology is weird.) You will still need to treat every trip into a non-oxygenated area like a deep dive or cave dive. With buddy-systems and checklists and safety-areas and people "up top" ready to call in a rescue if you don't check in on cue. (And pure CO₂ doesn't have to leak much around your mask before you're symptomatic.)

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Re: SpaceX's Martian Underground
« Reply #105 on: 01/29/2017 12:07 AM »
Reply to myself....

Highest town in the US is about 3000m so it is possible to live higher for us sea level dwellers.

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Re: SpaceX's Martian Underground
« Reply #106 on: 01/29/2017 12:23 AM »
Curious! But don't understand the last part about avoiding iron-bearing foods. Why?

I interpreted it as trying to reduce the load on the liver, while it's removing excess haemoglobin.



Now remember that 2.4 psi O2 partial pressure I was talking about? In an 8 psi habitat that would be 30% O2. Slight increase in fire risk, so hab designers need to take that into consideration.

No. You can't expect a whole colony to be like a vehicle/lander. You have to assume that you can't control the materials that closely. Hence, any increased fire risk is unacceptable.

IMO, even the baseline fire risk of Earth at sea-level is unacceptable in a closed atmosphere. That's why I've suggested higher total pressure (right back to 14-15psi) but the lowest O₂ levels we can get away with, without making people lethargic/clumsy when doing heavy work or complex mental tasks, say 2-2.25psi. Keep the oxygen fraction below 15%. Reduce the fire risk, not debate how much we can increase it.

Remember, you're going to be doing stuff that would never be allowed in a more conventional NASA moon/Mars mission. Welding, grinding, fabbing, moulding, lubing, etc. Fumes and sparks and hydrocarbons and random materials and machinery. And those are precisely the areas where the workers themselves will need the most oxygen for breathing (coz they're working). And if you aren't running the workshop/machine-room/repair areas at reduced pressure, what's the point of doing it through the rest of the hab?

the interior of the lava tube or tunnel can be at 4.7 psi with 100% inert gas (no fire risk at all) and anyone having to work exposed in the pressurized lava tube will only need an oxygen mask.

Although it's worth remembering that even with nitrogen, the effects of losing oxygen are quick and deceptive. (Faster than holding your breath. Biology is weird.) You will still need to treat every trip into a non-oxygenated area like a deep dive or cave dive. With buddy-systems and checklists and safety-areas and people "up top" ready to call in a rescue if you don't check in on cue. (And pure CO₂ doesn't have to leak much around your mask before you're symptomatic.)
So basically, you're guaranteeing terrible bends if pressure is lost.
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Re: SpaceX's Martian Underground
« Reply #107 on: 01/29/2017 12:25 AM »
Reply to myself....

Highest town in the US is about 3000m so it is possible to live higher for us sea level dwellers.

Thanks for that!

To me the problem is that while generalities make this seem like a minor problem, for most people who'd go to Mars these would be big deals! 3000 m is really high, and I seriously doubt that, even with acclimation, most people could prepare for a trip to Mars. I could be totally FOS, but that's my opinion. Better to go slow on this, rather than risk the lives of a bunch of guys and gals on Mars.

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Re: SpaceX's Martian Underground
« Reply #108 on: 01/29/2017 12:40 AM »
3000m is not that high, really. I've stayed at such altitudes for weeks at a time on several occasions. Almost anyone can adapt, given enough time. Some people who have only a single lung engage in strenuous physical activity (skiing) above this altitude. 3000m is only about what a commercial jet operates at internally, so if you've flown on a jet, you've gotten close.

It takes time. I've gotten my butt kicked by high altitude before (hiking near the tree line), but your body WILL adapt if you live there for months unless you have such serious health conditions that you might not even be cleared to fly to Mars in the first place.

Ultimately, this is a pretty minor compromise that makes EVAs easier and safer and faster and more productive, fire risk lower, power requirements less, reduces tissue damage from rapid decompression, improves structural safety, and reduces mass and cost for habitable structures while also bringing us closer to living on a terraformed Mars.
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Re: SpaceX's Martian Underground
« Reply #109 on: 01/29/2017 12:48 AM »
Another benefit: everything being equal, EVA performance will be much higher if the oxygen partial pressure of the hab is lower. As your body adapts, you get less winded even at sea level oxygen levels. This is one reason why athletes train at high altitude.

By the way, I'm going to make a splinter thread.
« Last Edit: 01/29/2017 12:51 AM by Robotbeat »
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Re: SpaceX's Martian Underground
« Reply #110 on: 01/29/2017 12:50 AM »
Here, in the general Mars section, is a better home to these discussions: http://forum.nasaspaceflight.com/index.php?topic=42174.0
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Re: SpaceX's Martian Underground
« Reply #111 on: 01/29/2017 03:46 AM »
Now remember that 2.4 psi O2 partial pressure I was talking about? In an 8 psi habitat that would be 30% O2. Slight increase in fire risk, so hab designers need to take that into consideration.

No. You can't expect a whole colony to be like a vehicle/lander. You have to assume that you can't control the materials that closely. Hence, any increased fire risk is unacceptable.

IMO, even the baseline fire risk of Earth at sea-level is unacceptable in a closed atmosphere. That's why I've suggested higher total pressure (right back to 14-15psi) but the lowest O₂ levels we can get away with, without making people lethargic/clumsy when doing heavy work or complex mental tasks, say 2-2.25psi. Keep the oxygen fraction below 15%. Reduce the fire risk, not debate how much we can increase it.

Remember, you're going to be doing stuff that would never be allowed in a more conventional NASA moon/Mars mission. Welding, grinding, fabbing, moulding, lubing, etc. Fumes and sparks and hydrocarbons and random materials and machinery. And those are precisely the areas where the workers themselves will need the most oxygen for breathing (coz they're working). And if you aren't running the workshop/machine-room/repair areas at reduced pressure, what's the point of doing it through the rest of the hab?

There are many engineering tradeoffs to consider. It will depend on what the colony can produce. A Mars research base could easily be designed with flame resistant materials, but if a colony can't produce those materials then a higher pressure would be safer.

We can discuss the options, but without actually designing all the colony systems we can't definitely say which option is best.

the interior of the lava tube or tunnel can be at 4.7 psi with 100% inert gas (no fire risk at all) and anyone having to work exposed in the pressurized lava tube will only need an oxygen mask.

Although it's worth remembering that even with nitrogen, the effects of losing oxygen are quick and deceptive. (Faster than holding your breath. Biology is weird.) You will still need to treat every trip into a non-oxygenated area like a deep dive or cave dive. With buddy-systems and checklists and safety-areas and people "up top" ready to call in a rescue if you don't check in on cue. (And pure CO₂ doesn't have to leak much around your mask before you're symptomatic.)

Maybe it's not a good idea to pressurize the lava tube. Might be better to use a spacesuit anyway.

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Re: SpaceX's Martian Underground
« Reply #112 on: 01/29/2017 05:21 AM »
Conversely, when losing the adaptation, one steers clear of iron bearing items in ones diet to allow for the liver to absorb the load of too much hemoglobin breaking down.

Curious! But don't understand the last part about avoiding iron-bearing foods. Why?

Your liver can be damaged by excessive iron. Fairly easily.

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Re: SpaceX's Martian Underground
« Reply #113 on: 01/29/2017 05:49 AM »
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. :)

When I visit my relatives in Denver it takes me 1 to 1-1/2 days before my high altitude headaches go away, but I remain short of breath for a good week or more. They tell me that it took them almost a full year after they moved there before they were fully comfortable with the lower pressure and able to always breath easy like they used to in Connecticut before the move without shortness of breath.

I think low pressure acclimation here on Earth for altitude changes is something that is not completely understood, or at least not predictable without actually experiencing it.

For instance, I've done a lot of backcountry backpacking, mostly at altitudes between 7-12,000 feet, and once even to 14,000.  I live along the coast (but you knew that) and I've never had altitude sickness.  At most we would acclimate for one night before doing our backpacking trips.  And this is while humping 50 lb loads on our backs while climbing sometimes aggressively vertical trails.

But one of my backpacking buddies was concerned about altitude sickness, and his doctor prescribed him something for our 14,000 foot trip - which apparently helped (or at least didn't hurt).

So maybe one way to know ahead of time if someone is going to being able to acclimate quickly or not is to send them to a high altitude camp for a couple of weeks of strenuous work?  Cheaper than taking the trip to Mars and finding out that low pressure is an issue.

NASA is incorporating that into their HI-SEAS (Hawai’i Space Exploration Analog and Simulation) Mars simulation on Hawaii's Mauna Loa, located at an altitude of only 8,200 feet.

We used to bring diamox sequels for climbs above 18,000 feet.   there was one incident with other folks on the mountain who were unprepared.  We shared some with them and they recovered.

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Re: SpaceX's Martian Underground
« Reply #114 on: 01/29/2017 11:58 AM »
Remember, you're going to be doing stuff that would never be allowed in a more conventional NASA moon/Mars mission. Welding, grinding, fabbing, moulding, lubing, etc. Fumes and ...

As an aside it's worth noting that an additional angle to this is the normal outgassing of very commonly used solvents and lubricants that can contaminate the atmosphere in close loop systems. Used normally on earth they are simply absorbed into the air and dissipated with no harmful effects. In closed loop systems, like submarines for instance, studies have demonstrated the O2% of the breathable air and the ambient pressure both, individually and in conjunction with each other, affects the outgassing process. So it's not just a matter of how much oxygen is available to breath. Naturally produced outgassing of the materials we use everyday that are health harmful need to part of the equation of determining the pressure/O2 mix ratio. And because we don't have a planet's whole atmosphere readily available to dissipate them into, removal of those contaminates may be harder than one would normally expect before they can be vented into the Martian air.
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Re: SpaceX's Martian Underground
« Reply #115 on: 01/29/2017 05:34 PM »
There are many engineering tradeoffs to consider. It will depend on what the colony can produce. A Mars research base could easily be designed with flame resistant materials,

I disagree that it would be "easy". A real working civilisation cannot operate under the same restrictions of the inside of a 3 or 4 man capsule, or the inside of a spacesuit. Unless you want to restrict your colony to always be a limited outpost, you have to deal the bulk of materials are not being chosen from the NASA safe-materials catalogue, and where not every activity is merely operating systems under approved conditions (with manufacture and maintenance done on Earth).

We can discuss the options, but without actually designing all the colony systems we can't definitely say which option is best.

But that doesn't stop people from casually (and in some cases insistently) suggesting increasing the fire risk.

the interior of the lava tube or tunnel can be at 4.7 psi with 100% inert gas
[wah, wah, inert can be bad too]
Maybe it's not a good idea to pressurize the lava tube. Might be better to use a spacesuit anyway.

In spite of what I said, even if you had to wear a full "bunny suit", that's still vastly easier on you (and on the technology) than a spacesuit.

So IMO the deciding factors are: whether there's enough activity outside the hab but inside the tube/tunnel to justify it; whether there's enough resources to waste on such an area; and just how hard EVAs remain after years of Mars-suit development.

For eg, if you have a lot of extra gas lying around, either waste or low value, you might as well shove it into the tube/tunnel ahead of where you're working and deliberately move certain operations there just because you've got a lot of low cost volume (for vehicle & systems maintenance, etc.)

Likewise, if it's difficult it is to seal the tube/tunnel, you would only do it in areas you are actually using, the actual hab. If it's easy, you might as well run ahead of habitat construction, even if there's only a minor benefit from having all that extra volume.

Similarly, how much time your crews need to spend on the actual surface, versus how much time they would spend in the tube, versus how much time in the habitat? It might turn out that most activity is either in-hab or on the open surface, with very little time spent in the unfinished tube/tunnels, hence creating an inert-gas volume isn't worth any extra construction cost. Whereas if there's a lot of activity inside the tube/tunnel but not inside the habitat (such as habitat construction), there may be a huge advantage to pressurising that space.

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Re: SpaceX's Martian Underground
« Reply #116 on: 01/29/2017 05:38 PM »
Re: Lava tubes specifically.

The two main downsides of lava tubes is that you are site limited, and the site of an accessible lava tube may not be where the other key resources are located. And that, AIUI, they generally occur in higher altitude areas, hence reduced pressure, lower temps, higher radiation, blah blah.

But... Once you go past collapse-openings, the inside of a lava tube should be at or close to the average annual surface temperature for that location (underground sites generally are), which is far enough below freezing that water vapour might collect there as it does at the poles, through the handful of collapse-openings along the length of the tube. Even at higher altitude, hence lower pressure, the temperature may be far enough below the sublimation temperature for accumulation to dominate. Shaded from sunlight, kept at near-constant temperature, without seasonal evaporation. Millions of years, perhaps hundreds of millions of years, of gradual accumulation.

It might be the easiest site on Mars to access pure-ice water. With new shelter created as you excavate the ice. Plus a heat-sink for habitat and fuel-processing waste heat.

Offline Space Ghost 1962

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Re: SpaceX's Martian Underground
« Reply #117 on: 01/29/2017 07:04 PM »
Remember, you're going to be doing stuff that would never be allowed in a more conventional NASA moon/Mars mission. Welding, grinding, fabbing, moulding, lubing, etc. Fumes and ...

As an aside it's worth noting that an additional angle to this is the normal outgassing of very commonly used solvents and lubricants that can contaminate the atmosphere in close loop systems. Used normally on earth they are simply absorbed into the air and dissipated with no harmful effects. In closed loop systems, like submarines for instance, studies have demonstrated the O2% of the breathable air and the ambient pressure both, individually and in conjunction with each other, affects the outgassing process. So it's not just a matter of how much oxygen is available to breath. Naturally produced outgassing of the materials we use everyday that are health harmful need to part of the equation of determining the pressure/O2 mix ratio. And because we don't have a planet's whole atmosphere readily available to dissipate them into, removal of those contaminates may be harder than one would normally expect before they can be vented into the Martian air.
Correct. There's more too.

There are studies of interesting effects WRT biological agents/viruses/bacteria/mold/fungus/biofilms behaving differently on atmospheric partial pressure/mixtures. Also, in mines, contaminates from the walls/tunnels have interesting surprises. And we've known about them for some time.

In my youth I explored abandoned railroad tunnels from the 1800's. Many had buildups of explosive and or poisonous gases, which led to them needing to be carefully vented with positive airflow. Found interesting things growing in them when they were abandoned and left untended. I suppose forms of what would later be called "extremophiles".

Which Dr. Chris McKay suspect might exist on Mars. Possibly as a surviving form of paleo Mars life from the past ...

And no, not "concern trolling" but what is called positive "threat assessment".

Online guckyfan

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Re: SpaceX's Martian Underground
« Reply #118 on: 01/29/2017 09:54 PM »
Just mentioned in the Hyperloop life stream. Elon Musk mentioned his tunneling plans. They are doing tests. His plan is to increase tunneling speed by at least a factor of 5, maybe 10. He believes, physics will allow that. Sure he is thinking not only about traffic in cities on earth but about Mars habitats even if he did not mention it.

Offline Dalhousie

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Re: SpaceX's Martian Underground
« Reply #119 on: 01/31/2017 10:58 PM »
Well the highest inhabited village in Europe is Ushguli at about 2100m (7000'). Populations live higher than that, and in large numbers, but they are genetically adapted to the altitude.

If you are thinking of having permanent populations of physiologically adapted I'd suggest that as an upper limit for now.

Much higher than that is possible.

I was in Ladakh last year, capital Leh, 3,400 m.  The plane was depressurised when we landed.  Many of the 270,000 people who live there are low landers and do fine after acclimatisation. 

I was seedy the first day, spots in front of the eyes, headaches, having come from Delhi. Blood O2 82%. Basically slept for 24 hours.  Three days later I crossed a 5,400 m pass and felt fine although short of breath.  Five days later I was back at the pass and doing field work.  Blood O2 at the pass second time was 87% and 92% back at Leh.  By the time I finished working in the area (two weeks) blood O2 was 97% at Leh which was normal for me.  The only difference I noted was I was still more prone to headaches.

Low landers can adapt to living and working at altitude given time and patience (a few weeks)
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Online philw1776

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Re: SpaceX's Martian Underground
« Reply #120 on: 02/01/2017 01:49 AM »
Breckenridge CO is 3 Km altitude.  Was there at age 50 in a pickup hoops game on days 1 & 2 vs 20 somethings.  Sucking wind but OK.  Then X/C skied at higher altitudes. Average people can readily adapt to lower psi.  Test colonists at Cripple Creek 10,000 ft in the Rockies for 2 weeks.  If they can't adapt, send someone else.  Enough of this concern trolling.
« Last Edit: 02/01/2017 01:50 AM by philw1776 »
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Offline Oersted

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Re: SpaceX's Martian Underground
« Reply #121 on: 02/03/2017 07:55 AM »
Low landers can adapt to living and working at altitude given time and patience (a few weeks)

Also remember that on Mars the colonists would be at 40% Earth gravity which - all things being equal - should place less strain on their system. Maybe less oxygen in the air will be compensated by less demand for oxygen by the organism.

Offline sghill

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Re: SpaceX's Martian Underground
« Reply #122 on: 02/03/2017 02:57 PM »
The air pressures at La Paz Bolivia (Lake Titicaca @12,500 feet) or Lhasa, Tibet (12,000 ft.) are about as low an air pressure (9 psi) as you'd want to go IMHO. 

Why that choice?  Because humans are already self-selecting.

Those two places are an interesting mix of having the world's highest population densities at that altitude combined with also having pronounced effects on humans.  Above 12,000ft there's not much of anything in terms of large populations.

The mining town of La Rinconada at 16,700ft. in Peru is a slight exception.  30,000 inhabit the town, and live at 8 psi, though much of the population actually lives in towns lower down, and I can't imagine there are many kids running around up there, as it's generally thought of as a horrible place to live.

A college student (and competitive athlete) died at Lake Titicaca from common altitude sickness in 2010, and the local populations have notably different physiology than the rest of humanity (larger lungs, shorter limbs). 

To have a population regularly living at a lower pressure invites even more drastic problems.

« Last Edit: 02/03/2017 02:59 PM by sghill »
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Offline lamontagne

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Re: SpaceX's Martian Underground
« Reply #123 on: 02/03/2017 04:34 PM »
I have to admit I don't really understand why the air pressure is such an issue.  We need to design in safety factors anyway, so why not design for full pressure, and over time optimise for lower pressure if it turns out to be useful or beneficial?  Creating the atmospheres for habitats will not be a major energy drain on the colony, compared to fuel and food production.
Yes, lower pressure would allow for less massive habitats, but using in situ resources is that an issue?  What construction problems does a 30% lower pressure solve, or even 50% lower?  Isn't radiation protection more massive than whatever structural element is used anyway?


Offline RonM

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Re: SpaceX's Martian Underground
« Reply #124 on: 02/03/2017 07:24 PM »
I have to admit I don't really understand why the air pressure is such an issue.  We need to design in safety factors anyway, so why not design for full pressure, and over time optimise for lower pressure if it turns out to be useful or beneficial?  Creating the atmospheres for habitats will not be a major energy drain on the colony, compared to fuel and food production.
Yes, lower pressure would allow for less massive habitats, but using in situ resources is that an issue?  What construction problems does a 30% lower pressure solve, or even 50% lower?  Isn't radiation protection more massive than whatever structural element is used anyway?

The advantage of lower pressure is the ability to put on a spacesuit and go outside without prebreathing.

If only a small number of colonists are workers that need to don spacesuits, then there can be a work area with airlocks at lower pressure while the rest of the colony can be at full pressure.

If it turns out crops grow better in a low nitrogen and lower pressure area, then the greenhouses can also be at a different pressure to optimize crop yield.

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Re: SpaceX's Martian Underground
« Reply #125 on: 02/03/2017 09:39 PM »
I have to admit I don't really understand why the air pressure is such an issue.  We need to design in safety factors anyway, so why not design for full pressure, and over time optimise for lower pressure if it turns out to be useful or beneficial?  Creating the atmospheres for habitats will not be a major energy drain on the colony, compared to fuel and food production.
Yes, lower pressure would allow for less massive habitats, but using in situ resources is that an issue?  What construction problems does a 30% lower pressure solve, or even 50% lower?  Isn't radiation protection more massive than whatever structural element is used anyway?

Depends. That geodesic dome would become a lot easier with low pressure. But drilled underground habitats can be any pressure desired. I tend to agree that prebreathing for space suit activities may not be a driving factor because they may be quite rare except for the very first years and they could be done from a habitat that gradually reduces its pressure over night or a number of possible arrangements.

Daily work in low pressure greenhouses may profit a lot from a lower habitat pressure.


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Re: SpaceX's Martian Underground
« Reply #126 on: 02/03/2017 09:48 PM »
what was the pressure limit for no prebreathing? I know it is up thread someplace.
bob

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Re: SpaceX's Martian Underground
« Reply #127 on: 02/03/2017 10:51 PM »
what was the pressure limit for no prebreathing? I know it is up thread someplace.

I have read on diving that going to half pressure does not require prebreathing. So if the spacesuit pressure is 25% earth sea level then from a habitat at 50% no prebreathing required.

Or for diving coming up from 10m depth does not need any considerations. You can go straight up no matter how long you have been down.

Offline ThereIWas3

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Re: SpaceX's Martian Underground
« Reply #128 on: 02/04/2017 12:11 AM »
There are decompression considerations for any dive over 6m.   For shallow dives this is just a limitation on ascent rate, to about 10m per minute.   How long you spend on the bottom is also a factor.
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Offline nacnud

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Re: SpaceX's Martian Underground
« Reply #129 on: 02/04/2017 01:58 AM »
Pressurize a large part of the base at normal earth surface pressures. As stated above sea level populations can't breed below certain pressures. Some populations can breed in lower pressures than others but they have genes that compensate for altitude, see below for info on the problems with long term exposure to low pressures.

Hypoxia, fetal growth and early origins of disease: the Andean curse on the Conquistadors

Have another area at double suit pressure where people working outside in rovers or suits can go to save time pre breathing before missions.

Treat the whole base like a diving support vessel, with it's associated pressure chambers, diving bells, and diving suits.
« Last Edit: 02/04/2017 02:02 AM by nacnud »

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Re: SpaceX's Martian Underground
« Reply #130 on: 02/04/2017 02:25 AM »
EVA prebreathing definitely isn't the only reason to operate at reduced pressures.
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Offline KelvinZero

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Re: SpaceX's Martian Underground
« Reply #131 on: 02/04/2017 02:32 AM »
If you are going to design for a civilization and not an outpost, then you need to be at 9 psi or higher. 

Why? Because we literally have thousands of examples of towns and cities here on Earth where the cutoff is at 9 psi.  People just don't breed and live at lower pressures. It's ok temporarily, but not for living.
So 9psi is totally reasonable on earth? (where sealevel is 14.7)

I totally agree arguing to fine detail is not of much purpose, especially when there are all these other factors that we can't possibly really know, like the amount of EVAs required, the mass of other elements of our entire architecture. I mean, we can make reasonable guesses but there is probably at least 25% errors in all these guesses, and they all multiply together.. and it will all be sorted out by engineers in the end anyway.

But just for personal interest, if 9psi is reasonable on earth, then about what would you end up with if you kept the same partial pressure of oxygen while lowering the total pressure.. to exactly the point where the fire risk rises to again equal earth sealevel?
« Last Edit: 02/04/2017 02:33 AM by KelvinZero »

Offline Paul451

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Re: SpaceX's Martian Underground
« Reply #132 on: 02/04/2017 07:04 AM »
But just for personal interest, if 9psi is reasonable on earth, then about what would you end up with if you kept the same partial pressure of oxygen while lowering the total pressure.. to exactly the point where the fire risk rises to again equal earth sealevel?

If I'm interpreting your question correctly, then you could drop the total pressure to around half sea-level before the equivalent pp of 21% @ 9psi (1.89psia) becomes high enough to equal the average fire risk at ordinary sea level.

However, materials don't react uniformly to changes in percentage, partial pressure and total pressure. There's a trend, but it's not uniform across materials. Likewise, a material may have a higher burn rate, but lower ignition rate in a lower oxygen PP but higher percentage. Or vice-versa. Or some other counter-intuitive trait.

So you'd still need to test every material you use, and rewrite all fire-rating regs for equipment intended for Mars.

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Re: SpaceX's Martian Underground
« Reply #133 on: 02/04/2017 11:01 AM »
So we could probably get to 6 psi with 33% O2.
2 psi partial pressure O2 with 33%.
Is this conservative enough?
bob

Offline Jcc

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Re: SpaceX's Martian Underground
« Reply #134 on: 02/04/2017 02:28 PM »
I wonder if a higher O2 PP will help increase tolerance of relatively high CO2. It seems to me CO2 scrubbing will be an ongoing concern, and if tolerance for it can be increased it can mitigate some risk.

Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #135 on: 02/04/2017 07:11 PM »
I wonder if a higher O2 PP will help increase tolerance of relatively high CO2. It seems to me CO2 scrubbing will be an ongoing concern, and if tolerance for it can be increased it can mitigate some risk.

That's an interesting question, with possible positive consequences for all of the reasons discussed above. However, what leads you to believe that higher O2 would combat CO2 toxicity?

Online rsdavis9

Re: SpaceX's Martian Underground
« Reply #136 on: 02/04/2017 08:45 PM »
Can't a simple cold trap get almost all the CO2 out? Like a LOX(or LN2) cooled vessel with air circulating through it.
bob

Offline Paul451

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Re: SpaceX's Martian Underground
« Reply #137 on: 02/04/2017 08:56 PM »
I wonder if a higher O2 PP will help increase tolerance of relatively high CO2.
[...] However, what leads you to believe that higher O2 would combat CO2 toxicity?

Blood CO₂ levels are directly related to deoxygenated hemoglobin levels, which are inversely related to blood-O₂ levels. Increase available O₂ levels and you might reduce the production of bicarb in the blood, reducing the risk of acidosis in a high-CO₂ atmosphere.

However, individual response to higher O₂ levels varies. There are two independent drivers for the breathing reflex, high CO₂ and low O₂. Some people have a reduced CO₂-trigger, and rely on the O₂-trigger; in those people increased O₂ tends to reduce their breathing rate, which allows CO₂ levels to build up to dangerous levels. This is an issue for some COPD and sleep-apnea sufferers who use supplemental oxygen at night.

[I'm sure I'll be accused of "concern trolling", but the point is that none of this stuff is linear, none of it is a uniform effect. Once you start playing with oxygen, nitrogen and carbon-dioxide levels, you will get weird interactions and side-effects. You can't isolate one aspect from the others, nor predict health effects.]

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Re: SpaceX's Martian Underground
« Reply #138 on: 02/05/2017 02:05 AM »
I would go the opposite. By the end of this century, /outside/ CO2 levels on Earth may be around 1000ppm (or higher under a "drill, baby, drill" scenario), which is high enough to noticeably cause a sensation of stuffiness. Indoor levels would be higher, as well, of course, perhaps 1500 ppm or higher. A very stuff room.

I'd go for lower than Earth-level CO2 levels as a kind of marketing point. Bring it to 280 ppm (except in the greenhouses), just so you can say the air is clearer than on Earth, going back to pre-industrial levels.

CO2 scrubbing is a well-known technology, and you're going to need it on Mars, anyway. So scrub it down to low levels. Then you also have more margin in case of power loss or equipment breakdown.
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Offline sanman

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Re: SpaceX's Martian Underground
« Reply #139 on: 02/05/2017 09:21 PM »
It seems increasingly likely that Musk is going with his new tunneling venture with an eye to Mars. When he first outlined his plans for Mars, he talked about people living in geodesic domes on the Martian surface. But he was probably called out on that part, by skeptics who didn't feel the dome idea could work (pressure forces, etc). So because of this, he's probably now shifting to the tunnel idea and sees the importance of getting cracking on the tunneling technology. And if there's a business case for a useful market to serve/disrupt on Earth, then all the more reason to do it.

But I don't see anything disruptive in the technology yet - it all seems off-the-shelf existing hardware. What improvements could he have in mind?

Offline Paul451

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Re: SpaceX's Martian Underground
« Reply #140 on: 02/05/2017 09:44 PM »
When he first outlined his plans for Mars, he talked about people living in geodesic domes on the Martian surface. But he was probably called out on that part, by skeptics who didn't feel the dome idea could work (pressure forces, etc). So because of this, he's probably now shifting to the tunnel idea

Just to be pedantic, he originally said people live in domes, industry in tunnels. So there's nothing inconsistent with his original statements in his pursuing tunnelling technology.

Online guckyfan

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Re: SpaceX's Martian Underground
« Reply #141 on: 02/05/2017 10:19 PM »
Elon Musk sees that large panorama window in ITS as an indispensible part of the system.

I am not sure that people would actually live in such domes. But I am sure that Elon Musk sees at least one such dome with green plants as indispensible for the colony from the early days on. If only people know it is there and they can go and spend some time between plants and see the outside, if they want to.

Offline Jcc

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Re: SpaceX's Martian Underground
« Reply #142 on: 02/06/2017 02:33 AM »
Also to keep radiation exposure to within acceptable limits, time spent in domes on the surface should be controlled, although valuable for aesthetic and psychological reasons.

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Re: SpaceX's Martian Underground
« Reply #143 on: 02/06/2017 02:41 AM »
What is acceptable on Mars and Earth may end up significantly different.

Also, I imagine people would live in buildings themselves inside the dome. Those sub-buildings could be easily shielded by water or plastic.
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Re: SpaceX's Martian Underground
« Reply #144 on: 02/06/2017 03:59 AM »
Also to keep radiation exposure to within acceptable limits, time spent in domes on the surface should be controlled, although valuable for aesthetic and psychological reasons.

With experience gathered on Mars about radiation the limits will likely get redefined. We must remember that Sievert are a value that can not be directly measured. Radiations of different types need to be weighted for their biological relevance and not knowing the relevance exactly means they put safety factors in. Getting better understanding through animals living under such conditions the values can be refined and very likely limits get higher.

All tests done yet are limited in value due to the fact that such radiation is applied in bursts which is not the same as applying them at a continuous low level.

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Re: SpaceX's Martian Underground
« Reply #145 on: 02/07/2017 01:45 AM »
We have a rover on Mars (MSL) which includes an instrument capable of measuring the biological equivalent of the radiation received, not just raw radiation level.
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Re: SpaceX's Martian Underground
« Reply #146 on: 02/07/2017 09:21 AM »
We have a rover on Mars (MSL) which includes an instrument capable of measuring the biological equivalent of the radiation received, not just raw radiation level.

No we don't. The only instrument capable of measuring the biologic impact would be a living organism. Once a sufficiently large number of living organisms have been exposed to the radiation and effects determined we can then apply that info to the readings of radiation measuring devices. The relation is presently only based on assumptions.

Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #147 on: 02/07/2017 10:55 PM »
When he first outlined his plans for Mars, he talked about people living in geodesic domes on the Martian surface. But he was probably called out on that part, by skeptics who didn't feel the dome idea could work (pressure forces, etc). So because of this, he's probably now shifting to the tunnel idea

Just to be pedantic, he originally said people live in domes, industry in tunnels. So there's nothing inconsistent with his original statements in his pursuing tunnelling technology.

But EM is a visionary, and visionaries often use expansive, unsupported claims for their vision(s). That doesn't mean that they are right - or wrong. So, he might truly have plans for tunneling there - or alternatively for domes - or not. For me, all of this is TBA.
« Last Edit: 02/07/2017 10:56 PM by pobermanns »

Offline pobermanns

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Re: SpaceX's Martian Underground
« Reply #148 on: 02/07/2017 11:05 PM »
But I am sure that Elon Musk sees at least one such dome with green plants as indispensible for the colony from the early days on. If only people know it is there and they can go and spend some time between plants and see the outside, if they want to.

On that I agree, because I think that the feeling of confinement will eventually become a major health issue. For some people more than others. People will want to be able to feel like they are 'outside'. Perhaps, that will be moderated over time, just like for submarine crews and the groups who stay on Antartica. Being totally honest here, I have no insight or experience as to how that might play out. Just saying.
« Last Edit: 02/07/2017 11:10 PM by pobermanns »

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Re: SpaceX's Martian Underground
« Reply #149 on: 02/07/2017 11:05 PM »
We have a rover on Mars (MSL) which includes an instrument capable of measuring the biological equivalent of the radiation received, not just raw radiation level.

No we don't. The only instrument capable of measuring the biologic impact would be a living organism. Once a sufficiently large number of living organisms have been exposed to the radiation and effects determined we can then apply that info to the readings of radiation measuring devices. The relation is presently only based on assumptions.
No, we can measure the actual radiation type received on Mars with that instrument and using accelerators on Earth expose organisms to the same type.

As far as "assumptions" go, it's rock solid (within the accuracy we care about), as much as expecting 2+2 to equal 4 on Mars as well as it is here on Earth.
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Re: SpaceX's Martian Underground
« Reply #150 on: 02/08/2017 07:13 AM »
Accelerated or burst exposure to radiation will not give a sufficiently accurate biologic response. But that is what we can do on earth. We don't have affordable radiation sources that can provide constant low simulations of cosmic background radiation.

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Re: SpaceX's Martian Underground
« Reply #151 on: 02/08/2017 08:45 AM »
Yes I believe we have them. They are called airplanes. And the test subjects are called pilots and flight attendees. They might not operate at the same radiation level as there would be on Mars, but that a start with a large sample size. The other experiment using astronauts has probably a too small sample size and time of exposure for a statically significant conclusion.

Before you name the missing magnetic field of Mars, I think that is only applicable for solar flare radiation but irrelevant for cosmic radiation. Not 100% sure though.

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Re: SpaceX's Martian Underground
« Reply #152 on: 02/12/2017 03:11 AM »
Accelerated or burst exposure to radiation will not give a sufficiently accurate biologic response. But that is what we can do on earth. We don't have affordable radiation sources that can provide constant low simulations of cosmic background radiation.
We actually can do it. Langley has a project that can examine the response.
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Offline Ionmars

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Re: SpaceX's Martian Underground
« Reply #153 on: 02/14/2017 11:35 AM »
Yes I believe we have them. They are called airplanes. And the test subjects are called pilots and flight attendees. They might not operate at the same radiation level as there would be on Mars, but that a start with a large sample size. The other experiment using astronauts has probably a too small sample size and time of exposure for a statically significant conclusion.

Before you name the missing magnetic field of Mars, I think that is only applicable for solar flare radiation but irrelevant for cosmic radiation. Not 100% sure though.
Cosmic radiation is high-energy radiation, much higher than radiation from the sun. It consists of protons and atomic nuclei that originate from outside the solar system from sources currently unknown. Solar photons can be “high energy” but the extra mass of cosmic particles pushes their potential kinetic energy into a different and higher class.

On Earth we are protected from the full effects of cosmic radiation by Earth’s magnetic field and by the atmosphere. High-speed particles break up when hitting the atmosphere and even the astronauts on the ISS do not experience the full effect because of the magnetic field.

So our experience with radiation and measurements on Earth and vicinity may lead us to underestimate the exposure problem beyond Earth orbit and on Mars where there is less atmosphere and attenuated magnetic fields. Sometimes enthusiasts (like Elon) will say that the radiation danger is overblown based on our experience so far. He may be right but we don’t yet have experiential proof of that.

Doesn’t mean we can’t transit to Mars and colonize, just that we need to know more and take CR into account when planning habitats and cities.
* Mars: a convenient service station for an asteroid-sized spaceship en-route to Ceres. *

Offline john smith 19

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Re: SpaceX's Martian Underground
« Reply #154 on: 03/04/2017 08:36 AM »
Just a reminder.

To give the equivalent protection that Earth's atmosphere provides people at Sea Level takes about 3m of Martian Regolith.

Something tells me that making a dome that gives equal protection, while being transparent enough to see the outside, and perhaps color matched to not look too Orangeto th einhabitants inside, is going to be a tricky piece of materials and structural engineering.  :(

Plants seem to be more tolerant of lower pressures and higher radiation, so slightly pressurized "green houses" seem to be the way to go to grow food without the huge cost of artificial light while staying underground (or burrowed into a cliff face) seems to be the way to go for humans.
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Online guckyfan

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Re: SpaceX's Martian Underground
« Reply #155 on: 03/04/2017 08:47 AM »
Something tells me that making a dome that gives equal protection, while being transparent enough to see the outside, and perhaps color matched to not look too Orangeto th einhabitants inside, is going to be a tricky piece of materials and structural engineering.  :(

Elon Musk mentioning a geodesic dome suggests a different approach. Build the dome to just contain pressure and be transparent. Think the panorama window in ITS. Build structures with radiation shielding inside. Those can have windows and a shielded porch to look at the plants and going outside for an hour or two a day would be OK in your radiation budget unless you are pregnant or an infant.

Offline Lampyridae

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Re: SpaceX's Martian Underground
« Reply #156 on: 03/04/2017 09:13 AM »
Just a reminder.

To give the equivalent protection that Earth's atmosphere provides people at Sea Level takes about 3m of Martian Regolith.

Something tells me that making a dome that gives equal protection, while being transparent enough to see the outside, and perhaps color matched to not look too Orangeto th einhabitants inside, is going to be a tricky piece of materials and structural engineering.  :(

Plants seem to be more tolerant of lower pressures and higher radiation, so slightly pressurized "green houses" seem to be the way to go to grow food without the huge cost of artificial light while staying underground (or burrowed into a cliff face) seems to be the way to go for humans.

Mars has quite a few magnetic anomalies, especially in the south, which will provide some protection.

As for the radiation protection - ice. Sandwich between two sheets of glass, and the internal pressure will counteract the weight, there have been plenty of threads on this, and papers on the net.

The sky colour won't be a problem. Human eyes adapt very quickly to coloured lighting conditions. Indoor lights are very different to natural "white" sunlight, yet white things still look white to you.

If you look at the exposed rocks from one of the rover pictures, they often look slightly blue - they aren't. They're a grey colour, as you'd find on the Moon or Earth, your eye is just auto-balancing against the ochre-orange of Mars.
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Offline Oersted

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Re: SpaceX's Martian Underground
« Reply #157 on: 03/04/2017 09:55 PM »
Elon Musk mentioning a geodesic dome suggests a different approach. Build the dome to just contain pressure and be transparent. Think the panorama window in ITS. Build structures with radiation shielding inside. Those can have windows and a shielded porch to look at the plants and going outside for an hour or two a day would be OK in your radiation budget unless you are pregnant or an infant.

Elon musks' actual words (Reddit AMA):

"Initially, glass panes with carbon fiber frames to build geodesic domes on the surface, plus a lot of miner/tunneling droids. With the latter, you can build out a huge amount of pressurized space for industrial operations and leave the glass domes for green living space."

- The "huge amount of pressurized space" of his base on Mars will obviously be subterranean.
« Last Edit: 03/04/2017 09:55 PM by Oersted »

Online Robotbeat

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Re: SpaceX's Martian Underground
« Reply #158 on: 03/04/2017 11:55 PM »
Just a reminder.

To give the equivalent protection that Earth's atmosphere provides people at Sea Level takes about 3m of Martian Regolith.

Something tells me that making a dome that gives equal protection, while being transparent enough to see the outside, and perhaps color matched to not look too Orangeto th einhabitants inside, is going to be a tricky piece of materials and structural engineering.  :(

Plants seem to be more tolerant of lower pressures and higher radiation, so slightly pressurized "green houses" seem to be the way to go to grow food without the huge cost of artificial light while staying underground (or burrowed into a cliff face) seems to be the way to go for humans.

Mars has quite a few magnetic anomalies, especially in the south, which will provide some protection.

As for the radiation protection - ice. Sandwich between two sheets of glass, and the internal pressure will counteract the weight, there have been plenty of threads on this, and papers on the net.

The sky colour won't be a problem. Human eyes adapt very quickly to coloured lighting conditions. Indoor lights are very different to natural "white" sunlight, yet white things still look white to you.

If you look at the exposed rocks from one of the rover pictures, they often look slightly blue - they aren't. They're a grey colour, as you'd find on the Moon or Earth, your eye is just auto-balancing against the ochre-orange of Mars.
Unfortunately, I once calculated what good, if any, those magnetic anomalies would do for radiation shielding, and the answer is diddly squat, even lower energy solar energetic particles. Just too weak.

But the Mars atmosphere itself does a good job. And overall, the radiation environment is more benign than in LEO, especially at low altitude. Not a big deal. Just live with it.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline lamontagne

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Re: SpaceX's Martian Underground
« Reply #159 on: 03/05/2017 12:17 AM »
Elon Musk mentioning a geodesic dome suggests a different approach. Build the dome to just contain pressure and be transparent. Think the panorama window in ITS. Build structures with radiation shielding inside. Those can have windows and a shielded porch to look at the plants and going outside for an hour or two a day would be OK in your radiation budget unless you are pregnant or an infant.

Elon musks' actual words (Reddit AMA):

"Initially, glass panes with carbon fiber frames to build geodesic domes on the surface, plus a lot of miner/tunneling droids. With the latter, you can build out a huge amount of pressurized space for industrial operations and leave the glass domes for green living space."

- The "huge amount of pressurized space" of his base on Mars will obviously be subterranean.
I would expect that if you don't sleep under the dome, and don't work under the dome, and don't do most of your entertainment under the dome, then the radiation problem is much less important.  Limiting exposure to a few hours or less per day.  After all, we don't spend all that much time close to windows ourselves, even up here in Canada, where we sometimes crave natural light.
Thinking of my adolescent son, playing in front of his computer, I don't think he sees natural light more than a few minutes every week ;-)




Offline CuddlyRocket

Re: SpaceX's Martian Underground
« Reply #160 on: 03/05/2017 01:29 AM »
Just a reminder.

To give the equivalent protection that Earth's atmosphere provides people at Sea Level takes about 3m of Martian Regolith.

But how much of Earth's atmosphere is needed for adequate radiation shielding? After all, people live quite happily in Nepal and Tibet, which have approximately only 30% of the atmospheric pressure at sea level (ref).

Also, Mars does have an atmosphere, which provides some shielding, and the Solar radiation flux is less.

Offline Paul451

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Re: SpaceX's Martian Underground
« Reply #161 on: 03/05/2017 02:56 AM »
Thinking of my adolescent son, playing in front of his computer, I don't think he sees natural light more than a few minutes every week

You should hope so. Current research on near-sightedness suggests that a major part is the lack of exposure to bright lights while growing up. It doesn't take much, a few minutes a day. You don't have to drag them outside for hours. Even wearing sunglasses (under full sun) is sufficient, or through cloud cover without sunglasses. (The sun, hidden behind tinted lenses or clouds, is still much brighter than indoor lights directly.)

(Likewise, childhood sun exposure may be a significant factor in adult depression and other mental illness.)

Online Robotbeat

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Re: SpaceX's Martian Underground
« Reply #162 on: 03/05/2017 03:17 AM »
Literacy in general is a risk factor in nearsightedness. Reading books.
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Offline Paul451

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Re: SpaceX's Martian Underground
« Reply #163 on: 03/05/2017 03:45 AM »
Literacy in general is a risk factor in nearsightedness. Reading books.

No, that's what the new research tested. It's not books or TV or video-games. (Or close work in general.) It's that kids who preferred those activities tended to spend less time in the sun. Once you correct for that, the link with reading/education, or other activities is eliminated.

(The Sydney Myopia Study tracked 4000 school-age children from 55 schools. The only statistically significant link was time spent outdoors. Follow-up animal studies showed the that light levels alone can alter eye elongation (the cause of myopia.) It seems to be related to dopamine levels in the eye, which is related to switching between rod and cone dominated vision. Block the dopamine pathway (yet further follow-up research) and you not only induce 100% myopia in the animals, but eliminate the protective effect of light exposure. In a school trial in Sydney, they added 50 minutes of additional sun exposure to the school day, and saw a 25% reduction in myopia. In Taiwan, researchers were able to convince authorities to add 100 minutes of extra sun exposure to school days, and saw a 50% reduction in myopia.)

[Aside: I said "a few minutes a day". I was wrong. Actually for the full protective effect, it's about 3hrs/day at 40,000 lux, which is about mid-winter sun or mid-summer under cloud. A typical "bright" indoor room gets about 1000 lux. So you do need to drag them outside for hours. Sorry Michel.]



This was originally and off-topic aside but this may be an issue for Mars. If colonists are essentially living underground, what is their typical light exposure? Can you afford to illuminate entire habitats to 40,000 lux?

Offline Adaptation

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Re: SpaceX's Martian Underground
« Reply #164 on: 03/05/2017 06:08 AM »
Most materials are actually more flammable at martian gravity than than earth gravity.  Lunar is even worse.  By more flammable I do not mean that it burns faster or more vigorously but rather things which would self extinguish do so slower or not at all under these lower gravities.  There is still adequate convection to deliver fresh oxygen to keep the flame fed meanwhile the total amount of convection is lower providing less cooling which is aids in self extinguishing. 

For me these were counter intuitive results.  I correctly anticipated the weaker convection to deliver less oxygen, causing a lower rate of combustion.  I had assumed this would scale proportionally with the decrease in convective cooling.  When adding in the fact that radiative cooling would not be effected by gravity I had expected the total flammability to be lower.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130010991.pdf

Offline Oersted

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Re: SpaceX's Martian Underground
« Reply #165 on: 03/05/2017 07:19 AM »
So, what you are saying is that the Mars colonists living in tunnels and caves for the first couple of generations will become a race of blind moles?  :-O

Offline Paul451

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Re: SpaceX's Martian Underground
« Reply #166 on: 03/05/2017 04:50 PM »
So, what you are saying is that the Mars colonists living in tunnels and caves for the first couple of generations will become a race of blind moles?

Depressed, schizophrenic, myopic, gangly, pasty moles.

Offline gospacex

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Re: SpaceX's Martian Underground
« Reply #167 on: 03/05/2017 05:15 PM »
Literacy in general is a risk factor in nearsightedness. Reading books.

No, that's what the new research tested. It's not books or TV or video-games. (Or close work in general.) It's that kids who preferred those activities tended to spend less time in the sun. Once you correct for that, the link with reading/education, or other activities is eliminated.

My personal data point does not support this theory.
I was 7 many years before computers became widely available, and I did play outside a lot. Yet, I also started reading a lot. A LOT. Like, two books a day. That's when myopia started for me.
« Last Edit: 03/05/2017 05:16 PM by gospacex »

Offline john smith 19

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Re: SpaceX's Martian Underground
« Reply #168 on: 03/07/2017 09:47 AM »

But how much of Earth's atmosphere is needed for adequate radiation shielding? After all, people live quite happily in Nepal and Tibet, which have approximately only 30% of the atmospheric pressure at sea level (ref).

Also, Mars does have an atmosphere, which provides some shielding, and the Solar radiation flux is less.
Just a reminder.

Mars surface pressure is 1/160 that of Earth at SL.

(The Sydney Myopia Study tracked 4000 school-age children from 55 schools. The only statistically significant link was time spent outdoors. Follow-up animal studies showed the that light levels alone can alter eye elongation (the cause of myopia.) It seems to be related to dopamine levels in the eye, which is related to switching between rod and cone dominated vision. Block the dopamine pathway (yet further follow-up research) and you not only induce 100% myopia in the animals, but eliminate the protective effect of light exposure. In a school trial in Sydney, they added 50 minutes of additional sun exposure to the school day, and saw a 25% reduction in myopia. In Taiwan, researchers were able to convince authorities to add 100 minutes of extra sun exposure to school days, and saw a 50% reduction in myopia.)
This is very exciting, suggesting myopia can be radically reduced in developed countries.

But it is a concern for Mars and future generations of Mars.

Given Mars is so much farther away from the Sun it already starts out with a lower solar level than Earth. Multiply by lack of regular exposure and the long term effects could be severe.

Unless people are prepared to look at "anti-myopia" pills.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline gospacex

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Re: SpaceX's Martian Underground
« Reply #169 on: 03/07/2017 02:32 PM »
Given Mars is so much farther away from the Sun it already starts out with a lower solar level than Earth. Multiply by lack of regular exposure and the long term effects could be severe.

Unless people are prepared to look at "anti-myopia" pills.

Or have brighter indoor lighting?

Offline Paul451

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Re: SpaceX's Martian Underground
« Reply #170 on: 03/07/2017 09:39 PM »
The Sydney Myopia Study tracked 4000 school-age children from 55 schools. The only statistically significant link was time spent outdoors. Follow-up animal studies showed the that light levels alone can alter eye elongation (the cause of myopia.) It seems to be related to dopamine levels in the eye, which is related to switching between rod and cone dominated vision. [...]
This is very exciting, suggesting myopia can be radically reduced in developed countries.

I found it interesting when I first heard of it a year or so back, which I why it stuck in my memory. It subverts the obvious and expected causes.

Given Mars is so much farther away from the Sun it already starts out with a lower solar level than Earth.

That doesn't concern me. The sun is so frickin' bright that even on Mars you're looking at 50,000 lux for a typical day, and probably averaging over 30,000 during the year. And dust matters less than water-clouds on Earth (it scatters the light, reducing direct sun brightness drastically, but the overall sky-illumination remains higher than an equivalent reduction via water-clouds.)

People being trapped inside may be the issue.

Or have brighter indoor lighting?

If you are currently in a brightly lit room, the lighting level will be around 1000 lux. We need 30-40,000 lux. So multiply the number of lights in your room by 40-fold over the same area. Then, even allowing for LED efficiencies, think about the power consumed, the heat released, and the annoyance of working on anything with a screen. It seems unlikely anywhere outside a grow-chamber (indoor greenhouse).

The cheat would be to exploit the inverse-square law and have lights right in front of your eyes. IIRC, the photosensors in the eyes for secondary effects (body-clock, dopamine, etc) are clustered in the peripheral vision. That means you can wear glasses with bright LED's around the edges of your cone-of-vision. (You can still do normal work through the centre.) It shouldn't take much experimenting with animals to prove whether that's sufficient to offset the heightened myopia risk.

As a bonus, if you time it right, it will also reset your body-clock each morning, helping deal with the slightly longer day.

Offline gospacex

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Re: SpaceX's Martian Underground
« Reply #171 on: 03/07/2017 10:41 PM »
Or have brighter indoor lighting?

If you are currently in a brightly lit room, the lighting level will be around 1000 lux. We need 30-40,000 lux. So multiply the number of lights in your room by 40-fold over the same area. Then, even allowing for LED efficiencies, think about the power consumed, the heat released, and the annoyance of working on anything with a screen. It seems unlikely anywhere outside a grow-chamber (indoor greenhouse).

It's not necessary to have 30K lux all the time, right? How about this: (if the theory about myopia caused by dim lighting is proved with much more research,) Mars health regulations might mandate that spaces such as corridors, shops, other similar public places should be lighted not lower than below $BIGNUM lux.

(Thankfully, higher power consumption on Mars is less of a problem than on Earth: with outside temps of around -60 C average, even underground bases likely will need heating.)
« Last Edit: 03/07/2017 10:41 PM by gospacex »

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