human habbitat on another planet

[chebby]

Hi, I am a returning space.com poster (hey you all!) and I decided to post an idea I had today while reading some sci-fi books. I hope I can get some feedback into how feasible this idea is.

There is a lot of sci-fi literature out there that mentions spheres made of (glass? metal? forcefields?) that serve as bubbles on foreign planets to hold atmosphere and provide a human habbitat.

The problems with this are: 1) It can be easily destroyed by meteorites 2) I can't imagine any real human techology that can achive this, hence it's sci fi.

I have an different idea that I think is much easier (although I would be surprised if noone thought of this before already.) Simply make a hole on a foreign planet that has no atmosphere and fill it with air! Or use an existing crater. Below I list some aspects and problems of it and possible solutions.

1) How deep? It has to be deep enough to hold something to 1 atm for this to be useful but even 70-80 percent would be good enough. Based on the average thickness of earth troposhpere (7 miles/12 km) which contains about 75% of atmoshpere's gases, I think 12 km should be enough? King's crater on moon is 5km deep, so not deep enough, but maybe it can be widened?

reference for atmospheric info: http://mediatheek.thinkquest.nl/~ll125/en/atmos.htm

2) Can we dig it? I was thinking about nuclear charged detonated at depth. Would this make a hole? and How big a charge is needed to make a 12 km hole in the ground?

3) What about gas leaving into space? I don't know, I was hoping someone could tell me how fast air would naturally would be able to fly away (let's say we have moon's grafity)

4) Wouldn't planet's rotation thow the gas off? Maybe, but we can also make this hole at the rotational pole.


thank you for attention and looking forward to hear some ideas

 

[yevaud]

Chebby!!! Welcome back!!! (Still work up the street?)

This idea has been bandied around for a long time, and written about by many people. It is feasible, as far as I know the engineering of it.

 

[yevaud]

Btw, this should properly be in Ask The Astronomer; I'll wait till you acknowledge me, and then move it there.

 

[chebby]

Hey Yevaud, yep I'm still at BU, although I had a small reincarnation into an MS student and back. I hope you won't shoot darts at me You still live around Allston?

Yep feel free to move this to the other section, sections changed a bit since I can remember.

(well the space.com message board just froze for 30 mins before I could reply with this, nice to see some things never change

 

[kelvinzero]

It was either many people or me several times
I calculated once that a 60km deep hole on mars would have earth sealevel pressure. Or under a mere 30 meters of water.

 

[tampaDreamer]

If you put it under water you'd be back to needing a bubble.. What method would you use to dig this big hole? Could we maybe send a vasimr to an asteroid and collide it to deepen an existing crater without causing more problems than we solve?

 

[JeffreyNYA]

Why would you need to do this? Can't you just find existing caves or tunnels, such as Lava tubes. Just seal it up and pressurize it. Would be a much eaiser than blasting a huge hole in the ground. Doesn't the moon and mars have lava tubes on them? The mars one's may be risky if there is even a possibility of active Volcanic activity.

 

[chebby]

Kelvin, I would be very interested to look at your calculations if you can find them. Water trick sounds neat, but as Tampa mentioned you would need a bubble still. I was also thinking that if there was a jupiter like planet somewhere in other system with a solid core, a pretty shallow hole could be used as all the outer layer of hydrogen would produce the requred pressure on top of the hole filled with air.

TampaDreamer, because naturally occuring craters on moon do not exceed 5 km, somehow I don't think asteroid bombardment could produce a hole deep enough. Although maybe if you get one big enough

JeffreyNYA, you would do it because you would get direct sunlight coming though. If you just sealed yourself in a hole on another planet, you would need to create a heating source for any vegetation to grow. I like the lava tubes idea too. I never knew such things existed, even on earth though.

After reading this forum for a little while today, I found some information about gas velocity needing to be less than 1/6 of orbital verlocity to stick around on the planet. This makes me think that the velocity for the gas to simply stick around in the hole can be much lower. This makes me afraid the whole thing might not be feasible as it would just slowly fly away over the hole edge into the planet's surrondings. But...because higher levels would be very cooled, maybe gas velocity would be reduced. Or if the process is slow enough, maybe it can be replentished somehow.

 

[JeffreyNYA]

I am not sure direct sunlight on mars is going to produce enough heat to help with much of anything. If you want natural light, then you can always have light reflected into the tunnels through skylights of some sort. Maybe solar collectors to focus it for heat. Just not sure there is enough sunlight for that.

Nuclear will probably be the best way to get heat, and power. Then you can have underground greenhouses with artifical light. Will still be much more cost effective and much more easy.

 

[crazyeddie]

I am not sure direct sunlight on mars is going to produce enough heat to help with much of anything. If you want natural light, then you can always have light reflected into the tunnels through skylights of some sort. Maybe solar collectors to focus it for heat. Just not sure there is enough sunlight for that.

Nuclear will probably be the best way to get heat, and power. Then you can have underground greenhouses with artifical light. Will still be much more cost effective and much more easy.

Nuclear reactors will probably be necessary for any early outpost on Mars, but there's no reason why sunlight can't be utilized to grow plants in greenhouses. Unless the colonists opt for a completely underground existence, it would be much more cost effective to grow crops on the surface, and save the energy from the reactors for better purposes than lighting. Growing plants from artificial light alone gobbles up a LOT of electricity.

 

[JeffreyNYA]

I am not sure direct sunlight on mars is going to produce enough heat to help with much of anything. If you want natural light, then you can always have light reflected into the tunnels through skylights of some sort. Maybe solar collectors to focus it for heat. Just not sure there is enough sunlight for that.

Nuclear will probably be the best way to get heat, and power. Then you can have underground greenhouses with artifical light. Will still be much more cost effective and much more easy.

Nuclear reactors will probably be necessary for any early outpost on Mars, but there's no reason why sunlight can't be utilized to grow plants in greenhouses. Unless the colonists opt for a completely underground existence, it would be much more cost effective to grow crops on the surface, and save the energy from the reactors for better purposes than lighting. Growing plants from artificial light alone gobbles up a LOT of electricity.

ya, no doubt. I agree completely. I think the original poster was trying to get away from having enviornment issues like metors and such from having a negitive effect on the settlement. Thats the only reason I made the suggestions I did. I would think that having the greenhouses outside would be the best. However could natural light be brought into and underground structure to grow food, thus eliminating the need for grow lights?

As far as underground goes, I would think that for settlements that if the right location could be found that it would be the best option for living and working space. Would help eliminate issues that surface living would have. But of course the first settlement would be above ground as it will take a while to be able to get a underground facility going.

As for the moon, I think it is really the only option if we are going to stay for a long time.

 

[crazyeddie]

ya, no doubt. I agree completely. I think the original poster was trying to get away from having enviornment issues like metors and such from having a negitive effect on the settlement. Thats the only reason I made the suggestions I did. I would think that having the greenhouses outside would be the best. However could natural light be brought into and underground structure to grow food, thus eliminating the need for grow lights?

As far as underground goes, I would think that for settlements that if the right location could be found that it would be the best option for living and working space. Would help eliminate issues that surface living would have. But of course the first settlement would be above ground as it will take a while to be able to get a underground facility going.

As for the moon, I think it is really the only option if we are going to stay for a long time.

Yes, the downside of growing crops in greenhouses on the surface is that the Mars colonists will have to spend a lot of time tending to the plants in a high-radiation environment. Perhaps they could have greenhouses underground, with a system of mirrors reflecting a lot of sunlight into the growing rooms, supplemented with artificial light....but the cost of such underground structures may be prohibitively expensive in the early years. On the moon, with it's two weeks of darkness, it really is not a matter of choice. Artificial lighting underground is the only way to go.

 

[tampaDreamer]

The upside of solar power on mars or the moon, if we are living underground, is that surface real estate will be cheap! You could have a solid square mile of solar panels right by your habitat. Unless we manage to mine uranium in situ..

I really like this hole idea.

 

[marsbug]

naturally occuring craters on moon do not exceed 5 km, somehow I don't think asteroid bombardment could produce a hole deep enough. Although maybe if you get one big enough

]

The best natural example I can think of is 9km deep Hellas basin on mars, where the atmospheric pressure is high enough to allow metastable liquid water at temperatures as high as ten degrees celcius, although the average temperature there is still well below zero.

 

[crazyeddie]

The best natural example I can think of is 9km deep Hellas basin on mars, where the atmospheric pressure is high enough to allow metastable liquid water at temperatures as high as ten degrees celcius, although the average temperature there is still well below zero.

There will undoubtedly be lava tubes on Mars, due to it's long history of volcanism. Those may be the best places of all to set up colonies.

 

[neilsox]

Dark glass can be made easily from regoth, perhaps more like brick or tile. To get transparent glass requires separating impurities from the silicon dioxide and a few metal oxides which are transparent. Strong glass which can survive small meteor hits, and temperature changes also needs high purity, which will be challenging for early colonists. The glass or metal needs to be about one meter thick to give good radiation protection = more than two tons per square meter. We don't build 100,000 square meter glass domes on Earth as the required infrastructure is huge.
My guess is the 60 kilometer Mars crater would lose about one percent of it's gas per century, less if the gas is mostly oxygen at about 5 psi (at the bottom) instead of 12 to 14 psi air. 5 psi of oxygen is less than optimum, but most of the colonists would likely adapt. The lava tubes are the best bet even if they need modifying. Neil

 

[chebby]

great input, thanks!

I was thinking, what if instead of a mixture of N and O2 we fill the crater with a mixture of Xe and 02? Xeon is 5 times heavier than air, so crater would have to be 5 times smaller. It is inert gas so it shouldn't affect our health....much. Although I have a feeling that O2 might just fly away displaced by much heavier Xe. But I guess we can just wear oxygen masks? Oh and on the upside, we'll all speak as Barry White :shock:

http://www.youtube.com/watch?v=hwnLiXK-v5U

Oh and about lava tubes...yeah it's possible but who would want to fly to another planet to live in a tube undeground? We can do that on earth. It's all about the quality of life that can be provided, otherwise noone will want to live or work there. For example if I told people that I built an oasis in Antarctica and would pay for their relocation and they would have work there, i'm sure i'd get a lot of applicants. But if I told them I have an undground bunker there, I don't think I'd get the same responce. Maybe I'm underestimating allure that foreign planets have on some individuals, but I personally would only move to another planet to live if it was pretty damn nice and comfy.

 

[JeffreyNYA]

Oh and about lava tubes...yeah it's possible but who would want to fly to another planet to live in a tube undeground? We can do that on earth. It's all about the quality of life that can be provided, otherwise noone will want to live or work there. For example if I told people that I built an oasis in Antarctica and would pay for their relocation and they would have work there, i'm sure i'd get a lot of applicants. But if I told them I have an undground bunker there, I don't think I'd get the same responce. Maybe I'm underestimating allure that foreign planets have on some individuals, but I personally would only move to another planet to live if it was pretty damn nice and comfy.

Actually there are a lot of people who would love the chance to do that. The lava tube as housing allow for faster colinization. They will protect us from solar radiation and from the dust storms that are so common. Now just because they live in these tubes does not mean that they never leave them. They will be going out all the time for work.

First you wanted to dome over a deep crator to get to a certian depth. I would say, who wants to live in a giant hole in the ground. All you will ever see is dirt walls and the red sky. thats about it. Nothing special. I guess I would rather do it in a cheaper way and really get the ball rolling. If at some time in the future they are about to build domes that are strong enough and protect them from everything with very little upkeep, then great. Build away. But sorry to say, thats a long way off.

And if you are planning to move to another planet don't expect it to be all comfy. Expect it to be hard, very hard.

 

[MeteorWayne]

Really chebby, how do you think people live in Antarctica? Basically they are inside all the time except when taking measurements of the environment. Why? Because that's how you can survive and conserve resources enough so you can live there.

And Antarctica is FAR more hospitable than the moon or Mars.

 

[chebby]

JeffreyNYA, if you read my original post, you would see that I dismissed idea of a dome as an impossible engeneering task.

Oh and if you filled the hole with air, they sky would be blue Also big craters are usually thousands of
miles across (Hellas basin is 2,500 miles across), so the walls would look very distant or even not seen because air is not as transparent as vaccum.

All I was trying to do with my previous post was to illustrate the difference between a colony and a scientific outpost.

A colony is where people come to live, reproduce and live until they die (ex: british colonizing North America).

A scientific outpost is where people come to do science for a few years and then leave (ex: ISS, antarctica stations)

We have scientific outposts in Antarctica, but we don't colonies there.

I would love to live in a lava tube on Mars for a few years doing science, but there is no way in hell I want to spend my entire life there.

 

[SpaceTas]

Craters are very shallow for their size: the simple and smaller bowl shaped craters have a depths to diameter of 1:6 while larger craters are more like 10:1 (MeteorWyne will probably have the answer) or more. So if you find a crater deep enough it will be very large, nice for wide open spaces, terrible if you have to make the atmosphere.

Wikpedia gives the formula for scale height: = height over which pressure drops by a factor of e=2.718.
The scale height increases with Temperature (absolute scale O deg C = 273 Kelvin) and decreases with average molecular weight (so adding Xenon etc would help, double molecular weight half scale height) and decreases with gravity (Mars has a bit under half the surface gravity so scale height needed for same bottom pressure as on Earth is a bit more than double).
So for the Earth the scale height is 8 km a 0 deg C.

You will need a crater/hole deeper than the scale height: at 1 scale height 1/2 the atmosphere is above your crater wall,
at 2 scale heights 1/4 .... The amount above the wall is what you'd expect to be lost to the rest of the planet and then to space. This loss is different from the molecular diffusion you get from a planet. Note this diffusion lose depends on the molecular weight of the gas (not the average for the atmosphere) being lost.

So lets use 4 scale heights 1/16 lost to rest of planet. On Mars a 0 deg C the scale height is 20 Km (gravity 0.4 Earth).
So need a crater about 80 km deep.

is there a crater this deep on Mars?

To reduce depth you could lower the pressure a bit to say to about 2000 equivalent, people have adapted to higher altitude (lower oxygen levels) but above 3000 m altitude sickness becomes much more common. At 2000m equivalent reduces scale height by 0.778 (includes exponential) so only need 62 km deep hole.



The main problem with replacing nitrogen with say xenon, is that xenon (and all the other inert gasses) is very rare. It has been tried a few times by deep divers; they didn't die or get the bends; that's what's known about the medical effects.

Going to a lower pressure higher percentage oxygen atmosphere (nearly 100% at 5psi in shuttle space suits) is not a good idea. Shuttle astronauts need many hours decompression, recompression, oxygen gets toxic with over exposure, and lots of materials burn really well in high percentage oxygen atmospheres.

For comparison, the deepest mine of Earth is 3.3 km deep.

 

[yevaud]

Hey Yevaud, yep I'm still at BU, although I had a small reincarnation into an MS student and back. I hope you won't shoot darts at me You still live around Allston?

Yes, behind / near the Shaw's on Comm. Ave. I might be moving a short distance soon though, into Brookline (into the "Communist Triangle!"). Still local though.

 

[eburacum45]

If you want to live in a crater on Mars by all means do so; but you will have to put a membrane over the top to stop the air from escaping. Ah; but the membrane would be punctured by micrometeorites, you say? Then you need a double layer. The top layer would vapourise the micrometeorite, and the vapour would be too feeble to puncture the second layer. If the top layer is arranged into multiple cells, each micrometeor would only deflate one cell at a time. Eventuall the dome would have a significant number of deflated cells- so you'd have to replace it over time.

Unfortunately. attempting to make an open-roofed region of high pressure on Mars would fail, as Spacetas demonstrated, unless you bring the pressure over the whole planet to a significantly higher value.

 

[chebby]

SpaceTas, great read, thanks! I read up on the scale height, it is a useful concept. I guess I'll save this idea for planets in other solar systems, that are more massive than Mars and are located closer to the sun or something.

Yevaud, I park by the Shaws (bu parking lot) 3-4 times a week cause I'm at the Ring boxing club like all the time. We should meet up for a beer, haha.

eburacum45, that is a great idea. Especially if a planet had an existing atmosphere, than a membrane like that could be built to separate breathable atmosphere from the native nonbreathable one.

But I agree, this idea doesn't have a lot of steam to be practially used. I had fun thinking about it though.

 

[yevaud]

SpaceTas, great read, thanks! I read up on the scale height, it is a useful concept. I guess I'll save this idea for planets in other solar systems, that are more massive than Mars and are located closer to the sun or something.

Scale Height is a known and useful tool in Meteorology and Atmospheric Physics.

Yevaud, I park by the Shaws (bu parking lot) 3-4 times a week cause I'm at the Ring boxing club like all the time. We should meet up for a beer, haha.

Heh. I (currently) live on the street behind that lot, down towards Linden Street a ways. Familiar territory indeed (a good friend of mine was until a year ago the night manager of that Shaw's Deli). So's the boxing club; on Comm. Ave., second floor, just up from the Shaw's, IIRC. Mebbe I'll meet you at TT's one of the days, hoist a few! :mrgreen: