Author Topic: Lifesupport System in Outer Space  (Read 17992 times)

Offline doge

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Lifesupport System in Outer Space
« on: 09/06/2014 06:01 am »
How are we supposed to produce water in space. We have oxygen from photosynthetic bacteria and are thinking of sustaining life on a lifeless, barren planet with no resources pertaining to human life. Specifically, hydrogen and water.

Offline IslandPlaya

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Re: Lifesupport System in Outer Space
« Reply #1 on: 09/06/2014 11:00 am »
What!? Please be more coherent.
Welcome to the forum, I think.

Offline KelvinZero

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Re: Lifesupport System in Outer Space
« Reply #2 on: 09/06/2014 01:44 pm »
Hydrogen is the most common element in the universe, oxygen is the third most common (after helium). The moon is about 40% oxygen, though tightly chemically bound to other elements.

Mars has very large amounts of water. It has poles which are kilometers deep in ice. It has surface ice in craters well away from the poles. It has evidence of ice just below the surface, in permafrost and buried glaciers in other places.

The moon is very dry in general, but has evidence of a few percent of ice mixed in with the regolith in certain areas at the lunar poles. Probably plenty to get started with.

Going further out, the solar system is littered with icy bodies. Ceres, the largest object in the asteroid belt, is expected to have a layer of ice about 200km deep. Europa is expected to have a liquid water ocean under its ice crust. Beyond a certain distance from the sun almost all the bodies will contain ice, I expect. The water on earth is believed to have come from a bombardment of comets from the outer solar system.

Offline doge

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Re: Lifesupport System in Outer Space
« Reply #3 on: 09/06/2014 04:39 pm »
We are supposed to colonize space. Suppose the moon. (Note: No Cycler option, simple human colony). Problem arises in the production of water. How would you suggest we establish a sustainable water cycle on the moon ?

Offline doge

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Re: Lifesupport System in Outer Space
« Reply #4 on: 09/06/2014 04:44 pm »
What!? Please be more coherent.
Welcome to the forum, I think.
Um, sorry, i'm not used to forums, so i probably lack the accepted etiquette. You see, we are to colonize space.
We have photosynthetic bacteria  for oxygen, solar power for almost all energy production, IF we get hydrogen, we can use a hydrogen fuel cell and get water as a byproduct, but that one is a bit out of hand. 
We have assumed that there wont be 100% water recycling from human beings and that it will be used up by the plants in the lab like green house. On the moon, how would we establish a self sustaining supply of water? and in doing so, establish a water cycle.

Offline IslandPlaya

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Re: Lifesupport System in Outer Space
« Reply #5 on: 09/06/2014 06:50 pm »
We would extract it from regolith.

Offline Lars_J

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Re: Lifesupport System in Outer Space
« Reply #6 on: 09/10/2014 01:04 am »
We are supposed to colonize space. Suppose the moon. (Note: No Cycler option, simple human colony). Problem arises in the production of water. How would you suggest we establish a sustainable water cycle on the moon ?

Recycling? Already being done on ISS to a degree... But any mission longer than a couple of months will have to be close to a closed loop system, where as much as possible is recycled. Water is one of the easiest things to recycle.

If a colony is established on an arid body, that will have to be scaled up.

Offline pathfinder_01

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Re: Lifesupport System in Outer Space
« Reply #7 on: 09/10/2014 02:45 am »
Water itself in the form of ice is pretty common in places like the lunar poles. It also can be shipped in and recycled. The ISS can recycle both water and recapture oxygen from CO2 via turning the C02 into methane.

Offline Dalhousie

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Re: Lifesupport System in Outer Space
« Reply #8 on: 09/10/2014 07:28 am »
We are supposed to colonize space. Suppose the moon. (Note: No Cycler option, simple human colony). Problem arises in the production of water. How would you suggest we establish a sustainable water cycle on the moon ?

Recycling? Already being done on ISS to a degree... But any mission longer than a couple of months will have to be close to a closed loop system, where as much as possible is recycled. Water is one of the easiest things to recycle.

If a colony is established on an arid body, that will have to be scaled up.

recycling of O2 and H2O on the ISS is already at ~90%.  This is good enough for ferry missions and more than good enough for Mars.  Very high closures are hard to achieve and may not be worth it initially.
Apologies in advance for any lack of civility - it's unintended

Offline Nilof

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Re: Lifesupport System in Outer Space
« Reply #9 on: 09/10/2014 05:38 pm »
Oxygen in particular is everywhere. Architectures that include local industries on the Moon, Mars, or the asteroids tend to produce massive ammounts of it as a waste product. Hydrogen is very common in most places, except for some asteroids and most of the surface of our Moon, though there's likely quite a lot of it at the poles. Ditto for Carbon.

As for reuse, hydrogen and oxygen reuse tends to be rather trivial. Reusing carbon and nitrogen by turning CO2 and nitrogen back into food is somewhat harder but closed loops are perfectly possible with space agriculture.

If we ever go for large scale colonization of anything, I believe aquiring nitrogen to fill living space with air is probably going to be one of the harder issues to solve. Once you make structures large enough, the mass of the air inside them tends to increase very rapidly. For O'Neill cylinders or martian air-filled domes, the air inside constitutes the majority of the total mass, and while finding the oxygen to fill them tends to be easy, making nitrogen in large enough quantities for use as a buffer gas tends to be a harder problem to solve. Even for small colonies it can be a bottleneck as it is needed to make fertilizer.

That's for the inner solar system. The outer solar system is very rich in volatiles of all kinds. A colony there would likely never be limited by chemical elements, and is more likely to be limited by energy requirements and travel time.
« Last Edit: 09/10/2014 05:41 pm by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Online guckyfan

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Re: Lifesupport System in Outer Space
« Reply #10 on: 09/11/2014 06:58 am »
recycling of O2 and H2O on the ISS is already at ~90%.  This is good enough for ferry missions and more than good enough for Mars.  Very high closures are hard to achieve and may not be worth it initially.

Are you sure about the 90% on the ISS? My understanding was that 50% of the oxygen comes from eletrolysis of water. The produced hydrogen is then used in a Sabatier process to get the other 50%  from waste CO2. The produced methane is then dumped outside.

Online guckyfan

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Re: Lifesupport System in Outer Space
« Reply #11 on: 09/11/2014 07:04 am »
If we ever go for large scale colonization of anything, I believe aquiring nitrogen to fill living space with air is probably going to be one of the harder issues to solve. Once you make structures large enough, the mass of the air inside them tends to increase very rapidly. For O'Neill cylinders or martian air-filled domes, the air inside constitutes the majority of the total mass, and while finding the oxygen to fill them tends to be easy, making nitrogen in large enough quantities for use as a buffer gas tends to be a harder problem to solve. Even for small colonies it can be a bottleneck as it is needed to make fertilizer.

On Mars nitrogen is part of the air and is easily obtained in required amounts. Especially with large scale fuel ISRU for return flights to the earth, nitrogen will be a byproduct, probably in amounts far exceeding need for fertilizer and air. Even oxygen will likely be the same. Rocket engines are run fuel rich and the fuel production process produces O2 in stochiometric proportion to methane. So large amounts of oxygen will be produced in excess just as nitrogen.

On other places in the inner solar system I agree.

Offline KelvinZero

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Re: Lifesupport System in Outer Space
« Reply #12 on: 09/11/2014 08:01 am »
If we ever go for large scale colonization of anything, I believe aquiring nitrogen to fill living space with air is probably going to be one of the harder issues to solve.
I think the martian atmosphere is about 3% nitrogen. We don't seem to need it in our breathing air and there would be a couple of huge advantages of omitting it: reducing base structural stresses by a factor of 3, the ability to step straight from base to rover to suit without prebreathing.

It does seem sort of incredible that about 75% of the atmosphere we evolved in could be omitted without any bad side effects but we have discussed it here a few times and Im not aware of anyone producing evidence for it.

Online guckyfan

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Re: Lifesupport System in Outer Space
« Reply #13 on: 09/11/2014 08:20 am »
If we ever go for large scale colonization of anything, I believe aquiring nitrogen to fill living space with air is probably going to be one of the harder issues to solve.
I think the martian atmosphere is about 3% nitrogen. We don't seem to need it in our breathing air and there would be a couple of huge advantages of omitting it: reducing base structural stresses by a factor of 3, the ability to step straight from base to rover to suit without prebreathing.

It does seem sort of incredible that about 75% of the atmosphere we evolved in could be omitted without any bad side effects but we have discussed it here a few times and Im not aware of anyone producing evidence for it.

Yes it has been discussed on this forum. No evidence that a nitrogen componenent is needed was presented. It may well be a good option for a research station with a scientific crew. Nevertheless it will need more than that for me to be convinced that it is the best solution for a colony, where everyone from pregnant women to newborns to the disabled and sick needs to live under those conditions. I am sure, data are out there even if we don't know them. If not work on the matter needs to be done.

Data to validate or invalidate my or your position.


Offline Stormbringer

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Re: Lifesupport System in Outer Space
« Reply #14 on: 09/11/2014 02:42 pm »
ask the poor spouses of the Apollo crew that got incinerated in their capsule if there is no drawback to omitting nitrogen from their air. There is at least one: living without diluting gases in an oxygen environment will kill you sooner or later especially as so many things that have to be done will generate an ignition source.

and i also vaguely recall that pure o2 damages biological tissue in various ways. I don't recall from where i read that but that is the feeling i get from the vast swamp of my memory. :)
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Offline hopalong

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Re: Lifesupport System in Outer Space
« Reply #15 on: 09/11/2014 03:46 pm »
In my personal view, the atmosphere should be as close to earth standard as we can reasonability manage. We do not need 1000Mb pressure, something in the order of 800Mb (Say Denver) will be fine for 99% of people (I am an overweight asthmatic, I was fine in Denver, a tad uncomfortable at the top of Pikes Peak). The percentage of oxygen can always be increased by a point or two.

 Having a ‘high’ pressure environment does give extra engineering difficulties, but I think it would be worth it for the following reasons –

It is what we evolved to live in.
Sound travels well – I remember that they had issues in Skylab with hearing each other (Skylab used low pressure 100% oxygen).
Cooking – water still boils at high enough temperature to cook things @93’C
Nitrogen is needed as a buffer gas.
Many plants need nitrogen in the air to grow – people will want plants around them and not just in the CO2 rich greenhouses.


Offline momerathe

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Re: Lifesupport System in Outer Space
« Reply #16 on: 09/11/2014 04:04 pm »
ask the poor spouses of the Apollo crew that got incinerated in their capsule if there is no drawback to omitting nitrogen from their air. There is at least one: living without diluting gases in an oxygen environment will kill you sooner or later especially as so many things that have to be done will generate an ignition source.

and i also vaguely recall that pure o2 damages biological tissue in various ways. I don't recall from where i read that but that is the feeling i get from the vast swamp of my memory. :)

Oxygen toxicity is related to the partial pressure; a low-pressure-pure-oxygen atmosphere has no demonstrated adverse health effects.

The same applies to fire hazards - Apollo 1 had a pure-oxygen atmosphere at above atmospheric pressure
thermodynamics will get you in the end

Offline Nilof

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Re: Lifesupport System in Outer Space
« Reply #17 on: 09/12/2014 12:26 am »
The apollo missions all used pure oxygen atmospheres at one third of sea level pressure. The issue with apollo one was that the inside of the capsule had to be pressurized at above sea level pressure before launch, and on the first mission they used pure oxygen for that, which went horribly. Later missions had the capsule pressurized with regular air which was steadily vented during ascent. When the astronauts removed their helmets most of the nitrogen would be gone. They still breathed pure oxygen inside their suits before and during the launch to avoid the bends as the pressure decreased during launch.

The pure oxygen atmosphere did cause some problems with oxygen toxicity though. Skylab used the same pressure as the apollo capsule(since the two had to dock) but it used a mixed atmosphere with about two thirds oxygen and one third nitrogen.

The one-third to one half of sea level pressure range is probably the sweet spot for medium-term habitats since it allows for fast EVA's without decompression. A higher pressure is a luxury, but on the other hand it is likely to be a rather desired one. Less water evaporating from membranes in your body, an improved sense of taste, better hearing ect ect. Future colonists are likely to want to spend some time in higher pressure environments.
« Last Edit: 09/15/2014 10:52 am by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline KelvinZero

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Re: Lifesupport System in Outer Space
« Reply #18 on: 09/12/2014 01:33 am »
As an aside, I have this pet SF idea that air pressure becomes a class status thing (this was on the moon though)
Earth sealevel pressure in the cities, for white collar workers and people who are "loyalists". Blue collar workers live in the lower pressure pure oxygen environment. It creates a huge class division because passing from one side to the other (at least from high to low) is as bothersome as taking an international trip on earth.

Whenever I see discussions like this it just makes me think about what we should be doing right now. There are several issues that would be addressed by a DSH prototype attached to the ISS. Multi-year experience in pure oxygen could just be one of them. Some of these things will just take time, but we have that time. We have at least ten years to prepare for the first two year mars mission.

The only thing Im really worried about is that in ten years time we will still have think big plans for mars but have made no more attempt to answer these basic questions that can be investigated in LEO or even without leaving earth.

Offline hop

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Re: Lifesupport System in Outer Space
« Reply #19 on: 09/12/2014 09:14 pm »
a low-pressure-pure-oxygen atmosphere has no demonstrated adverse health effects.

The same applies to fire hazards
This is not really correct. ~4 PSI pure oxygen is far safer than 17 PSI, but it's not the same as air. To sustain combustion in air, you need to heat up a bunch of effectively inert nitrogen. Similarly, the heath issues aren't as cut and dried as you suggest. See the references in this old post http://forum.nasaspaceflight.com/index.php?topic=26898.msg814693#msg814693

I'd still put my money on a pressure similar to inhabited altitudes on Earth (e.g Denver or a bit above) with a modestly elevated O2 fraction. The benefits of going to greater extremes don't appear to be very compelling.

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