Indefinite duration ECLSS general thread

[tdperk]

Proposing a thread to bring together information about the current state of the art in ECLSS technology and advancing the same, with respect to long term use, with expendables minimized if not eliminated.  But not how the electrical power which goes in to it is generated--

--just the nuts and bolts of breathing, drinking, raising ( and preparing, consuming) food, dealing with liquid and solid waste with recycling.

EDIT my apologies to any responders prior to this edit, I felt the original post did not quite express my concept of the thread.

[Coastal Ron]

Proposing a thread to bring together information about the current state of the art in ECLSS technology with respect to long term use, with expendable minimized.  But not how the electrical power which goes in to it is generated--

--just the nuts and bolts of breathing, drinking, raising ( and preparing, consuming) food, dealing with liquid and solid waste.

I hope this thread becomes popular, since it would seem to a lay-person like me that we'd have figured out long-term ECLSS by now, but that is obviously not true. So it would be very educational to hear what the challenges are, and what the potential solutions could be - and how soon they could be implemented.

[tdperk]

Links of general knowledge concerning long duration ECLSS.

https://en.wikipedia.org/wiki/Life_support_system

https://en.wikipedia.org/wiki/MELiSSA

https://en.wikipedia.org/wiki/CyBLiSS (article stub)

[tdperk]

Postulate that a useful approach to a workable system without over-engineering it, is to place analogs of human metabolisms into closed systems which could sustain them insofar as we know, and fix what breaks--applying lean decision tree making principles instead of attempting a 100% known flawless system from the outset.

[blasphemer]

I hope this thread becomes popular, since it would seem to a lay-person like me that we'd have figured out long-term ECLSS by now, but that is obviously not true.

Indeed, I was also pretty surprised about how little research there was in closed loop life support systems. Especially since this is not something that must be developed in space, you can easily mature such system on Earth and it could have applications on this planet, too.

https://en.wikipedia.org/wiki/Biosphere_2

Biosphere 2 was an attempt to make a closed loop ecosystem, something similar might be a basic requirement for long term living in space.

[tdperk]

I hope this thread becomes popular, since it would seem to a lay-person like me that we'd have figured out long-term ECLSS by now, but that is obviously not true.

Indeed, I was also pretty surprised about how little research there was in closed loop life support systems. Especially since this is not something that must be developed in space, you can easily mature such system on Earth and it could have applications on this planet, too.

https://en.wikipedia.org/wiki/Biosphere_2

Biosphere 2 was an attempt to make a closed loop ecosystem, something similar might be a basic requirement for long term living in space.

Given the acrimony of the participants, and the surreptitious nature of some actions taken to avoid collapse of the system--I'm not sure what Biosphere 2 was.

I'm thinking a handful of rats and figure out how to make plants/fungi/air/water they can eat/breath/drink out of their waste with only electricity as an input for a year running.  Then figure out how to make it work and start from a cold stop in weightlessness.  Another goal would be always minimizing what must be removed and become bio unavailable and what must be introduced from stock.

[Johnnyhinbos]

Though perhaps tangentially related, Elon has tweeted that images of the SpaceX flight suit will be released this week - so we'll get at least a peek into one component of the SpaceX ECLSS system...

[tdperk]

Though perhaps tangentially related, Elon has tweeted that images of the SpaceX flight suit will be released this week - so we'll get at least a peek into one component of the SpaceX ECLSS system...

No so much related.  Spacesuits have a very definite duration to them.

[A_M_Swallow]

Though perhaps tangentially related, Elon has tweeted that images of the SpaceX flight suit will be released this week - so we'll get at least a peek into one component of the SpaceX ECLSS system...

No so much related.  Spacesuits have a very definite duration to them.

Although a space ship's ECLSS may be able to recharge the spacesuits.

[Johnnyhinbos]

I believe the suits plug into the ECLSS, rather than being on an independent supply.

[Coastal Ron]

Sort of related:

Astronaut Pee and Sweat Could Be the Key to Getting Humans to Mars - Gizmodo

"Researchers from Clemson University are studying how molecules from astronauts’ sweat and pee can be converted into plastics that can be used for tools aboard a spacecraft.?"

Recycling in a different way...

[speedevil]

Biosphere 2 was an attempt to make a closed loop ecosystem, something similar might be a basic requirement for long term living in space.

I question if it was anything remotely close.

Biosphere II is to a serious attempt at a closed loop ECLSS  what Mad Max is to a serious attempt at predicting future society.(*) (I note Mad Max beyond the thunderdome is set ~2018, so maybe we've got time)

Biosphere II weighed of the order of half a million tons. To support four people. Call it a hundred thousand tons a person.

A hundred thousand tons of resources will supply one person for quite a long time indeed, with open-loop recycling, indeed of the order of 500 people for 70 years at 10kg/day.

Consider which loops it's worth closing.
Closing only the water loop (partially), and recovering from dehumidifiers and urine, with oxygen and dehydrated food gets you to pretty close to a kilo a day.
Electrolyse the water to get oxygen, and you're at about half a kilo.

You're now looking at 6 tons of supplies for 30 years.

It'd be moderately challenging to design a garden in 6 tons to produce enough food for one person, even assuming optimum conditions and no need for ECLSS type functions.

At some point you should probably wonder if investing $100M in improving palatability and nutrition of dehydrated food is a better return than ECLSS that is more than closing the water loop, plus a greenhouse for occasional tasty treats.

*)  Mad Max beyond the thunderdome is set ~2018, so maybe we've got time

[speedevil]

I recently came across https://www.carbontrust.com/media/672719/calysta-feedkind.pdf .

This is a process to convert methane into protein edible by animals (they are initially targetting fish).

Their efficiency - in somewhat strange units admittedly of CO2 emitted per ton of protein is around 25% or so.
So, it takes ~400W of methane, to power a 100W human.

Is this diet optimal - clearly not. But it sets an interesting starting point.
Clearly, you would also need to recycle the H2O and CO2 back into methane, oxygen and water, as well as deal with trace contaminents, but this sort of 'hard' recycling could add a _lot_ of robustness to a garden based approach. Or allow you to stretch stores.

[AncientU]

Biosphere 2 was an attempt to make a closed loop ecosystem, something similar might be a basic requirement for long term living in space.

I question if it was anything remotely close.

Biosphere II is to a serious attempt at a closed loop ECLSS  what Mad Max is to a serious attempt at predicting future society.(*) (I note Mad Max beyond the thunderdome is set ~2018, so maybe we've got time)

Biosphere II weighed of the order of half a million tons. To support four people. Call it a hundred thousand tons a person.

A hundred thousand tons of resources will supply one person for quite a long time indeed, with open-loop recycling, indeed of the order of 500 people for 70 years at 10kg/day.

Consider which loops it's worth closing.
Closing only the water loop (partially), and recovering from dehumidifiers and urine, with oxygen and dehydrated food gets you to pretty close to a kilo a day.
Electrolyse the water to get oxygen, and you're at about half a kilo.

You're now looking at 6 tons of supplies for 30 years.

It'd be moderately challenging to design a garden in 6 tons to produce enough food for one person, even assuming optimum conditions and no need for ECLSS type functions.

At some point you should probably wonder if investing $100M in improving palatability and nutrition of dehydrated food is a better return than ECLSS that is more than closing the water loop, plus a greenhouse for occasional tasty treats.

*)  Mad Max beyond the thunderdome is set ~2018, so maybe we've got time

Merit function isn't mass alone, it includes cost and sustainability.  While stockpiling tonnes of supplies gives a system robustness, unless the ECLSS systems (not just food, but it is the example on the table -- so to speak) become able to solve the problem indefinitely without supply of consumables from off-planet, then ECLSS is still not up to the task.

On day one on Mars, for instance, the ECLSS should carry a majority of the load for air regeneration, part of the load for recycling water, and very near zero of the load supplying food -- so it's not all or nothing. 

Air: Initial atmosphere will be regenerated during the transit and reserve volumes will be held in tankage; this will start to change after landing.  Make-up oxygen will soon need to be made from in-situ resource water (with the hydrogen used for propellant generation or directly), carbon dioxide will be sent overboard, nitrogen will be extracted from in-situ atmosphere resources.  De-humidification will recycle to the water loop. 

Water: Gradually, say over the first few 100 days, make-up water supply can become totally ISRU derived, and the storage tankage recharged as an emergency supply; recycling needs to supply a large percentage of the water used (not 100%, though) and the rest can come from in-situ resources.  Grey water will eventually become a principal supply for agriculture.  (Note: this is a great example of why we don't need to make the ECLSS 100% closed loop/bullet proof/never fail/extraordinarily expensive.)

Food: Will start off as 100% from delivered supplies.  Early agriculture will be more testing and experimenting than production.  Food crops will gradually come on line, one at a time, and begin to replace delivered supplies.  This process could take several synods to approach self-sustaining of basic nutrients; 'luxury' foodstuffs (e.g., coffee, chocolate) will continue to be shipped in indefinitely.

[savuporo]

Indefinite duration of reading materials:

https://www.google.com/search?q=site:ntrs.nasa.gov+iss+ECLSS&tbs=cdr:1,cd_min:1/1/2010

Just one hit:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170005618.pdf

[zhangmdev]

Biosphere 2 is an experiment with artificial biomes. A few hundred square meter of ocean is not an ocean. It is a grossly simplified model of ocean. Same goes with the wetland, the grassland, and the desert. They can hardly sustain themselves, let along supporting a handful of people. Subsistence farming on a quarter of hectare of land? Maybe that is possible to support a small family, if they grow rice or maize. But that would be living dangerously on the edge. There is no margin for error. If anything goes wrong, plight, pest, drought, people will starve.

I think using some miniaturized biome as life support system will be very difficult. It needs to be impossibly large and complex to be viable. Very hard to test it to make it reliable.

Better approach will be developing more efficient way to produce food. Food provide more energy per gram than rice, while using less resource, light, water, labor, space, and time to grow.

Comparing to food, water and air supply is relatively easy.

[speedevil]

Merit function isn't mass alone, it includes cost and sustainability.  While stockpiling tonnes of supplies gives a system robustness, unless the ECLSS systems (not just food, but it is the example on the table -- so to speak) become able to solve the problem indefinitely without supply of consumables from off-planet, then ECLSS is still not up to the task.

This seems to be an odd, and meaningless distinction.
As one extreme point, if your ECLSS system can - with limited closed loop, supply for more than the lifespan of the astronaut, and your garden based solution masses more, how is either one 'more sustainable'.

As another, you're going to have to for the forseeable future trade mass for gardening with mass to be able to do ISRU stuff, or more crew, or more comforts of home.

Sustainability is a basically meaningless question on Mars in the full sense unless you can make _everything_ including semiconductors and all of the thousands of tiny niche items.

For a large amount of stuff, we already pay the equivalent of >$1000/kg for it. Why would you make this locally on mars, if the plant to make it is tens or hundreds of billions of dollars and weighs megatons.

Proper design of the ECLSS needs to include minimising its cost as a fraction of the whole system, so as to make the whole system economic.

Carefully considering what is an 'idyl' and what is actually required is important.
If you drive your requirements so you can have grassfed steak for every meal, well, that is a choice, but it's very much a choice that impacts negatively on your requirements.

If your astronauts are eating food that is better than 50% of the population at home, you're probably doing it wrong.

[speedevil]

As one datapoint.
I came across some interesting papers from the 80s.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880002887.pdf

To sum up.
Potatos, grown in 24h light, at 75W/m^2 of the right sort of LEDs can produce enough to feed one person in 39m^2 of field, for a total of 3kW of light, 39m^2 of area (this can obviously be stacked).
A pessimistic figure of 100kg/m^2 of 'farm' equipment including soil would mean that the entire farm module could come in well under 10 tons per person, compared with biosphere II's 100000 per person.
Increase this to 5kW, and you can do it in 25m^2.

[ThereIWas3]

I'm reading Scott Kelly's book "Endurance" about his year on ISS.  The most troublesome piece of equipment they had on board was the CO2 scrubber, referred to as a CDRA ("Sidra").  There were actually two of these and they were constantly breaking down and Houston only would power up one of them at a time.   Each was about the size of a car engine.

Kelly thought that NASA was allowing the CO2 levels to get too high most of the time.  One CDRA could theoretically deal with the CO2 produced by 6 residents (if it kept running that is).  Having more than 6 people on board would require both CDRA's working.   BFS with its much larger potential passenger count is going to need something more efficient and more reliable.

[A_M_Swallow]

I'm reading Scott Kelly's book "Endurance" about his year on ISS.  The most troublesome piece of equipment they had on board was the CO2 scrubber, referred to as a CDRA ("Sidra").  There were actually two of these and they were constantly breaking down and Houston only would power up one of them at a time.   Each was about the size of a car engine.

Kelly thought that NASA was allowing the CO2 levels to get too high most of the time.  One CDRA could theoretically deal with the CO2 produced by 6 residents (if it kept running that is).  Having more than 6 people on board would require both CDRA's working.   BFS with its much larger potential passenger count is going to need something more efficient and more reliable.

There are several firms working on ECLSS equipment. Have they produced a CO₂ scrubber for say 12 people that can work for at least 6 months?