Needed: Medium & Long Term Life Support Systems (TACLS)

[stratochief66]

For missions longer than 2 week Gemini/Apollo missions, the parts for life support are a bit lacking, I think.

[ ] Water - Currently, water is once through. Both real world and in-game research is needed to check if parts already exist for partial water re-cycling (ie. moisture removal from air, urine recycling, etc.). This is a rather complex issue in-game, I think, since it would need to be implemented in such a way that some water ends up as un-cycleable waste, as is realistic.

[ ] CO2 - As best I know, only the custom Skylab part has a sane post-Apollo CO2 scrubber. This part just extracts CO2 from the air, which is better than existing LH scrubber systems)

Further research is required to determine if we already have a more modern CO2->O2 converter (for O2 re-use rather than removal once it is bound to C) or if that is even feasible. So, both game side and real science research.

RealismOverhaul/GameData/RealismOverhaul/RO_SuggestedMods/RaiderNick/RO_RN_Skylab.cfg

Lines 139 to 145 in b100bdb

	MODULE
	{
	name = TacGenericConverter
	converterName = CO2 Extractor
	conversionRate = 6.0 // # of people - Figures based on per/person
	inputResources = CarbonDioxide, 0.006216, ElectricCharge, 0.10 // See RO Github #844 & #1146 for explanation of values
	}

@Schnobs tag, because we were talking LS.

[Schnobs]

Just left a large comment on CO2 scrubbing in #1146.

About reclaiming water: as per Wikipedia and http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100033089.pdf, the machinery takes up two "racks" and by the looks ought to be of substantial weight. No word about power demands; from description I expect <1500W, maybe as little as 300W.

It can reclaim about 70% of urine (up to 9kg/day, 6-person equivalent) and most everything coming in from drains and condensers (nominal 5+kg hour, actual average over 1.5 years is 73kg/day; may include downtimes).

As best I can tell, stool is not collected for reclaiming water.

It requires some flourine (mg/day) and filters need to be swapped regularly. From the sound of it, every couple of days, so not much waste from filters. But of course, 1.5kg of brine from urine.

That's a 2000s device but I don't think there's any recent breakthroughs involved. Something functionally similar could be had in the 80s as well, even 1970s. Probably not as lightweight, but working.

I'd like to know more about what the russians did on their stations.

[Schnobs]

Say, can it be that the whole LS needs a workover?

FoodConsumptionRate = 6.77E-05      // 5.84928 / 1640g /day
WaterConsumptionRate = 4.48E-05     // 3.87072 /day
OxygenConsumptionRate = 0.00685     // 591.84 / 833g /day
EvaElectricityConsumptionRate = 0.3333
CO2ProductionRate = 0.00592     // 511.488 / 997g /day
WasteProductionRate = 6.16E-06      // 0.532224 / 399g /day
WasteWaterProductionRate = 5.7E-05  // 4.9248 /day

stratochief comment: food contains lots of water, so yes, more waster water out. water and ww have different densities I think, but not enough to account for much difference.
schnobs: (waste)water have identical densities (1.005). Which is ok, really. Food bugs me, though: 1600g is the wet weight of what I put on my table. Density ~0.28 indicates either freeze-dried fruit (not powdered), or very bulky packaging.

Regarding water, it seems as if gray water (from sinks and AC) is easy to recover at near 100% efficiency.

Depending on mission and equipment, there either was very little washing water (Apollo &c) or it was recovered (Saljut); Skylab may be the exception. I'd therefore propose to just ignore gray water for purposes of wastewater.

[SirKeplan]

sounds like the crew are eating quite moist food.

[Schnobs]

Proposal:
A: we assume 4l per person-day

• 3l/day are actually needed as water (remainder assumed to come from food)
• 1.5l of wastewater (=urine) per day

B: a vessel may have

• no water reclaiming (most capsules);
• a basic reclaiming system, creates 2.5l of water/person-day from condensate. 1970s. (I suggest to make this a CO2->Water converter so you only get your crew's worth of water)
• wastewater purifier, 66% efficiency for 1l of water from 1.5l urine. About 1990 (first soviet system 1989).

That way, a Saljut-like station needs a net 500ml per person-day, while ISS creates a slight excess of 500ml. Which isn't quite enough to replenish lost oxygen (833g needed per TACLS, 500g water yields 444g O2 at best).

Question: is it possible to make a TACLS converter that sheds excess resources? Would be evil if you couldn't dispose of CO2 just because your water tank is full.

Edit: dang, forgot about stool. AFAIK it's still waste, even today; and not exactly dry matter.

Answer: IIRC, that is what the 'True' element means here. As in True, keep running if the output is full and dump the excess.
https://github.com/KSP-RO/RealismOverhaul/blob/master/GameData/RealismOverhaul/RO_SuggestedMods/FASA/RO_FASA_ApolloCSM.cfg#L614

[Schnobs]

OK, this won't get any further until we settle on some assumptions about resources needed and wasted.

(edit: removed longish bit about weights and densities, to be taken to KSP-RO/TacLifeSupport#34)

[stratochief66]

Can you do a comparison of your stated desired values with what TACLS for
RO has now?

I have a few problems with changing the consumption and waste production
values as you've suggested.

First, if we change the TACLS rates, that means every crewed part in RO
would in turn need to be adjusted (again) and I'm not going to do that,
I've done it enough times. (operational complaint. simply, if someone is
willing and does the work and test to confirm, this complaint goes away)

Second, citations please. I don't expect your citations to match precisely
the values you've suggested, but they will provide background support and
bracketing bounds on reasonable values. (should be easy to address, I know
you research these things and don't bring them from whole cloth, you just
should save them in these Issues threads)

The paper I found the most easy to digest and contain lots of useful data
and citations:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040012725.pdf

Suggests 0.09kg + 0.06kg = 0.15kg of solid waste per day from stools,
0.06kg solids from urine per day.

I would suggest we seek a source for estimating food carried for a Mars
mission. I expect that they would suggest going the 'American' route for a
few reasons. First, rehydrated dehydrated food makes sense in a largely
closed water system. Why pack lots of water in food, when it can be
introduced to calorically dense food using recycled water? Both the Russian
and American routes for food make sense in LEO. I'm unsure how best to
handle that, I'd like to think that can be/has been abstracted away in the
way TACLS handles resources.

@NathanKell (or anybody), any idea where the value for the density of food
originiated from in RO/TACLS?

On Sun, Aug 21, 2016 at 6:06 AM, Schnobs notifications@github.com wrote:

OK, this won't get any further until we settle on some assumptions about
resources needed and wasted.

Regarding food, I'm getting the impression that there's quite a difference
between the russian and american approach. US tended towards dehydrated
stuff, that could be reconstituted with "free" water from fuel cells.
Soviets were doing duration records without fuel cells, necessitating a net
influx of water; they could afford a wetter selection of foods. I see lots
of tin cans there (or probably aluminum, but cans nonetheless).

Likewise, we can adjust our assumptions about food densities a little.

1600g "food" is perfectly alright; somewhat dehydrated, perhaps, so as to
include other consumables like paper napkins, soap and whatnot. 50% water
content perhaps? I'm not happy with the density, though, 0.28 is way too
light. I'd expect one of these vacuum pouches to be on the order of 0.8,
and a bundle of them held together by a rubber band >0.4; cans would be
0.7-0.85 depending on how you stack them.

1200g wastewater/day seems like a reasonable average.

Stool varies a lot. No matter what number we pick, it will be wrong. I
suggest 400g/day with 75% water content. That would be "waste".

Another 200g of waste per day from this and that, does that sound right?

A trash bag worth of plastic packages is very lightweight. Even allowing
for some compacting, and tossing in the stool, waste density should be
lower than that of packed food (currently it's 0.75).

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[Schnobs]

(Talk about resources needed / created removed, taken to TACLS)

[Schnobs]

To be continued in KSP-RO/TacLifeSupport#34 for now.

[Schnobs]

About the MIR urine treatment system:
http://www.nap.edu/read/9892/chapter/8#118
"has been in operation aboard Mir since January 1990. This system was designed primarily for regenerating cabin oxygen through electrolysis."

The treatment starts out very similar to the US system above. Destillation-condensation, most is recovered, some brine is discarded. Main difference is that they skip the last few steps, don't deal with volatiles in the destillate. They're content when it can be used in an electrolyzing unit without clogging it up.

ETA: per Wikipedia, "a 100%-efficient electrolyser would consume 39.4 kilowatt-hours per kilogram (142 MJ/kg) of hydrogen" -- that would be ~2kWh/CM-d for oxygen, 85W continuous power. Actual efficiency is probably way less than 50%, plus whatever pretreatment takes. 300W overall perhaps?

[morden96]

All US spacecraft prior to ISS either depended on H2/O2 fuel cells (Apollo/STS) which provide a surplus of water or transported all the water from the ground (Gemini/Skylab). The Soviets had more experience with long-term life-support over that period that the US did. Their first water recycling system was tested in 1974 on Salyut 3, however it was limited to condensing water from the atmosphere (ie no purification of waste). By Salyut 6 in 1977, they had systems capable of recycling 50% of their wastewater.

[ctiberious]

The CO2 scrubbing systems we have (i.e. talked about in #1146 ) represent fairly early systems. Skylab, and later ISS, did away with the older Apollo/Soyuz systems, but don't represent a good "Medium & Long Term" system. Skylab and ISS (at least until 2011) handled CO2 by simply collecting it and dumping it into space. This is only a good solution when you can continuously resupply. But it's a lot of waste when you're talking about long term, long distance missions (like moon and mars bases).

In 2011, ISS added a Sabatier Reactor which recycles CO2 into Water and Methane. The water gets converted back into breathable air. Currently, the Methane gets collected and dumped into space. But the goal would be to make use of the Methane rather than dumping it. Either as a fuel source or (as a better life support solution) in a pyrolysis reaction to free up the hydrogen for reuse in the Sabatier Reactor.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120016419.pdf is an interesting document that talks about a newish, light weight Sabatier reactor that boasts near 100% efficiency.
http://www.chemicalprocessing.com/articles/2015/researchers-crack-methane-cracking/ is a report from 2015 about Methane Cracking which reliably converted about 70% of the methane put through the process into hydrogen gas and carbon.

Based on this research, you can see nearly closed systems which simply rely on having a steady supply of electricity.

1. Electrolysis of water to produce breathable air and hydrogen (4 H2O nets 4 H2 + 2 O2)
2. Hydrogen and CO2 (from respiration) put through a Sabatier Reactor to produce water and Methane (4 H2 + CO2 nets CH4 + 2 H2O)
3. Methane Crack to free up remaining hydrogen (CH4 nets 2 H2 + C)
4. Resulting Carbon is collected as waste