eggrobin

Cross-posting this from the realism overhaul thread. I made models for an electrolyser and a fuel cell (technically a 12-cell stack). They are available at https://drive.google.com/folderview?id=0B4y-shYXMH9BcEhsUWNyLXpXZEU&usp=sharing. Electrolyser (from the Elektron diagrams, ignoring safety features such as a blast-proof housing and a nitrogen pressure hull). Fuel cell (from tweaking the previous model and looking at the Apollo Operations Handbook). It's shown packed inside a service module with RCS tanks, O2 tanks, with MechJeb providing some awkward lighting. Caveat: I do not use the same colour-coding as regex for O2, H2 and H2O. I sort of followed ISO 14726 for the pipes (http://www.maritimeprogress.com/downloads/M2-Pipe-Identification-Tape-to-ISO14726.pdf) and although this is probably bad practice, I used the same colour-coding for the tanks. It follows for instance that the O2 tanks in the electrolyser and fuel cell are gray-blue-gray (this happens to match the tanks in the Mk1 pod and on the launchpad), while the regex O2 tanks are yellow. Water is okay, it's blue. EDIT: Updated version, CEN EN 1089-3 compliant. Regarding licensing, This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

jrandom: I have tweaked the electrolyser model and called it a fuel cell (changes include, but are not limited to, a condenser and coolant pipes, a single H2 -> cell -> H2 + H2O -> Condenser -> Centrifuge -> H2 loop, reversing all the arrows, painting it black, making the cells look like stock batteries). I have also tweaked the electrolyser a bit (nicer pipe labeling, added a vane). It will take me a while to figure something out for the Bosch and Sabatier reactors (not to mention the water recovery system), so you can already integrate this if you want. Caveat: I do not use the same colour-coding as regex for O2, H2 and H2O. I sort of followed ISO 14726 for the pipes (http://www.maritimeprogress.com/downloads/M2-Pipe-Identification-Tape-to-ISO14726.pdf) and although this is probably bad practice, I used the same colour-coding for the tanks. It follows for instance that the O2 tanks in the electrolyser and fuel cell are gray-blue-gray (this happens to match the tanks in the Mk1 pod and on the launchpad), while the regex O2 tanks are yellow. Water is okay, it's blue. Screenshots (The weird lighting is from a mechjeb module. I tried to see how it looked crammed with other things inside a service module.) The models and texture are available in the same place, under the same license.

It should be fairly easy to retexture this for the other recyclers, but I intend to just change the model a bit for the fuel cells (they should be quite similar, but with only one loop (cell -> O2+H2O -> centrifuge -> O2 -> cell) and H2 pressure being maintained on the other electrode). The other recyclers should probably look quite different in order to make sense; I need to think about that.

I made a model for an electrolyser (https://drive.google.com/folderview?id=0B4y-shYXMH9BcEhsUWNyLXpXZEU&usp=sharing, you'll want to use a scale and rescalefactor of 1.125 in the TACLS Water Splitter cfg to get the result above): It somehow looks awkward though, should I try to put a couple of carter panels so that the rocket looks more continuous? I tried to stay away from the 'textured cylinder' look, as there are going to be a lot of recyclers: electrolyser, Sabatier reactor, Bosch reactor, fuel cell, water recovery system, etc. It would be difficult to come up with convincing and distinctive textures for all of these (how do you make texture for a Sabatier reactor that distinguishes it from a Bosch reactor?). As far as licensing goes, This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

That's what I meant. I think for now, we can just go with Oxygen and Hydrogen for life support, LiquidOxygen and LiquidH2 for propulsion, and we can decide what they are when we define a tank. The biggest challenge remains the naming of the life support to propellant converter.

Technically, the fuel cells use gases (the stuff is just stored as a liquid, see the SM2A-03-Block II-(1) Apollo Operations Handbook, page 2.6-21/2.6-22: the O2 and H2 go through a preheater before reaching the fuel cells (or the CM)). In many life support systems (e.g. Apollo, STS), the O2 used for breathing is also stored as a liquid, so we might as well argue to replace Oxygen with LiquidOxygen altogether. The density of resources in KSP is not fixed however, so we could have denser 'cryogenic' tanks for Hydrogen and Oxygen (LS) as well as the normal ones. If having different densities for the same resource is a problem, we can just assume everything to be liquid. Having one resource per physical state is problematic anyway: the density depends on the temperature and pressure of storage. I think the dichotomy here really is the circuit the O2/H2 is in (life support vs. propulsion) rather than the physical state.

The life support consumption includes the carbon scrubbers (which are assumed to be regenerative in TAC). You should probably rescale the EvaElectricityConsumptionRate in TAC too. For reference: the Orlan spacesuit consumes ~54 W, A7L consumed ~48 W. 50 W seems to be a nice round number. Regarding LOX/LH2: the point is not so much their state (O2 and H2 seem to always be stored as liquids for fuel cells), but the separation of the life support and propellant circuits. I have found no instances where LOX/LH2 used for life support was also used for propulsion. While it may be useful to use O2 and H2 from electrolysis as a propellant (there could be a converter for that), you don't want the Apollo fuel cells to start using up the propellant from the S-IVB. We already have a separate Oxygen resource for life support oxygen, so having a separate Hydrogen resource doesn't seem too outlandish. We don't really care about the physical state of the life support resources. This allows for accurate modeling of the Apollo life support system: the same Oxygen supply is used for breathing and power/water production. The Hydrogen and Oxygen used to power the fuel cells is completely separate from the LiquidH2 and LiquidOxygen used to propel the spacecraft. (They are all liquids, but the point isn't really the state they are in, we only care about their intended use.) This is also how the STS life support system worked. For fancier mission profiles such as sending electrolysers to Mars in order to produce LH2 and LOX to go back, a converter from Hydrogen and Oxygen (the life support stuff) to LiquidH2 and LiquidOxygen (the propellants) could be used. Whether we call that a liquefaction unit, a glorified pump or an atomic cat remains to be seen. As far as methane goes, unless we want to model pyrolysis, we can get away with modeling the Sabatier reaction as a the following kind of converter: CarbonDioxide (LS) + Hydrogen (LS) --> LqdMethane (MFS) + Water (LS). The correct amounts are left as an exercise to the reader.

I'm confused... That means a new (life support) Hydrogen resource, the LiquidOxygen and LiquidHydrogen are already in MFS/RF. Do you mean additional liquid life support O2 and H2? That would be terribly complicated, you would have 3 kinds of oxygen and hydrogen (LS gas, LS liquid, propulsion liquid) and you would need converters between the 3. I was thinking about having 2 kinds of those: the life support variant (gas) and the existing liquid propellant. The problem is of course that some life support systems use LOX and LH2, but we can ignore that (just make tanks that have the right density). Boiloff shouldn't be too much of a problem for the life support O2/H2 if the Wikipedia article on Apollo 13 is to be believed:

I'm not sure what to think about that. On the one hand, there are projects to use hydrogen from electrolysis as fuel, and that would allow for accurate modeling of the Sabatier reaction. (It just has to produce LiquidMethane. There are plans to use that as fuel too.) On the other hand, you then need to use the Oxygen from the electrolysis as fuel too, so it should be LiquidOxygen, but that interferes with the nice kerbal*day numbers. Moreover, for most applications, you want to keep the O2 and H2 life support circuits separate from the propulsion system. You wouldn't want the fuel cells to start drawing from your transmunar injection fuel... I think the way forward is to keep O2 and H2 as separate resources, as they are used in fuel cells, kerbals etc., and to have a life support to propulsion interface that converts Oxygen to LiquidOxygen and Hydrogen to LiquidH2 (I think they are supposed to be gases in the TACLS system, so this could just model the liquefaction). Methane can be LiquidMethane without any harm. (Unless you want to model methane pyrolysis. Actually this is a very realistic alternative to the Bosch reaction for closed-circuit life support. We are doomed.)

The numbers look good. I'll check them in more detail (and finish my electrolyser model) when it is not 04:44.

Do not forget to rescale the ElectricCharge requirements (Also, I had not yet downloaded the latest version. I keep missing posts and edits in this conversation...)

It probably makes sense to match the outputs rather than the inputs for these. If you have a CO2 supply (on Duna) and a Bosch reactor rated for 3 kerbals, it would be embarrassing to have them suffocate, same if you are shipping water (as on the ISS).

Elektron is actually just the electrolyser. The ISS Water Recovery System is called the Water Recovery System (they plan to extend it. It will be called the Extended Water Recovery System), and Bosch reactors don't quite exist yet (in space). The conversion rate is too high if you just want to sustain three kerbals though: conversionRate=1 supplies 4.23 kerbals with oxygen, and is thus equivalent to Elektron. conversionRate=n is equivalent to n Elektrons. The water purifier should get between .8 and .94 Water out of 1 WasteWater, and the Waste should be the mass difference (the stuff you send down in a Progress). See http://forum.kerbalspaceprogram.com/threads/40667-0-22-WIP-TAC-Life-Support-0-6-8Dec?p=807493&viewfull=1#post807493. Edited to add: I'm almost done with my electrolyser model (see some WIP screenshots: http://forum.kerbalspaceprogram.com/threads/40667-0-22-WIP-TAC-Life-Support-0-6-8Dec?p=831724&viewfull=1#post831724). It's Elektron (12 electrolytic cells with a pump-driven KOH loop) without any of these fancy unkerbal safety features such as a blast-proof housing or a pressure hull with an inert atmosphere (what could go wrong with hot gaseous hydrogen and oxygen aboard a spacecraft anyway?).

I had not heard of their existence on the ISS, but hydrogen-oxygen fuel cells were in the Apollo and STS spacecrafts. I computed some specifications for fuel cells (and better specifications for the electrolyser) on page 33 of this thread, so it should be fairly easy to make this part yourself while waiting for Taranis to add it. Edit: Actually, the hydrogen on the ISS is vented, so I'm quite sure they don't use it to turn oxygen back to water (that would be a great way of throwing power out the metaphorical window).

The various models of Elektron have weighed between 150 kg and 110 kg (http://www.jamesoberg.com/elektron2_tec.html). Stuff outside of stock KSP is light! (Well, light considering it has a pressurised hull with an inert atmosphere and a blast-proof housing).

You used my numbers for the Electrolyser, so that was based on kerbals. If you want to replicate the performance of Elektron, your Water Electrolyser should read inputResources = Water, 1, ElectricCharge 86400, // 1 kW * 1 day outputResources = Oxygen, 4.229055504417308397, false // Assuming 100% oxygen recovery. Reduce to your liking. I think 4 would be fine. Elektron does this in a day, so if you want to go with the small parts approach, setting conversionRate=1 allows for fine tuning of the capacity of your station by adding the right number of electrolysers. Again, as Mir had 2 of those and the ISS has 3, this seems to be a nice way to partition stuff.

I edited my post while you were replying to it, so you missed the consumption for the Water Purifier: 1 775 kJ for 4l. The WasteWater is sewage and grey water (and sweat &c) I think. Standard TAC assumes 2 kerbals have the same requirements as 1 human.

I would advocate making small recyclers (3-4 kerbals, maybe some 1-kerbal units) and using several of these. This is what happens in real life: the ISS has 3 Elektron units which supply oxygen for 3-4 crewmembers each, the Apollo service module had 3 fuel cells, Mir had 2 Elektron units, the STS had 3 fuel cells, etc.

Some of it is It turns out that there is a bug in your CO2 density: A big kerbal day is 112 g, this should be 1.12 kg. Using the corrected density, the amount of O2 produced makes sense. Bear in mind that the efficiency is more that 90%, as the theoretical maximum here would be ~0.969, the respiratory exchange ratio of your kerbals (the ones from TACLS have a respiratory exchange ratio of ~0.866, I guess they work less). The amount of Waste should be 0.32407407407407407 to conserve mass. The electric consumption looks good. The name is inaccurate though: there is no Sabatier reaction (CO2 + 4H2 --> CH4 + 2H2O) going on here (It is also possible to run a closed circuit with the Sabatier process, but you need to pyrolyse the methane, CH4 --> C + 2H2, and I haven't done the calculations for that). This is just the Bosch reaction (CO2 + 2H2 --> C + 2H2O, requires higher pressures and temperatures than the Sabatier reaction), coupled with an electrolysis (2H2O --> O2 + 2H2).

It is probably a good idea to abstract the Bosch reactor+electrolyser in a single part for now (this works in closed circuit as far as hydrogen is concerned, and the waste is indeed graphite), but the power consumption for that is on the order of 43 000 kJ for 840 g of oxygen. Calculations: 9959 kJ to turn 1 standard kerbal day of CO2 into 0.232 standard kerbal days of H2O 51776 kJ to split 1 standard kerbal day of H2O rescaling factor for O2: 1 big kerbal day = 840/429 standard kerbal days (9959 kJ + 51 776 kJ * 0.232) * 840 / 429 = 43 000 kJ (rounded to 3 significant figures) Edit: answer to the edit H2 is complicated. I don't know of any instances where life support O2 or H2 were also used for propulsion (I think there are plans for that, but there are plans for just about everything), so I'm not sure they should be identified with the MFS/RF LiquidOxygen resp. LiquidH2. Using it later on in a fuel cell might make sense if you need a really big battery.

I may be misunderstanding something, but your electric consumptions for the recyclers seem to be all over the place (from reading the cfgs). The electrolyser needs a whopping 954 kW to sustain 8 crewmembers (one ISS Elektron unit sustains 3 to 4 and consumes ~1kW), while the water purifier uses only 3 W to sustain 8 crewmembers (for some reason, the one that sustains 16 crewmembers is half as efficient). Note that (with existing systems) CO2 to O2 cannot consume less than electrolysis for a given amount of oxygen, as both the Sabatier and Bosch processes produce water. You might want to look at the the calculations I did on the TACLS thread (electrolyser and fuel cell, Sabatier and Bosch reactors), these are just linearly scaled performances for existing devices. Realistic masses can be found at http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40487/1/04-3358.pdf.

These are EC/day (1 EC/day = 11.57 mW under the usual assumption that 1 EC = 1 kJ). This means that the base consumption of a pod is 13.8 W, and that the additional consumption per kerbal is 27.7 W.

I don't think methanediol (methane-di-ol by the way, not methanedoil) makes much sense as Waste, considering that this mod assumes kerbals to be rescaled humans. Human solid waste is definitely not methanediol. Moreover, Waste encompasses more than this, as it also includes graphite from CO2 recycling, whatever remains from the reprocessing of waste water, etc. As far as methanogenesis is concerned, bear in mind that it produces methane, carbon dioxide, and water, not oxygen. Regarding methane though, you can get that from the Sabatier reaction (I gave the specs for a Sabatier reactor a couple of pages ago, just replace the Waste output with a [WhateverYourMethaneResourceIs] output). Remember to conserve mass. On an unrelated note, I made an electrolyser model inspired by Elektron (it's basically Elektron without any of that fancy blast-proof housing and inert atmosphere stuff, fitted awkwardly inside a cylinder). Suggestions and criticism are welcome (I have no experience with either modeling or texturing, so it's going to take a while to finish).

A 1-kerbal Sabatier CO2 reprocessing unit (source: http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40487/1/04-3358.pdf). MODULE { name = TacGenericConverter converterName = Sabatier Reactor conversionRate = 1 inputResources = CarbonDioxide, 1, Hydrogen, 3.4623213297201505, ElectricCharge, 300 outputResources = Water, 0.23258488055756316, false, Waste, 3.313853064479525, true } The main problem for the Bosch reactor seems to be that the catalyst is fouled by the graphite deposit. Apparently, newer catalysts solve this. This paper does not mention power consumption, but the operating temperatures seem to be similar. I just reused the characteristics from the 1971 prototype, assuming they can be replicated with non-expendable catalysts. A 1-kerbal unit: MODULE { name = TacGenericConverter converterName = Bosch Reactor conversionRate = 1 inputResources = CarbonDioxide, 1, Hydrogen, 1.7311606648600752, ElectricCharge, 9959 outputResources = Water, 0.23258488055756316, false, Waste, 2.481022167311451, true }

They already do (they are modeled as half a human). The specifications I am computing take this into account: the electrolyser above supplies a bit more than 3 kerbals, while Elektron supplies a bit more 3 humans. Using the SM2A-03-Block II-(1) Apollo Operations Handbook, page 2.6-19/2.6-20, as a reference (H2O produced at a rate of 2.297E-2 lb/(A*h), voltage 29 V), producing one TACLS unit of Water yields 18014 kJ (18014 ElectricCharge), so if we want to supply one kerbal with water, we will produce 208 W = 0.208 ElectricCharge/s. Compare with the OX-STAT panel's 750 W under normal Kerbol exposure at Kerbin, or with the Mk-1 Pod's life support consumption of 41.6 W. This seems reasonable. This yields the following spec for a 1-kerbal fuel cell, MODULE { name = TacGenericConverter converterName = Fuel Cell conversionRate = 1 inputResources = Oxygen, 3.7215675, Hydrogen, 7.443135 outputResources = Water, 1, false, ElectricCharge, 18014, true } or the following for a 3-kerbal fuel cell. MODULE { name = TacGenericConverter converterName = Fuel Cell conversionRate = 3 inputResources = Oxygen, 3.7215675, Hydrogen, 7.443135 outputResources = Water, 1, false, ElectricCharge, 18014, true } Using the same Hydrogen resource, we can also update the spec of the electrolyser---also, new numbers based on computations with a ridiculous number of significant figures. I changed the density of Hydrogen very slightly. These numbers conserve mass well enough (the error is 1E-7): MODULE { name = TacGenericConverter converterName = Electrolyser conversionRate = 1 inputResources = Water, 1, ElectricCharge, 51776 outputResources = Oxygen, 3.7215675, false, Hydrogen, 7.443135, true } RESOURCE_DEFINITION { name = Hydrogen density = 0.0000270274 flowMode = ALL_VESSEL transfer = PUMP } Next up: Sabatier and Bosch! A remark concerning the power consumption of the pod (41.6 W for the Mk I): It seems okay. the Orlan spacesuit consumes a maximum of 54 W, but it's a spacesuit. We can handwave that a human spacesuit has the same volume/heat losses as a 1-kerbal pod. This also appears to work gameplay-wise. The 2.31 W consumption on EVA seems very low though. This means you can survive with 18 times less power by staying outside the pod (and resupplying every 12 h)...