Open Schnobs opened 8 years ago
Schnobs
commented
8 years ago Forgot a source: The ISS purifier (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100033089.pdf) can handle 9l of urine/day and is rated for six people. Assuming that they'd design it with some capacity to spare, I went with 80% or 1200ml/day for an average output. Would be sad if the machine couldn't cope on a day when everybody choses cranberries for dessert.
JPLRepo
commented
8 years ago The only thing I am thinking is the users of TAC LS come in many different shapes and sizes. There will be those that: a) are used to the way it is and don't want it to change. b) are used to the way it is but don't care if it changes or see that is a challenge c) want it as real as possible
I need to read through all this when I have a bit more time and consider do we propose a base change to the figures or an alternative MM config file - and whether that is in fact an RO MM config or there be another config for RO. Again, I haven't read everything above but I will.
Schnobs
commented
8 years ago Basically just wanted to do a few new resource converters, then noticed some oddities with resources, now here I am and don't quite know how to tackle this. I'm aware that RO is a niche market, while density of food would affect a lot more users. Hence my Q if it even can be changed. I'd like to get that out of the way first.
JPLRepo
commented
8 years ago bit busy this week, I'll look the figures over on the weekend. and what's next. Assume these are defined in CRP, but that's ok. If we want to change them, and we think it's right to do so, and probably want to run it past the users as well. Leave it with me to do that and then I'll get back to you.
Schnobs
commented
8 years ago Just notice that I have given no rationale for why I want the figures to be like I propose.
a) 1kg food / 1kg consumables are nice round figures. b) by all accounts, US space food is no longer as badly dehydrated as it once was.
The dry mass of food is fixed (and IMO 620g is a tad little), so I tweaked down the water content to arrive at 1kg. 35% is entirely credible, but not based on any actual number I found in a document somewhere.
Dehydrated food is good for missions where you have "free" water from a fuel cell (Gemini, Apollo, Shuttle); space stations need water and IRL some of it is left in the food (US are no longer as strict about dehydration, and russian space food actually includes canned food). Gameplay-wise, food/water makeup is a zero-sum game if you don't have a water source. Hence I felt I should keep the water content low.
Density of garbage is documented, see above. I set the density of food to 0.45 because I wanted to.
Rationale: the single-serving pouches I see on photographs can't be packed very tight. If you try, the contents will un-pack with some gusto when you open the container in space. I guess this explains the low density (as per the paper: 0.37 including the drawer, 0.29 without). However, if you want to send a long-term mission to mars, the volume required for food storage at these densities becomes outright silly. I'm pretty certain that a solution can and will be found.
I chose 0.45 because in my experience, even compacted garbage is less dense than the packaging it comes from. Then again, the plastic packaging is probably denser the food itself (on pics it looks like tough polyethylene), so I didn't want to go over the top.
JPLRepo
commented
8 years ago Should these be Stock/TAC Config changes or RO changes? In which case can be worked into new LifeSupport.cfg Module Manager file I will be doing. But I suggest you discuss this with the RO guys and come to a conclusion of what settings you want for TAC LS.
Schnobs
commented
8 years ago paging @stratochief66 ...
stratochief66
commented
8 years ago I appreciate you being upfront with your rationales @Schnobs, but "Because I like this round number" doesn't do much to convince me this change is needed, or is the right one.
That said, I appreciate that you're trying to progress things, since (compared to when TACLS was young) RO is mature enough now to start carrying out very long term station and Mars missions.
I would suggest that any changes to consumption rates be discussed and (possibly, eventually) put into place on the RO side, unless stock TACLS is seeing similar complaints?
Really, food density is the only thing that needs to be resolved on or near the TACLS side itself. I personally don't care what the density of food is/ends up being, provided any changes don't require us to rejigger the current configs for the amount of food carried on craft. schnobs, if you can managed that, or use a clever script that changes all the config values to match your change in density, go for broke. Honestly though, craft volume is never really an issue, therefore food density doesn't strike me as a particularly important topic.
Schnobs
commented
8 years ago First off, as far as I'm concerned this is only about RO.
Second, I see a need to change the current figures because they don't make sense. Nearly 5l wastewater/day? Puh-lease.
For every resource, we have to arrive at a single figure that will have to do for all missions, from Mercury to ISS to two years on Mars. With that premise, "as realistic as possible" is doomed from the outset. I think we have to settle for "reasonable more often than not". I also think we should weigh this towards long-term missions because give-or-take a few percent on Apollo is barely noticeable, while on a Mars mission we're talking tons.
There's no really fixed numbers here: changing the water content of food only means that you need to bring more or less water on top of that. Same mass either way. Except if you have a fuel cell, in which case dry food is obviously beneficial. That's why I tweaked down the water content; I don't know how far one can take this, but I do know that many foods we'd consider to be bone dry still have 10-15% water content. 35% seems to be on the safe side (by which I mean entirely possible). It could be 30% or maybe I'm overdoing it and it should be no less than 38%, I have no reason to prefer one over the other -- except that 35% lets me arrive at a nice round figure of 1kg/day.
Likewise the amount of garbage. Read the breakdown of what made up the garbage, and if you can determine at a figure that is "right" without qualifications, you're better than me. It should definitely be more than just the food packaging, but just how much more is anybody's guess / varies by mission and what goes into your assumptions. Watching my own needs the past week, 500g of varied consumables per day seems to be a lot. I'd need to throw away worn socks in order to arrive at that number. Then again, isn't that just what they do on ISS?
You may think that nice round figures are conspicuous; I say they don't pretend to be more accurate than they really are. Besides, they're easy on the mission planner.
stratochief66
commented
8 years ago Isn't half of that water, by your own admission, breath & body humidity? Anyway, I will read more of this later when I have more time and less alcohol in my system. I'm still interested, just busy. I agree in keeping the complex discussion in RO. :)
On Mon, Aug 29, 2016 at 7:21 PM, Schnobs notifications@github.com wrote:
First off, as far as I'm concerned this is only about RO.
Second, I see a need to change the current figures because they don't make sense. Nearly 5l wastewater/day? Puh-lease.
For every resource, we have to arrive at a single figure that will have to do for all missions, from Mercury to ISS to two years on Mars. With that premise, "as realistic as possible" is doomed from the outset. I think we have to settle for "reasonable more often than not". I also think we should weigh this towards long-term missions because give-or-take a few percent on Apollo is barely noticeable, while on a Mars mission we're talking tons.
There's no really fixed numbers here: changing the water content of food only means that you need to bring more or less water on top of that. Same mass either way. Except if you have a fuel cell, in which case dry food is obviously beneficial. That's why I tweaked down the water content; I don't know how far one can take this, but I do know that many foods we'd consider to be bone dry still have 10-15% water content. 35% seems to be on the safe side (by which I mean entirely possible). It could be 30% or maybe I'm overdoing it and it should be no less than 38%, I have no reason to prefer one over the other -- except that 35% lets me arrive at a nice round figure of 1kg/day.
Likewise the amount of garbage. Read the breakdown of what made up the garbage, and if you can determine at a figure that is "right" without qualifications, you're better than me. It should definitely be more than just the food packaging, but just how much more is anybody's guess / varies by mission and what goes into your assumptions. Watching my own needs the past week, 500g of varied consumables per day seems to be a lot. I'd need to throw away worn socks in order to arrive at that number. Then again, isn't that just what they do on ISS?
You may think that nice round figures are conspicuous; I say they don't pretend to be more accurate than they really are. Besides, they're easy on the mission planner.
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danfarnsy
commented
8 years ago Perspiration and respiration are huge for waste water. As for consumables, everyday living and trash compared to the waste overhead associated with packaged meals, small packages of hygiene products, and so forth, trash can build up very quickly. I'm not an astronaut, but I was a soldier, and that living environment generates tremendously large amounts of trash, with "cheaper" disposables. I'm not going to go to bat here and suggest that the TACLS numbers for RO are great right now, but there is a lot of personal intuition, based in everyday life, which is almost completely inapplicable to these kinds of problems. The current data we have is based in a solid design document. It needs updating for longer-term missions, and better data needs to drive improvements. Intuition about how "that seems too high or too low" has a reference base in everyday experience which does not apply to these scenarios. I recommend we design (and reference) an update that is more rigorous than what we've got, in lieu of suggesting better numbers that feel right.
Just chiming in my two cents.
DBowmanUDA
commented
8 years ago I'd done some hypothetical hobby mission planning based on the Baseline doc referenced in the OP. A couple of things I found trying to minimise mass:
fwiw I'm with danfarnsy re using the most accurate real world numbers one can get and not fudging them at all. You will have something unassailable.
spillover from https://github.com/KSP-RO/RealismOverhaul/issues/1348:
TanrisElsu's old spreadsheets: https://docs.google.com/spreadsheets/d/1DkWf210viRSNcV8tvDv30vZ_iACj6GeY1Lf_4JdZYds/edit?pref=2&pli=1#gid=0
Relevant figures seem to come from http://ston.jsc.nasa.gov/collections/trs/_techrep/CR-2004-208941.pdf Tables 3.3.6, 4.3.1, 4.3.4, 4.3.7 are cited as source in the spreadsheet.
I'll call this the "Hanford paper". Section 4.3 deals with food, 4.5 with trash. It has figures for densities, but TA seems to have missed them and made up his own.
As per the paper it's 1150g food (42% water content) + 260g individual packaging + 350g for the food locker it's stored in, for a total of 1760g / 4.8l (density 0.366). By our reckoning, the locker would probably be part of the spacecraft; then again, some kind of box or crate will be needed and I'm not sure if we can trust ServiceModule tanks to handle all of that.
The paper's figures for waste include uneaten food, so they're of limited utility. FWIW, waste density is very low (0.1) unless a trash compactor is used, raising it to 0.4+. Waste generated is on the order of 1500g, including uneaten food (which accounts for 24% on the one mission where we have a detailed rundown). All figures are STS.
So... I'd like our astronauts to require 2kg of "food" per day, density 0.45, half of which is actual food with 35% water content. The other kilo is both packaging and various other consumables.
That's less trash than on a shuttle mission or ISS; I rationalize this by special circumstances, short-term Apollo missions need less stuff to begin with, serious long-term missions would re-use more. Still, for long-term it's probably not enough. The whole topic of clothes hasn't been touched.
I'd also like to assume a waste density of 0.4 (waste compactor figure). On short-term missions it doesn't matter much either way, long-term 0.1 will be maddening.
proposed baseline LS figures, CM-d: 2000g food 3500g water 1120g waste (garbage & feces, incl. 100g unrecoverable water) 1200g urine (wastewater)
Condensate reclaiming could create 2.9l water out of thin air. That's 1970s tech and seems to work at near-perfect efficiency. I'd tie that to a CO2 scrubber so water creation is linked to available dioxide.
Peroxide scrubbers could create an additional 2.9kg of waste; let's call it dessicants. Problem is that this would inflate waste volume quite a bit, another 400l for Apollo. For all I care we could just allow the mass to disappear.
Wastewater purifier: 1200 wastewater -> 840 water, 360 waste (70% recovery, 2000s tech).
I hear hints that the Soviets electrolysed urine, dumping H2 and keeping the oxygen. Some concentrated brine (waste) remained. Probably Mir, late 1980s. This would be the more interesting approach as it allows you to resupply water instead of oxygen.