Rebalance resource usage

[taraniselsu]

After conversations with NathanKell and others, I decided to rebalance all resource usage based on a more realistic estimate of Kerbals' size and consumption. I am also using better sources for the numbers.

My spreadsheet is here: https://docs.google.com/spreadsheet/ccc?key=0Aioc9ek3XAvwdGNsRlh3OVhlbTFBR3M4RW0zLUNTRFE&usp=sharing

Sources:

• http://en.wikipedia.org/wiki/Life_support_system#Human_physiological_and_metabolic_needs
• http://ston.jsc.nasa.gov/collections/trs/_techrep/CR-2004-208941.pdf
• http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120015507.pdf, slide 3
• http://www.projectrho.com/public_html/rocket/supplement/102202_LifeSupportPart1.pdf, slide 2
• http://www.nasa.gov/pdf/146558main_RecyclingEDA(final)%204_10_06.pdf, page 5
• http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140005433.pdf, slide 3
• http://www.agrospaceconference.net/sperlonga2006/07%20Wheeler%20-%20NASA%20research.pdf, slide 2

Are there any other good sources that I should be aware of?

Please look over my numbers and give feedback. Thanks!

[qberticus]

This isn't much of a comment on the numbers per say. This is more of a comment on the 'gameplay aspects' that feels similar to 0.8 and 0.9. Once you unlock the life support modules you don't really have to worry about them anymore beyond putting them on your ship. Early Mun and Minmus missions are over supplied and once you attach a life support module you don't have to worry about it. Similarly for early space stations. It's really easy to setup a year+ supply and never have to worry about it.

I suggest having some progression in the storage density and effectiveness of the recyclers as you progress through the tech tree. This would introduce the requirement of having to put more thought into the management and supply of your early space program. As you progress through the tree you could unlock newer higher density / efficiency life support modules at the expense of increased mass maybe. In this way as you unlock the ability to create interplanetary missions you also unlock the ability to keep the kerbals alive.

[NathanKell]

The main page from which that Life Support PDF comes: http://www.projectrho.com/public_html/rocket/lifesupport.php
Doubt it's new info though, it's mostly a rundown of others' work. (Not that doing that is easy; but you get my point).

On first skim numbers look good. I do tend, for reasons of neatness, to prefer 0.8kg/meal, 3 meals a day (it divides neatly); but presumably more than 7 grams per meal is packaging, so if it's 2.4kg of packaged food then it will be at least ever-so-slightly dehydrated.

[MunSeeker]

The consumption numbers in the spreadsheet look good. So these are now slightly different than in the current 0.9 alpha, correct?

Also, I agree with qberticus: The small life support containers seem to be too full. Even if by weight/volume it is correct, the current containers in TACLS have too much stuff in them.

If I attach two mid-sized life support combo-containers to a command module and put two Kerbals in, they have food, water and oxygen for roughly 270 days. For me, that reduces the play value of TACLS since it is trivially easy to support even a 6-Kerbal 4-year mission to Duna with a stack of large resource containers and maybe a recycler and a scrubber. I'd rather have more of a challenge with life support in KSP.

[RedAV8R]

Possible error, or not explained. In your spread sheet on 'The typical NASA astronaut weights 175 lbs (80 kg)' Then you change the follow a few cells over to 70kg?

[toadicus]

I had a look over the numbers and in the general sense everything makes sense to me. I also noticed the 80 kg vs 70 kg discrepancy that RedAV8R noted above.

[taraniselsu]

I've seen both the 80kg and the 70kg quoted in various NASA documents. Sometimes both within the same document. I changed it to 70kg because that is what http://ston.jsc.nasa.gov/collections/trs/_techrep/CR-2004-208941.pdf seems to use in places when it talks about the ISS or future planning (i.e. Mars). See Table 3.3.6 as an example.

[NathanKell]

Your food is much less dense than the number RedAV8R came up with! I take it that's because yours is dehydrated?
Also, RedAV8R mentioned something about the .835 being for a mostly resting human...

[RedAV8R]

Actually the 0.835kg is for light-moderate activity, which I completely agree with and is the figure NASA came up with...and would be roughly equivalent to 630L.

550L what RO consumption was is something like 0.73kg.

So while I completely agree with oxygen consumption, food and water are based on dried foods, which while there is some, the ISS uses a lot of pre-packaged food that is already hydrated. Think MREs.

Maybe what could happen is have both say 'Food' and 'FoodDried' resources and when Dry is used use one Water requirement, and when regular Food is used use a different smaller Water requirement.

[taraniselsu]

Dehydrating the food should make it more dense, not less.

Where did you get your numbers from?

I got my numbers for Oxygen from http://ston.jsc.nasa.gov/collections/trs/_techrep/CR-2004-208941.pdf, Table 3.3.6 (which matches table 4.1.1). Those numbers agree, with some rounding, with slide 3 in http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120015507.pdf. That slide is included in a lot of different presentations, see my other sources in the spreadsheet. They also match the (older) numbers on wikipedia: http://en.wikipedia.org/wiki/Life_support_system#Human_physiological_and_metabolic_needs.

For food, I used the last column of http://ston.jsc.nasa.gov/collections/trs/_techrep/CR-2004-208941.pdf, table 4.3.7. Table 4.3.1 has some numbers for the ISS, which are somewhat close to the other numbers. Also look at 4.3.4.

Note that the "as-shipped" includes some water (1.37 kg vs. 0.66 kg dry), but additional water is added to get the "as-consumed" number (2.38 kg). I think that even with mostly non-dehydrated foods, they will still add some water. We even do on Earth, for Tang-like drinks or rice or whatever.

I took the total water consumed (3.909 kg) from http://ston.jsc.nasa.gov/collections/trs/_techrep/CR-2004-208941.pdf, tables 3.3.6 and 4.3.4, adjusted it for the water already in the food (1.37-0.66kg) and added some usage for minimal hygiene (0.67 kg), table 4.6.2.

[RedAV8R]

Our O2 550L was based upon resting rate, obviously not realistic and would like to settle on a more realistic number of 630L, close to your calculated, but based upon the 0.835kg of O2 at a density of 0.001331 O2 at the NIST STP of 20C and 101.325kPa (1atm). Which is closer to what room temp/pressure would be than the 0C and 100kPa to boot.

Our food density of 0.8kg/L is based upon the average density of over 40 different food commodities (water weight included). We had both seen in multiple places 'average' food weight of 2.4kg/day or very close too it, as witnessed by your own resource 'as consumed' as well. It was quite the irony that 2.4kg/day divided by 3 meals is 0.8kg matching 1L. Effectively making 1L = 1 meal. Further helped by the fact that the average normal distended stomach has a volume of approximately 1L. Seemed like a very fine place to fix things at.

Water density is obviously pretty well established, while consumption is something we based upon, don't recall where, but that number to me is flexible and can be changed. As to whether we add hygiene to this figure or not is up in the air, i'm ok either way.

CO2, pretty self explanatory, using again CO2 density of 0.001839 (NIST STP of 20C and 101.325kPa (1atm) which again is closer to room temp and real life than another definition. That would give ~540L of CO2 production.

Waste and WasteWater were guestimates.

[RedAV8R]

I've given it some thought, and considering that hygiene items are spacecraft specific I propose they are NOT included with basic production/consumption rates. Let the basics be for general purpose kerbal/person metabolic rates, and leave hygiene rates be craft/part specific.

That said, according to table 3.6.6 basic human water consumption is 3.909L/day, I propose we subtract from that figure the amount of water to bring 'dry' food requirements to the 2.4kg/day, leaving basic water consumption at 2.659L/day for a human (kerbal consumption based accordingly)

I also bring to the table that WasteWater (human urine) is generally accepted to have a density of 1.02kg/L. Such that average daily urine production is 1.945kg/day, provides average production of 1.907L/day.

I have generally not found an average density of human fecal mater, other than around 1kg/L and that it is generally ~75% water. According to the same paper it appears to be 0.123kg/day of poo.

[taraniselsu]

I think that "room temperature" does not matter much because volume only matters when we are talking about storage. I don't think they would climate control the storage area, except for food products. I can switch to NIST SATP of 20C and 101.325 kPa (1 atm) if you guys really think that I should. I just think we should agree on a standard so that resources can be at least a little compatible.

My food volumes come from Table 4.3.7, "Locker Volume m³/CM-d 0.00354, Freezer Volume m³/CM-d 0.00231". I know that it seems a little low, but it is probably accounting for racks, accessibility, or some such (don't want to empty the entire container just to find tonight's dinner).

Until I can implement #17 or something similar, I cannot vary the water usage based on the parts so I want to include some basic hygiene water usage. It might be a little while before I can implement a change like that.

I agree with your reducing the water usage based on the water already in the food, and you'll see that I did that. Where we differ is that I only include the water in the "as-shipped", so they still need to use some water to bring it up to "as-consumed". I want to keep it that way because of the separate water recycling and food growing mechanisms. There is no reason they should not be able to use recycled water for that last part of the water needed instead of having to ship or grow the additional mass.

The Waste Water is not just urine, but also water recaptured from perspiration, respiration, washing hands or other hygiene, and preparing food. Also, I've seen a range of numbers for Urine, for example from http://en.wikipedia.org/wiki/Urine#Density_or_specific_gravity and http://www.healthline.com/health/urine-specific-gravity#Results4. It looks like the range is 1.002 to 1.030, although greater than 1.010 starts indicating health problems.

I got my numbers for bio-waste from Table 3.3.6 and http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120015507.pdf, slide 3.

[RedAV8R]

We like 20C and 1atm for density of gasses at least, and gas density and consumption of O2 and CO2 accordingly. We also really like the 2.4kg/day with food density of 0.8kg/L. Otherwise, you've gotten our feedback, it's your mod, do as you please.

[taraniselsu]

I did that before and everybody complained (when it was "1 unit = 1 day"). I'm trying to be more compatible with others' mods to make it easier for them and me.

[panarchist]

I need to find the NASA source, but the numbers I've seen support RedAV8R - 0.8kg/L for read-to-eat food and 0.4kg/L for packaged food. IIRC those numbers definitely apply to military MREs, but I seem to recall also seeing them in a NASA source. I agree that the 0.25kg/L currently in the mod is a bit low.

(BTW, I am "tgapw" on Github but "panarchist" in KSP-land)

[panarchist]

Ok, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140002843.pdf backs up the numbers in the Advanced Life Support Baseline document (which it likely drew from) - I'm pretty sure they're using dehydrated food, and it works out to 0.387kg/L. Dehydrating food REDUCES its density - food is mostly water, and the carbon compounds are less dense. Exceptions to that are meat. You can verify this experimentally at home - see how many foods actually sink in water. Very few. "Waste" according to NASA, with water removed, is about 0.1kg/L.

Looking at the Apollo days:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740020236.pdf (page 25 / page 34 of pdf)

Converting from imperial to metric: 2.20462 lbs/kg and 61.02361 in3/L:

Apollo baseline: 0.43325 kg/L
Apollo 7: 0.34067 kg/L
Apollo 11: 0.35144 kg/L
Apollo 14: 0.36513 kg/L

[RedAV8R]

Well O2/CO2 isn't 1U=1Day, Water wont' be, Food just happens to be that with 2.4kg/day and density of 0.8kg/L making 1L = 1 meal, just the way math worked out, we didn't plan it that way. It's not some ambiguous 1 unit = 1 day thing, it's basic math, and given the facts, like a 1L stomach, makes sense to me.

Face it, you are always going to have people complaining, that's people's nature, you asked for feedback and we gave you what we were using in RO.

[taraniselsu]

Good enough.