Well... I know you're just setting a metric, but I think fresh food won't last 250 weeks. Unless you're talking hydroponics, which I would assume has its own maintenance and volume requirements.
Replenish life support on a primitive planet
- Thread starter Pyromancer
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Well... I know you're just setting a metric, but I think fresh food won't last 250 weeks. Unless you're talking hydroponics, which I would assume has its own maintenance and volume requirements.
CO² and fresh food. Hmmm. Since this is a wild jump, we may not know how far we have to go to get back, so a week's worth of supplies may not be enough.
So something that may help lessen the burden on the atmosphere processing plant CO² scrubbers would be to break out hydroponics/aeroponics wherever you have available volume and sufficient lighting. Hydroponics on the ISS found that plants thrive, growing faster but require more water. This would allow you to have fresh veggies/fruits too.
But let's not be under any illusions here - hydroponics are heavy systems, and would cut into your cargo capacity, which may require you to lighten ship and remove excess cargo to open up volume and capacity. Abandoned cargo can be claimed as salvage - although if you're out far enough away, that may not be important.
So something that may help lessen the burden on the atmosphere processing plant CO² scrubbers would be to break out hydroponics/aeroponics wherever you have available volume and sufficient lighting. Hydroponics on the ISS found that plants thrive, growing faster but require more water. This would allow you to have fresh veggies/fruits too.
But let's not be under any illusions here - hydroponics are heavy systems, and would cut into your cargo capacity, which may require you to lighten ship and remove excess cargo to open up volume and capacity. Abandoned cargo can be claimed as salvage - although if you're out far enough away, that may not be important.
Pyromancer
SOC-10
GURPS Space has "total life support" that provides practically unlimited food, air and water at 1 dton per 5 person. That's really small in my eyes.
How many is a few jumps?
Players routinely stop off at places that can't provide starport servicing, so there has to be enough reserve for at least one or two extra jumps or we're affecting normal play. Warships would need to spend a chunk of time away from support too if they went commerce-raiding behind enemy lines. Scouts presumably have some capacity to go exploring the wilderness. So, there's likely to be reserve capacity, though how much may depend on the type of ship. I'd say at minimum there's a month aboard, since the ships are typically rated for a month of power plant fuel, maybe more on scouts and warships. Seems reasonable they'd have enough supplies to last out the power.
Average lung capacity in males is 6 liters, but on average a resting breath is only a half liter; lotta reserve volume for when you need to crank up the energy output. (Your lungs are actually only about half full when you take a resting breath.) I think all that assumes sea level - things change at altitude. With Earth norm being about 21% O2, you're taking in about a tenth of a liter of O2 on a resting breath, and you're probably breathing between 12-20 times per minute.
Normal atmosphere is about 0.04% CO2. Our exhalation's about 4-6% CO2, so your typical resting breath comes in at 21% O2 and leaves at ~16% O2 and ~5% CO2 - you consume very roughly 1/40th of a liter O2 per breath resting. We try to keep atmospheric CO2 concentration below 1%, because above that level we start breathing faster and using O2 more quickly. Up to 7% we start getting headachy. Above 7% we pass out. At about 15% we're dying. The CO2 will get you before the lack of O2 will.
Your own ship's volume is good for maybe 2-3 days air. Figure the 4 dTon per person volume, a bit less than a third of it is above what you need for head height so likely machine space between decks, and then there's furniture and stuff, but maybe half the volume is just air space for you to move through, so about 7 cubic meters - 7000 liters, or 1400 liters available O2 under the most ideal conditions, 40-50 hours except of course you'll be lucky to use half of it before the air becomes too toxic for life. Very roughly a day per dTon under the most optimistic conditions, likely much less.
A CAN33 O2 generator produces 440 liters O2 per liter storage, per its ad. Figure that as good for about 14-15 hours for one person. A CASPA CO2 absorber has a storage volume of about 16 liters; two of them will maintain a 28 cubic meter volume holding 10 people at under 1% CO2 for three hours, or so says the advertisement. So, you're storing more CO2 absorbers, figure 15-16 liters for every liter of O2 generator. Of course, that's a unit with a fan and such - the chemical itself takes up less volume. You can use that to estimate how much stuff you'd need. Depending on how many people are aboard your ship, you ought to be able to buy another month or two by just saying there are x number of these in the ship's locker for emergencies - a cubic meter of the thingies buys you about 5 weeks. A careful scout might store more in the cargo bay - but those O2 generators get wicked if a laser hits there.
So, your player's ship might be able to manage a couple or three months in space before they need to start worrying about harvesting wilderness supplies to breathe.
Players routinely stop off at places that can't provide starport servicing, so there has to be enough reserve for at least one or two extra jumps or we're affecting normal play. Warships would need to spend a chunk of time away from support too if they went commerce-raiding behind enemy lines. Scouts presumably have some capacity to go exploring the wilderness. So, there's likely to be reserve capacity, though how much may depend on the type of ship. I'd say at minimum there's a month aboard, since the ships are typically rated for a month of power plant fuel, maybe more on scouts and warships. Seems reasonable they'd have enough supplies to last out the power.
Average lung capacity in males is 6 liters, but on average a resting breath is only a half liter; lotta reserve volume for when you need to crank up the energy output. (Your lungs are actually only about half full when you take a resting breath.) I think all that assumes sea level - things change at altitude. With Earth norm being about 21% O2, you're taking in about a tenth of a liter of O2 on a resting breath, and you're probably breathing between 12-20 times per minute.
Normal atmosphere is about 0.04% CO2. Our exhalation's about 4-6% CO2, so your typical resting breath comes in at 21% O2 and leaves at ~16% O2 and ~5% CO2 - you consume very roughly 1/40th of a liter O2 per breath resting. We try to keep atmospheric CO2 concentration below 1%, because above that level we start breathing faster and using O2 more quickly. Up to 7% we start getting headachy. Above 7% we pass out. At about 15% we're dying. The CO2 will get you before the lack of O2 will.
Your own ship's volume is good for maybe 2-3 days air. Figure the 4 dTon per person volume, a bit less than a third of it is above what you need for head height so likely machine space between decks, and then there's furniture and stuff, but maybe half the volume is just air space for you to move through, so about 7 cubic meters - 7000 liters, or 1400 liters available O2 under the most ideal conditions, 40-50 hours except of course you'll be lucky to use half of it before the air becomes too toxic for life. Very roughly a day per dTon under the most optimistic conditions, likely much less.
A CAN33 O2 generator produces 440 liters O2 per liter storage, per its ad. Figure that as good for about 14-15 hours for one person. A CASPA CO2 absorber has a storage volume of about 16 liters; two of them will maintain a 28 cubic meter volume holding 10 people at under 1% CO2 for three hours, or so says the advertisement. So, you're storing more CO2 absorbers, figure 15-16 liters for every liter of O2 generator. Of course, that's a unit with a fan and such - the chemical itself takes up less volume. You can use that to estimate how much stuff you'd need. Depending on how many people are aboard your ship, you ought to be able to buy another month or two by just saying there are x number of these in the ship's locker for emergencies - a cubic meter of the thingies buys you about 5 weeks. A careful scout might store more in the cargo bay - but those O2 generators get wicked if a laser hits there.
So, your player's ship might be able to manage a couple or three months in space before they need to start worrying about harvesting wilderness supplies to breathe.
Timerover51
SOC-14 5K
The following data has been culled from FM 10-13, Quartermaster Reference Data, for the years 1950, 1957, and 1969. They can all be located on archive.org for those interested in more data or more precise data. It is supplemented by data from FM 101-10, Staff Officers' Field Manual-Organization, Technical,and Logistical Data, 1959, and FM 55-15 Transportation Reference Data, 1963.
In general, for fresh food with refrigeration, your shelf life is going to be about 30 days. Some items can go longer, a lot are shorter, but for game purposed, a figure of 30 days is reasonable.
The US Army's Class A ration or field ration consists of approximately 200 items, including such perishables as fresh and frozen meats, vegetables, and fruit. It is intended for use primarily under stable conditions and during static phases of military operations when normal cooking and refrigeration facilities are available. That would basically be the conditions onboard of most ships. The typical ration, or food for one person for one day, would weigh 6 pounds including packaging and occupy 0.183 cubic feet. It would supply about 4,200 calories per ration. Note that calories content, as it assume an active person engaging in strenuous activity. Based on World War 2 experience, in 1950 it was assumed that one man would require about 3 cubic feet of refrigerated space per 30 day month, while in 1969, the allowance was for 3.98 gross cubic feet of space. The "gross" is important, and that would include the refrigerator itself. Now, 0.183 times 30 days equals 5.49 cubic feet, but the difference between 1950 and 1969 means that we need to add about one cubic foot to that to allow for the added volume of the refrigerator/freezer, so food for 30 days for one person would weight 180 pounds and occupy 6.49 cubic feet.
If you use 13.5 cubic meters for the Traveller dTon, you have 476.748 cubic feet to work with, with about 60% of that being refrigerator/freezer space, which would be sufficient room for 70 persons (it is actually 73, but I am rounding down for lost space) for one month, at a total weight of 12,600 pounds. That seems a little high, as FM 55-15, Transportation Reference Data, 1963 assumes that one long ton of Class A rations will occupy 94 cubic feet. Five long tons of Class A rations would occupy 470 cubic feet, or almost exactly 13.5 cubic meters. Five long tons would weigh 11,200 pounds, a little less than our 12,600 pounds. I probably did not make enough allowance for wasted space. Our new figure of 11,200 pounds will feed 62 people for one 30 day month 4,200 calories a day. As the crew of a starship during Jump are not likely to be engaging in extremely strenuous activities, unless exercising like crazy, a more likely calorie need would be around 2500 to 2800 calories per day, Therefore a very adequate cushion exists. Once you are past the 30 day mark however, the equations change, as you can no longer assume fresh food.
On to the next lecture.
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Timerover51
SOC-14 5K
Once you get past the 30 day mark, you are in the realm of non-perishable foods, or the US Army's Class B ration, which "is designed for use whenever mess facilities and personnel are available and where NO perishable foods are issued. The use of canned or dried items, together with the use of staple items, constitute this ration." The ration weighs 6 pounds with packaging, occupies with packaging 0.127 cubic feet, and supplies 4,400 calories per day. Again, note the high calorie content. In general, non-perishable items are good for from 24 to 48 months, allowing for much longer endurance. Again, exact data can be found in FM 10-13. The lower volume allows us to pack a lot more food into a given space. In a 30 day month, the person rationed will consume 180 pounds of food occupying 3.81 cubic feet of space. To be on the safe side, let's round up to 4 cubic feet per person. When you divide 476 cubic feet by 4, you get 119 persons can be feed for one month from 1 Traveller dTon of storage space. Given the high calories content, we can safely call it 120 persons for one month.
For Scouts and ships with smaller crews, there is the small detachment ration intended for 5 persons for one day, using non-perishable pre-cooked food that just needs to be heated. This would be good for ships with compact galleys. A case of 5 rations weighs 28.5 pounds, occupies 1.1 cubic feet, and delivers 3,600 calories per ration. Sufficient food for 30 days for 5 persons would weigh 855 pounds and require 33 cubic feet of space. A Traveller dTon of 476 cubic feet could hold 14.4 months worth of cases, but again allowing for some lost space, let us assume 12 months worth of cases, or sufficient food to feed 60 persons for one month, or 5 persons for one year. Again there is a big cushion with respect to calories per day per person.
Lastly, there is this thing known as "water", which is requires for a person's continued existence. The US Army budgets between 30 to 60 gallons per person per day for a semi-permanent camp, and 60 to 100 gallons per person per day for a permanent camp. I would presume that a starship would have a highly efficient water recycling system, so that 60 gallons per person per day would be adequate, with a supply for 4 days per person onboard. A cubic meter of contains 264 US gallons, so a very conservative allowance would be one cubic meter of water per person onboard. A 13.5 cubic meter Traveller dTon should be more than adequate for 14 persons on board. If you went with a two day allowance per person, the 28 to 30 persons could be accommodated per Traveller dTon. If you cut it to 15 gallons per person per day, which would allow for bathing, and a two day supply cushion, you could accommodate about 120 persons per Traveller dTon. I suspect that would be the allowance for military ships.
Now, I am not saying that this would be how your ship would necessarily be provisioned, although the data for the Class A Ration might be pretty close for a month's supply, but to give you as players, Game Masters, and ship designers an idea of how much space you need to set aside for the necessities of food and water. That space will be dictated by how large the crew is, how many passengers can be accommodated, how long are you provisioning the ship for, and how are you planning to feed everyone. In the thread on Shipboard Accommodations, I have posted a couple of examples of ship's galleys of two different sizes, one for a fairly large ship and one for something the size of a Scout.
End of lecture.
For Scouts and ships with smaller crews, there is the small detachment ration intended for 5 persons for one day, using non-perishable pre-cooked food that just needs to be heated. This would be good for ships with compact galleys. A case of 5 rations weighs 28.5 pounds, occupies 1.1 cubic feet, and delivers 3,600 calories per ration. Sufficient food for 30 days for 5 persons would weigh 855 pounds and require 33 cubic feet of space. A Traveller dTon of 476 cubic feet could hold 14.4 months worth of cases, but again allowing for some lost space, let us assume 12 months worth of cases, or sufficient food to feed 60 persons for one month, or 5 persons for one year. Again there is a big cushion with respect to calories per day per person.
Lastly, there is this thing known as "water", which is requires for a person's continued existence. The US Army budgets between 30 to 60 gallons per person per day for a semi-permanent camp, and 60 to 100 gallons per person per day for a permanent camp. I would presume that a starship would have a highly efficient water recycling system, so that 60 gallons per person per day would be adequate, with a supply for 4 days per person onboard. A cubic meter of contains 264 US gallons, so a very conservative allowance would be one cubic meter of water per person onboard. A 13.5 cubic meter Traveller dTon should be more than adequate for 14 persons on board. If you went with a two day allowance per person, the 28 to 30 persons could be accommodated per Traveller dTon. If you cut it to 15 gallons per person per day, which would allow for bathing, and a two day supply cushion, you could accommodate about 120 persons per Traveller dTon. I suspect that would be the allowance for military ships.
Now, I am not saying that this would be how your ship would necessarily be provisioned, although the data for the Class A Ration might be pretty close for a month's supply, but to give you as players, Game Masters, and ship designers an idea of how much space you need to set aside for the necessities of food and water. That space will be dictated by how large the crew is, how many passengers can be accommodated, how long are you provisioning the ship for, and how are you planning to feed everyone. In the thread on Shipboard Accommodations, I have posted a couple of examples of ship's galleys of two different sizes, one for a fairly large ship and one for something the size of a Scout.
End of lecture.
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mike wightman
SOC-14 10K
What if you stick all the fresh food you gather in a low berth?
In the Dumarest novels the low berths were designed for livestock rather than humans...
In the Dumarest novels the low berths were designed for livestock rather than humans...
Condottiere
SOC-14 5K
Generally speaking, you tend to find units far exceed any water or fuel usage budgeted during a battle.
Unless, a lot of their personnel are dead before it ends.
Unless, a lot of their personnel are dead before it ends.
3D printers are doing a good job right now heading towards being able to print living tissue. If this is the progress so far, then it's entirely conceivable that a TL10 biomaker would be capable of using its stock chemical stores to create apparently fresh food. Would it be better than the real thing? Probably not until higher techs when it may be too difficult to tell the difference. Would it save on space? Possibly, maybe especially if vessels were able to renew their stocks of water in situ.
Timerover51
SOC-14 5K
A 3D printer printing "living tissue" is something that I would be extremely worried about bacterial contamination. When you use the term "living tissue", do you mean that the tissue will be able to continue to grow and develop after being printed? Do you mean that the printer is taking the raw materials of food and producing food?
If you are concerned about saving space, you can always recycle human waste through the printer, but I have my doubts about how well that would go over.
Condottiere
SOC-14 5K
Extract the water, and use it in the reactor.
The solid remnants as cheap printing ink.
The solid remnants as cheap printing ink.
What a great idea for sabotaging a Maker pattern used to generate "fresh" food on a ship: have it produce a nasty bacterial item in the food output! Old-Timer, you're brilliant!
Pyromancer
SOC-10
Back to the air issue:
A human exhales around 1 kg of CO2 per day.
1 gram of lithium hydroxide absorbs 450 ml of CO2.
Lithium hydroxide has a density of 1.46 g/cm³.
CO2 has a density of 1.98 kg/m³.
With those numbers, we need 1.17 kg of lithium hydroxide per day and person or 8 kg per person and week.
So 1 dton of lithium hydroxide can scrub the air for one person for 2400 weeks.
How many kg of oxygen can you fit into 1 dton if you use standard gas cylinders?
A human exhales around 1 kg of CO2 per day.
1 gram of lithium hydroxide absorbs 450 ml of CO2.
Lithium hydroxide has a density of 1.46 g/cm³.
CO2 has a density of 1.98 kg/m³.
With those numbers, we need 1.17 kg of lithium hydroxide per day and person or 8 kg per person and week.
So 1 dton of lithium hydroxide can scrub the air for one person for 2400 weeks.
How many kg of oxygen can you fit into 1 dton if you use standard gas cylinders?
Pretty sure that nowadays we call those "Freezers".
Low berth is more a low metabolism long term sleep state, not sure if it works very well on "dead" food that's slowly decaying in the refrigerator (i.e. things like tomatoes and cut meat).
This is in contrast to the home stasis fields ala Larry Niven that they had on the counter and would call "the cold spot", which were true time stop stasis areas.
Pyromancer
SOC-10
O2:
A human need .9 kg of O2 per day, or 6.3 kg per week
At 200 bar and 20 °C, we can store 3240 kg of O2 in 1 dton. Subtract a little bit for the containers themselves, I assume 2500 kg of O2, enough for 1 person and 400 weeks.
A human need .9 kg of O2 per day, or 6.3 kg per week
At 200 bar and 20 °C, we can store 3240 kg of O2 in 1 dton. Subtract a little bit for the containers themselves, I assume 2500 kg of O2, enough for 1 person and 400 weeks.
AnotherDilbert
SOC-14 1K
Cryogenic liquid oxygen has a density of about 1.14 tonne/m³, so ~16 tonnes per Dt.
If a human consume 550 l/day at 1.4 g/l, it would be 770 g/day or 0.77 kg/day.
So a Dt of lox would be sufficient for one person for 16000/0.77 ≈ 20800 days.
If you store the oxygen as water (H₂O) you would get about 16/18×14000 = 12400 kg oxygen and 2/18×14000 = 1500 kg hydrogen ≈ 1.5 Dt Lhyd to run the power plant. We can even use the water in the life support system until we split it into oxygen and hydrogen.
To split the water would take something like 40 kWh/kg(H₂), so 1500 kg × 40 kWh/kg = 60000 kWh = 60 MWh. A Scout or Free Trader can produce 500 MW power, so could split a Dt of water in little over ⅒ hour, say 10 minutes or so.
Timerover51
SOC-14 5K
A cubic foot of water weighs 62.4 pounds, and contains 55.46 pounds of oxygen at 20 degree Celsius and standard atmospheric pressure, no pressure tank needed. A Traveller dTon of 13.5 cubic meters equals 476.748 cubic feet. Allowing for some water expansion, call it 450 cubic feet of water at 55.46 pounds of oxygen in the water, which would give us 24,957 pounds of oxygen in a Traveller dTon of water. That equals 11,320 kilograms of oxygen per Traveller dTon, you just have to electrolyze it with your power plant, and as a bonus, you get the hydrogen to run the power plant. Actually, 3133 pounds of hydrogen, or 1421 kilograms of hydrogen. That should supply more than enough power to separate the oxygen and hydrogen. No pressure tanks, no special handling, what more could you want? Plus, you can always drink the water, and then run it through the electrolyzer for oxygen.
Storing Hydrogen as water is much more space and weight efficient than storing it as Liquid Hydrogen. You get 1421 kilograms of hydrogen to work with rather than 1000 kilograms, no pressure or cryogenic tanks, and all of that lovely oxygen.
The issue with that, though, is dissociating the hydrogen is a chokepoint on use.
Also, at the rates used, the oxygen is more a problem than a benefit. Something else to dump overboard, and it's corrosive, reacting with pretty much everything.
Timerover51
SOC-14 5K
I was thinking more of the oxygen for oxygen replenishment, rather than storing hydrogen for fuel. However, the hydrogen produced would be far more than enough to supply power for disassociating it. In my universe, I have most ships carrying a Class A power plant and a cubic meter of heavy water to supply deuterium for ship's power. This does ot supply power for the maneuver drive or jump drive, simply a smaller planet for keeping the ship internal power needs. The complete fusion of 1478 grams of deuterium will supply 10 Megawatts of power per hour for an entire year. I believe that should be more than sufficient to supply internal power to the average Free Trader for an entire year.
It's NOT a power issue. It's a matter of how fast can you separate the two, and how to you keep the concentrated Oxygen from corroding the hell out of the purifier. Plos that you'll need to be either cryostoring or dumping surplus O2. And cryostoring it is a minor power but a significant space issue.
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