[rtkwe]

Mostly because they don't need to retain it though, a sub doesn't need to reprocess the CO2 into C and O2 but the process can be done. The process is largely the same instead of ejecting it as a waste product continue to break it down into useful products like injecting it into a Sabatier process.

[idlewords]

The Sabatier reactor on the space station broke after processing about a thousand liters of water because deodorant and astronaut urine poisoned the catalyst beds.

Everything is easy to do in theory. Recycling carbon in practice is very, very hard if you don't have plants to help you.

[shagie]

Hypothetically... after you have separated the carbon from the oxygen (discounting the human waste which has a significantly more amount of carbon)... what would you do with it as part of a recycling process in a submarine?

[rtkwe]

In current tech not much comes to mine. Maybe it could be reprocessed into dry graphite lubricant but there's not much need for raw carbon or principally carbon materials in a submarine. That's another reason it just gets tossed there's just not a real use for it. On a hypothetical extraplanetary colony though it's a pretty important material just to keep people alive.

[idlewords]

You can store it as methane and cook with it in the galley.

[rtkwe]

You don't want to be simply reintroducing it into the atmosphere again that would just increase the amount you need to scrub out of the air because now your cycle just reintroduces all the CO2 you remove back into the air along with the stuff the sailors are breathing out. Submarines as far as I can see have basically always used electric cook tops for that reason, at least since they were designed to stay submerged most of the time. UBoats probably didn't because electric power was so limited they probably just didn't cook hot food while submerged.

[shagie]

Its a bit worse than that.

Going CO2 -> C + O2 -> (+ 2x H2) -> CH4...

But the combustion of CH4 is CH4 + 2x O2 -> CO2 + 2x H2O.

The loss of O2 to water means that each time through this removes O2 from the atmosphere which would need to be replenished.

That ignores all the energy losses in the process and requirements...

As to the uboat - https://uboat.net/men/foodstuffs.htm

> The galley was located on the starboard side, between the chiefs' quarters and the wardroom, and was made up of three hotplates and two small electric ovens. It also contained a refrigerator, self-heating soup kettle, provision lockers, and an enamel sink with hot and cold fresh water and hot salt water.

https://maritime.org/tour/cm.php?pano=nr

https://maritime.org/pres/potrack/pots.php

> The custom built pots were designed fit the Edison Type B range/oven built used on the fleet boats.

https://forums.spacebattles.com/threads/pig-boats-fleet-boat...

> Fleet subs of the Gato (SS 212) and Balao (SS 285) classes boasted sizable freezer and refrigerator compartments, and their galleys, though diminutive, were well-equipped, generally with two griddles, a deep-fat fryer, two electric ovens, a hefty electric mixer, and a two-gallon coffee urn. Fleet boats usually boasted an ice cream maker as well, even when lack of space in the galley or crew mess made it necessary to install the machine among the bunks in the crew's berthing space.

(Note the 'deep-fat fryer' bit and the modern sub https://youtu.be/bPJUVKizh90?t=364 )

Do note that submarines were built by the Electric Boat Company founded in 1899. Electric systems were in use since the start.

[rtkwe]

> The loss of O2 to water means that each time through this removes O2 from the atmosphere which would need to be replenished.

Well you're missing half the equation on the CO2->CH4 process. To get the 2 H2 molecules you'll need to split 2 H2O in all likelihood so you're already getting the 2 O2 from splitting the CO2 and then the 2 H2O so in theory it's oxygen neutral.

That said it's a silly process to go through because there's already absolutely massive electrical supplies available on submarines to power the engines while submerged or to recharge those batteries while on the surface in the case of old subs or modern diesels. Why add a whole "mini" sabatier reactor just to cause more problems with your air quality and recycling when you can just cook electric and toss the captured CO2 overboard.

Neat info about the UBoats. Wonder if they were allowed to use the electric ranges while submerged. UBoats exist in this fascinating in between period where they were both surface and subsurface ships because of the limitation on things like their speed underwater.

[shagie]

A follow up to the "food on a sub" question... if you happen to be in the midwest and can make the trip...

https://www.wisconsinmaritime.org/programs-and-events/think-...

> April 6: Food Stories of WWII

> Ever wondered what the food was like in WWII? During this talk, we will explore common meals for those on the Wisconsin home front as well as submariners at sea.

They even have a Sub BNB (through Air BNB) https://www.airbnb.com/rooms/44643094

[shagie]

On a modern nuclear submarine, they're currently electrolysis of seawater for a baseline of oxygen production. The reason I don't consider it oxygen neutral is that they're not doing electrolysis of water in compartment air.

As to the ranges while submerged...

https://www.wearethemighty.com/popular/life-aboard-wwii-subm...

The serving of food was often times also dictated by restrictions on the submarines movements. Submarines were under strict orders not to surface during the day when they were within 500 miles of a Japanese airfield in order to avoid aerial observation and attack. In the early days of the war in the Pacific this meant just about everywhere as the Japanese were in control of vast swaths of territory and ocean.

This meant that the submarines stayed submerged during the day and only surfaced at night. In order to compensate, many crews flipped their schedules doing their normal daily routines at night. The crews called this “going into reverse.” This allowed the crew to take advantage of the time the sub was on the surface.

This was important because once the submarine dove after running its diesel engines for hours, the boat would quickly heat up. The engine room temperature could soar to over 100 degrees before spreading throughout the sub. Combine that with the 80 men working and breathing and the air inside could quickly become foul.

The men knew the air was getting bad when they had trouble lighting their cigarettes due to the lack of oxygen (oh the irony).

---

That leads me to https://web.archive.org/web/20170121073605/http://www.public...

Much of a submariner's limited physical activity consequently took place after dark. Some crews still adhered to the standard meal schedule for a U.S. warship at sea, but others turned night into day, adapting meal times to their upside-down shipboard routine.13 The crews called this "going into reversa." Breakfast was served at nightfall. Lunch was dished out at midnight. And dinner, the heaviest meal, came at dawn. The "reversa" timetable was particularly suited to the oppressive conditions on the antiquated S-boats, with their lack of air conditioning. Cool night air entering the surfaced submarine not only reinvigorated the sweating, oxygen-deprived crewmen but helped counter the additional heat of a busy galley.

Even on air conditioned fleet subs, some kitchen crews chose to do heavy cooking at night, when the submarine would not be buttoned up and the ventilation system could whisk cooking smoke along with other foul odors right out of the boat.14 Having the boat open to the atmosphere was particularly helpful for dissipating the intense heat of baking. USS Gudgeon (SS 211), which conducted the first submarine war patrol out of Pearl Harbor, continued to serve meals at standard Navy hours throughout the patrol, but her galley crew put off baking until after dark.15 A bold submarine commander might keep his boat on the surface for all or part of the day, but the galley crew could never count on that, and a boat exposed on the surface in daylight was more likely to make a crash dive at any moment, not an ideal situation for anyone trying to do something complicated in the galley.

...

Bad cooks could certainly decimate a potential meal. Battle could do the same. Whenever Bullhead's deck guns fired, Piatt's muffins and cakes invariably collapsed into lifeless deflation.25 A maritime cooking disaster occurred on USS Harder (SS 257) in 1942 when torpedomen flooded the forward tubes with far too much water. Result: an unexpected nosedive of many fathoms. The crew quickly regained control, and the boat leveled off. A safety inspection revealed no injuries or damage — until it got to the galley. There stood Ship's Cook and Acting Commissary Steward Thomason, "ankle-deep in mashed potatoes garnished with a glittering sea of what had been steaks, gravy and fried eggs."26 In all probability, the meal that eventually got served was a mixture of tinned ham, sugar, salt, water, and modified potato starch, with a little dash of sodium nitrate to preserve its rosy color.

---

That article is a good read for some of the stories. It appears that cooking was preferably done on the surface - not for battery reasons but rather air / veneration. Also not the USS Harder was cooking while firing torpedoes - suggesting submersed operation.

[idlewords]

Then you can use it to make fizzy drinks.

[shagie]

That's not exactly a closed loop recycling system.

Additionally, flame is very restricted on a sub. You wouldn't be using any sort of methane to cook.

https://qr.ae/prgBKF

https://qr.ae/prgBsh

https://www.answers.com/Q/What_fuel_does_a_submarine_use_for...

[midoridensha]

The idea of using a combustible gas to cook is archaic and really dumb. It's amazing that people are still cooking this way today in many places. We've had better technology for ages.