Replenish life support on a primitive planet

[robject]

But I need to know what to roleplay. For me, Traveller is a science fiction game, and where setting elements can be grounded in reality, I'd prefer to do so.

This thread has been a great help so far!

Urrrh, I understand.

 

[atpollard]

I believe TCS is no longer canon. Aramis is this correct or is my memory faulty in another area?

I think it is just the economics that was decanonized. You can't extrapolate TCS economics across the 3I, they were only valid for the wargame.

 

[aramis]

I think it is just the economics that was decanonized. You can't extrapolate TCS economics across the 3I, they were only valid for the wargame.

That is also my understanding. Especially since the astrography has separately been canonized by inclusion in later products.

I know nothing of this chemistry, but reading wiki it seems that energy is the limiting factor. Luckily Traveller ships have plenty of power.

Using a reversible process very little of the reaction base would be consumed.

The reaction is, ideally, anhydrous lithium hydroxide (LiOH); hydrated, it's a liquid (LiOH•H20).

2 LiOH + CO2 → Li2CO3 + H2O.
2 LiOH•H2O + CO2 → Li2CO3 + 3 H2O

At higher temperatures, the reverse becomes the standard reaction...
but you have to balance temperature and pressure, and not lose the water, while venting the CO2...

Plus you have to clean the post-scrubber and pre-scrubber filters - because LiOH is alkaline (a base) and toxic; it can cause chemical burns in wet tissues readily.

Note also Lithium Carbonate (Li2CO3), while far less toxic than Lithium Hydroxide, is psychoactive. So you don't want it escaping into the airflow, either...

 

[Enoki]

I think the quicklime (CaO) process would be better. You have CaO + H20 and simply pass the atmosphere of the ship through the scrubber. CO2 is removed forming CaCO3. You get H2 as a byproduct, and the process is exothermic meaning you can use the energy generated to do other stuff.

The chemicals involved are common and basic and you aren't dealing with anything toxic being left over. You are left with a viscous material that solidifies into limestone.

 

[aramis]

I think the quicklime (CaO) process would be better. You have CaO + H20 and simply pass the atmosphere of the ship through the scrubber. CO2 is removed forming CaCO3. You get H2 as a byproduct, and the process is exothermic meaning you can use the energy generated to do other stuff.

The chemicals involved are common and basic and you aren't dealing with anything toxic being left over. You are left with a viscous material that solidifies into limestone.

Quicklime isn't used for the very reason you mentioned: it's quite exothermic.
It's also harder to recover after use, and in large installations, it becomes essentially cement, as it self-dries...

Plus, it's just as much an irritant and caustic.

Getting rid of heat is the #1 concern for habitability of large space stations. It's an area much handwaved in Traveller

 

[AnotherDilbert]

I think the ISS uses a zeolite reaction base, rather than a lithium based reaction base. The principle would be the same, but at least it's not psychoactive?

 

[aramis]

I think the ISS uses a zeolite reaction base, rather than a lithium based reaction base. The principle would be the same, but at least it's not psychoactive?

Yep, also called sodium aluminosilicate AlNaO6Si2 . It's less selective, less toxic, not pychoactive, and not as efficient, but easier to regenerate. Takes a bit of nitrogen with it.

 

[AnotherDilbert]

Ok, so from a black box perspective they would work the same: Not requiring additional consumables every week, but requiring some power to recycle?

 

[aramis]

Ok, so from a black box perspective they would work the same: Not requiring additional consumables every week, but requiring some power to recycle?

Wrong. You'll need additional nitrogen with the Quicklime. You'll need additional O2 with both.

Quicklime can be used as a nitrogen scrubber as well as a CO2 scrubber. In fact, it's often used to generate oxygen in tankless oxygen concentrator, which it does by scrubbing the CO, CO2, and N2.

The choice of quicklime for the ISS has more to do with cost than efficiency - quicklime has a much higher production and use rate outside the space industry, while Lithium Hydroxide is pretty much divers and submarines.

 

[Enoki]

As I've pointed out NH3 gives you the nitrogen if you are running a fuel processor so replacing it shouldn't be a problem. Even if not, I'd think any ship would have extra aboard as compressed gas to pressurize tanks and such as it's nonflammable and would be cheap and available for that use.

As for quicklime being exothermic, I'd think that'd be the least of a ship's problems. The ship would already be generating considerable heat from the power plant and what not. Just add the CO2 scrubber as another source of waste heat to be dumped or used as a low grade propulsion supplement.

I'd think that given the usual economics of running a starship in Traveller, cheap would be high on anyone's list of desirable traits for equipment operating costs...

 

[AnotherDilbert]

Wrong. You'll need additional nitrogen with the Quicklime. You'll need additional O2 with both.

I was thinking about the reaction base, e.g. the zeolite.

Once we have separated the CO₂ we can, at least theoretically, split it into C and O₂ with all the power we have available, as is apparently being looked into for a potential Mars mission?


We will of course always lose some reaction base and gasses so they will need topping up eventually, but probably not every week?

 

[aramis]

I was thinking about the reaction base, e.g. the zeolite.

Once we have separated the CO₂ we can, at least theoretically, split it into C and O₂ with all the power we have available, as is apparently being looked into for a potential Mars mission?


We will of course always lose some reaction base and gasses so they will need topping up eventually, but probably not every week?

The zeolite reset works best by heating it in vacuum, so the CO2 is lost. As is the trapped Nitrogen. At least according to the NASA paper on it I read a few years ago.

Note that the nitrogen literally clogs the molecular pores in the crystalline structure, resulting in surface-only reactions with the CO2. It's best removed by vacuum. Nitrogen also chemically reacts with some of the zeolite.

So, you're going to need supplementary air-volume.

And that's before accounting for the inevitable leaks, the lock-cycle losses, the dump-overboard-and-replace cycles due to other chemical contaminants detected in the airflow, etc.

A human uses 550L of gaseous O2 per day. Roughly.

Cracking that from the CO2 when the CO2 is scrubbed by anything other than cryogenic distillation is a problem of delay, as well as hazardous chemical reactions. Cryo, on the other hand, has other issues, like power, thermal waste heat, thermal isolation, and scale efficiencies.

The best carbon scrubbing option for long term is to use plants, not inorganic chem. But that's volume inefficient.

 

[kilemall]

The best carbon scrubbing option for long term is to use plants, not inorganic chem. But that's volume inefficient.

Good thing IMTU has hyperalgae, genetically altered and treated like a radioactive re: safe handling.

One thing to keep in mind, any atmosphere that is not primarily oxygen isn't going to have all these oxidized minerals.

No MOGE, no sand.

 

[AnotherDilbert]

A human uses 550L of gaseous O2 per day. Roughly.

That's hardly a problem if we can electrolyse water.

 

[Timerover51]

While the thread appears to focus mainly on the oxygen and carbon dioxide issue, there is another aspect of life support that needs to be considered. That is food. I would normally assume that a ship would carry at least a month's supplies for the crew and all possible passengers. A Traveller dTon can hold a lot of food, but a ship might not emphasis carrying large reserve.

A Tech Level 4 planet with a reasonable atmosphere, and a population exponent of at least 5 should be able to supply a ship with canned and frozen food of acceptable quality. A Tech Level 3 planet might be able to supply canned food, with the requirement that the safety of the canning be checked. It should be noted that the canned vegetable industry in Australia had some problems safely feeding US servicemen there in World War 2 as there were 2 significant botulism occurrence with deaths among the US servicemen. Safe canned goods should not be taken for granted.

With Tech Level 1 and 2, a ship could acquire salted meat provisions, which might not exactly thrill the consumers, and fresh provisions. Unless the ship has adequate refrigerator and freezer space for the fresh foods, an adequate food supply for a Jump might prove to be a problem.

 

[aramis]

That's hardly a problem if we can electrolyse water.

It's additional complexity, additional points of failure, additional maintenance, and space & cost ineffective for commercial craft.

Electrolysis also generates several undesired side chemicals - Ozone, Nitrous Oxide, others. When filtering for Hydrogen, Deuterium, and Tritium, no biggie... you're dumping everything else, and using molecular sieves for cleanup.

Replaceable scrubbers/filters (remembering 2 weeks per cycle) are far safer than rechargable of the same compounds - but skilled crews can still recharge those in a pinch... and the safest and sanest for civil crews with frequently marginally competent crews.

Something that can be stored and swapped, and needs only a working fan and an O2 tank to be used.

that's LiOH; Add an N2 tank, and Ca(OH)2 works, too. But that's more tankage needed.

 

[Pyromancer]

With Tech Level 1 and 2, a ship could acquire salted meat provisions, which might not exactly thrill the consumers, and fresh provisions. Unless the ship has adequate refrigerator and freezer space for the fresh foods, an adequate food supply for a Jump might prove to be a problem.

There are a lot of fruits and vegetables that won't spoil within the week or two it takes to jump. Flour, cereal and rice last months or years without cooling, as probably would the local equivalents. So if there are humans on the world, my stranded spacefarers probably will find stuff to eat. Food IS a problem, but probably quite a way down on the list.

 

[coliver988]

Relating to the other thread of living accommodations, and a published adventure: the lab ship apparently has a walk in freezer with enough space to store a few people (I did run that for my players close to Halloween - timing was just about right!).

 

[GypsyComet]

the lab ship apparently has a walk in freezer

I think that would depend on the mission of the lab ship. A bio-medical lab ship should have cold space in at least a couple different temperature ranges, while an astronomy or earth sciences ship won't unless they brought along a high class chef to help pass the time.

 

[Pyromancer]

What about volumes? I vaguely remember that in GURPS Space, the numbers boiled down to 1 m³ of food per man and year. Although I can't find the quote right now, it sounds plausible.

For Traveller, this would mean that 1 dton of durable food would be enough for 750 weeks for one person. I would set 1 dton of fresh food (good for morale!) as 250 weeks for one person (of course, it wouldn't be fresh any more after 250 weeks). Other opinions?

And what about the air? O2 and chemicals for CO2 scrubbers? Any good rule of thumb for volume?