I was watching the movie last night and it occured to me as the oxygen problem became more critical, what if they had a plant? maybe a few? and a grow light (which would have used valuable power but…)? Could a plant produce enough oxygen over that course of time in a space that size to have made any difference?
Actually, it wasn’t an oxygen level problem, since they still had reserves of oxygen in tanks, or, at last resort, in the suit supplies.
Their problem was carbon dioxide buildup.
Usually, the CO2 was ‘scrubbed’ out of the air with cartridges of lithium hydroxide. Additional oxygen was simply bled into the cabin to keep the oxygen level up.
(That was the whole Junkyard War thing with the hose, sock and duct tape- they were trying to make one module’s square LiHox cartridge fit into the other module’s round fitting.)
A plant wouldn’t be able to reclaim/recycle CO2 fast enough, given the very limited volumes, relatively high CO2 production from the astronauts’ respiration, and limited sunlight.
On something like a huge space station or self-sustaining (moon) base, a large “greenhouse” of the right kind of plants could help compensate for the CO2/O2 levels, but I’d wager it’d have to be in the several hundred plants per human range…
That brings up the question. There are millions and millions of animals all breathing O2. There’s a billion Chinese alone
So there must be several hundreds of plants times all those millions and millions of animals on this planet. Are there that many plants? Or does each blade of grass count as one plant? If it does, then my lawn is helping to keep a few hundred animals alive!
In that case, they could have seeded the floor with grass. Then they could have eliminated on it too to continue the cycle. Perfect.
(1) 1 plant’s respiration does not balance 1 animal’s respiration (I don’t have the numbers, but I’d say that’s a safe assumption).
(2) “plants” (green things that generate oxygen) probably outnumber animals…again I don’t have the numbers, but it’s probably a safe assumption given that plants are at the base of the food chain (ok, ‘web’)…the most significant numbers coming from phytoplankton in the oceans.
I grew up in a desert, which certainly didn’t have enough natural plant growth to compensate for the animals living there. But then I visited (then moved) to the Washington DC area. I’d never seen plant cover so dense in person.
Knowing that there is much denser plant growth elsewhere, I feel better.
Also, the oceans’ plankton growth also absorbs a lot of CO[sub]2[/sub].
As to the plant:animal ratio. A tuft of grass is a single plant as much as a redwood tree is. But of course, the latter absorbs much more CO[sub]2[/sub].
A better measure would be a plant biomass to animal biomass ratio.
Also remember that when a plant isn’t photosynthesizing that it’s respirating just like an animal. It’s burning some of the carbohydrates that it’s made in the daytime, and must use some O[sub]2[/sub] to do that.
This is intended as the agricultural portion of a CELSS (Closed Environment Life Support System) designed to support 10,000 people. So, according to this plan, you need an average of 86.92 m[sup]2[/sup] to support each person, assuming normal food crops including wheat, soybeans, potatoes, strawberries, etc. An algae-based system might provide more space-efficiency for atmospheric recycling, but wouldn’t have the food value of the crop system. A search on “CELSS” will turn up quite a few more interesting hits.
For those who are interested, the document includes detailed calculations for various elements of the design, including O[sub]2[/sub] and CO[sub]2[/sub] control.