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Comment by zeteo | Hacker News Reader

>you need to classify what gives the highest percentage edible matter in the whole plant and needs the least mass of things like water

Maybe if you don't care about total area. Stalks and all, grains and tubers are the most efficient at transforming square footage of sunlight into edible calories; water would get completely recycled in any case.

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Square footage of sunlight is not necessarily the limiting factor in space as it is on earth; (solar) energy for grow lights is cheap, pressurized volume is very very expensive. And even if water is recycled, tying a certain amount of it up in your food production system still has a cost.

Scaling to sustainable numbers though heat rejection will be a serious consideration. Plants essentially convert light to chemical energy that would then sustain the astronauts. The catch is plants aren't really that efficient. They're around 1% if I remember rightly. That means there would be 99 people worth of additional heat for each one you're feeding full time.

Trying to argue on the basis of photosynthesis being inefficient doesn't really help, I mean sure PV is more efficient in energy conversion, but you can't eat electricity. So given they'd be eating plants anyway, eating ones that have not been shot up the gravity well is probably more efficient.

My point was that for the current ISS, you're talking about designing, building, launching, and attaching more infrastructure.

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