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Comment by zeteo | Hacker News Reader

>Leafy greens are ideal, ready to be consumed as soon as they’re plucked [...] The most outlandish crops would be wheat and rice. [...P]lants that need processing make less attractive candidates for space travel.

Well, these "outlandish" cereal crops currently provide the bulk of calories for almost everyone on the planet. If you're serious about feeding astronauts in space, they are exactly the plants that you need to start with. And don't tell me equipment to grind wheat or hull rice would be complicated, compared with other stuff that's in orbit already.

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The calculus for what plants make sense in space is entirely different than what plants make sense on earth. Cereals provide the bulk of earth calories because they optimize things like warm days, long term storage, transportation, water consumption, etc. The critical resources in space are things like 3D space, waste, preparation requirements, or even smell, so it would make no sense to choose space crops based on what stacks best in a grain silo.

We didn't choose to farm grains based on what would stack best in a grain silo. We built grain silos because we liked grain so much. Lettuce is mostly water; you won't be able to feed even one person on it, no matter how efficiently you can grow it.

I don't think that's true -- we didn't choose grain because "we like it so much". Grain is easy to store and has a long shelf life, which means it can last long enough to get you through the long non-growing seasons. When you scale up production, you need somewhere to put it... hence silos. By way of another analogy: refrigeration is the motivating force behind much of the food we consume now.

In my grandmother's day, all food post-harvest was either dried (grains and meats), canned, or pickled.

This is fair. We chose grain because we hated starving to death in the winter. But we like grain now! History and evolution are on its side at this point. Refrigeration enables us to eat many things that people two generations ago literally couldn't, but I note that cereals are still a very large portion of what we, in all our riches, choose to eat. My family eats a lot of bread, without bothering to refrigerate it.

Some things that we refrigerate now, but historically didn't have to, are eggs and milk. Do you know how those were treated in your grandmother's day? The image I have from history is that milk was produced and consumed in large quantities, and "refrigerated" (iceboxed) then as now. But clearly (?), what was good enough for milk was too good for... lettuce? ;)

Just as a fun side observation, there are some other obvious concerns, if you're starting from a hunter-gatherer state: jerky keeps significantly better than grain does, and is packed full of calories, and is ultra-low-tech, but grain production can be scaled up in a way that would be extremely difficult for jerky. So we built granaries and tolerated massive losses to rats essentially because even after the losses we could produce more grain than "other food".

Eggs and Milk came right from the chickens and cows. Thankfully, I was spared this lifestyle (thanks mom!).

Some of the earliest practical refrigeration on the farm (eg. the Icy Ball [1]) is from the early-late 1920s. That was during my grandmother's lifetime. If you think about it, the change in lifestyles she's witnessed in ~100 years is pretty bloody impressive: refrigeration, electricity, telephones, computers, etc.

[1] https://en.wikipedia.org/wiki/Icyball

Be careful with your "we." The US is one of the few countries where eggs are typically refrigerated. Eggs will last for months if merely kept cool.

Historically, milk was "preserved" by turning it into cheese.

Lettuce and grains are hardly the only options. Potatoes, rice, olives, a wide range of beans, even aqatic plants etc are all with considering. After all the fact grains need little water is one of there main apeals, but water can easily be recycled in an enclosed environment so the constraints are vary different.

Of course, and I wouldn't be making fun of a plan to grow potatoes (such a plan was already discussed in another comment when I made mine). But what they are growing is lettuce, and the comment I responded to specifically supported lettuce over grains because it was easier to grow. And I'm sure that that's why they're growing it right now... but if we wanted to produce food in space, lettuce would be a terrible choice, because it's barely food.

The current efforts are more of a because-it's-there thing than a what-would-we-like-to-grow thing, and at some point "the calculus for what plants make sense in space" will have to take into account which plants we actually want to consume.

EDIT:

> Potatoes, rice, olives, a wide range of beans, even aq[u]atic plants etc are all w[or]th considering. After all the fact grains need little water is one of the[ir] main ap[p]eals

Rice is a grain. A grain that grows in swamps. It could best be described as "water-intensive".

More like water-tolerant. Rice field flooding is for weed control (or use of land that naturally floods), rice itself prefers not to be waterlogged.

I think the current goal is fresh food and fiber vs reducing takeoff weight. Basicly they can store everything else for over a year but lettuce to make a sandwich in space. Astronauts are also working 12+ hour days so having something that's really easy to grow and harvest can be worth it for morale if nothing else. Not to mention the space and energy costs of trying to be self sustaining.

Colonization or really long term missions is where your arguments really take off.

I agree with your criticism, at least against the article as written.

By volume, potatoes (the 2nd option beyond leafy greens according to NASA) have 30x the calories as lettuce. I don't see how the math could ever work out.

In fact, potatoes might be a good optionally nutritionally. Chris Voigt went on an all potato diet for 60 days and seemingly suffered no ill effects: http://wholehealthsource.blogspot.com/2010/12/interview-with... I wouldn't want to see someone try the same thing with lettuce.

Potatoes, milk and molybdenum[1]. Considering powdered milk is pretty light, this might be first-generation space chow. They've got a lot of free time to eat dozens of pounds of potatoes anyways.

1. http://www.straightdope.com/columns/read/2828/could-i-surviv...

I would aim for equipment likely to have less complications, traditional methods for grinding most grains kicks up a lot of fine particles so the filtration of those particles would be a big concern. I do not know much about rice harvesting, but would not wheat have to be effectively dried to replicate what happens in nature before it would be harvested?

Now, cooking them down might be an option more suited, either that or most food prep is going to be done clean room style, isolated from the rest of the area. If we go along the route of wet, cannot some sea products be used as substitutes?

Also, the idea of using various combinations of plants to replicate existing animal products is coming along well, there are artificial egg products coming to market. http://www.dailymail.co.uk/sciencetech/article-2416808/Artif...

If you are serious about feeding astronauts in space, then you need to classify what gives the highest percentage edible matter in the whole plant and needs the least mass of things like water. Leafy plants with minimal root systems seem like a good start.

Grains have loads of stalk and root that you don't eat, tend to need a lot of water and need extra equipment in preparation and are often used as powders, which easily form combustible suspensions in low gravity.

>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.

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.

>Leafy plants with minimal root systems seem like a good start.

yes, or one can consider potatoes. 2-3 times higher calorie/water efficiency than grains.

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