Nuclear Powered LEDs For Space Farming

DevotedSkeptic writes with an interesting article on possible lighting sources for growing food on the moon and other off-world locations. From the article: "... Agriculture remains the key to living and working off-world. All the mineral ore in the solar system can't replace the fact that for extended periods on the Moon or Mars, future off-worlders will need bio-regenerative systems in order to prosper. Here on earth, researchers still debate how best to make those possible, but nuclear-powered state of the art LED technology is arguably what will drive photosynthesis so necessary to provide both food and oxygen for future lunar colonists. ... Although during the two weeks that make up the long lunar day astronauts might be able to funnel refracted sunlight into covered greenhouses or subsurface lava tunnels, they will be left without a light source during the long lunar night. Current solar-powered battery storage technology isn't adequate to sustain artificial light sources for two weeks at the time. Thus, the most practical solution is simply to use some sort of Radioisotope Thermoelectric Generator, not unlike the one powering the current Mars Science lab, to power the LEDs that will spur photosynthesis in lunar greenhouses. ... On earth, Mitchell says it takes roughly 50 square meters of agriculture to provide both food and oxygen life to support one human. But, as he points out, who can say how productive plants are ultimately going to be on the moon, in gravity that is only one sixth that of earth?"

Comments

We should know this already...

[Anonymous Coward]

We should freakin know how well plants grow in gravity based on the nearly 3decades of shuttle experiments... Did this Mitchell not bother to look that up?

Re:We should know this already...

[fuzzyfuzzyfungus]

Trying to settle on the Moon and Mars without such stuff is like trying to jump before even being able to stand.

I'd argue entirely to the contrary: Open space, from anywhere in high-enough-so-the-atmosphere-doesn't-get-you earth orbit out to the darkest edges of nowhere where Azathoth lurks in the dark places between the stars, is about as hostile an environment as one can reasonably imagine operating. Other than a reasonably steady supply of photons there is nothing there that you didn't bring with you(at considerable cost).

By contrast, any planet that isn't actively trying to murder you(eg. Venus and Mercury probably aren't at the top of the list) has massive amounts of potentially useful elements in the same gravity well as you. Just lying there for the taking. An overwhelmingly less hostile situation; but with more scientific novelty than just building a mockup in some place cold and dusty.

Satellites are crazy useful to the inhabitants of the planets that they orbit; but actually putting humans on them is a waste of time and space(with the one quite specific exception of doing low and zero-g medical research, which you can't easily do under other circumstances.

If you want cool planetary research, spewing robots at interesting planets is very likely the cheapest way to get it. If you want human populations that aren't on earth, colonizing objects that come with large amounts of free matter, and maybe even an atmosphere, rather than building teeny little bubble-capsules is overwhelmingly more practical. If you want to do research on long-term closed-system design and engineering, it's probably a waste to leave earth at all. Just buy up a bunch of warehouse space somewhere cheap, and you can run a dozen simultaneous experiments on earth for less than you could a single experiment in earth orbit(plus, if something goes wrong, you can just scrub the experiment, open the door, and resupply from home depot, rather than having to resort to mass deaths or heroic measures....)

Really, the only reason to have humans in open space for any nontrivial period of time would be research on how to deliver them reasonably safe and intact to an eventual planetary colony elsewhere(which may or may not actually involve sending humans at all. If team biotech can get amniotic tubes working, there would be some major benefits in just shipping a big cryo-flask full of iced zygotes, rather than dealing with adult astronauts....)

Re:We should know this already...

[mlush]

I guess the sun doesn't work in space...why not create greenhouses and use the sun to grow plants rather than create some overly complex system?

Perhaps its something to do with the 2 week lunar night that a lunar colony would experience.

Huh?

[rs79]

"Current solar-powered battery storage technology isn't adequate to sustain artificial light sources for two weeks at the time"

Oh rly? Use enough Tesla power packs and they'll be fine. Lithium is light.

"But, as he points out, who can say how productive plants are ultimately going to be on the moon, in gravity that is only one sixth that of earth?"

Other than the fact we know already and that plants could be grown in earth gravity in a centrifuge yeah, good point.

Sheesh.

No actually not

[Sycraft-fu]

Notice the reasons that NASA was interested in a pen: Pencils could break and cause a hazard, and additionally were susceptible to a fast burn in the oxygen rich environment.

Pencils worked. They didn't work "just fine" they were a hazard, but nobody has a better system, until the pressurized pen.

While high tech for its own sake can be a bad idea often there's good reasons for new technology. The old tech may work but the new tech works better, more efficient, more reliable, less dangerously, etc.

As a simple example you've probably used, take optical mice vs ball mice. Yes ball mice work, however they have numerous problems. Optical mice work better. They are less susceptible to dirt, easier to clean, track on more surfaces, work at all angles including upside down and so on. As an extension, newer ones are getting even better, they have greater precision, track on even more surfaces, and so on.

So if you want, you can heat your water in your low tech "works just fine" fire pit with wood and a metal bucket. I think I'll heat mine in my high tech sealed water heater that is very efficient, safe, and convenient, because it works better.

Re:Problem with the opinion

[crunchygranola]

Actual research with LEDs, which can selectively emit light in the bands actually used for photosynthesis, suggests that the amount of electricity required for illumination is in the order of 1000 watt/m^2 period, no "factor of 10" multiplier needed. So 50 KW is needed continuous (no, you don't turn the lights off for most crops - only photoperiod sensitive ones light strawberries).

http://hortsci.ashspublications.org/content/43/7/1947.full

Re:I can easily Halve the space needed.

[Khyber]

"2: no it can't. try running an indoor grow house off batteries for a week solid. it's not a trivial task"

Done. It's more trivial than you think with LED.

"1: you piss away half your energy converting to battery and back again."

Hey, I have a novel idea. Why not power the LEDs via STRAIGHT DC ONCE IT'S AT THE BATTERY? LEDs *ARE* DC devices, after all.

I feel so alone in this whole thread. Not a single one of you seems to have a clue. The downside of being a horticultural research director with a heavy focus on optoelectronic horticulture.