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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?"
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?
"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.
Need Mercedes parts ?
If you build a habitat at one of the lunar poles it will be possible to build photovoltaic power plants which are both in sunlight and close enough to the habitat to directly feed power to it with electricity transmission lines. Additionally, this makes it easy for a habitat to be accessible for polar orbiting spacecraft. Habitats anywhere else on the moon move way from the orbit of your vehicle with the rotation of the moon. If your landing site is on the equator, then you can use an equatoral orbut, but for landing sites away from the poles or equator the orbitor continually moves away from the landing site, requiring that place correction manoeuvres be done before landing or docking with a returning vehicle.
http://michaelsmith.id.au
First, I've never heard the 50 sq meters (538 sqft) to sustain 1 human before. It's about the same area as an ultra-efficiency apartment. I assume that's for high-efficiency hydroponics. Interesting. I wonder if it'd be possible to grow some sort of edible algae to suppliment the more traditional crops? IE have an intense 2 week growing season, harvest when the sun goes down, then reseed when it comes back up? That would reduce the need to use your nuclear generator to keep the plants alive/in the proper growing cycle.
The gravity might mean you needing a slightly different breed, but given what I've seen with hydroponics/areoponics, I doubt that 1/6th gravity will have that much of a negative effect - but that would be something for the ISS to figure out!
I don't read AC A human right
Experiments proved that you can grow plants in microgravity.
The reason they taste like crap is not just because they were transported, but because they are varieties that have been selected for their longevity so that they can be transported.
Given that the tomatoes will probably be left on the vine until they are consumed, there's no reason to use the crappy modern supermarket tomato varieties - they can use heirloom breeds. There's always been a high emphasis on morale considerations in the American space programme, and food has always been one of the things that they pay attention to for morale purposes.
Only 1/6th gravity, no atmosphere - why not use mirrors? You can afford some inefficiency, such cheap materials would mean you don't need to worry too much about replacement costs due to meteorite hits.
It doesn't always have to cost gazillions - I refer you to the Russian use of pencils.. :)
Insert
So now I must either admit that I'm stupid, or burn you at the stake for your blatant heliocentric viewpoints.
I'm stupid.
Exactly! We should be setting up a farm on the moon. Just to test it out. Start small: 1 m2 of soil in a greenhouse.
The cost of such a mission is for a small part related to the cost of the boosters to get things in orbit and to the moon, and for a large part to the over-engineering that NASA is doing. That over-engineering is caused by a fear of failure. It's not like it's rocketscience to get anything to the moon. The fear of failure is the only thing that seems to hold us back.
If it costs 5000 $/kg to launch anything into a high orbit (which I will equate with getting it to the moon), a decent sized farm (1000 tons of material) would cost 5 billion $ in launch costs, which is nothing.
We could set up some practice greenhouses for a fraction of the cost. If failure is an option, that should be cheap enough in an age when more than that is spent on warfare every day...
This is all about the moon's 14-day, Lunar–night power famine. The solution is simply to use solar power satellites sitting at one of the Earth-Moon Lagrangian points, where the solar collectors will be in perpetual sunlight. Perpetual power means always-on growing lights so the problem is solved without the need for RTGs, and their pretty horrible thermal inefficiency (not to mention the problem of where do you get all that Pu239 from).
The main problem with using solar power satellites for supplying power to the Earth (the huge cost of launching them into space) is neatly inverted in the Lunar context as, by placing a solar colony's power hardware in space, you have a large mass of hardware that doesn't have to be soft-landed on the moon, representing a substantial saving.
Sorry. Use this.
http://gravitationalandspacebiology.org/index.php/journal/article/download/2/2
In fact just Google NASA Plant Growth Chamber
I love Jesus, except for his foreign policy.
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.
There is a huge issue with scale here. Lets do some rough calculations. A person needs 50^2 m of green space lit 1/3 of the time. To duplicate sunlight, we need about 1kW/m^2. Assume we have an LED that is about 10% efficient. That comes out to about 167kW per person. RTG like those on deep space probes have outputs measure in Watts, not kilowatts. RTGs don't scale well. If you need these kinds of outputs, you will be looking at conventional reactor. Getting rid of the excess heat is going to be a real challenge.
LEDs are inefficient. Photosynthesis is inefficient. If you need to make oxygen from water and you have electricity, there are much more efficient ways of doing it than using LEDs and plants.
You also would not store the power to run the LEDs, you would store plant products that are created during the two weeks that there is light.
"cost 5 billion $ in launch costs, which is nothing."
You sure you are not planning on a career in politics?
I only look human.
My mother is a halfling and my dad is an ogre, so that makes me an Ogreling
If all you want is visible light, then an RTG is a horribly inefficient way to get it. As has been previously suggested, a full-blown fission reactor is a bit of a problem due to heat dumping and safety. Why not take the middle ground?
Use a powerful alpha-only emitter such as Gd-148 and a mix of phosphors to give you the spectrum and intensity you need. Alpha particles are stopped by almost anything, and as long as you don't inhale/ingest them, they're relatively harmless. Since you're talking a space environment and can generally trust the astronauts to not make too many errors in judgement, you could even use a beta emitter with a little shielding. We already have the phosphors to generate RGB, unless we've forgotten how to make them (think CRT - the electron gun is nothing more than an electronic beta emitter).
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
The DOD is looking at some thorium reactors. By having small ones (10 MWe) they can bring these in via chopper, put them in a hole, and then provide power for bases, esp. FOB. These would then be easy to destroy if being overrun. Now, what is the advantage of this for the moon and mars? Ppl do not get too upset about thorium being sent up to space. The amount of uranium that would be needed to power it would be minimum. And one of the nice advantages is that the thorium reactor in sodium would have little to no chance of water in either locations. In addition, the 800C can be used not just to provide power, but also a number of chemical reactions and industrial operations (i.e. metal smelting for casting purposes). In addition, it provides the heat for the base without needing any real shielding.
I prefer the "u" in honour as it seems to be missing these days.
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
Second class citizen of the New Gilded Age
I mean, I grow some plants that require lots of sunlight but that for reasons beyond my power cannot be cultivated in the open air.
If the NASA sends me a couple of these atoms, I can assure them that I will use them on my plants, that I will keep a serious control of its growth and that I will tell them if some unexpected toxic byproduct appears in them.
Why can't
A. You're rating LED efficiency by lumens - WRONG. Photon flux density. Remember, lumens are for humans.
B. "Now LED's are at about 100 lumens per watt" - WRONG AGAIN. We have 5500K white LEDs with 150+ lumens per watt, and Cree has already broken 220+ lux/w - LAST YEAR.
C. "So you need about 1,300 watts to light up one square meter to the same intensity as sunlight. Very roughly." Sure, but you're implying most of our food crops even need that sort of intensity - they don't.
D. "Solar cells and inverters and wiring have an end-to-end efficiency of around 10%" Yea, if you use cheapo garbage. The stuff powering my research facility, end-to-end, pushes roughly 22%.
E. "So we need about 13 meter-square panels at right-angles all the time to the Sun to get 13,000 watts during sunny days on the Moon." I see you totally ignore the fact that our moon has no atmosphere worth mentioning, so that photon flux density is actually much higher versus on earth, you also forget that the moon is closer to the sun then we are roughly half of the time, so again, the photon flux is even greater.
F. "So we're back up to about 20 meter-square panels to light up one meter. To light up 50 square meters, one person's worth, that's ONE THOUSAND SQUARE METER STEERABLE PANELS." Except again, you're implying that plants need such intense light to grow. That's wrong. Totally wrong.
G. "And oh, where are you going to get the water for 50 square meters of whatnot growing?" Plenty of hydrogen and oxygen on the moon, plus we've found water there. We can make fake snow by just expelling compressed hydrogen and oxygen in a shared jet nozzle (it's how we make snow during the summer on mountain ski resorts) so I bet making water from scratch components would not be that difficult. On top of that, we've got hydroponics systems that can drop water requirements as much as 99% for many crops.
Your numbers fail to take into account how plants grow and just how much space is needed.
And as an aside - I do this professionally. I'm going to have to say your words are sorely lacking in knowledge on the relevant subjects.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
Bacteria that break down organic matter into ammonia, then ammonia to nitrite then nitrite to nitrate would be important if you're trying to compost waste. But, see, the thing is, bacteria are pretty light and can grow pretty quickly. If you wanted to do this you would't actually need to keep sendig bacteria up there.
Not that you'd actually need it to grow plants, just to compose waste back into fertilizer. Initially, you'd send up a few tons of fertilizers to get going but that's a one time deal. Eventuall there'd be enough N, P, K and micronutrients that recycling would be enough.
There's really no mystery about bugs and insects, it really is pretty well understood. Any good aquarium book can explain it.
As the dork who created sci.aquaria I have it on good authority that JPL has at the very least, one fishtank and it's not like this (wait for it) is rocket science.
Need Mercedes parts ?
"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.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
If you need to grow plants for food/oxygen off-world, that means you have people there.
If you have people there, that means they're going to be doing other stuff.
If they're going to be doing other stuff, that means they're going to need power.
If they're going to need power, you should just have a power generator which pumps out electricity, and channel some of that electricity to the LEDs providing light for your hydroponics lab. There's no need to put an RTG inside each LED.
Especially considering that most of the energy given off by an RTG is thermal (the RTG aboard Curiosity gives off about 2 kW of thermal energy, about 110 W of which is converted to electricity). With an RTG inside each light source, every minor light source is also a major heat source, and your heating/cooling problems become that much more complicated. With all your power centralized in a few places (for redundancy), you can centralize heat pumps which deliver only as much heat only where needed.
I couldn't give you numbers but I can tell you that given how a fair bit of vegetative food/herb crops don't require much in the way of light (300-500umol) we don't have to worry much about power if we utilize LED. Also, newer systems currently in design are specifically made to grow the same area with (in my current tests) with half of what typical LED lighting would need.
On top of that, many have proposed excellent power sources. RTG are one idea, and we can use the lunar sub-surface as a heat sink. Nuclear batteries are another possibility. Lithium packs that are rechargeable are also viable (someone mentioned a Tesla pack somewhere in the thread.) Hell, just turn Eternity peak into a solar farm and HVDC the power to the site.
We're already well past farming in space. We have the diode efficiencies, we have the power technology, we have the knowledge, and we have willing people. It's the getting resources to the site problem, and our government that's holding us back.
I'd gladly spend my entire remaining life on the moon being a space farmer. Give me what I need, and watch me get to work. Hell, the actual building and equipment should be CHEAP compared to the cost of getting it and myself and a capable crew there.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.