On earth ordinary sunlight is freely available and effective for growing plants. But in space there are problems with excess heat production from plant-growth lighting, and the vacuum of space makes it difficult to shed this heat. The key to the problem is finding an efficient light source, one that converts as much of the electricity it consumes into light that plants use for photosynthesis.

I have compared the performance of numerous lighting systems and discovered some very interesting things. First of all sunlight is the best choice especially in space. However as a spacecraft orbits the earth the sun is frequently rising and setting every 45 minutes, and this makes it impossible to utilize. This may change for space platforms orbiting the sun, or on mars. Besides sunlight I have discovered that the next-best source of "white" light is the Sulfur Microwave Lamp. This light can be used both for growing plants and for ordinary illumination. The next best alternative are orange or green light-emitting diodes. These are not as good for general illumination (people can't see well under orange or green light) but they are extremely efficient for plant growth and produce less heat than any other light.

For more detailed info visit the "Agricultural Lighting" section of the Starship Generations website:

http://www.geocities.com/womplex_oo1/StarshipGenerations.html

Hey, cool (pun?) light source. Beats Gro-Lux. This raises a variety of very interesting issues of space-horticulture probably not appropriate here.

:D

Not appropriate? Me thinks you'll have to explain that - this being the general sci-tech board!

Clue #1:

'ere.

Come on man. Expain it to me. Quit wasting my time.

Unless you are in a low orbit that tracks the equator exactly. The sun will shine far longer than 45 minutes at a time. And even if it did, that is not as you say "impossible to utilize". If using sunlight on orbiting spacecraft was "impossible to utilize" due to the reason you site. Then NASA would never have put solar arrays on their satellites and orbiting space platforms. No spacecraft experiences exact amounts of sunlight and darkness on every orbit. Orbits are such that they pass in and out of the Earths' shadow and experience more sunlight than darkness. It seems to me that you know little about the life and needs of plants. And just as little about orbital spaceflight.

Come on man. Expain it to me. Quit wasting my time.

Your link doesn't work.

On earth ordinary sunlight is freely available and effective for growing plants. But in space there are problems with excess heat production from plant-growth lighting, and the vacuum of space makes it difficult to shed this heat. The key to the problem is finding an efficient light source, one that converts as much of the electricity it consumes into light that plants use for photosynthesis.

I have compared the performance of numerous lighting systems and discovered some very interesting things. First of all sunlight is the best choice especially in space. However as a spacecraft orbits the earth the sun is frequently rising and setting every 45 minutes, and this makes it impossible to utilize. This may change for space platforms orbiting the sun, or on mars. Besides sunlight I have discovered that the next-best source of "white" light is the Sulfur Microwave Lamp. This light can be used both for growing plants and for ordinary illumination. The next best alternative are orange or green light-emitting diodes. These are not as good for general illumination (people can't see well under orange or green light) but they are extremely efficient for plant growth and produce less heat than any other light.

For more detailed info visit the "Agricultural Lighting" section of the Starship Generations website:

http://www.geocities.com/womplex_oo1/StarshipGenerations.html

There's some incorrect information here. The periods of light and dark are not as you described them as most orbiting bodies are in sunlight for much greater periods than they are in the dark.

Also, intermittent light does not harm plants in the least. In that respect, the only thing that they DO require is eight hours of darkness out of every 24, Otherwise, they will be under too much stress to perform and grow properly.

I believe you need to do additional basic research on orbiting bodies AND horticulture.

Also, intermittent light does not harm plants in the least.
well technically you are correct, but, plants rely on night length to "know" when to flower. some plants will fail to flower if their dark cycle is interrupted for even a short period of light.

as soon as it gets dark a chemical starts collecting in the stems.
when a certain amount of this chemical accumulates flowering starts.
as long as the night cycle is under a certain amount of hours the flowering process doesn't start.

so, in this regard, intermittent light does harm a plant.

edit:
and cosmictraveler is correct, the page cannot be found

LEDs would be the most efficient, but the technology to get natural light from them is elusive.

Use a mix of LEDs. They are now pretty cheap even in ultraviolet.

How would a plant in zero gravity know where its roots went?
here, even if I plant a tulip bulb upside down, the roots will always grow down. What would it do in zero gravity?

How would a plant in zero gravity know where its roots went?
here, even if I plant a tulip bulb upside down, the roots will always grow down. What would it do in zero gravity?

Plants would get very confused in zero G, because yes, they need gravity to tell them which way what part should grow.

So there would have to be a rotating ring shape, or at least pods on the end of some spoke rotating on an axis, to generate false G and to be honest, if we could launch enough hardware to make such a structure it would make sense, and free up astronauts from having to exercise so much to prevent muscle and bone atrophy.

I think they'll figure something out for the negative effects of zero G. As for plant growth, I dont think it would really be a big problem. And if it is, genetic understanding will fix it in a few years/decades.

As for plant growth, I dont think it would really be a big problem.

It's not a big problem, but it is still a problem, many plants grow toward light, so the stems work out fine but without G, but the roots go a bit weird and that could be a problem for root vegetables. Some plants often do not flower or produce seeds in zero G. There may be a genetic fix for that, or hormonal stimulation perhaps, but that could have a cumulative effect after a while.

air circulation is the key to thermal problems associated with space agriculture

also....

perhaps bioengineering the plants themselves to absorb thermal energy for their own benefit...might be the key to the problem here.

http://www.moonsociety.org/images/changing/rillesettlementsection.gif

It's not a big problem, but it is still a problem, many plants grow toward light, so the stems work out fine but without G, but the roots go a bit weird and that could be a problem for root vegetables. Some plants often do not flower or produce seeds in zero G. There may be a genetic fix for that, or hormonal stimulation perhaps, but that could have a cumulative effect after a while.



well you could train roots by growing the plant through a funnel. Do you know what plants don't flower/produce seeds in zero G? I am just curious :bugeye: