LED Grow Lights (vs. Sunshine) in Space Habitats

LED grow lights are the best source of light for plants in space, as well as for animals. LED lighting is far superior to natural sunshine in space habitats, for many reasons, as discussed in this article.

The main reason for writing this article is to promote research and development which can be done on very low budgets and in peoples' garages and other personal and commercial facilities, to find optimal lighting for various food crops in order to try to maximize food crop productivity in space.

Plants utilize only certain wavelengths of light for photosynthesis and growth. LED grow lights are tuned to these wavelengths. The advantages of LED light include:

• Optimization of light wavelengths for growth
• Optimization of light intensity for growth, at specific wavelengths
• Optimization of lighting schedules for growth
• Minimization of harmful radiation by locating plants in well shielded units
• Flexibility in habitat design, whereby plant growth boxes can be fitted in most anywhere
• LEDs are low power and very efficient in converting electricity to light
• LEDs are long lived
• LEDs do not release harmful materials like some alternative grow lights could

(Before LEDs, fluorescent and high pressure sodium (HPS) lamps were used as grow lights.)

LEDs can provide a much higher intensity of light at specific wavelengths without burning the plants because of the omission of other wavelengths which are not useful but would cause overheating. The small sizes of LEDs also allows the LEDs to be arranged close to each plant so that the power is used efficiently, and various other kinds of plants located nearby can receive different optimal wavelengths and intensities.

For example, LEDs have manipulated plants to increase greenhouse plant flowering, crop yield, and nutritional quality.

NASA has performed extensive work going back to the 1990s in developing LED grow lights for space, and has used them to grow different food plants on the International Space Station over many years.

LED lighting is also good as a general light source for humans and other animals in space, of course, as it can synchronize lighting to our natural rhythms of sleeping and waking hours. These would otherwise be disrupted in orbital space (such as 90 minute sunrise and sunset cycles in low Earth orbit) as well as places such as the lunar surface (two week days and two week nights).

Further, trying to design a space station or lunar or Mars surface habitat using windows creates engineering complications, risks, and costs. Instead, burying habitats far underground, and putting thick light-blocking shielding around orbital habitats, is far better, for:

• Shielding from damaging and dangerous cosmic and solar radiation
• Shielding from meteoroids and space debris
• Thermal insulation and temperature regulation
• Much simpler and less risky habitat designs

Monitors inside habitats connected to video cameras outside of habitats can give everybody inside the habitat the best "window views" of their own choices.

There is already a large amount of technical literature on LED grow lights and plants. Commercial facilities such as vertical farms (including in urban centers), greenhouses, and other horticultural environments have also experimented with LED grow lights and produced food commercially.

However, there are also many gaps in the literature, especially as regards high calorie and nutritious food crops most applicable to space habitats in particular, as regards optimal wavelengths, intensities, and schedules of lighting.

In addition to research into LED lighting, there can also be research on varying hydroponics and aeroponics parameters.

It would be good to systematically review and identify gaps, and then create proposals for small scale research projects.

What is learned from such research projects might be of commercial value to vertical farms on Earth before we deploy them to space.

Vertical farming has become increasingly popular in order to grow fresh food in city centers, grow food all year, isolate plants from pests and disadvantageous environmental conditions, and improve the quality of foods.

After harvesting, LED lights have also improved the storage life and nutritional value of some foods (together with control of the storage atmosphere). Some wavelengths can inhibit bacteria and fungi without heating the produce significantly, such as selected UV wavelengths, and of course without chemicals or applying heat for this purpose. Research has also shown that some LED wavelengths can promote further nutritional composition of some foods after harvesting by their secondary metabolism (which is not part of the growth and development of primary metabolism).

There should be many opportunities for nongovernmental, commercial development of best practices.

(Indeed, it is interesting to consider volunteering for or seeking employment with ongoing commercial vertical farming projects such as in city center buildings ...)

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