NASA has found another way to experiment with LED grow lights on the International Space Station, as it has installed a hydroponic and aeroponic system that taps the LEDs already in place in the craft’s Veggie racks.
The new “XROOTS” gear arrived on a cargo delivery in February and is now cultivating vegetables such as mizuna greens and radishes inside one of the two Veggie chambers on the ISS.
Veggie is the general set of grow lights and apparatus that has been onboard since 2014. The ISS houses at least two Veggies and is likely still using the “PONDS” nutrient delivery system in the other.
NASA hypothesizes that XROOTS might scale up better than PONDS.
Astronauts use the Veggie chamber to grow their own edible greens and help research the growth of plants in space, which in turn can provide insights for growth on Earth.
For at least three years, they have been feeding plants inside Veggie with PONDS (Passive Orbital Nutrient Delivery System). Unlike XROOTS, PONDS is not strictly hydroponic or aeroponic. It uses a combination of water and fertilizer pellets — released automatically without human intervention or a power source, thus the use of “passive.” Veggie also houses soil-based growth.
XROOTS (eXposed Root On-Orbit Test System) is different. It uses only hydroponic or aeroponic growth techniques, which between them apply nutrient-enriched water, air, or mist. NASA suggests that XROOTS might take up less room than PONDS, especially as the ISS or future spacecraft attempt larger-scale growth.
“Current plant-growth systems use soil or growing media, and the eXposed Root On-Orbit Test System (XROOTS) evaluates alternative approaches to reduce the overall system mass,” NASA explained. In an apparent reference to PONDS, it notes that current “particulate media–based water and nutrient delivery systems… do not scale well in a space environment due to mass, containment, maintenance, and sanitation issues.”
By comparison, “hydroponic and aeroponic techniques could provide a vital alternative for plant systems of sufficient size to contribute to future space exploration,” NASA stated on an XROOTS webpage.
One thing that XROOTS has in common with PONDS is LED lighting, as NASA explained earlier this year in describing how XROOTS would be installed.
“Following launch, the Base Plate and bellows is removed from the Veggie Facility and the XROOTS module is mounted below Veggie, with data and power connections made to the EXPRESS Rack,” the space agency noted. “Following a thorough checkout of the system, seed cartridges are placed in the XROOTS chambers, the nutrient solution is mixed and placed in the XROOTS reservoir, Veggie lighting is turned on, and the XROOTS module is powered up and initiated to begin testing.”
NASA has several other horticultural projects underway on the ISS. Its enclosed Advanced Plant Habitat uses more spectral tuning than Veggie does, and is not intended for delivering immediate crop consumption by the astronauts. Rather, astronauts freeze or chemically fix the harvest before sending it back to land for analysis. APH’s chamber includes cameras and more than 180 sensors connected to Kennedy Space Center, where a team operates the habitat remotely.
Late last year it initiated a project to examine how plants’ regulatory RNA and molecular mechanisms sense and respond to the unfamiliar space environment. Another project looks at the psychological benefits for humans growing plants in space.
A Japanese team on the ISS is also investigating plant growth using “just regular light,” as opposed to LED grow lights.
MARK HALPER is a contributing editor for LEDs Magazine, and an energy, technology, and business journalist ([email protected]).
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