A new collapsible "greenhouse" could be the key to growing fresh and healthy food to sustain future lunar or Martian colonies, a recent project found.
Scientists at the University of Arizona's Controlled Environment Agriculture Center (CEAC) are experimenting with growing plants without the use of soil. Instead, they are trying to demonstrate that potatoes, peanuts, tomatoes, peppers and other vegetables can be grown in only water?a process known as hydroponic growth.
The team built a prototype lunar greenhouse in the CEAC Extreme Climate Lab that is meant to represent the last 18 feet (5.5 meters) of one of several tubular structures that would form part of a proposed lunar base.
The tubes would be buried beneath the moon's surface to protect the plants and astronauts from deadly solar flares, micrometeorites and cosmic rays. As such, the buried greenhouse would differ from conventional greenhouses that let in and capture sunlight as heat. Instead, these underground lunar greenhouses would shield the plants from harmful radiation.
The membrane-covered greenhouse module can be collapsed down to a 4-foot-wide disk for easy storage during interplanetary travel. It would be fitted with water-cooled sodium vapor lamps and long envelopes that would be filled with seeds, primed to sprout hydroponically.
"We can deploy the module and have the water flowing to the lamps in just ten minutes," Phil Sadler, president of Sadler Machine Co., which designed and built the lunar greenhouse, said in a statement. "About 30 days later, you have vegetables."
The contraption will rely on robot-like components to grow its organic life. Algorithms to analyze data collected by attached sensors and a control system to optimize performance are in the works.
"We want the system to operate itself," said Murat Kacira, an associate professor of agricultural and biosystems engineering at the University of Arizona. "However, we're also trying to devise a remote decision-support system that would allow an operator on Earth to intervene. The system can build its own analysis and predictions, but we want to have access to the data and the control system."
In fact, the engineers can take cues from an existing analog on Earth?a similar CEAC food-production system has been operating at a South Pole research station for the past six years.
The South Pole Growth Chamber, which was also designed and fabricated by Sadler Machine Co., provides fresh food to the U.S. South Pole Station in Antarctica, which is physically cut off from the outside world for six to eight months each year.
Several ideas used in the development of the lunar greenhouse were inspired by the functioning South Pole Growth Chamber.
Another important aspect of the greenhouse design is the effective and efficient use of resources, which would be crucial on a lunar base.
"On another planet, you need to minimize your labor, recycle all you can and operate as efficiently as possible," said principal investigator and CEAC director Gene Giacomelli.
In developing such a system, there will likely be applications for our planet as well, he said. "All that we learn from the life support system in the prototype lunar greenhouse can be applied right here on Earth."
Carbon dioxide is fed into the prototype greenhouse from pressurized tanks, but astronauts would also provide CO2 at the lunar base simply by breathing. Similarly, water for the plants could be extracted from astronaut urine, and the water-cooled electric lights might be replaced by fiber optic cable?essentially light pipes?which would channel sunlight from the surface to the plants underground.
Giacomelli said the research could also lead to plant colonization in another traditionally hostile environment?large urban centers.
"There's great interest in providing locally grown, fresh food in cities, for growing food right where masses of people are living," Giacomelli said. "It's the idea of growing high-quality fresh food that only has to be transported very short distances. There also would be a sense of agriculture returning to the everyday lives of urban dwellers. I think that idea is as exciting as establishing plant colonies on the moon."
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