Similar to Mark Watney, the hero of “The Martian,” future astronauts will likely rely on “space gardens” to sustain their long stays off-Earth. These gardens would function as a “bioregenerative life support system” — a miniature version of the Earth’s biosphere supplying food, water, and oxygen by recycling waste and carbon dioxide, thus cutting down on the volume of supplies astronauts bring on their spaceships.
An exterior shot of Lunar Palace 1. Credit: Beijing University of Aeronautics and Astronautics.
To test how a bioregerative system could work, scientists from the Beijing University of Aeronautics and Astronautics created the “Permanent Astrobase Life-support Artificial Closed Ecosystem” (P.A.L.A.C.E.), or Lunar Palace 1 for short. The scientists detailed the results from their experiment in the journal, Astrobiology.
Lunar Palace 1 crew member Dong Chen in the garden. Credit: Beijing University of Aeronautics and Astronautics.
Lunar Palace 1 gets its name from the legendary home of the Chinese moon goddess, Chang’e, and her pet jade rabbit. The quarters were, in actuality, a bit less palatial — the crew dwelt for 105 days in a cabin that covered an area of roughly 450 square feet, including four private bedrooms, a living room, and a bathroom. In the final 80 days of the 2014 experiment, Lunar Palace 1 housed two women, Xie Beizhen and Wang Minjuan, and one man, Dong Chen, all from the Beijing University of Aeronautics and Astronautics.
Lunar Palace 1 crew member Wang Minjuan making dumplings. Credit: Beijing University of Aeronautics and Astronautics.
In contrast to the tight living quarters, the attached garden covered nearly 625 square feet. Twenty-one species of plants grew under LED lights in the garden — including wheat, soybeans, carrots, green beans, kidney beans, cucumbers, scallions, lettuce, strawberries, corn, and peanuts — all planted to provide the right mix of nutrients for the volunteers. In addition to their fruits and veggies, the crew also munched on protein-rich mealworms, as well as meat occasionally supplied from the outside.
After the volunteers harvested crops, the stalks and other inedible parts of the plants were dried and ground into powder. A little of that powder was used to raise the mealworms, while the rest was either mixed with human excrement to create soil or was fermented to provide carbon dioxide for the plants to use during photosynthesis. Water for drinking and bathing came from condensed, purified vapor stemming from the humidity given off by the plants. Treated wastewater and urine from the crew was used to fertilize and water the plants.
Mealworms that the Lunar Palace 1 grew and ate. Credit: Beijing University of Aeronautics and Astronautics.
“Lunar Palace 1 could have a future.”
During the experiment, Lunar Palace 1 was cut off from the rest of the world by a shell of welded stainless steel plates and by doors tightly sealed with silicon gaskets, and the researchers analyzed how well it could recycle its contents. The final results of the experiment were promising: the system regenerated 55% of the food and recycled all of its oxygen and water. “Lunar Palace 1 could have a future,” said Cary Mitchell in an interview with Now.Space. Mitchell is the director of NASA’s Specialized Center of Research and Training for Advanced Life Support and a professor of horticulture at Purdue University.
The approach that China pursued with Lunar Palace 1 differed in some key respects from that of NASA, according to Mitchell. “NASA puts astronaut safety first and foremost, and would never have let people get closed up in something like Lunar Palace 1 without a lot of testing and vetting and doing closed safety checks for volatile organic contaminants first without humans.”
U.S., Russian, Japanese and European space agencies have all previously explored bioregenerative life support systems, but they weren’t sustainable. Some were underfunded, while others were subject to changing priorities when new administrations came in, Mitchell explained. “If we are going to live in space, we need to have continuous and sustained work on bioregenerative life support systems, instead of starting and stopping programs,” said Mitchell. “Voyages to distant space destinations ought to be international efforts, and we might as well start now since the budget from any one country is always at risk of changing with administrations.”
In the report, the researchers noted some improvements for future bioregenerative life support systems. One of those was for more efficient urine recycling. The system recovered just 20.5% percent of the nitrogen from urine. “To recover 100 percent of that, it’ll likely require an order of magnitude more money to go into the technology to do that,” Mitchell said. The researchers also proposed a second garden for Lunar Palace 1, which would allow up to five people to live there.
The crew of Lunar Palace 1 eating a meal. From left to right: Dong Chen, Xie Beizhen, and Wang Minjuan. Credit: Beijing University of Aeronautics and Astronautics.
However, whereas Lunar Palace 1 operated for a little over three months, “a projected Mars mission might take three years,” Mitchell added. Still, “they’re just getting underway — it looks like they’ve done a good job so far.”
“Now that we’ve seen work on Lunar Palace 1, where will Lunar Palace 2 be? Will it be on the moon? Is that the mission they’re preparing for here? That would be interesting to know.”