Recycling for Moon, Mars and Beyond
Astronauts who visited the Moon during the Apollo missions had to be knowledgeable in a variety of areas. They had to be pilots who could fly a spacecraft. They had to be geologists who could identify rocks on the Moon. They had to be astronomers who could recognize stars to navigate in space. They were paramedics who could deal with any emergency medical problems thousands of miles from Earth. But, the astronauts who return to the Moon to stay may have a job title their Apollo predecessors did not. They may have to be farmers, as well.
Image to left: This device recycles waste in a reduced-gravity environment. Credit: NASA
Scientists have already researched growing plants on the Moon. They have learned that provided with air, water, light and fertilizer, plants can grow in the lunar "soil," or regolith, as it is properly called. Now, a team of NASA scientists from Ames and Glenn Research Centers are working on a device that could be used to create fertilizer on the Moon. It would do so by recycling waste produced during the mission by burning it. In addition, the device could be used to incinerate waste produced by astronauts flying on a spacecraft on long-duration missions. In doing so, it would substantially reduce the mass of the waste and eliminate the presence of decomposing organic matter on the craft. It would also free up valuable resources for reuse. Its ability to function in variable gravity environments means that it could be used to recycle waste into fertilizer on Mars, as well. The device is being researched in a project called Vortical Oxidative Reactor Technology Experiment (VORTEX).
Image to right: A candle flame in microgravity looks quite different from a flame in normal gravity. Credit: NASA
Burning something on Earth is relatively easy. Ignite something flammable and the fire spreads to consume it. In the microgravity environment in space, however, it's a different story. Things don't burn the same way in space as they do on Earth. Fires in microgravity generally are weaker, do not spread as effectively and require an airflow to burn for very long. Since burning an object in microgravity requires more than just lighting part of it on fire, the VORTEX causes the waste to swirl above the burner. This provides ample exposure time and airflow for the waste to burn. Similar devices are used today, but they suspend the waste particles by balancing the lift from the air currents with the force of gravity. Such a system would not work consistently in variable gravity environments and would not work at all in microgravity. The VORTEX device uses variable direction air currents, rather than gravity, to suspend the waste particles. During Earthbound tests, the device demonstrated an ability to suspend the waste particles indefinitely and incinerate them. In the future, microgravity tests may be conducted on a microgravity airplane.
In addition to ash that could be used as fertilizer on planetary missions, the device would free several other resources by recycling waste. This is vital on long-duration spaceflights to other worlds, on which resupply missions would be extremely difficult or impossible. Burning, or oxidizing, organic waste would produce four major by-products: ash, carbon dioxide, water and heat. In fact, the water may be the most valuable asset the device would produce. The water could be used by the crew. It could also be electrolyzed to produce hydrogen and oxygen. On planetary missions where the ash is used as fertilizer for plants, those plants could also use the carbon dioxide for photosynthesis. This, of course, would produce oxygen, which could be breathed by the astronauts. (In fact, the inedible portion of plants could be included in the incinerated waste, recycling plant matter to grow new plants.) Alternatively, using a Sabatier reaction, hydrogen could be combined with the carbon dioxide to produce methane and water. The methane could be used to provide fuel for the incinerator. And, since electrolysis of the water could produce both oxygen to oxidize the waste and hydrogen for the Sabatier reaction, the process produces some of the resources it requires.
Astronauts on missions to other worlds will have to be able to make the most of what they have. And, a device that can turn something that seems useless into useful resources goes a long way toward that goal.