Producing a bountiful supply of oxygen will be a top priority for astronauts when they return to the moon and begin setting up living and working quarters. The question is, of the more than 20 different technologies capable of extracting oxygen from lunar soil, what’s the best approach?
Goddard technologist Eric Cardiff believes he has the answer. He’s put his money on a technology called vacuum pyrolysis, and has used Internal Research and Development (IRAD) funding to build a prototype system that he hopes will advance the technique and ultimately lead to a technology-demonstration mission in 2010 or 2012.
Lunar Rocks Contain 45-Percent Oxygen
“There’s really nothing mysterious about the technology,” Cardiff said. “Researchers have long known that moon rocks and soil contain 45 percent oxygen bound up in various minerals, and vacuum pyrolysis is potentially the most efficient technique to extract oxygen from the lunar regolith. Unfortunately, very little research has been done. My team hopes to change that.”
Principal Investigator Eric Cardiff uses a mirror to direct sunlight into a vacuum chamber, where he vaporizes and decomposes lunar-like material to produce oxygen.
Unlike some techniques, which use a complicated chemical process to reduce the oxygen inside rocks and soil, vacuum pyrolysis incinerates the rock to release oxygen bound up in the material, Cardiff said. With pyrolysis, a lunar processing facility would collect the oxygen-rich soil or regolith, place the material inside the plant’s reactor, and use solar flux, or concentrated sunlight, to heat the soil to about 4700 °F (2600 °C). Under such extreme temperature conditions, the soil would vaporize, releasing gaseous oxygen that would then be pumped into a holding tank and stored.
Method Could Produce Rocket Fuel
In addition to supplying breathable oxygen, the technique could produce oxygen for rocket propulsion, drastically increasing the amount of equipment NASA could send to the Moon on each trip. The incinerated remains or metallic slag could be used for other purposes, like spare parts.
“Pyrolysis is more efficient, especially when you put it up against the other techniques that have gotten more attention in the past,” Cardiff explained. “It doesn’t require as much infrastructure to build a processing plant. Therefore, it would take fewer flights and less assembly time to get a plant up and running. But perhaps more important is the fact that vacuum pyrolysis takes complete advantage of the lunar environment,” he said. “Any kind of regolith can be used and the Moon has a natural vacuum and a high solar flux. In addition, you don’t need additional fuel from the Earth to begin the processing, just the resources on the Moon itself.”
To take the technique to the next level of technical sophistication, Cardiff developed a prototype to conduct experiments. The current model is equipped with a large Fresnel lens that concentrates solar light before it passes through a window and into a vacuum chamber where it heats the regolith. The soil vaporizes and decomposes, ultimately releasing oxygen. Cardiff also plans to complete a larger prototype system that uses a large parabolic reflector to concentrate light from the Sun.
Since completing the Fresnel prototype, Cardiff said he has demonstrated run times of up to one hour,successfully vaporizing and condensing several different lunar “simulant” materials, including ilmenite — a metal-rich mineral that is very common on the Moon. Measurements taken by a mass spectrometer and an electron-scanning microscope indicate that small quantities of oxygen are being extracted.
Cardiff is taking his preliminary success in stride. “We still have a long way to go,” he said. “Our performance predictions indicate that vacuum pyrolysis could produce more than 1 kilogram of oxygen per 10 kilograms of regolith processed, which is 10 times more than with reduction techniques. But this technique is still much less mature and we still need to prove its value. My hope is that we can create a flight experiment using the basis of our work here.”
The Office of the Chief Technologist is involved in a variety of projects, missions, and technologies.