NASA’s Mars Rover Sets New Oxygen Creation Record
With NASA’s future plans of landing humans on Mars and transporting them to and from the planet, one of the most important challenges is the lack of air. There is less than 1% of air on Mars as there is on Earth, and carbon dioxide makes up about 96% of it on Mars. While not ideal, this does present an opportunity to turn that CO2 into oxygen.
A few years ago when the Perseverance Rover landed on the Martian surface, it not only began its main purpose related to sample collection but also creating oxygen. It does this using MOXIE, the Mars Oxygen In-Situ Resource Utilization Experiment. Just recently, researchers pushed MOXIE to a maximum production level — a factor of two higher than reached earlier.
This was able to produce a substantial amount of oxygen compared to previous tests. With this, the agency is more confident in what the future holds as they continue to develop this technology. Here I will go more in-depth into this new milestone, the MOXIE payload, what to expect in the coming months, and more.
New Oxygen Test
MOXIE is a Perseverance Rover payload on Mars. MOXIE uses a scroll pump to capture the thin, carbon-dioxide dominate air of Mars and flows it into a Solid Oxide Electrolysis (SOXE) stack. The SOXE performs an electrochemical process that strips oxygen atoms off the carbon dioxide. This oxygen is a valuable resource for rocket propellant oxidizer and life support systems.
Over two years ago on April 20, 2021, MOXIE created oxygen on Mars for the first time. Since then, NASA has only been pushing the limits of what this technology is possible of. Regarding the recent test, Michael Hecht, MOXIE’s principal investigator and an associate director of the Massachusetts Institute of Technology’s (MIT) Haystack Observatory in Westford, Massachusetts said, “We got great results. This was the riskiest run we’ve done. This could have gone wrong,” he said, and could have led to minor damage to the instrument, but it didn’t. The milestone setting Mars run took place on June 6, operating during the Martian night, and lasted 58 minutes.
In this case, the requirements for MOXIE were to produce 6 grams of oxygen an hour, a rate that was eventually doubled. “We rolled the dice a little bit. It was ‘hold your breath and see what happens,'” Hecht said. Informally dubbed by Hecht and his team as “the last hurrah,” MOXIE delivered the goods on its 15th run on Mars since first gulping up Martian atmosphere within Jezero Crater on April 20, 2021. The challenge all along, Hecht added, has been to define ways to operate on Mars more efficiently by cranking out a higher yield of oxygen.
On Mars, oxygen is only 0.13%, compared to 21% in Earth’s atmosphere. If we want oxygen on Mars, we either have to bring it along, or make it ourselves. It’s also important to point out that on Earth, we are always getting energy from the reaction between oxygen and whatever fuel we are using — whether it’s a log in a campfire or gasoline in a car tank. The oxygen weighs several times more than the fuel it burns, which is not an issue on our planet. However, when we have to bring it with us to other locations in space, we need to think a lot about that weight and other factors.
In terms of the future of MOXIE, Hecht said the experiment results encourage the development of a full-scale system here on Earth, one that pumps out oxygen continuously in auto-mode and is able to generate 25 to 30 tons of oxygen to support a human mission on Mars. “It’s all about lifetime. We run an hour at a time. To do this in the future we will have to run for 10,000 hours. On Mars you don’t get a second chance. We could turn it on at 12 grams an hour and let it rip for a long time” he said.
Unfortunately, MOXIE is a technology demonstration, and like many other demonstrators, its long-term life is tied to funding. Research money for MOXIE is set to end at year’s end, Hecht said, with the MIT lab that carries out the work on the lookout for new collaborations. Either way, the information it provided between Mars touchdown and now has been extremely valuable.
MOXIE Overview
In the relative short period of time MOXIE has been operating, its completed a lot of different tests. Specifically, MOXIE has conducted 13 oxygen production runs on Mars and has generated over 100 grams of O2 over 1,000 minutes of operation. MOXIE exceeded expectations in nearly every metric, proving that NASA can confidently lean on MOXIE’s technology for the creation of oxygen depots on Mars.
As partially mentioned prior, MOXIE’s first run (FM-OC9) was conducted on April 20, 2021, and was the first manmade oxygen production on Mars. This test demonstrated that MOXIE is a feasible technology for Mars and validated that in-situ resource utilization is possible.
On August 18, 2021, a test (FM-OC13) was conducted to optimized oxygen production purity by varying flow (and pressure as a result) across the SOXE cells. A detailed flow sweep during the warm Martian day was also conducted during MOXIE’s most recent test on February 18, 2023. High purity oxygen production showed us that MOXIE can meet the quality needs for future Mars mission. Between October 2, 2021 and January 11, 2022 three MOXIE runs tested MOXIE’s ability to operate during the night and day during the low-density period on Mars. This data was key in demonstrating that MOXIE could operate continuously on Mars in extreme conditions, a feat needed for any human rated system.
On Nov 28, 2022, MOXIE set a record oxygen production rate of 10.56 grams per hour. This record was set by controlling the voltage across the SOXE instead of current. This technology was first demonstrated in the two previous runs and was developed to improved SOXE cell safety when running at high production rates. This leads up to the most recent tests which saw a production rate even closer to 12 grams an hour.
To launch from Mars, a small crew of human explorers will need 25 to 30 tons of oxygen, or about the weight of a tractor-trailer. To make that much oxygen would require a 25,000 to 30,000 watt power plant. The Perseverance power system only provides about 100 watts, so MOXIE can only make a small fraction of the oxygen that a future “Big MOXIE” would need to make. In addition, fuel needs oxygen to burn—for example, on Earth, oxygen is constantly being converted to carbon dioxide by animals, or fires, or other chemical reactions. Plants and trees use water and sunlight to convert the carbon dioxide back to oxygen, replenishing the air. On Mars, MOXIE also makes oxygen from carbon dioxide, about as much as a modest-sized tree, though using a very different process.
Earth and Mars line up for a trip every 26 months. When they send an astronaut crew to Mars, one idea is to send all the things they’ll need – a place to live, rovers, a power plant, and maybe a “Big MOXIE” – on one launch opportunity, then send the astronauts on the next opportunity, 26 months later. If they do that, then the base would be in place for about 20 months before the astronauts start their trip. The goal of a Big MOXIE would be to make and store all the oxygen that the astronaut and their rocket would need for their mission before they even launch.
That means the Big MOXIE would need to make 2,000 to 3,000 grams of oxygen per hour, compared to the 6-10 grams that the current MOXIE is making. And it would need to do that all day and night, without stopping, for most of the 20 months. The agency expects that the astronauts would need at least 25 kilowatts of power for their mission, and that the Big MOXIE relies on being able to use that power plant for making oxygen until the astronauts arrive. They also expect Big MOXIE to be the size of a small chest freezer and to weigh about 1 ton.
As far as alternatives, using water to make oxygen on Mars would be a great idea if they had easy access to the water. But to get water, astronauts would have to travel to the far north or south to find ice, or to mine for ice buried deep in the ground. On the Perseverance MOXIE, the “solid oxide” in a solid oxide electrolyzer cell is a ceramic that is heated to 1,472 degrees Fahrenheit (800 degrees Celsius) inside a special miniature oven. When MOXIE runs, it first has to heat up that ceramic to its operating temperature. That takes about two hours. The rover batteries have enough available charge left to make oxygen for about an hour after that. During that hour, they sometimes change the voltage or the compressor speed to learn more about the instrument. When MOXIE runs, very little else gets done on Perseverance. There isn’t enough power left to drive, or to abrade rocks, or even to run the other instruments for very long. So MOXIE doesn’t run very often, maybe once every one or two months.
Lastly, looking at the applications of this technology, when NASA send the first crew to Mars, they would need to think about how to bring them home at the end of their visit. And the single biggest user of oxygen in their entire stay on Mars will be the rocket that takes them back to orbit. While the astronauts may breathe 2 to 3 tons of oxygen in their 18-month stay on the planet, the ascent rocket would use 25 to 30 tons.
Conclusion
NASA just completed a significant milestone related to creating oxygen on Mars with the MOXIE payload. As it nears the end of its life scientists pushed the payload to its limits and produced more oxygen per hour than ever before. We will have to wait and see how it progresses and the impact it has on the space industry.