Ten Times More Efficient Oxygen Generation on Mars

Ivan Ermanoski, Arizona State University, has NASA NIAC funding to evaluate, computationally and experimentally, the feasibility of a process–thermal swing sorption/desorption (TSSD)–to generate oxygen from the Mars atmosphere with 10x less energy than the state of the art, and bring other breakthrough performance improve-ments.

The basis for TSSD is a two-step thermally-driven cycle operating below ~260 C. One of the critical challenges of human Mars missions is the need for in-situ resource utilization (ISRU), especially oxygen–both as Mars Ascent Vehicle (MAV) propellant, and for life support. In addition to the MAV and habitation (same ISRU unit), a baseline “commuter” Mars architecture also envisions small, pressurized rovers for mobility and science. Reliable, portable oxygen generation could extend rover endurance, broaden the exploration zone from the habitation area, and increase the number of science and resource regions of interest accessible permission. Further, larger exploration zones ease the tradeoff between landing site appeal (low risk to astronauts) and proximity to regions of interest (mission success). While desolate to humans, the Martian atmosphere nonetheless contains oxygen.

this approach is motivated by thermodynamics: the minimum theoretical work to separate oxygen from the Mars atmosphere is ~30-50 times lower than to obtain it by splitting carbon dioxide. Efficiency: TSSD is expected to be ~10x more efficient than MOXIE. For MOXIE, the target power requirement for oxygen propellant production is 30 kW. The TSSD estimate is only 4 kW; i.e., 90% less than MOXIE. Applying TSSD in rovers, the estimated power for oxygen production is only ~50 W/person. These advantages expand further if the input is heat, rather than electricity. Flexibility: TSSD has startup times of minutes (versus hours for MOXIE), and is inherently capable of handling intermittencies and restarts. Sealant limits in MOXIE strongly constrain transient tolerance. Simplicity and robustness: TSSD is exceedingly simple, inexpensive, and robust, with no moving parts, and long life. Unlike MOXIE, TSSD is not susceptible to carbon deposition. The maximum process temperature is ~260 C vs. 800 C for MOXIE. If successful as envisioned, TSSD will be a giant leap in Mars ISRU capabilities and can be expected to significantly improve and de-risk human Mars exploration. The potential to expand considerably the exploration zone is especially exciting, as it would allow a far more comprehensive Mars exploration program than currently envisioned. Furthermore, TSSD-based Mars ISRU could pave the way for ISRU in many other environments of interest (e.g. Venus, Europa, or Titan), and ISRU of other gases of interest, such as water (vapor), nitrogen, and carbon monoxide.

4 thoughts on “Ten Times More Efficient Oxygen Generation on Mars”

  1. I do see one problem with this approach: While breaking down CO2 to produce Oxygen requires more power, nearly 100% of the atmosphere is CO2, so the ‘air’ flow necessary is manageable. Challenging, but manageable.

    Mars’ atmosphere is only 0.13% Oxygen; This approach requires processing nearly 800 times the volume of gas. It’s going to be challenging to maintain those kind of flow rates, especially in portable applications.

    If my calculations are right, each person would require processing 66 million liters of Martian atmosphere, per day, with this approach. Assuming it’s 100% efficient at extracting Oxygen. That’s a LOT of pumping!

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  2. For methane fuel, the carbon has to come from somewhere, and getting it from the air (or mined dry ice) produces oxygen as a by-product. Are there other, easier to use sources than CO2?

    And generating methane and oxygen for rockets will leave an excess of oxygen, as the rockets are run a bit fuel rich to prevent engine burn-up. So probably this is mainly useful for mobile oxygen extraction

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  3. There’s precious little about the methodology, but it looks like the principle is isolating O₂ from the 1% or so concentration in the Martian atmosphere, which is itself 1% of the pressure of Earth atmosphere (very roughly). It may be cheap energetically speaking, but can it perhaps simply exhaust the oxygen in the atmosphere in the medium term?

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    • That’s the one thing I wouldn’t worry about. Not only is the atmosphere really huge, but the surface of Mars is super-oxidized; It preferentially lost so much hydrogen over the planet’s life that there’s just a huge excess of Oxygen around. All those perchlorates in the soil, detectable levels of hydrogen peroxide…

      The atmosphere free oxygen is probably in equilibrium with the super-oxidized surface.

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