Making oxygen from carbon dioxide: this time on Venus
As investigators on the Perseverance Mars Rover mission, the MOXIE team led by MIT Haystack Observatory’s Michael Hecht and Jeffrey Hoffman of the AeroAstro Dept. successfully demonstrated production of oxygen (O2) and carbon monoxide (CO) from the martian atmosphere. The long-term objective of MOXIE was to provide O2 for rocket propellant to bring the first astronauts home safely and to provide for their life support in habitats and vehicles. With the MOXIE program complete, the team has its sights on an entirely different application—this time for the planet Venus.
People might think of Venus as a hellish planet, shrouded in clouds, with a blistering 450ºC surface subjected to enormous pressure, 90 times that of Earth’s surface. But 50–60 km above the surface, just above the cloud layer, the atmosphere consists predominantly of carbon dioxide (CO2) at a temperature and pressure similar to those on Earth. Scientists believe that from a balloon platform at that altitude it would be possible to conduct extraordinary studies of the physical and chemical properties of the dynamic atmosphere, detect seismic activities through infrasound waves propagating through the air, and map the surface at substantially higher resolution than would be possible from orbit.
A new project, Exploring Venus with Electrolysis (EVE), resolves what has been thought to be an intractable obstacle to establishing such a long-lived floating platform: the inevitable leakage of helium from a balloon. EVE takes advantage of the unique opportunity offered by a CO2 atmosphere to create buoyant gases by simply breaking down the CO2 into smaller, lighter components, namely CO and O2. Fortuitously, this is the same transformation that was demonstrated by MOXIE using a technique called solid oxide electrolysis (SOE). EVE proposes to use these gases to replenish the lost helium and ultimately to support the balloon in entirety. EVE has now been awarded a Phase I NASA Innovative Advanced Concepts (NIAC) grant to pursue this vision. The NIAC program “nurtures visionary ideas that could transform future NASA missions with the creation of breakthroughs – radically better or entirely new aerospace concepts.” Challenges to be addressed by EVE under the award include demonstrating compatibility with the sulfur compounds in the atmosphere as well as a fine sulfuric acid mist.
But EVE doesn’t stop with simply keeping the balloon aloft. In winds blowing at 200 mph, the balloon will circle the planet approximately every 100 hrs, collecting solar power for 50 hours on the day side and drawing on stored power on the night side. EVE has the capability to operate as an SOE system in the daytime and as a solid oxide fuel cell (SOFC) at night, using some of the stored CO and O2 instead of batteries to allow operations to continue uninterrupted.
In the longer term, the EVE team dreams of a future where the CO and O2 products can be used more extensively as fuel, driving propellors with SOFC to enable navigation to different latitudes or providing propellant to rockets that might sample the planet’s surface. Visionaries have even talked about humans someday living in floating cities above Venus. If it happens, EVE may be the first step along that road.
“We tend to think of Mars as the most Earth-like of human destinations, even though we would be restricted to walking around in a climate-controlled pressure suit,” notes Hecht, “but on a platform in the middle atmosphere of Venus we would be able to walk out on the roof deck to water the plants with little more than an oxygen mask – possibly fed by an SOE oxygen generator!”
The NIAC award asks investigators to offer a conceptual design of a mission that would provide the first test of the new technology. In a nod to MIT’s mascot, Hecht has dubbed the mission the “Balloon Exploration of the Atmosphere of Venus with Electrolytic Replenishment,” or BEAVER.
After a long period of comparative neglect relative to Mars exploration, Venus will be the subject of three visits in coming years: the NASA VERITAS and DAVINCI missions and the European EnVision mission. VERITAS and EnVision are orbiters, with DAVINCI performing a flyby and deploying a probe through the Venus atmosphere. EVE is looking for an opportunity in the following generation of missions.