This Thursday February 18th at 3:55 p.m. EST, the Mars Perseverance rover will either land in a crater on Mars—or perhaps create a new one. The “seven minutes of terror” involves a complex sequence of timed events to take a spacecraft hurtling into the Martian atmosphere at 12,000 mph to a gentle landing on the Martian surface.
While there are a number of scientific instruments on board, I want to tell you about an experiment that hopes to demonstrate technology for future Mars missions, both human crewed and robotic.
All our trips to Mars have been one way. To lift off from the Earth’s surface requires powerful rockets burning fuel and oxidizer at prodigious rates. To lift off from the Martian surface, even with its lower gravity, would similarly require a powerful rocket with fuel and oxidizer on board. Carrying all that to Mars would mean that the rocket lifting off from Earth has to be even bigger and more powerful. Imagine traveling cross country and back, and having to pack all your fuel for the entire trip. It’s why the Apollo missions to the moon began with this…
https://upload.wikimedia.org/wikipedia/commons/1/16/Apollo_11_Launch_-_GPN-2000-000630.jpg
…and this was all that came back.
https://s.hdnux.com/photos/01/04/14/41/17877101/19/rawImage.jpg
But Mars has some resources that we can use to produce fuel and oxidizer for a return trip. Its atmosphere, although tenuous, is 95% CO2, carbon dioxide. On board the rover is a small experimental device that can chemically separate out the oxygen. On a larger scale, this could provide both oxidizer for a rocket and breathable oxygen for human explorers.
https://upload.wikimedia.org/wikipedia/commons/thumb/0/05/PIA24201-MarsPerseveranceRover-MoxieTwin-2021019.jpg/1920px-PIA24201-MarsPerseveranceRover-MoxieTwin-2021019.jpg
This is a demonstration experiment, small enough and light enough to be carried on this mission. It produces only the oxidizer that a rocket would need. What about the fuel? It turns out that carbon dioxide can provide both the fuel AND the oxidizer, if we can provide a third element: hydrogen.
Carbon dioxide can be reacted with hydrogen to produce oxygen (O2) and methane (CH4), with the methane making a fine rocket fuel. Water (H2O) is a by-product, and splitting the water into hydrogen and oxygen can provide more oxygen and some of the hydrogen needed for the primary reaction. It doesn’t produce quite enough, though, so you would need an external source of hydrogen.
The chemical reactions I’ve just described have are known as the Sabatier process, and have been around for more than 120 years. The technical difficulties involved in running this on Mars don’t revolve around the process itself—it’s just getting all of that chemical engineering machinery, a power source, and storage facilities for the products—getting all that in an efficient, lightweight, and robust package deliverable to the Martian surface. If you could, however, it’s as though you had a vehicle capable of going on a single fill-up from New York to Los Angeles, and setting up a refueling station in L.A.
To watch the Thursday afternoon landing online, go here. May your journey be smooth and your landing a soft one!
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