NASA's Mars rover Opportunity on Mars

A futuristic way of making oxygen in zero-G could save us as we head to Mars and deep space

Contributed by
Jul 16, 2018

A futuristic way of making oxygen in zero-G could save us in deep space. We already know our species is headed to Mars. Rockets, habitats, space suits, zero-G 3D printing tech, and extraterrestrial gardens are all being prototyped for future missions, but humans will need one more thing to stay alive out there.

Human bodies are not made to last outside Earth’s atmosphere. To say that fuel and oxygen are mandatory is an understatement. The process of electrolysis uses semiconductors to harness energy—which in this case would be sunlight or starlight—and split water containing a soluble electrolyte into hydrogen and oxygen. As a new study discovered, this method of producing hydrogen fuel and breathable oxygen by dissociation is actually possible in zero-G.

Being hundreds of thousands of miles away is going to be an issue when it comes to refilling and refueling. Electrolysis could provide unlimited resources with the right equipment, producing breathable oxygen and hydrogen to power the spacecraft and electronics on board. It could even launch rockets and eliminate the need to take off carrying explosive fuel and oxygen. But. Everything depends on how the technique is conducted in microgravity.

On terra firma, sunlight is captured by solar cells and electrolytes, which then convert it into a current. An alternate method that weighs much less involves photocatalysts, which use a semiconductor submerged in water to accelerate the reaction by absorbing photons (light particles).


A diagram of the electrolysis process on NASA's Oxygen Generator System (OGS), which supplies oxygen to the ISS.  Credit: NASA

Electrons in the semiconductor material absorb the energy from these photons. They then jump from that material and react with protons in water to form hydrogen, while the hole forms oxygen and protons when it absorbs electrons from H2O molecules.

Energy can also be recycled by recombining hydrogen and oxygen into water when the process is reversed, and astronauts headed to Mars and deep space are going to have to reuse everything they can.

There is just one problem that became apparent to the research team when they let their photocatalytic experiment fall from a 394-foot drop tower. The acceleration created an environment as close to microgravity as possible, with equal and opposite forces neutralizing the effects of gravity. Another thing it created as the water molecules split was bubbles. That sounds innocuous until you realize that bubbles get in the way of gas creation in space, because they don’t just float to the surface as they do on Earth.

Since water is denser than bubbles in gravity but not microgravity, they accumulate around the catalyst as a foam instead of floating to the surface. This can make the process less efficient. The scientists did make nano-adjustments to the semiconductor, but even that wasn’t an answer to the bubbles remaining in the solution.

So long as that obstacle gets figured out by the time Elon Musk plans to blast off to Mars, humanity should be ready.


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