Molecular Monday: Turning Water Into Rocket Fuel

Welcome to Molecular Mondays! Every other Monday, we examine the atoms and molecules that serve as the building blocks of our universe, both in reality and in science fiction.

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Humans need water. Our spaceships, however, may need it more than we do.

Human space exploration will never succeed if we have to carry everything we need from Earth. Instead, we have to learn to exploit the material resources space provides.

The Electrolysis of Water

Electrolysis is the process of using electricity to trigger a chemical reaction. Stick a pair of electrodes in water and turn on the power. This will break the chemical bonds holding water molecules (H₂O) together.

Hydrogen will then accumulate around the negatively charged electrode. Oxygen will gather around the positive electrode.

Hydrogen, the Ultimate Rocket Fuel

Hydrogen makes the best rocket fuel (in more technical lingo, hydrogen has the highest specific impulse of any known substance). All you need is an oxidizer for the hydrogen to react with… and oh look, you’ve got plenty of oxygen! Just put the two back together in a reaction chamber, and you’re good to go.

Ideally, you’ll want to store your hydrogen and oxygen fuel in liquid form, which means you’ll need a lot of refrigeration equipment to keep them both below their boiling temperatures (roughly 20 Kelvin for hydrogen and 90 Kelvin for oxygen).

Asteroid Hopping

Of course, you’ll have some trouble finding water in space. If you’re planning an extended voyage through the Solar System, plot a course that will take you near some asteroids, specifically carbonaceous asteroids. They tend to contain relatively large amounts of water in the form of ice.

So long as you can find a few places to refuel your spacecraft, and so long as you bring the appropriate equipment along with you, you should be free to travel wherever you like.

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Today’s post is part of asteroid belt month for the 2015 Mission to the Solar System. Click here for more about this series.