Electrolysis Propulsion


The centerpiece of the Cislunar Explorers program is the use of water as a green, dense, and effective propellant.

Water doesn’t burn, of course. But its constituents do. Hydrogen and oxygen have been used in rockets from the early days of space exploration, including the upper stages of the Saturn V used in the Apollo program. Historically, the two are stored separately on the launch vehicle or spacecraft, as cryogenic liquids. To carry enough hydrogen, in particular, necessitates the use of extremely high pressures and extremely low temperatures. It takes a complex apparatus to achieve this: pumps, pressure vessels, and heavy insulation to keep the storage units cold.

There is another way.

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Water electrolysis can be done with a 9V battery and two pencils! Spacecraft sold separately. Photograph by Nevit Dilmen, distributed under a CC-BY 3.0 license
Water electrolysis can be done with a 9V battery and two pencils! Spacecraft sold separately. Photograph by Nevit Dilmen, distributed under a CC-BY 3.0 license

Zapping H2O with electricity can overcome the bond between hydrogen and oxygen, decomposing the liquid into a gaseous mixture that readily combusts.

Instant rocket, just add water!

In a space environment, the water will float around the propellant tank and mix with the gas and spoil any attempts to . To fix this problem, we spin the spacecraft like a top around its thruster, flinging the water out like a centrifuge and helping to separate inert from electrolyzed propellant.

In the image below, you can see our 3D printed titanium thruster test stand, where we use a six-axis strain gauge to measure the force of the thruster when fired. In the propellant tank at the bottom of the image are a number of electrolyzers, more than are used in our spacecraft, so that we can test-fire the thruster more rapidly than it will be used in space.

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