Sciency Words: Aldrin Cycler

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


The term cycler can refer to two different but related things in orbital mechanics: an orbital trajectory that continuously and perpetually cycles between two planets, or a spaceship that’s been set on such a continuously, perpetually cycling trajectory.

The mastermind behind this idea is none other than the famous Buzz Aldrin, astronaut extraordinaire. Turns out Dr. Aldrin is more than just a pretty face. In 1985, Aldrin proposed using cyclers to transport equipment and personnel to and from the planet Mars. After crunching the numbers, physicists at NASA’s Jet Propulsion Laboratory confirmed that Aldrin’s idea would work.

The cycler trajectory Aldrin proposed is now known at the Aldrin Cycler. Aldrin’s plan would actually use two spaceships, one for outbound journeys to Mars and another for inbound trips returning to Earth.

According to Aldrin’s book, Mission to Mars: My Vision for Space Exploration, the outbound cycler ship would take roughly six months to reach Mars from Earth; the inbound ship would take about the same amount of time to reach Earth from Mars. Both ships would then spend the next twenty months looping around the Sun to catch up with their home planets and start the cycle again.

Presumably the ships would only carry human passengers during the shorter six-month legs of their respective journeys. The rest of the time, they could just fly on autopilot or remote control.

If the Aldrin Cycler proposal or something similar were implemented, traveling to and from Mars would be sort of like catching a train, with boarding taking place regularly every twenty-six months. I’ve even found a video showing what these cyclers might look like.

Okay, that’s actually an anime that I liked when I was a kid. We don’t have to make cycler ships look like trains (though we totally should).

The major drawback with the cyclers is that the upfront cost of building them will be enormous; however, if we’re serious about establishing and maintaining a permanent human presence on Mars, these cyclers would easily pay for themselves in the long run. The laws of orbital mechanics keep them going, so they’d require little to no fuel.

And since a cycler could keep cycling for decades or centuries or even millennia (in theory, they could go on forever, or at least until the day the Sun explodes), we Earthlings would always have guaranteed access to Mars, and our Mars colonists would always have a guaranteed means of getting home if they needed it.

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