Our Place in Space: The Aldrin Cycler

Hello, friends!  Welcome to Our Place in Space: A to Z!  For this year’s A to Z Challenge, I’ll be taking you on a partly imaginative and highly optimistic tour of humanity’s future in outer space.  If you don’t know what the A to Z Challenge is, click here to learn more.  In today’s post, A is for…


Even in the future, space travel will be expensive.  True, new technologies should make it less expensive than it is today, but there’s one problem that will never go away, no matter how advanced our technology gets: gravity.

Anywhere you want to go in space, you’re going to have to fight against gravity to get there: Earth’s gravity, the Sun’s gravity, the gravity of other planets and moons—at some point on your journey, you’re going to have to fight against any or all of these gravitational forces.  And fighting gravity uses up fuel.  Lots and lots and lots of fuel.

And yet, despite the unforgiving and unrelenting force of gravity, human civilization will eventually spread out across the Solar System.  I’m not going to tell you it will happen in the next twenty years.  I won’t tell you it will happen in the next century, even.  But someday, it will happen.  I’m sure of it!  And so today, I want to talk a little about what the future transportation infrastructure of the Solar System might be like.

American astronaut Buzz Aldrin is, of course, most famous for being the second person to set foot on the Moon.  Aldrin is also a highly accomplished scientist and engineer.  In 1985, he did some math and discovered a very special orbital trajectory that would make traveling from Earth to Mars (and also from Mars back to Earth) far more fuel efficient.

The term “Aldrin cycler” refers to that very special orbital trajectory Aldrin discovered.  The term can also be used to describe a spacecraft traveling along that special orbital trajectory.  The initial investment to build an Aldrin cycler (the spacecraft, I mean) would be really high.  We’d probably want to build a rather large spacecraft for this, and once it’s built, maneuvering the thing into the proper trajectory would require a stupendous amount of fuel.

However, once we’ve done all that, the cycler will cycle back and forth between Earth and Mars, over and over again, pretty much forever.  Traveling to Mars would be a little like catching a train.

I was going to have the Aldrin cycler make a “choo-choo” sound, like I train, but then I realized that would be silly.  Things don’t make sounds in outer space.

Passengers would board the cycler as it flew past Earth; about five months later, they’d disembark and head down to the surface of Mars.  The cycler would then take a long journey (about twenty months) looping around the Sun before flying past Earth once more; then the “cycle” would begin again.

The trip from Earth up to the cycler would still require some amount of fuel.  So would the trip from the cycler down to the surface of Mars.   The cycler itself would also require a little bit of fuel for maneuvering thrusters; otherwise, over time, the ship could start to drift ever so slightly off course.

Obviously this is not a cost-free form of space travel, but I’m sure you can see how this could help keep the cost of space travel down.  And so I imagine in the distant future, the Aldrin cycler (or something very much like it) will be a key part of the Solar System’s infrastructure, just as trains are an important part of our modern day infrastructure here on Earth.

Want to Learn More?

Click here to see a short animation of the Aldrin cycler orbital trajectory, showing several cycles worth of Earth-to-Mars and Mars-to-Earth journeys.

I’d also recommend Buzz Aldrin’s book Mission to Mars: My Vision for Space Exploration, where Aldrin describes the Aldrin cycler (and other cool Mars related things) in more detail. Click here to see the book’s listing on Amazon.

23 thoughts on “Our Place in Space: The Aldrin Cycler

    1. Pretty much! The initial investment of building and launching a cycler would be pretty steep. Over time, though, it would more than pay for itself.

      I doubt we’d build something like this any time soon. In the distant future, though, when human civilization is spreading out across the Solar System, I think launching an Aldrin cycler (or maybe multiple Aldrin cyclers) would make a lot of sense.


    1. Aldrin also did calculations for cycler orbits between Earth and the Moon. Apparently the math didn’t look so favorable. Cyclers only make economic sense when we’re traveling to other planets, unfortunately. But there are other options for “local travel,” which I’m planning to talk about later this month.


  1. It’s a cool idea. (Didn’t they have that architecture in The Martian? Or something like it?)

    One thing I wonder about, is how often the Aldrin cycler would need to be replaced. The ISS appears to be aging out after about 20-25 years, and that’s with a relatively short supply / maintenance line. It’s probably still pretty economical compared to the other options, but not a one time only cost.

    Maybe it could be built one module at a time, and then later replaced one module at a time. Although getting rid of the older modules might not be worth it. After a few decades / centuries, there’d be a collection of old sections, that might start to feel like a haunted junk yard.

    Liked by 1 person

    1. Oh yeah, they did have something like this in The Martian! I forgot about that. The orbital trajectory was wildly different from what Aldrin described, as I recall, but the basic idea is the same.

      I think you’re probably right about needing the replace the vehicle at some point. I’m guessing in the distant future we could build a spacecraft that’s sturdier and lasts longer than the I.S.S. Still, there would be some degree of wear and tear on the spacecraft. At some point, it would probably be more economical to just replace the cycler with a newer model.

      Liked by 1 person

    1. Hah! Yeah, it is a long time to wait for a train. And five months is a long journey, too. Space travel takes a lot of time. Somehow I suspect the people who really want to go to Mars are not going to let the long travel times deter them, though.

      Liked by 1 person

    1. I still need to watch the William Shatner documentary about his trip to space. I mean, I know it was more of a publicity stunt that anything else, but there is a lot of exciting stuff happening with space exploration right now. It gives me hope for the future.

      Liked by 2 people

  2. 5 months just drifting through space! But, I can understand how this would be a more efficient way to travel to Mars. Maybe, way into the future, it will be like taking a long train!

    I always learn something interesting here in your blog. Looking forward to this month of space travel with you.

    Liked by 1 person

    1. Thanks, friend! I’m excited to see what you’re doing, too, not just with A to Z but with your National Poetry month series too. Doing two of these challenges at the same time is really impressive!


  3. I wonder if building the ship on the Moon would make sense – cheaper to launch from there. But that would require a whole ‘nuther project to create a capability on the Moon. Space is hard.

    Liked by 1 person

    1. Seems plausible. Setting up shop on the Moon would be hard, but if we’re imagining a distant future where humans are spreading out across the Solar System, that does seem like one of the projects people would want to tackle early.

      Liked by 1 person

  4. I also laughed at choo-choo sounds in space and went back to see if you’d included someone in a Casey Jones hat in the cycler. This is fascinating James. I always thought of Buzz Aldrin as a mad scientist, with more emphasis on the mad, but this moves him properly back into scientist (which is where he should always have been, if I’m being honest).

    Debs visiting this year from
    Debs Carey-NLP Coach

    Liked by 1 person

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