Spaceflight Insider

Lunar Cycler: To cheaply go ‘how’ no one has gone before

Apollo 11 Earthrise.

Apollo 11 Earthrise. Photo Credit: NASA

Buzz me up to the Moon! The second man to walk on the lunar surface, Buzz Aldrin, really meant it when he proposed thirty years ago to use Cycler orbits for future better and cheaper transportation to the Moon. The Lunar Cycler Orbit, also known as the Earth-Moon cycler, is a periodic orbit that passes close to both of these bodies repeatedly, enabling an economical trip. To support sustained operations at a lunar research station or mining base, this approach would use less propellant than would be required by more traditional methods.

While this sounds great, how is it possible?

A spacecraft would be placed into a permanent, highly elliptical orbit around the Earth and the Moon. Once a Lunar Cycler vehicle has been propelled into this orbit, it should require relatively little fuel over the years to maintain its orbit. It would complete an orbit once every two weeks, and make a close approach to the Moon every other orbit. The cycler journey from the Earth to the Moon would take about a week.

The Lunar Cycler Orbit could provide a permanent reusability in cislunar navigation. If everything proceeds according to plan, a normal cycler mission would work like this:

A reusable space shuttle would send crews into Earth orbit. They would then use the Cycler to travel to cislunar space, where a reusable lunar shuttle would deliver them to the Moon’s surface and back. The proposed Cycler spacecraft would rely on gravity assist maneuvers to keep it going with occasional powered corrections to maintain a proper trajectory.

The Cycler approach could support both lunar and Mars exploration. Photo Credit: Andrew Chaikin

The Cycler approach could support both lunar and Mars exploration. Photo Credit: Andrew Chaikin

By avoiding ‘throw-away’ technologies, like those used during the Apollo missions in the late 1960s and early 1970s, the Cycler approach could provide a far cheaper method for sustained human operations on the Moon. The Cycler would offer a stable link between the Earth and the Moon, allowing three Earth-return opportunities every two months. Adding more Cycler spacecraft would allow more frequent trips and more options, according to a study by researchers at the University of Colorado, Boulder.

“A two-Cycler program provides twice-monthly Earth-return windows,” the researchers found. “The two-Cycler system recommended here is particularly amenable to incremental growth and efficiency because of the ability of the two Cyclers to rendezvous with each other and join, if desired, into a larger station while a third Cycler takes the now empty place of one of the first two.”

They note that another benefit would come from the ability of the Cycler to provide a propellant depot capability as well as a safe-haven for astronauts during solar storms. Moreover, by using this method, heavy life support equipment would only have to be pushed out of Earth’s punishing gravity well once. In terms of size, some Cycler concepts suggest the spacecraft could be some 200 feet (61 meters) long and accommodate 12 passengers and crew.

The researchers also underline that a full-time Cycler could provide extensive traffic between Earth and Moon and that it will almost certainly have an emergency maneuver capability (if there was cause to return to Earth or the Moon) drawing on its stores of cryogenic propellant normally used for the transfer shuttles.

The concept is a promising one for future human beyond-low-Earth-orbit missions, and the Earth/Moon Cycler could also serve as a logistical and technological prototype for deep-space Cyclers to other destinations in the Solar System. So, as NASA plans for journeys to Mars and beyond, Buzz Aldrin’s Cycler concept is worth considering.

This story was produced for The Lunar Initiatives newsletter: The Lunar Initiatives it includes the opinions of the author – and does not necessarily reflect the views of SpaceFlight Insider

Video Courtesy of TheSpaceNavi


Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.

Reader Comments

Michael D Moody

Had a couple of questions for the writer of this piece. A shuttle would carry astronauts and cargo from earth orbit. Wouldn’t the fact that the shuttle has to rendezvous with the cycler and then launch from the cycler affect its momentum? Would a shuttle have to race to catch up with the orbiter and then have a very limited time at station before it would have to take off again?

Hi Michael,
From what we understand, the cycler would require occasional minor “boosts” (or reboosts as it were) – it is likely any changes caused by arriving shuttles – would be factored into this adjustment.
Sincerely, Jason Rhian – Editor, SpaceFlight Insider

Looks like a great concept. Maybe Buzz should have a t-shirt that says “Get Your Ass to the Moon!” Now all we need is a lunar exploration program that makes use of this idea.

Orbital mechanics is not my forté. Pardon me if this is a dumb question : Is it possible to have many different spacecraft staggered along this Lunar Cycler ellipse , somewhat like the A Train orbit used by that chain of NASA earth science satellites? Or does each E-M Cycler spacecraft travel its own separate orbit?

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