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Quirks and Quarks·Analysis: Bob's blog

Running horizontally could help future lunar settlers stay in shape on the Moon

Scientists have taken a clue from a carnival stunt known as the Wall of Death to help future astronauts on the moon stay healthy. Instead of riding motorcycles, the moon colonists will simply run around the walls.

Researchers used bungee cords to hoist test subjects and simulate the effects of lunar gravity

Bob McDonald · CBC Radio ·
A woman with a pink top is suspended by a cord inside a wooden "wall of death" contraption, which is a wooden circular apparatus with high walls, as she runs almost horizontally.
Running horizontally inside the circular walls of a Wall of Death-like structure on the moon could be a way for lunar settlers to exercise in low-gravity conditions. (Alberto E. Minetti/University of Milan/Royal Society)

Scientists have taken a clue from a carnival stunt known as the Wall of Death to help future astronauts on the moon stay healthy. But instead of riding motorcycles, moon colonists will simply run around the walls.

For decades, carnival goers have been thrilled at the spectacle of stunt drivers taking motorcycles and even cars up the vertical walls of large wooden circular structures roughly 10 metres in diameter known as the Wall of Death.

The vehicles use the principles of inertia, which cause an object to move in a straight line unless acted upon, and centripetal force, which is the net force pulling the vehicle inward in its circular motion. This allows the vehicle to stick to the walls of a cylinder.  

A report in the journal Royal Society Open Science tested whether the same principle could be used on the moon to keep long-term colonists who may someday be stationed on the moon healthy and strong by simply running around walls in the low lunar gravity.

This is a collage of four images. On the bottom right, we see the outside of the "Wall of Death" carnival attraction that was set up for this research. On the bottom right, we see inside this contraption where a runner is getting harnessed up inside this wooden cylinder. Inset in the middle is a close up shot of a motorcyclist riding in one. Inset on top in the centre is what contraption looks like when it's set up for a carnival.
Scientists repurposed a Wall of Death carnival stunt exhibit to conduct horizontal running experiments to emulated lunar gravity. (Alberto E. Minetti/University of Milan/Royal Society)

The researchers rented a carnival Wall of Death and rigged a crane over the centre of the barrel shaped structure so the volunteers could be suspended sideways by bungee cords to represent lunar gravity, which is a sixth of that of Earth. This enabled them to easily run around it. 

This feat would be impossible on Earth because our planet's stronger gravity would pull runners down to the floor. That is why carnival stunt drivers have to maintain a speed of about 50 km/h to remain on the wall.

Someone on a motorcycle is up high on the inside wall of a wooden circular track. The photo is blurry to give a sense of how fast the guy is riding.
The Wall of Death is a carnival sideshow where motorcyclists, like Zoran Milojkovic at this 2022 Serbian bike rally, can perform stunts as they ride perpendicular to Earth's surface. (Darko Vojinovic/AP Photo)

But in moon gravity, astronauts could sprint at 20 to 23 km/h to stay up. That sounds fast but on the moon you can take much larger steps and cover ground more quickly, yet each step on the wall would still experience the force of Earth gravity. 

The idea of using a cylindrical track to simulate gravity is not new. In 1973, the crew of Skylab 3, America's first space station, was able to run around a circular ring of storage lockers that lined the inside walls of the station, even though they were in zero gravity.

This grainy gif shows three people running around a vertical circle inside a small space after starting in a crouch.
Three NASA astronauts in 1973 on the second crewed mission to the American space station, Skylab, got some of their exercise by running around a circular array of storage lockers. (NASA)

Science fiction has portrayed the same principle in movies such as 2001: A Space Odyssey where a ring shaped space hotel slowly spun creating artificial gravity on the inside.

There's even an idea to tether two spaceships together and swing them around each other to produce artificial gravity during a long journey to Mars. NASA tested this during its Gemini XI mission in 1966 when the astronauts generated a small amount of artificial gravity after tethering their spacecraft to the Agena Target Vehicle and then spinning the whole assembly.

Exercise is an important element for long space flight to fight off the negative effects of weightlessness on the body such as bone loss.

A woman with medium-length hair in a navy top and shorts is mid-stride running on a small treadmill in a cramped space station space. She's tethered to the treadmill with white bungee cords.
NASA astronaut Sunita Williams, equipped with a bungee harness, exercised on a treadmill when she was aboard the International Space Station in 2012. (NASA)

The International Space Station has a space gymnasium where astronauts must spend two hours a day working out to stay in shape.

Crews living in habitats on the moon in the future will also need to exercise regularly to battle the effects of the low gravity there. Rather than sending treadmills equipped with harnesses to simulate Earth gravity, or an actual Wall of Death, the walls of the habitat could be made circular and provide a simple running track available anytime.

ABOUT THE AUTHOR

Bob McDonald

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.