Pedalling to Mars: So long and thanks for all the pants

Think how much underwear you get through in a month. Now spare a thought for an astronaut embarking on an 18-month trip to Mars – and no, taking an entire suitcase of boxer shorts isn’t an option. Rather than weighing down the shuttle with spare pants, however, one enterprising Harvard student has arrived at a rather more elegant solution: a pedal-powered washing machine designed for outer space.

Pedalling to Mars: So long and thanks for all the pants

It might sound zany, but the idea attempts to (at least partially) address two of the major issues with such a lengthy mission. First, to provide the astronauts with freshly laundered clothes, and second, to keep them in good physical health by combating the effects of living in zero gravity for such a long period of time.

Yo, smell you later

The second bit isn’t entirely new: the International Space Station already has an exercise bike so that crew members can keep fit and prevent bone loss by working out for two hours a day. What they don’t have is any way to clean their clothes – even the ones they wear to work up a sweat during their exercise sessions.

“They have to wear gym kit for three days, socks and pants for two days, and everything else for ten days.”

On average they have to wear gym kit for three days, socks and pants for two days, and everything else for ten days – even if they or their companions can’t stand the odour any more. This also means that all the smelly, dirty garments have to be stored for as long as four months until a Progress supply ship arrives, at which point all the dirty undies are offloaded and incinerated as the supply ship is released to burn up in Earth’s atmosphere.


To Meghan McCarthy, an undergraduate studying mechanical engineering at Harvard University, this seemed impractical – particularly for a Martian expedition, where there wouldn’t be any supply ships to cart away the astronautical undergarments.

Her ingenious solution was to take a terrestrial pedal-powered washing machine and adapt it to work with the Danish-built exercise bike on the space station – the computer-controlled Cycle Ergometer with Vibration isolation and Stabilisation System (CEVIS).

In a feat of endearingly low-tech lateral thinking, Meghan’s zero-gravity washing concept employs a horizontal drum that can be hooked up to the drivetrain of the CEVIS. The dirty clothes are put inside and tumbled through the soapy water as the cranks are turned. Want an extra-quick spin cycle? Best get pedalling, then.

You spin me round

“This project serves as the first step towards making clean clothes a reality for astronauts.”

Part of her invention might sound familiar: hand-cranked washing tubs are still bought and used around the world. Designers from Dalian Nationalities University in China hit the headlines in April 2015 with their own bicycle-powered version for off-grid laundry. Meghan’s design, though, doesn’t rotate the drum. Instead, it has an internal axle arrangement designed to agitate the clothes. It’s also designed to ensure that the weightless liquid inside evenly wets the clothes to carry away gathered dirt and bacteria.

She has run computer simulations of how everything will move around inside the drum without the effect of gravity, and the software shows it all checks out. “This project serves as the first step towards making clean clothes a reality for astronauts,” she wrote.

In fact, it’s not quite the first step. The commander of the sixth expedition to ISS, Ken Bowersox, did find a way to wash his favourite pair of shorts by hand inside a plastic bag back in 2002, a feat never to be repeated by other crew members.

Zero-gravity spin class

However, even with a guarantee of clean clothes, astronauts will want to return to Earth in good health. Being weightless can affect many parts of the body, and muscles and bones can weaken because they’re no longer bearing weight – the sessions on the exercise bike can help stave off the most severe side effects, but it can’t replicate the forces of gravity. Or at least not yet.


Once again, an adapted version of the CEVIS exercise bike could solve the problem.

The brainchild of a team in the Man Vehicle Laboratory at MIT, the idea is to create artificial gravity by making the whole exercise bicycle spin, rather like a giant centrifuge. This spinning movement would be powered by a crew member on the exercise bike.

“You really don’t want to send a jellyfish to represent us on another planet,” said Laurence Young, the Apollo program professor in MIT’s Department of Aeronautics and Astronautics. “With exploration-class missions, like Mars, you could run the risk of having astronauts not sufficiently conditioned to perform effectively, and also to not be in good health when they finally get to the surface of Mars.”

The MIT team has built a compact centrifuge that includes sensors to measure blood pressure, heart rate, respiration rate, muscle activity and foot forces. The entire system is just 1.4m tall, so that it can fit within the compact body of a spacecraft.

A dozen healthy human lab rats have taken part in testing the system. They each worked out for up to 25 minutes under different artificial gravity levels: zero G, in which the centrifuge did not rotate; 1 G, measured at the feet, in which the centrifuge spun at 28rpm; and 1.4 G, also measured at the feet, at 32rpm.

“When it spins, we create centrifugal force, which depends on the angular velocity, or how fast we are rotating – the higher the angular velocity, the greater the artificial gravity,” said former graduate student Ana Diaz. “During the spinning process, participants were pushed against the chair due to the centrifugal force, making them sit comfortably, and facilitating their leg biomechanics for biking.”


As the spin speed and the artificial gravity increased, the volunteers naturally used correspondingly more force to pedal – an unsurprising but encouraging result.

“That tells us that if we use artificial gravity, we’re able to get higher foot forces, and we know higher foot forces are good for bones, and help you generate more bone,” said Diaz. “Even if we expected this, we were able to quantify it and find a relationship between foot forces and artificial gravity.

Similarly, as artificial gravity intensified, so did participants’ overall cardiovascular activity, a response that may be beneficial over the long term. It looks to be a double-whammy success, with both bone and muscles benefiting from the combination of artificial gravity and workout.

“The principal finding here is supporting the conclusion that exercise alone is not a sufficient countermeasure,” said Professor Young. “For the first time, we’re showing there’s a symbiosis when one combines the best aspects of exercise, and the best aspects of artificial gravity. So I feel this is an important demonstration.”

The interstellar laundrette?

At the time of writing, both these projects are yet to join forces – but, with a bit of legwork (sorry), it looks like an exercise bike might hold the key to both solving the difficulties of outer-space laundry and keeping our interstellar travellers in tiptop health. Now, anyone fancy giving me a backie to Mars?

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