In 1969, US astronaut Russell Schweickart peed into a plastic receptacle in the Apollo 9 capsule on the way to the moon.

The condom-like vessel allowed Schweickart - and the other crew members - to relieve themselves in space.

But they often made a big mess when they removed the receptacle - painfully, they learnt that size does actually matter. The astronauts would reach for the largest of the three receptacles, when perhaps a smaller one was sufficient.

"You only make that mistake once," Schweickart said after his return.

Since then, going to the toilet in space has become easier.

Modern space toilets even allow astronauts a brief, intimate timeout. But personal hygiene remains one of the greatest challenges onboard the International Space Station (ISS).

German astronaut Reinhold Ewald, who stayed at the space station MIR, told DW he was often pushed to the edge of his own limits. "It's not for the highly sensitive," he said.

Make sure you buckle up for the ride

Astronauts have to belt themselves down to the space toilet. Strong sucking pressure allows them to relax on the throne, despite the zero gravity. For missions outside of the craft, diapers can be used.

Reuse everything

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Zero-gravity ablution: it's hard to maintain German-style personal hygiene in space