But salvation could be at hand from invisible helpers - bacteria that eat pants.
The reason for astronauts' infrequent changes is that in orbit, space is - ironically - at a premium. Space stations such as Mir are cramped, and each astronaut produces an average of 2.5kg (5.5lb) of waste each day, occupying a volume of nine litres if uncompressed. Washing machines are hardly standard fittings, and although Mir does have a shower, frequent changes of the single-use underwear - made of a paper-cotton mix - are not part of procedure. It would just create too much rubbish.
But now Russian researchers are trying to find a solution, and generate fuel into the bargain. New Scientist magazine reports today that scientists at Russia's Institute for Biological and Medical Problems in Moscow have begun looking for the perfect cocktail of bacteria that will physically digest the astronauts' underpants. "This will be a revolution in the science of biodegradation," Vyacheslav Ilyin, the project manager, told the magazine. "Cosmonauts identify waste as one of the most acute problems they encounter in space."
All the waste produced in Mir is compressed and stored in sealed containers, and swapped for fresh supplies from cargo ships, which then burn up on re-entry to the Earth's atmosphere. But that waste could provide useful fuel. Many bacteria on Earth, particularly in landfills, eat waste that humans find noxious, producing methane gas, which can be burnt as fuel, as a by-product.
The Russian project aims to find the most suitable combination of microbes. The search could take up to a decade but would eventually produce a disposal unit able to eat plastic, cellulose and what is delicately termed "other organic waste" from the spacecraft.
According to the timetable, there should be a fully working version ready by 2017, when Russia hopes to send a team of astronauts to Mars. That mission would take at least two years each way - and planners are keen to avoid any source of argument. Especially over questions such as: "Are you really wearing those pants for another day?"Reuse content