A whole new way to crap yourself.

Four words you don’t want to hear in space:
“The toilet is broken.”

The crew aboard the International Space Station is working on a problem with the system for collecting solid and liquid waste, which is a trickier proposition without gravity than it is on the Earth. Space toilets use jets of fan-propelled air to guide waste into the proper container.

A NASA status report noted that last week, while using the toilet system in the Russian-built service module, “the crew heard a loud noise and the fan stopped working.” The solid waste collector is functioning properly, but the system for collecting liquid waste was not.

The crew tried replacing one device, an air/water separator, and then a filter, but nothing seemed to bring the toilet back to full operation. Russian mission control told the crew — Russian Cosmonauts Sergey Volkov and Oleg Kononenko, and Garrett Reisman, a NASA astronaut, to use the toilet on the Soyuz capsule that is attached to the station as a lifeboat. But that system has very limited capacity, and so repairing the system has become an increasingly urgent issue.

As so often happens when there’s a plumbing problem, house guests are on the way: the space shuttle Discovery is scheduled to launch on Saturday, with seven astronauts aboard. The shuttle, however, has its own toilet.

Nicole Cloutier-Lemasters, a spokeswoman for NASA, said that mission managers are working on plans to carry replacement toilet parts to the station. In the mean time, she said a temporary work-around has been put in place: “they’re bypassing the troublesome hardware” for urine collection with a “special receptacle” that has been attached to the toilet, she said.

Of all the technological achievements of space travel, none has captured the popular imagination as much as bathroom physics. Mike Mullane, a former astronaut and professional speaker, said questions about the operations of space toilets are the most popular questions from audiences by “more than ten to one” over such questions as “have I seen any aliens” and “did we fake the moon landing.”