Astronauts have fixed the toilet at the international space station (ISS) and were on the verge of opening up a grand new science lab.

The toilet problem had fast become the most pressing issue of the mission, so much so that a spare pump was rushed from Moscow to Cape Canaveral last week for a last-minute ride aboard space shuttle Discovery.

Russian Oleg Kononenko put in the new pump, and the toilet started working normally again.

For two weeks, the three men living aboard the space station had to manually flush the Russian-built toilet with extra water several times a day. It was a time-consuming job and waste of water, not to mention an unpleasant chore.

So everyone, especially in orbit was thrilled that the new pump seemed to solve the problem.

“Let's start using it,” Russian Mission Control told Kononenko. “We will keep our fingers crossed.”

The space station's toilet woes seemed to capture the world's attention. It ended up being the main topic of conversation at NASA news conferences, with fastidious suit-and-tie managers having to describe the ins and outs of using the restroom in weightlessness.

“It's unfortunate we are talking about toilets, but that really is the life, that's the future of human exploration in space,” Kirk Shireman, Deputy Space Station Program Manager, said on Tuesday night.

The door to the billion-dollar Japanese lab named Kibo, or hope was swung open on Wednesday afternoon, a day after its installation at the space station.

“This is a great moment for the Japanese folks,” Japanese astronaut Akihiko Hoshide said before floating into the brightly lit chamber with a welcome sign.