Astronauts Heidemarie Stefanyshyn-Piper and Shane Kimbrough, both STS-126 mission specialists, work in the Unity node of the International Space Station

The U.S. space agency NASA says astronauts on the International Space Station appear to have resolved problems with a water recycling system that is essential in supporting the doubling of the station's crew.

NASA officials say the astronauts completed two successful tests Tuesday of the newly installed system that recycles urine into drinking water.  The system will enable the space station to support six crew members on a continuing basis.

The system had shut down four times during earlier tests.

In other news, NASA says a test on a rotating joint on the outpost indicates the joint is working well, following repairs during four extensive spacewalks.  But officials say it will take several subsequent tests to ensure the joint is fully functioning.

The joint must work properly for the space station's solar arrays to track the sun for maximum power.

NASA has extended the mission of the space shuttle Endeavor one day, to 16 days.  The shuttle is now scheduled to return to Earth on November 30.

Astronauts completed repairs to the solar arrays during the fourth and final spacewalk of the mission Monday.

The shuttle mission coincided with the 10th anniversary of the space station, which has traveled more than a billion kilometers since its first component Zarya was launched on November 20, 1998.

Some information for this report was provided by AP and Reuters.