Toilet breaks down on crowded International Space Station

CAPE CANAVERAL, Florida (Reuters) - Astronauts aboard the International Space Station used a pair of robot arms to install a pallet of equipment on Sunday, but when break-time came they may have found long lines at the bathrooms.

With a record 13 people aboard the station, the main toilet broke down, sending astronauts scrambling to the use backup commodes on the Russian side of the station and aboard the visiting U.S. shuttle Endeavour.

"Put an 'Out-of-Service' note on the WHC (waste and hygiene compartment)," Mission Control's Hal Getselman told a crewmember after a fruitless attempt at repairs.

The commode, which is connected to the station's wastewater-recycling system, had been the crew's main bathroom. NASA was limiting shuttle toilet use because it cannot dump the wastewater overboard, as is customary during flight.

Wastewater dumps could contaminate the station's newly installed platform for science experiments.

The porch-like facility was mounted on the front of the station's Kibo laboratory during a spacewalk Saturday. It will be used to hold experiments that need to be exposed to the open environment of space.

"For right now, having all (shuttle crewmembers) using the shuttle toilet is not going to be an issue," station flight director Brian Smith said.

If the toilet cannot be repaired within about six days, it could become a more serious matter, Smith added. "We don't yet know the extent of the problem," he said.

FUEL TANK FOAM

No experiments are aboard the new platform yet. Those will be installed later during Endeavour's planned 11-day stay. The crew Sunday transferred a pallet of spare parts over to the station, using robot arms aboard both the shuttle and station.

NASA also laid out plans on Sunday to test the foam on the external fuel tank earmarked for shuttle Discovery's launch next month to the space station. NASA has seven missions after Endeavour's to complete construction of the $100 billion orbital outpost and retire the shuttle fleet.

Endeavour's tank shed an unusually large amount of the insulating foam in a way not previously seen during shuttle launches.

NASA redesigned the tanks and implemented inspections after losing shuttle Columbia in 2003 from a foam debris impact during launch. The resulting damage to the heat shield caused the shuttle to break apart as it re-entered the atmosphere for landing. All seven astronauts aboard died in the accident.

Shuttle program manager John Shannon told Reuters the pieces of foam lost from Endeavour's tank were tiny compared to the 2.2-pound (1 kg) chunk that impacted Columbia's wing.

Endeavour's tank also is believed to have shed most of its debris late during ascent, when aerodynamic forces were too weak to slam the foam into the ship and cause damage.

"It looks like this foam, and the way it came off, would not have been an issue. We are still doing the reconstruction," Shannon told Reuters in an e-mail.

Before Discovery is cleared to launch, NASA will need to be sure it understands why Endeavour's tank shed foam and be convinced that a similar event would not occur earlier during ascent when it could do harm.

(Editing by Tom Brown)