NASA announced yesterday that the launch of space shuttle Discovery, which had been slated for February 12, will be delayed for at least a week.* The space agency said it needs more time to ensure that the valves controlling the flow of hydrogen gas into the external fuel tank do not pose a hazard. Engineers discovered that one of those valves had been damaged when another shuttle, Endeavour, lifted off in November—and NASA wants to find out why that happened and whether a similar occurrence could endanger the mission and crew.

"We want to make sure we've got this right," NASA associate administrator for space operations William Gerstenmaier told the Associated Press. "So we think standing down for a little bit of time and letting the folks do a little more work is a good thing."

During its two-week mission, Discovery is set to deliver the final group of solar panels as well as replacement parts to the International Space Station (ISS) for its much-hyped (and somewhat glitchy) urine-to-water recycling system. The beefed-up solar arrays will help to power the activities of an expanding ISS—the Endeavour mission increased the station's capacity from three astronauts to six, an occupancy the ISS is expected to reach later this year.

*UPDATE (2/6/09): NASA announced today that the launch would be postponed until February 22 or later to accommodate further review of the valves.