NASA today delayed its next space shuttle mission until July at the earliest after engineers at the US space agency found a possible manufacturing fault that could cause fuel level sensors to malfunction.
Shuttle program manager Wayne Hale said replacing the sensors meant NASA would not be able to make its original launch window scheduled from May 10.
The delay in getting the shuttle fleet back into the air after it was grounded again last July could further affect the multi-nation orbital construction of the International Space Station, which depends on the US space shuttles.
"That will take us about three weeks of work (to fix the fault) and that of course will move us out of the May launch window...," Hale told reporters in Houston.
"So today we are proposing that ... the earliest possible launch date will be July 1."
The US shuttle fleet has been grounded since last July, when insulation foam broke off the external fuel tank of the shuttle Discovery as it launched from Cape Canaveral in Florida.
Falling insulation foam was the same problem that doomed the shuttle Columbia in 2003, knocking a hole in its wing and allowing superheated atmospheric gases to tear the shuttle apart when it reentered Earth's atmosphere at the end of its mission.
All crew on board were killed.
The recurrence of the foam problem during Discovery's mission was a significant blow to NASA, which had spent $1 billion trying to fix the problem.
Discovery's mission was also plagued by a problem with a fuel sensor in the external tank. If the fuel sensors erroneously register that the tanks are empty when they are actually full, it could lead to an emergency shutdown of the shuttle's engines and throw a launch off track.