A computer due to be installed on the US space shuttle Endeavour for an August mission was found sabotaged, NASA said on Thursday, the latest in a string of shocks concerning the US space agency.
"One of our subcontractors noticed that a network box for the shuttle had appeared to be tampered with," NASA spokeswoman Katherine Trinidad told AFP. "It is intentional damage to hardware."
Endeavour is due to be launched on August 7 with seven crew members on board from the NASA base at Cape Canaveral in Florida , for a mission to continue construction of the International Space Station , a manned orbiting laboratory.
The workers who discovered the damage to the computer equipment intended for Endeavour notified NASA "several days ago," Trinidad said. "There is an ongoing investigation."
Safety is a major concern in US shuttle missions after damage sustained by the Columbia craft on launching caused it to break up on re-entry in February 2003, killing all seven astronauts on board.
"The tampering occurred at a subcontractor's facility and not while the unit was at the Kennedy Space Center ," NASA's Cape Canaveral base, Trinidad said of the damage to the Endeavour equipment.
She gave no details of who the subcontractors were nor exactly where the damage was.
"What we are trying to do now is repair that unit and try and fly it when possible."
The shuttle Atlantis successfully completed a mission to the station in June, a welcome bit of good news for the National Aeronautics and Space Administration (NASA) after several embarrassing incidents in recent months.
In February astronaut Lisa Nowak, a former crew member on the shuttle Discovery, was arrested, accused of a bizarre attempt to kidnap a love rival. NASA fired her in March.
Then in April, a NASA contractor Bill Phillips managed to sneak a revolver past security at the Johnson Space Center in Houston, Texas, and barricaded himself inside a building at the sprawling campus, police said.
He duct-taped a female co-worker to a chair and shot a male colleague dead before turning the gun on himself.
Also on Thursday, the trade magazine Aviation Week Space Technology citing an internal NASA panel said that astronauts had been allowed to fly spacecraft while drunk. A NASA spokesperson was not immediately available for comment.
The agency also faced political bother in May when NASA chief Michael Griffin drew fire for comments on the hot topic of harmful climate change. He publicly questioned the need to tackle global warming.
The successful Atlantis mission, meanwhile, was initially delayed by three months because the shuttle's external fuel tank was damaged during a freak hail storm as it stood on its launch pad.
The delay forced NASA to cut the number of planned shuttle flights this year from five to four.
On the August mission, astronauts are to deliver a giant truss to be attached to the ISS, along with an external stowage platform and a Spacehab module -- a pressurized cargo carrier.