CAPE CANAVERAL, Fla. (AP) – Over the past three months, workers at the Kennedy Space Center have tripped, dropped things, banged into sensitive equipment and started fires in a deadly string of accidents that has NASA perplexed.

The space agency has launched investigations into three accidents – the death of a worker who fell off a roof, the bumping of space shuttle Discovery's robotic arm by a platform, and damage last week to an instrument that supplies power to the orbiters. But there have been at least seven other incidents since the beginning of the year.

“There's enough going on that we're very, very concerned,'' said Bill Parsons, deputy director of the Kennedy Space Center.

One explanation for the accidents may be that workers have been out of the rhythm of preparing for shuttle launches, since there has been only a single liftoff since the Columbia disaster in early 2003, Parsons said.

“I think anytime you have big gaps in between doing something that's like launching shuttles ... or things like that, you are always concerned that you've lost a little bit of your edge,'' Parsons said.

Workers had been under pressure to meet a May launch date for Discovery, but the flight was pushed back to July last month so that technicians could replace troublesome sensors in the fuel tank.

Senior managers and contractors have been urged to get out in the field to talk to workers about any problems and emphasize safety and discipline.

In the meantime, a July launch could be threatened by a new problem – “whiskering'' on a shuttle engine circuit board. Whiskering is the formation of thin metallic protrusions that could lead to a short circuit.

“It's a problem that has been around for years,'' said Kyle Herring, a NASA spokesman. “It's probably of greater interest now because we're getting ready to fly.''

In one incident in January, workers accidentally started a fire while repairing the roof of the Vehicle Assembly Building.

In March, broken glass from a lamp fell into Discovery's payload bay. Workers cleaning it up the next day accidentally dented Discovery's robotic arm. Three days later, an X-ray film container was dropped on shuttle Endeavour.

Space center director James Kennedy called a two-hour work stand-down in mid-March to re-emphasize safety after another fire was accidentally started by roofers at the assembly building. But the accidents didn't stop.

The next day, roofer Steven Owens, 51, tripped on a wire and fell off a warehouse, the first worker death in years at the space center. Last week, electronic equipment was damaged at a spare parts depot when the electricity was reversed, and workers from New Orleans dropped a lamp on the nose of the external fuel tank while repairing it.

Lynn Beattie, a Machinists union leader at the space center, said he believes accidents are simply being reported more than they have been in the past.

But he noted that several accidents, including the roofer's death and the fires, involved outside contractors, not employees of NASA or its primary shuttle contractor, United Space Alliance.

“I sometimes think there's not a real serious attempt to make our contractors comply with the same safety standards that everybody else has to out here,'' Beattie said.

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