Crane Accidents

Alpha Crew Does ‘Bang Up’ Job Flexing Robot Arm


Cape Canaveral, Florida

The dress rehearsal for an upcoming space station construction job was not quite a resounding success. But it did begin with a resounding thump.

As astronauts prepared to test the international space station’s new robotic arm, it unexpectedly released its grip, rebounded and banged into the side of the orbiting outpost.

Jim Voss and Susan Helms, the American residents of space station Alpha, heard the $600 million crane strike their weightless home. Ground controllers said the bump did not damage Alpha or the robot arm.

“It seemed like the arm stuck on the grapple fixture,” Voss told reporters Friday, the day after the jolt. Temperature changes on super crane could have made its tip remain attached to the station longer than it should have, causing it to spring off, he said.

“It worked just fine while we operated it later in the day,” the former Army colonel said.

The robot arm was being tested ahead of the installation of a $164 million airlock, which future Alpha crews will use to stage spacewalks.

NASA had planned to ferry up the 12-ton airlock on space shuttle Atlantis in June. But nagging problems with the Canadian-built robotic arm have postponed the mission until July and could delay the flight even longer.

Mission control does have some grounds for optimism. The robot arm rebounded from its awkward start and performed well during the remainder of the test. Voss and Helms managed to guide the multi-jointed appendage through a series of maneuvers to make sure it could handle the airlock job.

The practice run had been postponed for weeks as mission controllers attempted to find the cause of an unknown ailment afflicting the crane, which arrived at the station in April.

The mobile, multi-jointed crane, designed to move like an inchworm, attaching to various data and power ports on the Alpha exterior, seemed to have a sticky shoulder joint during early tests of its backup command software.

Since then the problem mysteriously cleared up and Alpha technicians have been unable to resurrect the malady. But they would like to figure out the cause before using the arm to install the airlock.

Yet the astronaut expected to operate the arm during the job was optimistic.

“We have a lot of reason to hope that these were transient problems and we can proceed normally,” said Helms, as Alpha cruised about 240 miles (385 km) over the eastern coast of Australia, just before the station experienced one of 18 daily sunsets. Regarding Thursday’s bump, ground controllers suspect that the 58-foot (15-meter) crane accidentally unlatched from the station because tension had built up in the arm before a release command was sent up.

Friday marked the 100th day that Voss, Helms and Russian commander Yury Usachev had lived on the space station. They now expect to return home in August, more than a month later than planned.

Category: Accident Report


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