Astronauts failed late on Saturday to dislodge a stuck solar array on the International Space Station (ISS), setting the stage for a likely fourth space walk just to solve the problem.
Robert Curbeam and Sunita Williams ended their space walk at 2.56am GMT on Sunday, after seven-and-a-half hours of working as electricians in space. They completed a delicate rewiring of the ISS but were unable to get the jammed panel to fold into its box.
”They have made some progress … but it’s likely we will have a fourth EVA [extravehicular activity] Monday,” a Nasa spokesperson said, using the United States space agency term for a space walk.
”The management team is analysing the data but they have already told the crew to be prepared for an EVA,” the spokesperson said.
Earlier on Saturday, Nasa officials approved a possible fourth space walk if the team was unable to unstick the array.
Having finishing their scheduled tasks in little more than five hours, the two astronauts worked on the jammed solar panel, with one of them pushing on the box into which the array is supposed to fold in an attempt to free what Nasa called ”apparently misaligned guide wires”.
If ordered to do a fourth walk, Curbeam would be joined by another crewmember on Monday. The new space walk would push the shuttle’s scheduled landing in Florida back one day to Friday.
A delay would halve the shuttle’s two-day safety cushion for return to Earth. The shuttle would only have one day’s supply of oxygen and electrical power left, requiring a landing by next Saturday at the latest.
The problematic solar array, which got stuck partially folded in an attempt to retract it on Wednesday, prompted a less high-tech attempt to solve the problem on Friday.
At one point, Nasa engineers in Houston asked German astronaut Thomas Reiter to exercise vigorously for 30 seconds on the ISS’s training machine, hoping his vibrations would cause the panels of the stubborn array to fold all the way.
Reiter, who after a five-month stay on the ISS will be replaced by Discovery astronaut Williams, tried several times to shake the array into action but was unsuccessful.
”I’m very sorry to hear that,” said Reiter when told by the Mission Control Centre in Houston, Texas, that all his efforts came to naught. ”We’ll give you a silver medal for that,” a Nasa controller replied.
While the solar array needs to be fully retracted before it can be moved to another location on the ISS, its current position has allowed a new solar array to unfold and rotate properly.
Discovery astronauts went on space walks on Tuesday and Thursday to attach a two-tonne truss segment and to rewire the ISS for the new, power-supplying solar array delivered in September by the shuttle Atlantis.
Despite the stuck solar array — it has supplied electricity to the ISS for six years — astronauts late on Wednesday were able to activate the newer array so it could turn its photovoltaic cells to follow the sun.
Once it is fully installed and operational, it will double the ISS’s electrical output. The station, when completed, will have four solar arrays providing it with electricity.
The Discovery mission is part of 14 shuttle flights Nasa has planned over the next four years to finish the ISS by 2010, when the shuttle fleet, down to three vehicles, is to be retired.
Discovery and its seven-member crew blasted off last Saturday from Cape Canaveral, Florida, in the first nighttime lift-off in four years. — Sapa-AFP