"That was the ride of a century," Dr Robinson said after his spacewalk, at the end of the Discovery's 58-foot robotic arm. The astronaut had brought a hacksaw and forceps in case they were needed to remove the gap fillers which, scientists feared, could disturb airflow around the shuttle during re-entry causing turbulence and possible overheating of tiles low down on Discovery's underside.
Now it remains for Nasa to decide whether a fourth and final spacewalk will be needed to carry out repairs to a thermal blanket below the commander's window that appears to have been torn by debris during lift-off, and that might come off entirely during re-entry.
Nasa expected that yesterday's repair mission could take an hour to complete. In the event, it required just a few seconds and a couple of pulls by Dr Robinson's gloved fingers. "That came out very easily, probably even less force," he said after extracting the second piece.
The remarkable experiment in space DIY was beamed back live to Nasa headquarters and the world, showing the astronaut in balletic slow motion in the gravity-free environment more than 200 miles above the planet.
Afterwards, there was no concealing the relief both in space and the ground - the latest instalment in a roller-coaster series of emotions since Discovery blasted off from the Kennedy Space Center in Florida on 26 July.
Exhilaration at the resumption of the shuttle programme after almost 30 months was quickly replaced by fears of possible damage to the sheath of ceramic glass-coated tiles, that will protect the craft from the searing temperatures when it re-enters the atmosphere at the end of its mission.
That concern was unfounded but the displacement of the filler tiles and their possibly catastrophic effect on re-entry was quickly discovered. Wayne Hale, the shuttle's deputy programme manager, said Nasa could not be certain what the effect would have been. But the agency was taking no chances, after the disastrous fate of the Columbia mission on February 2003.
"It was a very easy decision," Mr Hale told reporters. "No one has a very good handle on aerodynamics at those altitudes and those speeds ... life could be normal during entry or some bad things could happen."
Dr Robinson, who was joined for the spacewalk by his crewmate Soichi Noguchi, had received instructions in a 12-page e-mail to prepare him for the removal operation.
The odds now must be that this most scrutinised space shuttle mission in history will end successfully. But it may well be the last for a long while.
Many months of painstaking work by Nasa engineers could not prevent a large chunk of insulating foam falling off Discovery's exterior fuel tank at lift-off on 26 July, in an incident similar to the one that dislodged some of Columbia's heat protecting tiles and led to its dintegration as it re-entered the atmosphere.
This time a piece of foam, measuring two square feet, missed Discovery. But Nasa announced that the entire shuttle fleet would be grounded until the problem is properly solved.
If that doesn't happen in a hurry there will be limited opportunities to advance America' space shuttle program before it is due to close in 2010.Reuse content