Shift in space mentality

As astronaut Steve Robinson dangled from the spindly limb of the space station's robot arm 220 miles above Earth, many Americans watched with utter fixation as the nation's spaceflight programme took one giant step towards returning to its legendary past.

It was but a single hour and the removal of two pieces of gap filler protruding from beneath the shuttle Discovery turned out to be as routine as a spacewalk could be. But the event had a significance beyond the safety of the shuttle.

To some space experts, the mission symbolised the spirit of derring-do forged by Nasa a generation ago. The shuttle Columbia was lost in large part because Nasa's "can do" attitude had waned amid the frustrations of tight budgets and a temperamental vehicle.

The same problems still exist. But Wednesday's spacewalk suggests that Nasa will not let itself be defined by them but hopes to return in part to the ethic of old, even if it means delays on the launch pad or sending astronauts under the shuttle with pliers and a lug wrench.

Throughout most of the shuttle era, "the approach was to ask if anybody could sit up and prove there was a danger", says Howard McCurdy, a Nasa historian.

"Now the question is: Can anybody prove that this is not a danger? It is a shift. Nasa is going back to the approach it had during the 1960s."

Sensitive tiles

It was this mentality that brought Robinson almost to within kissing distance of the shuttle's sensitive tiles on Wednesday.

While Nasa had made provision to send astronauts under the shuttle in the case of tile damage, no one had foreseen the problem that engineers spotted when Discovery arrived in space.

Two of the thin fabric fillers wedged between shuttle tiles had come loose and were peeking above the smooth skin of Discovery's belly.

The first reaction was to do nothing. The fillers might cause extra heating on reentry by disrupting the airflow across the shuttle's underside, but there was no proof that this would have dire consequences.

Then, over the weekend, the thinking changed. "They had a hard time showing that there was no risk," says James Oberg, a former shuttle engineer. "And if you can't prove it's safe, you have to do something about it."

As they became more concerned about the fillers, however, they became less concerned about the potential remedy.

True, no astronaut had ever gone beneath the shuttle on a spacewalk, but when engineers got down to calculating space-station arm angles and backup plans, it didn't seem as daunting as some had suspected.

In the end, Robinson needed none of the tools in his spacewalker's tool kit. He simply pinched the two pieces of filler between his thumb and forefinger and eased them out of the slot between tiles.

Indeed, the spacewalk suggests that Nasa has fundamentally changed the way it looks at the shuttle, seeing it as a truly experimental vehicle.