HOUSTON -- A key test of a daring yet wobbly spacewalking technique that could be used someday to repair space shuttle heat shields worked well yesterday and got good reviews from two of Discovery's astronauts who may have to put it to work for real on Wednesday.
The repair simulation put them at the end of an oscillating 100-foot combination of a robotic arm and an extension pole about 210 miles above the Earth.
Astronaut Piers Sellers said the maneuver made him feel ``like a bug on the end of a fishing rod here."
The space walk, which lasted about 7 1/2 hours, took place as the shuttle and the international space station orbited the Earth at 17,500 miles per hour. It was the first of three space walks planned for this mission.
Sellers and fellow Discovery astronaut Michael Fossum said they could do most of the mock tasks they were assigned with only moderate difficulty.
The technique using the extension on the robotic arm was developed to make sure there is never a repeat of the Columbia disaster, which killed seven astronauts in 2003.
A piece of foam from the shuttle's external fuel tank struck Columbia's wing during launch, creating a breach that allowed fiery gases to penetrate the shuttle during the return flight to Earth.
Last year, emergency spacewalking repairs were needed because of heat shield damage to Discovery.
NASA managers yesterday were still evaluating whether a piece of fabric filler protruding from the thermal tiles on Discovery's keel needs to be removed.
If it does, Fossum and Sellers might have to go back on the boom and yank out the filler during their third spacewalk scheduled for Wednesday.
NASA officials had been concerned that astronauts wouldn't be able to work well from the 50-foot extension boom attached to the 50-foot shuttle robotic arm. The agency's top spacewalk officer had compared it to painting a house from the top of a rickety ladder.
But as Fossum and Sellers were finishing up yesterday, NASA officials said they found less sway and oscillating than expected.
Fossum said one simulated operation was ``beyond my ability" and ``too much motion to handle" from the boom. Aside from that operation the worst Fossum reported was one he rated a 5 on a 1-to-10 scale, which translates to doable but with ``moderately objectionable deficiencies."
``I think we got all we needed there," Discovery pilot Mark Kelly told Fossum and Sellers after the simulation.
During Sellers's time on the boom-arm combination, he remarked as he was being moved into position that the ride was ``a very slow gentle sway in and out of the bay."
The astronauts were aided in the maneuver by pilot Mark Kelly and mission specialists Lisa Nowak and Stephanie Wilson, who operated the robotic arm from inside the craft.
Before their work on the boom-arm , the astronauts had an assignment on the outside of the space station, immobilizing a cable cutter on the station's mobile transporter, or railroad car, and rerouting a cable through it.
A duplicate cable cutter accidentally cut a cable leading to the transporter late last year, and NASA wanted to make sure it doesn't happen again because the cable is a conduit for power, data, and video images.
The transporter moves along the space station exterior and is used for constructing the complex. The severed cable will be replaced during a second spacewalk tomorrow.
The two astronauts also managed to enjoy themselves. At one point while waiting for Fossum, Sellers did a couple of flips. Both let out frequent ``woo-hoos" during their time in space.
They also had time to marvel at the view of the Earth.
``It's beautiful," Fossum said. ``The thin glow of the moonlit Earth below."
And when Mission Control pointed out to Sellers that he could view Britain over his left shoulder, the British-born spacewalker said: ``Wow! Oh, my goodness. It's a beautiful day in Ireland."
Looking down at the Caspian Sea several minutes later, Fossum said: ``This is a good view. . . . I'm in a dream; nobody wake me up."
In their morning message to the crew yesterday, the flight controllers had a request for the astronauts: Stop pouring unused drinks down the shuttle's toilet.
``An example of how closely Big Brother watches," the controllers wrote.
The space shuttle crew awoke yesterday to ``God of Wonders," a popular Christian music recording chosen by Fossum's family.
``I do think it's particularly appropriate as I prepare to step outside for about 4.5-trips around this chunk of creation we call Earth," Fossum radioed Houston.