Live In Orbit: Astronauts Wrap Up Final Spacewalk

Two American astronauts are back inside the U.S. Quest airlock at the International Space Station tonight after an all-afternoon excursion outside the orbiting outpost.

Discovery mission specialists Ricky Arnold and Joe Acaba produced mixed results during the six-hour, 27-minute spacewalk -- the third and final outing planned during Discovery's mission to the station.

The astronauts moved a mobile rail cart from one side of the station's central truss to the other -- a job that set the rail cart in place for future assembly and maintenance work at the station.

But they ran into trouble with one of their main tasks: The astronauts pushed, pulled and tried to pry a jammed experiment platform into place on the port side of the truss but they were unable to fully deploy the pallet.

Instead, the two teachers-turned-astronauts tied the platform down onto the truss with safety tethers, securing it while NASA engineers hatch a recovery plan to execute on a future spacewalk.

Arnold had much better luck lubricating the business end of the station's Canadian-built construction crane.

He used a high-tech grease gun to lubricate three snares and six bearings within the Latching End Effector -- the LEE -- of the 57-foot-long robot arm.

The job involved using needle-nose pliers to work with the snares, which are designed to capture grapple fixtures on parts of the station that are under construction or being moved from one location to another.

The astronauts likened it to a battery-operated Milton Bradley board game that has been in production since 1965.

"It's like that Operation game," one of the two said.

"Exactly," the other replied.

The spacewalk was the 123rd performed in the assembly and maintenance of the station since its first two building blocks were linked in low Earth orbit in late 1998.

Astronauts and cosmonauts in that time have accumulated 775 hours -- more than 32 days -- working in the vacuum environment.

Ninety-five of the spacewalks have been staged from either the Quest airlock or the Russian Pirs Docking Compartment, which doubles as an airlock. The other 28 were staged from shuttle orbiter airlocks.

Acaba, Arnold and crewmate Steve Swanson tallied 19 hours and four minutes of spacewalking time during the three excursions.

Swanson now has a career total of 26 hours and 22 minutes on four spacewalks.

Arnold performed two spacewalks that lasted a total of 12 hours and 34 minutes.

Acaba, who taught freshman science at Melbourne High School during the 1999-2000 school year, now has 12 hours and 57 minutes of spacewalking experience.

ABOUT THE IMAGES: Click to enlarge the NASA screen grabs from the third and final spacewalk planned during Discovery's ongoing mission to the International Space Station. The first shows spacewalker Ricky Arnold working at the business end of the station's 57-foot robotic arm. The second shows a view from Arnold's helmet-cam as he used specially designed pliers to work with snares inside the Latching End Effector of the robotic arm.