After successfully loosening bolts on a solar array battery pack, spacewalkers Steven Swanson and Joseph Acaba ran into problems fully extending an external hardware storage platform on the space station's port 3 power truss segment.

After unbolting clamps and rotating the platform toward its deployed position, interference with a locking pin prevented them from fully extending its support mechanism. Applying elbow grease, the spacewalkers attempted to muscle the hardware into place and discussed tools that might be able to provide additional leverage.

They were running about a half-hour ahead of schedule when they started work to deploy the unpressurized cargo carrier attachment system, or UCCAS, on P3 truss segment but they lost time struggling to get it fully deployed.

Earlier in the spacewalk, the astronauts completed the first task on their agenda, loosening six bolts holding batteries in place on the port 6, or P6, solar array at the far left end of the space station's power truss.

Working on the far end of the huge truss, the astronauts apparently imparted enough force on the structure to "saturate" the control moment gyroscopes that are normally used to maintain the orientation of the shuttle-space station "stack." This is not unusual, but it required flight controllers to switch attitude control to the shuttle Discovery's small vernier thrusters.

"Just to let you guys know, with all this work being done out at the end of the truss structure, the CMGs momentum has built up," astronaut George Zamka radioed from mission control. "Nothing to worry about. The bottom line is we may lose attitude control on the CMGs but we'll switch over to shuttle VRCS. Just so you guys are aware of it. Not a problem."

Inside the station's Destiny lab module, meanwhile, the astronauts began testing a new vacuum distillation assembly centrifuge unit that was brought up aboard Discovery and installed in the station's water recycling system Friday.

The system's original distillation assembly failed shortly after it was installed late last year. Recycling condensate and urine is critical to NASA's long-range plans to support a full-time crew of six on the space station.

The original unit experienced some sort of internal interference issue. After removing rubber vibration dampers in the DA's mounting system, the astronauts were able to coax it into operation but it eventually halted and could not be restarted.

The replacement DA is identical to the one that failed and engineers say it could suffer the same problem that derailed the original. But during an initial spin test with the new unit, space station commander Mike Fincke reported the centrifuge was running smoothly.

"And Houston, you can see the same good spinning," he said. "We can barely hear any change in noise, which is much different than the last time we did this."

The station crew plans to test the new distillation assembly by processing urine on Sunday.

Additional coverage for subscribers:
VIDEO: WALKTHROUGH OF SPACEWALK NO. 2 PLAN PLAY
VIDEO: FLIGHT DAY 6 HIGHLIGHTS MOVIE PLAY
VIDEO: FRIDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: NEWS MEDIA INTERVIEWS WITH CREW PLAY
VIDEO: SECOND SOLAR WING FULLY DEPLOYED PLAY
VIDEO: SECOND SOLAR WING DEPLOYED HALF-WAY PLAY
VIDEO: FIRST SOLAR WING FULLY DEPLOYED PLAY
VIDEO: FIRST SOLAR WING DEPLOYED HALF-WAY PLAY
VIDEO: NARRATED ANIMATION OF SOLAR ARRAY DEPLOYMENT PLAY

VIDEO: FLIGHT DAY 5 HIGHLIGHTS MOVIE PLAY
VIDEO: THURSDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SPACEWALKER STEVE SWANSON RELEASES LOCKS PLAY
VIDEO: STARBOARD 6 TRUSS ATTACHED TO THE STATION PLAY
VIDEO: WALKTHROUGH OF SPACEWALK NO. 1 PLAN PLAY
VIDEO: OVERVIEW OF THE STARBOARD 6 TRUSS PAYLOAD PLAY
VIDEO: NARRATED ANIMATION OF TRUSS INSTALLATION PLAY

VIDEO: FLIGHT DAY 4 HIGHLIGHTS MOVIE PLAY
VIDEO: WEDNESDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: POWER TRUSS HANDED FROM SHUTTLE TO STATION PLAY
VIDEO: STARBOARD 6 TRUSS HOISTED FROM PAYLOAD BAY PLAY
VIDEO: PREVIEW ANIMATION OF S6 TRUSS UNBERTHING PLAY
VIDEO: NARRATED TOUR OF DISCOVERY'S PAYLOAD BAY PLAY

VIDEO: FLIGHT DAY 3 HIGHLIGHTS MOVIE PLAY
VIDEO: TUESDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE CREW WELCOMED ABOARD STATION PLAY
VIDEO: SPACE SHUTTLE DISCOVERY DOCKS TO SPACE STATION PLAY
VIDEO: SHUTTLE'S POINT OF VIEW DURING BACKFLIP PLAY
VIDEO: DISCOVERY PERFORMS 360-DEGREE BACKFLIP PLAY
VIDEO: PREVIEW ANIMATION OF RENDEZVOUS AND DOCKING PLAY

VIDEO: FLIGHT DAY 2 HIGHLIGHTS MOVIE PLAY
VIDEO: MONDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: MONDAY'S MISSION MANAGEMENT TEAM UPDATE PLAY
VIDEO: PREVIEW ANIMATION OF HEAT SHIELD INSPECTIONS PLAY

VIDEO: FLIGHT DAY 1 HIGHLIGHTS MOVIE PLAY
VIDEO: THE FULL STS-119 LAUNCH EXPERIENCE PLAY
VIDEO: LAUNCH REPLAY: EXTERNAL TANK CAMERA PLAY
VIDEO: LAUNCH REPLAY: VAB ROOF PLAY
VIDEO: LAUNCH REPLAY: CAMERA CS-1 PLAY
VIDEO: LAUNCH REPLAY: CAMERA CS-2 PLAY
VIDEO: LAUNCH REPLAY: CAMERA CS-6 PLAY
VIDEO: LAUNCH REPLAY: FRONT CAMERA PLAY
VIDEO: LAUNCH REPLAY: BEACH TRACKER PLAY
VIDEO: LAUNCH REPLAY: PAD PERIMETER PLAY
VIDEO: LAUNCH REPLAY: PLAYALINDA BEACH PLAY
VIDEO: LAUNCH REPLAY: THE VIP VIEWING SITE PLAY
VIDEO: LAUNCH REPLAY: PRESS SITE PLAY
VIDEO: LAUNCH REPLAY: WEST TOWER PLAY
VIDEO: LAUNCH REPLAY: CAMERA 009 PLAY

VIDEO: SPACE SHUTTLE DISCOVERY BLASTS OFF PLAY
VIDEO: SHUTTLE'S CREW MODULE HATCH CLOSED FOR FLIGHT PLAY
VIDEO: MISSION SPECIALIST STEVE SWANSON BOARDS PLAY
VIDEO: PILOT TONY ANTONELLI BOARDS DISCOVERY PLAY
VIDEO: COMMANDER LEE ARCHAMBAULT BOARDS PLAY
VIDEO: CREW DEPARTS QUARTERS FOR LAUNCH PAD PLAY
VIDEO: ASTRONAUTS DON SPACESUITS FOR LAUNCH PLAY
VIDEO: TIME-LAPSE OF SUNRISE AT LAUNCH PAD 39A PLAY
VIDEO: TIME-LAPSE OF HYDROGEN ACCESS ARM RETRACTION PLAY
VIDEO: TIME-LAPSE OF SATURDAY NIGHT'S GANTRY ROLLBACK PLAY
VIDEO: SATURDAY'S PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: FRIDAY'S SHUTTLE AND WEATHER UPDATE BRIEFING PLAY

VIDEO: POST-SCRUB NEWS CONFERENCE PLAY
VIDEO: DISCOVERY IN THE PREDAWN DARKESS PLAY | HI-DEF
VIDEO: WEDNESDAY'S ROLLBACK OF PAD GANTRY PLAY | HI-DEF
VIDEO: TIME-LAPSE OF PAD GANTRY ROLLING BACK PLAY
VIDEO: THE PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: ASTRONAUTS ARRIVE IN FLORIDA FOR LAUNCH PLAY
VIDEO: POST-ARRIVAL COMMENTS FROM THE CREW PLAY | HI-DEF

VIDEO: FLIGHT READINESS REVIEW BRIEFING PLAY

VIDEO: SECOND LAUNCH POSTPONEMENT BRIEFING PLAY

VIDEO: NARRATED MISSION OVERVIEW MOVIE PLAY
VIDEO: MEET SHUTTLE DISCOVERY'S ASTRONAUTS PLAY
VIDEO: INTERVIEW WITH COMMANDER LEE ARCHAMBAULT PLAY
VIDEO: INTERVIEW WITH PILOT TONY ANTONELLI PLAY
VIDEO: INTERVIEW WITH MS1 JOE ACABA PLAY
VIDEO: INTERVIEW WITH MS2 STEVE SWANSON PLAY
VIDEO: INTERVIEW WITH MS3 RICKY ARNOLD PLAY
VIDEO: INTERVIEW WITH MS4 JOHN PHILLIPS PLAY
VIDEO: INTERVIEW WITH MS5 KOICHI WAKATA PLAY

VIDEO: NASA OFFICIALS ANNOUNCE LAUNCH DELAY PLAY
VIDEO: SPACE STATION'S VIBRATIONS DURING REBOOST PLAY

VIDEO: INFORMAL NEWS CONFERENCE AT RUNWAY PLAY
VIDEO: ASTRONAUTS ARRIVE FOR PRACTICE COUNTDOWN PLAY

VIDEO: DISCOVERY POSITIONED ATOP PAD 39A PLAY | HI-DEF
VIDEO: EARLY MORNING ROLLOUT FROM THE VAB PLAY | HI-DEF
VIDEO: TIME-LAPSE MOVIE OF DISCOVERY ARRIVING AT PAD 39A PLAY

VIDEO: DISCOVERY HOISTED FOR ATTACHMENT TO TANK PLAY | HI-DEF
VIDEO: CRANE ROTATES DISCOVERY VERTICALLY PLAY | HI-DEF
VIDEO: DISCOVERY MOVES TO ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: NOSE WHEEL LANDING GEAR RETRACTED PLAY | HI-DEF

VIDEO: TIME-LAPSE MOVIE OF DISCOVERY GOING VERTICAL PLAY
VIDEO: TIME-LAPSE MOVIE OF ASSEMBLY BUILDING CRANE WORK PLAY
VIDEO: TIME-LAPSE MOVIE OF DISCOVERY'S TRIP TO VAB PLAY
VIDEO: TIME-LAPSE MOVIE OF PAYLOAD'S MOVE PLAY

VIDEO: SHUTTLE AND STATION PROGRAM UPDATE PLAY
VIDEO: STS-119 MISSION OVERVIEW BRIEFING PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY
MORE: STS-119 VIDEO COVERAGE
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