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NASA moves Endeavour launch date to May 16
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: May 6, 2011;
Updated at 3:30 p.m. with NASA delay announcement


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KENNEDY SPACE CENTER, FL--Launch of the shuttle Endeavour, grounded April 29 by an electrical glitch in the ship's hydraulic system, will be delayed until at least May 16 pending additional troubleshooting and repairs, NASA managers said Friday.


Credit: NASA
 
Engineers have not yet pinned down the cause of the short circuit that vaporized fusing in a heater control power switch, but a replacement power switching box has been installed and NASA managers have approved a plan to replace wiring between the box and the heaters in question to clear the way for a second launch attempt.

During work to install the new wiring, engineers noticed a crimped cable in a wiring bundle, officials said Friday, and additional tests were planned to find out if that might be the cause of the initial short. NASA managers plan to brief reporters on the status of repairs and overall launch processing Monday.

Going into Endeavour's launch campaign, mission managers had been holding open an option to extend the flight by two days to give the shuttle crew time to help out with needed station maintenance. The idea was to add the extra days to the mission after Endeavour docked with the station.

But on Friday, NASA made that official, extending the flight to 16 days to eliminate multiple timelines and ease flight planning.

For a launch at 8:56 a.m. EDT (GMT-4) on May 16, Endeavour's countdown would begin around 7 a.m. on Friday, May 13. The shuttle would dock with the International Space Station around 6 a.m. on May 18, undock around 11 p.m. on May 29 and land back at the Kennedy Space Center around 2:30 a.m. on June 1.

Complicating mission planning, three of the space station's six crew members -- Dmitry Kondratyev, Paolo Nespoli and Catherine Coleman -- are scheduled to return to Earth May 23 aboard a Russian Soyuz spacecraft. Preparing for undocking will require sleep shifting that will put the station and shuttle crews on different schedules.

The primary goals of Endeavour's flight are to deliver a pallet of spare parts and to install a $2 billion particle physics experiment on the station's power truss. The Endeavour astronauts also plan to stage four spacewalks to perform critical maintenance, but the launch delay is expected to result in a major flight plan revision and the EVA schedule is not yet clear.

Endeavour was grounded during the final hours of a launch countdown April 29 when one of two "strings" of fuel line heaters used by one of the shuttle's three hydraulic power units failed to power up normally. While the system can safely operate with a single string, a subsequent failure could result in a fuel line rupture, knocking auxiliary power unit No. 1 out of action and possibly contaminating the aft engine compartment with toxic hydrazine.

At the time of the failure, engineers believed there were three possible explanations: trouble with a fuse panel in the shuttle's cockpit that routes power to the APU system; a problem with the aft load control assembly, an electrical distribution box upstream of the heaters; or trouble with downstream heaters or thermostats.

Subsequent testing showed the cockpit fuse panel was working normally and that commands were reaching ALCA No. 2 as required. Additional tests indicated the thermostats in question were healthy but not getting power from the distribution box. As a result, ALCA No. 2 was removed from avionics bay No. 5 in Endeavour's aft engine compartment for a detailed failure analysis.

Engineers quickly found vaporized fuse elements in a so-called "hybrid driver" circuit responsible for routing power to APU 1's B-string fuel line heaters. But it was not immediately clear whether the blown circuitry was the result of a problem inside the power box or the result of a short in external wiring.

At launch pad 39A, meanwhile, a replacement ALCA was installed, but fuel line heater power was not immediately reconnected to make sure whatever caused the initial problem did not damage the replacement box.

Engineers met Thursday and discussed three options: replacing the wiring between ALCA No. 2 and the heater thermostats; replacing all the wiring, thermostats and heaters downstream of ALCA No. 2; and pressing ahead "as is" with the replacement ALCA and the original wiring.

They opted to replace the wiring between ALCA No. 2 and the heaters. The original power line will remain in place but will not be plugged in to protect against the possibility of a short. Whether the crimped wire found Friday was a factor in the short remains to be seen.


Spaceflight Now Plus
Additional coverage for subscribers:
VIDEO: OLD ALCA-2 BOX OPENED UP FOR FORENSICS PLAY | HI-DEF
VIDEO: FAILED ALCA-2 BOX REMOVED FROM ENDEAVOUR PLAY | HI-DEF
VIDEO: WORKING ON OLD AND NEW SWITCHBOXES PLAY | HI-DEF
VIDEO: LAUNCH OF ENDEAVOUR DELAYED FURTHER PLAY

VIDEO: PRESIDENT OBAMA ARRIVES AT THE CAPE PLAY | HI-DEF
VIDEO: TOUR OF ATLANTIS AND ASTRONAUT MEETING PLAY | HI-DEF
VIDEO: FIRST FAMILY DEPARTS AFTER VISIT PLAY | HI-DEF

VIDEO: POST-SCRUB NEWS BRIEFING PLAY
VIDEO: LAUNCH DIRECTOR EXPLAINS SCRUB CALL PLAY | HI-DEF
VIDEO: SCRUB DECLARED FOR APU NO. 1 HEATER GLITCH PLAY | HI-DEF
VIDEO: ASTRONAUTS LEAVE QUARTERS BEFORE SCRUB PLAY | HI-DEF
VIDEO: CREW GETS SUITED UP FOR LAUNCH PLAY | HI-DEF
VIDEO: TIME-LAPSE OF PAD GANTRY RETRACTING PLAY | HI-DEF

VIDEO: ENDEAVOUR'S PRE-FLIGHT CAMPAIGN PLAY | HI-DEF
VIDEO: PAYLOADS' PRE-FLIGHT CAMPAIGN PLAY | HI-DEF
VIDEO: PREPARING ENDEAVOUR FUEL TANK FOR LAUNCH PLAY | HI-DEF

VIDEO: COUNTDOWN UPDATE AND WEATHER BRIEFING PLAY
VIDEO: THE PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: ASTRONAUTS ARRIVE AT LAUNCH SITE PLAY | HI-DEF
VIDEO: COUNTDOWN PREVIEW BRIEFING PLAY | HI-DEF

VIDEO: GUIDED TOUR OF SPACE STATION PLAY | HI-DEF
VIDEO: ENDEAVOUR MISSION PREVIEW MOVIE PLAY | HI-DEF
VIDEO: GET TO KNOW ENDEAVOUR'S ASTRONAUTS PLAY | HI-DEF

VIDEO: PRE-FLIGHT INTERVIEW WITH MARK KELLY PLAY
VIDEO: PRE-FLIGHT INTERVIEW WITH GREG JOHNSON PLAY
VIDEO: PRE-FLIGHT INTERVIEW WITH MIKE FINCKE PLAY
VIDEO: PRE-FLIGHT INTERVIEW WITH ROBERTO VITTORI PLAY
VIDEO: PRE-FLIGHT INTERVIEW WITH DREW FEUSTEL PLAY
VIDEO: PRE-FLIGHT INTERVIEW WITH GREG CHAMITOFF PLAY

VIDEO: ENDEAVOUR CLEARED FOR APRIL 29 LAUNCH PLAY

VIDEO: EVACUATION DRESS REHEARSAL PLAY | HI-DEF
VIDEO: ASTRONAUTS BOARD ENDEAVOUR PLAY | HI-DEF
VIDEO: SUITING UP FOR PRACTICE COUNT PLAY | HI-DEF
VIDEO: SHUTTLE INSPECTED FOR STORM DAMAGE PLAY | HI-DEF
VIDEO: CREW TEST-DRIVES PAD ESCAPE VEHICLE PLAY | HI-DEF
VIDEO: ASTRONAUT CHAT AT THE PRESS SITE PLAY | HI-DEF
VIDEO: CREW ARRIVES FOR PRACTICE COUNT PLAY | HI-DEF

VIDEO: PAYLOADS ARRIVE AT LAUNCH PAD 39A PLAY | HI-DEF
VIDEO: CANISTER ROTATED UPRIGHT FOR PAD PLAY | HI-DEF
VIDEO: PALLET OF SPARE PARTS INTO CANISTER PLAY | HI-DEF
VIDEO: AMS PAYLOAD PUT INTO TRANSPORTER PLAY | HI-DEF

VIDEO: SHUTTLE AND STATION PROGRAM BRIEFING PLAY
VIDEO: THE STS-134 MISSION OVERVIEW PRESENTATIONS PLAY
VIDEO: IN-DEPTH WITH ALPHA MAGNETIC SPECTROMETER PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY

VIDEO: SUN RISES OVER THE LAUNCH PAD PLAY | HI-DEF
VIDEO: ENDEAVOUR ARRIVES ATOP PAD 39A PLAY | HI-DEF
VIDEO: ROLLOUT FROM VEHICLE ASSEMBLY BUILDING PLAY | HI-DEF

VIDEO: HOISTING ENDEAVOUR TO TANK AND SRBS PLAY | HI-DEF
VIDEO: ORBITER GOES VERTICAL PLAY | HI-DEF
VIDEO: ENDEAVOUR LEAVES PROCESSING HANGAR PLAY | HI-DEF

VIDEO: PAYLOAD MEDIA DAY PLAY | HI-DEF
VIDEO: THE ALPHA MAGNETIC SPECTROMETER PLAY | HI-DEF
VIDEO: PAYLOAD REMOVED FROM C-5 PLAY | HI-DEF
VIDEO: AMS ARRIVES FROM EUROPE PLAY | HI-DEF

VIDEO: EXPRESS LOGISTICS CARRIER NO. 3 PLAY | HI-DEF
VIDEO: HIGH-PRESSURE OXYGEN GAS TANK PLAY | HI-DEF
VIDEO: PUTTING STATION ANTENNA ON CARRIER PLAY | HI-DEF

VIDEO: TANK UNLOADED TO ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: THE EXTERNAL FUEL TANK ARRIVES PLAY | HI-DEF
VIDEO: BOOSTER SEGMENT MOVED TO VAB PLAY | HI-DEF
VIDEO: KENNEDY SPACE CENTER SRB CEREMONY PLAY | HI-DEF
VIDEO: ENDEAVOUR FITTED WITH MAIN ENGINES PLAY | HI-DEF
VIDEO: ORBITER TOWED OFF RUNWAY PLAY | HI-DEF

MORE: STS-134 VIDEO ARCHIVE
HDTV: HIGH-DEFINITION COVERAGE
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