Spaceflight Now





Countdown begins anew for shuttle Endeavour's launch
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: May 13, 2011


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KENNEDY SPACE CENTER, FL--Engineers restarted the shuttle Endeavour's countdown Friday, setting the stage for a delayed launch Monday on a flight to deliver supplies, spare parts and a $2 billion particle physics detector to the International Space Station. There are no technical problems of any significance at pad 39A and forecasters are predicting a 70 percent chance of good weather.


Endeavour on pad 39A today. Credit: NASA TV
 
"We're counting and working on some of our avionics checkouts right at the beginning of the count as we normally do," said NASA Test Director Jeff Spaulding. "I am really proud of our teams working so hard over the last couple of weeks. They have done an outstanding job to get us ready for this launch on the historic and final flight of space shuttle Endeavour."

Working in Firing Room No. 4 at the Launch Control Center 3.4 miles from pad 39A, engineers started Endeavour's countdown at 7 a.m. EDT (GMT-4) Friday. Liquid hydrogen and oxygen will be pumped aboard to power the shuttle's electricity-producing fuel cell system Saturday. A protective gantry is scheduled to be pulled away from the shuttle at noon Sunday, exposing the ship to view and setting the stage for fueling.

If all goes well, the three-hour fueling procedure will begin at 11:36 p.m. Sunday and Endeavour's crew -- commander Mark Kelly, pilot Gregory H. Johnson, Michael Fincke, Gregory Chamitoff, Andrew Feustel and European Space Agency astronaut Roberto Vittori -- will begin strapping in around 5:41 a.m. Monday to await liftoff.

Shuttle missions to the International Space Station typically enjoy 10-minute launch windows centered around the moment Earth's rotation carries the launch pad into the plane of the station's orbit. To maximize performance, NASA usually targets the middle of the 10-minute window.

But because of recent changes to the station's orbit, rendezvous requirements and other factors, the opening of the window and the preferred "in-plane" launch time are roughly the same for Endeavour's second launch try. Liftoff is targeted for 8:56:26 a.m. EDT Monday and the window will close five minutes later.

Shuttle weather officer Kathy Winters said forecasters are predicting a 70 percent chance of acceptable weather Monday with the primary concerns being slightly high crosswinds at the shuttle's emergency runway. The odds drop to 60 percent "go" on Tuesday and improve to 80 percent favorable on Wednesday.

Winters said the timing of a trough expected to move through the area Sunday could bring afternoon storms and cause problems for engineers trying to move the gantry away from the space shuttle. But she said the system was expected to clear out in time for fueling and launch.

NASA attempted to launch Endeavour on its 25th and final flight April 29, but the countdown was called off when engineers were unable to activate a "string" of hydraulic system fuel line heaters used by auxiliary power unit No. 1. Extensive troubleshooting and analysis showed the problem likely involved a power switching circuit in an avionics box known as an aft load control assembly, one of three in the shuttle's engine compartment.

ALCA No. 2 was removed and engineers quickly discovered blown fuse elements in a so-called "hybrid driver" responsible for routing power to the heater string in question. But engineers were unable to find a problem in the box or the associated wiring that might explain the presumed short circuit that blew the fuse elements.

In a bid to cover as many failure modes possible, ALCA No. 2 was replaced and new wiring was installed between the box and the suspect B-string heaters. In addition, thermostats used to activate the heaters were replaced.

While that work was going on, engineers reviewing heater test data discovered a previously unnoticed 18-amp spike during a thermostat test last June. An inspection of the thermostat in question found an insulation breach and an exposed conductor that might be the cause of the short that blew the hybrid driver circuit in the original ALCA.

But a microscopic inspection of the thermostat found no obvious physical evidence of a short. The thermostat is considered the most likely cause of the heater failure that grounded Endeavour, but the data are not conclusive and the problem is still considered an "unexplained anomaly."


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Additional coverage for subscribers:
VIDEO: COUNTDOWN STATUS AND WEATHER BRIEFING PLAY | HI-DEF
VIDEO: ASTRONAUTS ARRIVE FOR SECOND COUNTDOWN PLAY | HI-DEF

VIDEO: ENDEAVOUR LAUNCH RESCHEDULED FOR MAY 16 PLAY
VIDEO: CHECKING ENDEAVOUR'S WIRING PLAY | HI-DEF
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
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