CAPE CANAVERAL, Fla. -- Shuttle Endeavour was cleared for a Friday launch attempt after NASA managers decided a pair of technical issues no longer posed a concern for mission success."We have no constraints to pressing on with the launch count and planned flight on Friday," shuttle program manager Ron Dittemore said late Wednesday during a telecon with news media.
The decision to proceed was made after tests in Canada proved that damage accidentally inflicted on shuttle Endeavour's robot arm by a moving work platform at pad 39A would not compromise the structural integrity of the crane.
Engineers in Toronto took a working test arm and damaged it in the same way Endeavour's arm was damaged.
They then applied loads to the bruised arm that matched the stress the shuttle arm would experience during its mission, especially during launch when the loads are greatest.
"We were able to prove to our satisfaction that the arm is fully functional, withstanding the worst-case loads," Dittemore said. "The manufacturer and all the space shuttle team agreed the arm is safe to fly."
The 50-foot-long (15-meter-long) boom will be used to lift the 14.5-ton P-One truss segment from Endeavour's cargo bay and then hand off the girder to the station's slightly larger Canadarm2 for installation at the orbiting outpost.
At the same time, managers cleared a concern about flex hoses within the orbiter fleet that are the same as the oxygen line that leaked and caused Endeavour's initial launch scrub on Nov. 10.Following the scrub and subsequent discovery that the oxygen flex hose failed because of a crack caused by a metal part wearing out, inspections were ordered on other flex hoses to make sure there was no generic problem that would ground the program.
"All the other lines that we have removed have been inspected and have been found clean, no damage at all. And so we feel confident that the hoses that we have replaced on (Endeavour) did the job, and we're safe to fly there also," Dittemore said.
Liftoff of NASA's fifth and final shuttle mission of the year is expected between 7 and 11 p.m. EST (0000 and 0400 GMT on Saturday). A more precise launch time will be announced late Thursday.
Although the weather forecast for Friday looks good in Florida -- winds could be a concern at the Shuttle Landing Facility -- the forecast at a pair of overseas emergency landing sites in Spain is pessimistic. At least one of the sites must be available for launch.
"The weather will be what it is and we'll just have to deal with it," Dittemore said. "Hopefully, Mother Nature smiles on us and we'll be able to have adequate weather for Friday."
Kennedy Space Center workers had already begun the standard three-day shuttle countdown and so far all preparations for the International Space Station assembly and crew rotation mission are going well.
Wednesday night the launch team was scheduled to load liquid hydrogen and liquid oxygen into storage tanks that supply Endeavour's electricity-generating fuel cell system.
Activation of the shuttle's communication systems and NASA's tracking network is planned for Thursday and the filling of Endeavour's external tank with its half-million gallons of supercold propellant is expected to begin about lunchtime on Friday.
The seven-member flight crew, which includes three men destined to spend the next four months living and working aboard the orbiting laboratory, have returned to KSC.
"I'm sure they're all geared up and ready to go and are anxious to get back into their countdown activities," Dittemore said.
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