Seven astronauts are officially set to ride NASA's Discovery orbiter towards the International Space Station (ISS) next week even as engineers tackle glitches with the orbital laboratory, top shuttle managers said late Wednesday.
"I think we're ready to go fly," Wayne Hale, NASA's shuttle program manager, told reporters during a press briefing at the agency's Kennedy Space Center (KSC) in Florida. "We're on track to getting a third flight done by the end of the year."
Discovery is scheduled to rocket spaceward on Dec. 7 at about 9:36 p.m. EST (0236 Dec. 8 GMT) to continue assembly of the ISS. The planned space shot, which follows successful July and September missions, will mark NASA's first night shuttle launch since the 2003 Columbia accident.
Veteran NASA shuttle flyer Mark Polansky is commanding the 12-day spaceflight, which includes the delivery of a new portside piece of the ISS, a trio of tricky spacewalks to rewire the outpost's electrical grid, and an astronaut swap for the station's Expedition 14 crew.
"One thing that really struck me in this review is really how complex this mission is," William Gerstenmaier, NASA's associate administrator of space operations, told reporters after a two-day Flight Readiness Review at KSC.
The STS-116 mission's launch window currently closes on Dec. 17 since Discovery's computers were not designed for missions that span the crossover from one year to the next. But that limitation would be revisited if required, shuttle officials said.
"My position is, we'll need to revisit it on the 15th or 16th, as we get close," Hale said, adding that the mission could even slip to January if deemed necessary.
While shuttle engineers prepare Discovery for its ISS-bound flight, space station engineers are puzzling over two glitches that arose in the last two days.
A circuit breaker regulating power for one of two motors designed to turn a massive rotary joint that allows the station's portside solar arrays to track the Sun--which is scheduled to begin during STS-116--popped open Tuesday during a software test, Gerstenmaier said, adding that having both systems operation so one can serve as a backup is preferred for the upcoming spaceflight.
"If it's on the software side, it's not a concern at all," Gerstenmaier said.
Engineers are also going over a curtailed reboost maneuver designed to push the ISS into a higher orbit so it will be in the best position to meet Discovery when the spacecraft arrives at the outpost on Dec. 9.
The nearly 20-minute burn using thruster aboard a Russian-built cargo ship shut down after only two minutes late Wednesday afternoon, though ISS flight controllers plan to try the maneuver again on Friday.
"That's pretty typical, if you follow the space station world," Gerstenmaier said of the glitch. "We planned ahead for that. On Dec. 1 we can go ahead and continue that reboost activity."
Night launches to resume
NASA's first three shuttle flights following the Columbia accident launched in daylight to allow clear views of any foam debris shed by their external tanks. A piece of fuel tank foam pierced Columbia's heat shield during liftoff and led to the loss of the shuttle and seven astronauts during reentry.
But after a series of fuel tank safety changes and two smooth liftoffs earlier this year, the time has come to resume night launches, NASA officials said, adding that radar stations should pick up any significant foam shedding events.
"There were really no dissenting opinions to a night launch," Gerstenmaier said.
Earlier this month, NASA officials decided to put off yet another shuttle fuel tank modification--the removal of about half the insulating foam covering a series of ice frost ramps protecting connection brackets--to allow more study and analysis. The so-called ice frost ramp redesign, an interim step to final, foam-less modification, was slated to fly aboard a shuttle fuel tank in March 2007.
"Unfortunately, we were not successful in getting a design that met with engineering approval," Hale said of the interim fix, but added that engineers now have a better handle of the debris risk posed by ice frost ramps after studying this year's earlier shuttle flights.
NASA launch director Michael Leinbach said the countdown for Discovery's STS-116 liftoff is slated to begin on Dec. 3 at 11:00 p.m. EST (0400 Dec. 4 GMT).
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