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.
ISS
glitches
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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