NASA's
Discovery orbiter will fly next month, with concerns it could suffer damage
from launch debris akin to that which doomed the Columbia mission all but
settled, shuttle officials said Friday.
Modifications
made to Discovery's external tank since April have lowered the risk from
potentially harmful ice debris, which shuttle officials feared could shake off
during launch and strike the orbiter, to within acceptable parameters, mission managers said. But more work is still needed to better understand
the risk of ice debris striking an orbiter's protective thermal tiles, they added.
"This is
going to require constant vigilance, but as far as [STS] 114 is concerned, I
believe our concerns are put to bed," said John Muratore, NASA's manager for
shuttle systems engineering and integration, during a teleconference with
reporters. "We're ready to fly."
Muratore's
comments came after shuttle managers concluded a debris verification meeting at
NASA's Kennedy Space Center in Florida.
Discovery's
STS-114 mission is slated to launch no earlier that July 13 and is expected to
mark NASA's return to shuttle flight. NASA grounded Discovery and its two
sister shuttles after the loss of the Columbia orbiter, which broke apart
during reentry on Feb. 1, 2003, killing its seven-astronaut crew. The STS-114
mission is designed to test new shuttle flight safety methods and hardware, as
well as resupply the International Space Station.
Shuttle
officials will hold a flight readiness review meeting for the mission between
June 29-30 before deciding on a final launch target.
"I would go
the flight readiness review with the mindset that we could make the opening of
the launch window," NASA space shuttle program manager Bill Parsons told
reporters. "Where we are today, we have every opportunity to make the opening of
the launch window."
Discovery's
launch window stretches from July 13 to July 31. A second window, currently
allocated to the second return-to-flight mission STS-121, opens on Sept. 9.
Launch
debris work
External
tank debris has been a major concern for shuttle managers and engineers
preparing the Discovery orbiter for flight.
Investigators
attributed the Columbia accident to a suitcase-sized chunk of insulating foam
that separated from the Columbia's external tank at launch and struck the
orbiter's left wing. That damage, investigators concluded, fatally wounded
Columbia and allowed hot atmospheric gases to enter the wing during reentry,
which led to its destruction.
Engineers
spent two years
redesigning portions of shuttle external tanks to cut down the amount of
foam debris shaken loose during launch.
In late
April, mission managers pushed
back their initial May flight target to July after realizing that ice debris
posed a larger hazard to the shuttle than previously thought, especially from a
section known as the liquid oxygen feed bellows. That unit expands and
contracts due to the supercold propellant that runs through it, allowing ice to
form and potentially break loose at launch.
Discovery swapped
external tanks earlier this month and is now attached to a tank equipped
with a bellows heater
to keep ice from forming on the bellows unit.
Meanwhile,
an independent safety panel - the Stafford-Covey Return to Flight Task Group -
is expected to hold its final public meeting on June 27. The group has
monitored NASA's return to flight progress and passed the space agency on all but
three of the 15 items which Columbia investigators recommended should be
completed before the another shuttle launch is attempted. Those items included
two debris mitigation recommendations and a third pertaining to orbiter repair.
"I believe
that at least two of the remaining three will be closed," Parson said. "I'm
fairly optimistic."
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