HOUSTON - NASA mission controllers are
planning a third spacewalk and an extra day in space for six astronauts aboard
the shuttle Discovery, the orbiter's lead flight director said Friday.
"It's a
done deal," said Tony Ceccacci, lead shuttle flight
director for Discovery's STS-121 mission, adding that the decision will be
finalized later today. "We're going to tell them we'll step up to do a 13-day
mission and we'll plan accordingly."
The extra
day will allow STS-121 spacewalkers Piers
Sellers and Michael Fossum a chance to test additional crack repair methods
in the reinforced carbon carbon panels that line the shuttle
wing leading edges, Ceccacci said during a mission
briefing here at NASA's Johnson Space Center.
A third
spacewalk was originally in the mission plan for Discovery's STS-121 spaceflight,
but was pulled
off the docket in May due to the flight's busy schedule. Sellers and Fossum continued
training for the extravehicular activity anyway, banking on the assumption
- since proven - that the supply of cryogenic liquid hydrogen and liquid oxygen
that powers Discovery's fuel cells could last an extra day in orbit.
Ceccacci
said the extra mission day also gives Discovery's crew some leeway in terms of
cargo transfer. The day could also be used to make heat shield repairs on the
off chance that today's focused inspections of Discovery turned up a
last-minute issue, such as the need to pluck a pair of gap fillers from between
the spacecraft's belly-mounted tiles, he added.
"There are
some concerns and that's why we're doing the focused inspections," Ceccacci said.
NASA set
aside four hours today for the STS-121 crew to examine six different concerns;
a gap
filler jutting out near Discovery's starboard external tank door, a gap
filler - dubbed "tadpole" - along the forward section of the orbiter, a white
spot that appears similar to bird droppings on the nose cap, two scuffs on a
right wing RCC panel and a dark spot on another RCC panel on the same wing.
Focused
inspections began about one hour late due to questions over the clearance
requirements when handling Discovery's orbital boom, which is a 50-foot
(15-meter) extension of its 50-foot (15-meter) robotic arm, near the ISS, Ceccacci said.
Meanwhile,
Sellers and Fossum are preparing for the first
spacewalk of their mission. The two spacewalkers are set to make repairs to a
cutting system used on the station's railcar-like Mobile Transporter and to
test the stability of the orbital boom as a work platform.
That
spacewalk will begin at 9:13 a.m. EDT (1313 GMT) and be broadcast live on
NASA TV.
advertisement
