This
story was updated at 10:58 a.m. EDT.
CAPE
CANAVERAL, Fla. - NASA's space shuttle Discovery will have to wait one more day
before joining its fuel tank and rocket boosters at Kennedy Space Center (KSC),
the space agency said Thursday.
Problems
with a sling designed to hoist Discovery into a vertical position inside the
massive Vehicle Assembly Building (VAB) here prevented the shuttle's move from
its hangar-like Orbiter Processing Facility. A sheared screw on the sling will
have to be replaced and tested before NASA can press ahead with Discovery's
move.
"We've
stood down on operations today," NASA spokesperson Bruce Buckingham said.
Discovery
is now set to move to the VAB, where its external fuel tank and twin solid
rocket boosters await its arrival atop their Mobile Launch Platform, at 8:00
a.m. EDT (1200 GMT) Friday, NASA said.
Engineers
hope to mate Discovery to its external tank-booster stack over the next week
and roll the entire launch system out to Pad 39B here on May 19. The orbiter's
rollover and rollout are key milestones for NASA, which hopes to launch
Discovery on its STS-121
mission - the agency's second post-Columbia test flight - on July 1.
NASA KSC
spokesperson Jessica Rye said a sheared jack screw on a spreader beam of the
sling, which keeps the hoist's outer components clear of an orbiter while they
are attached, led to today's delay.
"We do have
a spare," Rye
said, adding that it would take about three hours to swap out the jack screw.
But
engineers also want to understand what caused the faulty jack screw to shear
and ensure that its replacement is working properly before strapping the
100-ton Discovery orbiter in the sling and lifting it off the VAB floor.
"They've
got a metallurgist coming in to evaluate the issue," Buckingham said.
The threat
of thunderstorms over NASA's Florida
spaceport would also have challenged a late afternoon rollover for Discovery
today, he added.
Friday's
planned rollover for Discovery will be the orbiter's first move since the
spacecraft returned
to KSC following last summer's STS-114
spaceflight.
NASA is
preparing Discovery to launch seven astronauts to the International Space
Station (ISS) on the STS-121 test flight. The mission has a launch window that
stretches through July 19.
In addition
to rollover operations, shuttle workers also moved the Italian-built Leonardo
module - one of four Multi-Purpose Logistic Modules - into a payload canister
Thursday as part of NASA's STS-121 preparations. Packed with new equipment,
experiments and other cargo, Leonardo will launch toward the ISS inside
Discovery's payload bay and carry vital supplies to the orbital laboratory's
crew. Other cargo items, such as replacement ISS parts and spacewalk tools,
have also been installed in the payload canister.
Buckingham
told SPACE.com that current plans call for Leonardo to be delivered to
Pad 39B next week, possibly before Discovery rolls out from the VAB.
Discovery
launched NASA's first return to flight mission, STS-114, to the ISS last July
on a 14-day mission that ended with a successful
landing at Edwards Air Force Base in California's Mojave Desert. The
shuttle returned
to KSC on Aug. 21 atop NASA's modified 747 carrier jet.
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