This story was updated at 6:15 p.m.
EST.
A freak
hail storm that peppered NASA's space shuttle Atlantis late
Monday, damaging its external fuel tank and sending launch pad workers seeking
cover, has delayed the orbiter's planned
March liftoff by at least one month, mission managers said Tuesday.
Shuttle workers are now preparing to
haul Atlantis from its perch atop NASA's Launch Pad 39A for the slow trek back
to the Vehicle Assembly Building (VAB) at Florida's Kennedy Space Center, where
a cadre of inspectors will comb the orbiter' 15-story fuel tank and fragile
heat shield for hail damage and make repairs [image
1, image
2]. The resulting delay pushes Atlantis' planned
launch to no earlier than April 20 or so, NASA officials said.
"This constitutes, in our
evaluation, the worst damage that we have ever seen from hail on the external
tank foam," Wayne Hale, NASA's shuttle program manager, told reporters during a
Tuesday press briefing. "The bottom line is that, at this point, we do not
believe we can make the launch window for a March launch of Atlantis."
The announcement came in the middle
of NASA's standard, two-day pre-launch Flight Readiness Review meeting to
determine whether Atlantis is ready for its upcoming
spaceflight.
Commanded by veteran shuttle flyer Rick
Sturckow, Atlantis' STS-117
astronaut crew was preparing to launch towards the International Space Station (ISS) on March 15 to deliver a new set
of starboard solar arrays. In order to make a March flight, NASA had to launch
Atlantis by around March 25 to complete the planned 11-day STS-117
mission before the April 7 launch of a new crew
to the ISS, NASA has said.
Current NASA procedures call for a
72-hour buffer period between departing and arriving spacecraft to give the ISS
astronaut crew time to rest during
the busy schedule. The ISS crew swap – which will mark the station's shift
between its Expedition
14 and Expedition
15 missions – should be complete by April 20, clearing the way for an
arriving shuttle a few days later, Hale said.
Atlantis' solar array cargo will be
removed from the orbiter's 60-foot (18-meter) payload bay later this week,
setting the stage for its return to the VAB on Sunday or Monday, mission
managers said.
A hail "explosion"
Hale said Monday's
hail shower stemmed from an extremely localized storm, which NASA shuttle
weather experts dubbed an "explosion," right over the agency's Pad 39 launch
site at Kennedy Space Center in Cape Canaveral, Florida.
Initial estimates indicate that hail
up to the size of golf balls caused upwards of 7,000 dings around the nose cone
and upper regions of Atlantis' external tank, but it is possible that only a
few hundred of those will require repairs, said John Chapman, NASA's external
tank project manager at the Marshall Space Flight Center in Alabama, during the
briefing.
"The key right now is to get it back
[in the VAB] and look at it and assess exactly what we've got to do," Chapman
said.
Launch pad cameras [image]
offered initial glimpses of the fuel tank's hail damage and were followed up by
photographic inspections [image
1, image
2]. The damage is more extensive than that seen in 1999 when the fuel tank
for NASA's STS-96 mission aboard Discovery suffered 650 dings, which required
four days to fix and caused a one-week launch delay, shuttle mission managers
said.
A 360-degree area around the tip of
Atlantis' external tank suffered hail damage, as well as three protective ice-frost
ramps that insulate brackets along the vessel's exterior.
Preliminary surveys also found up to
27 minor dings on the heat-resistant tiles of Atlantis' left wing, though they
appear to be limited to minor surface damage. The damage apparently stems from
ricocheting hail that penetrated the protective Rotating Service Structure which
shrouds Atlantis from weather, NASA officials said.
"We have not seen any orbiter damage
that causes us real concern," NASA launch director Mike Leinbach
told reporters in the briefing, adding that pad shuttle workers took cover during the hail. "It was dynamic, the guys knew it was hailing on them."
If only minor repairs are required,
engineers could extend platforms and scaffolding around Atlantis' external tank
to sand, shape and pour new foam insulation into damaged areas inside the VAB.
But if the tank is completely unusable – a scenario NASA shuttle officials
believe is not likely – Atlantis would have to wait until April 10 for the
arrival of a replacement, pushing the STS-117 mission into June.
"Right now, we don't think that's
likely," Hale said. "But I can't rule it out."
The integrity of foam insulation
covering shuttle fuel tanks has been a top concern for NASA engineers since 2003, when a
briefcase-sized chunk shook free during the launch of Columbia and damaged heat
shielding along the orbiter's left wing leading edge. The damage later led to
the loss of Columbia and
its seven STS-107
astronauts during reentry on Feb. 1,
2003.
Since then, NASA has redesigned
shuttle fuel tanks to reduce the amount of foam debris at launch and taken
steps to avoid striking large
birds during liftoff [image],
which could also damage an orbiter's heat shield should they hit the
spacecraft, shuttle officials have said.
History of hail
Hail is not uncommon to NASA's
Florida launch site and has damaged NASA orbiters and fuel tanks in the past, shuttle
officials said.
In addition to the May 1999 damage
during STS-96, hail also damaged Atlantis' heat resistant tiles in 1990 as the
shuttle was being readied for launch of its STS-38 mission. Northern Flicker
woodpeckers have also damaged shuttle fuel tanks before a launch. The birds
pecked nearly 200 holes in the space shuttle Discovery's fuel tank foam during
preparations for NASA's STS-70 mission in 1995.
But Atlantis' current delay to April
will cause some schedule jockeying for NASA's four additional ISS-bound shuttle
flights slated for later this year. Prior to today's STS-117 launch delay, NASA
targeted a June 28 launch for the Endeavour orbiter's STS-118 flight, an Aug. 26
liftoff for Atlantis' on STS-120 mission,
and two fall shuttle flights to deliver new international laboratory components
to the ISS.
"I am fully confident that by the
end of the year, we'll be back to where we would have been barring any
additional complications," Hale said. "You'll see some launch dates change, but
it won't be by large amounts and it won't ripple out for a large number of
flights."
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