Production Slows Due To Changes, Other Shuttle Safety
Measures
NASA's contingency plan for an upcoming mission to service the
Hubble Space Telescope may be in jeopardy, due to production issues
with the modified external fuel tanks to be used on remaining
shuttle missions.
According to a CBS News report, the next mission to the
International Space Station, STS-124 onboard Discovery, remains on
track for a late-May liftoff. That will be the first launch to
utilize an "in-line" external tank, which sports built-in
modifications intended to reduce the risks of catastrophic damage
to the orbiter from chunks of insulating foam.
Previous tanks used since Discovery's first Return to Flight
mission in July 2005, following the 2003 loss of Columbia, featured
a number of modifications intended to reduce foam shedding... but
STS-124 will be the first to use an external tank designed from the
ground-up to incorporate such changes. The new design includes a
new protuberance air load (PAL) ramp design, and titanium
O2 line support brackets... both measures intended to resist ice
formation.
And therein lies the problem. The first redesigned tank,
destined for Discovery's flight, left Lockheed Martin's Michoud
Assembly Facility on Thursday, enroute to Florida...
but later tank deliveries might be delayed, sources say, due to a
slowdown in tank manufacturing as workers address new tank
construction processes, and other issues related to shuttle
modifications.
NASA will probably receive the external tank for the Hubble
mission onboard Atlantis, STS-125, in time for its scheduled August
28 launch. However, the space agency has also called for the
shuttle Endeavour to be launch-ready as well, should Atlantis
suffer damage that would prevent the orbiter from reentering the
atmosphere.
The tank slated for that emergency mission -- designated STS-400 --
will likely not be ready in time.
The space agency is exercising an abundance of caution with the
Hubble flight. If damaged, Atlantis would be essentially trapped in
orbit; it would not be possible for the shuttle to dock at the
International Space Station -- what NASA calls "lifeboating" -- so
its crew could await rescue on another shuttle, or Russian Soyuz
capsules.
STS-125 will be the first shuttle mission not to dock at the ISS
since the Columbia disaster, and is slated to be the last such
flight before the shuttle fleet is retired in September 2010. The
Hubble is in a much higher orbit than the ISS, and the shuttle does
not carry enough fuel to move to a different orbit.
The external tank production delays may also mean further delays
for remaining shuttle flights, as well... but for the moment,
anyway, the priority is STS-125. Assuming the STS-400 rescue
mission is not needed, Endeavour will fly to the ISS on STS-126 in
October.
NASA officials remain optimistic any current delays will be
resolved in the near future, as workers at Lockheed and NASA gain
experience with working with the new tanks. "We have margin in the
schedule to absorb small delays and we have learned a lot in the
process of putting these tanks together so that the '09 and '10
tanks will flow much faster," said Shuttle Program Manager John
Shannon, adding NASA has "added many new features to further ensure
the safety of this tank and since these were the first in-line
tanks, we took extra time to make sure we got it right."
Shannon would not comment on specific launch dates, according to
CBS. Following the return of STS-123, now in orbit at the ISS,
NASA's launch manifest calls for four more regular launches this
year, four in 2009 and three in 2010.