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.

FMI: www.nasa.gov