NASA confident of May window

by Chris Bergin

Despite a series of resent setbacks, including hurricanes and falling foam, the centerpiece of the US manned space program – the Space Shuttle fleet – is set to return to orbit as early as May 2006 (a window of May 3 to May 23 – target May 16), according to Shuttle program officials.

In a Friday press conference titled ‘Space Shuttle Program Status Briefing,’ “May [2006] looks very doable”, remarked William Gerstenmaier, associate administrator for Space Operations.

“I think we’re beginning to have our hands well around the technical problems that we have and to find the fixes that are going to be necessary to fly again,” Wayne Hale, Shuttle Program Manager added. The most recent technical problem originated during the STS-114 mission in July, when a briefcase-size piece of foam fell off Discovery’s external tank during liftoff.


Richard Gilbrech, the NASA engineer heading up the “tiger team” charged to investigate the foam loss during STS-114, has identified what may turn out to be a structural issue with the Shuttle’s external tank. The PAL (Protuberance Air Load) ramp was added to the tank to protect it from unstable air flow before the ramp’s aerodynamics were understood.

“If we find that [the PAL ramp] is not required or perhaps a much smaller ramp is required,” noted Hale, “and we can eliminate some of the foam from outside the tank, then we have eliminated something that can cause problems”. Hale added that the goal is to eliminate the need for the PAL ramp on future external tanks.


Regarding the external tank being built for STS-121, the Atlantis mission scheduled for May 2006, he continued “the PAL ramp will be dissected and looked at very carefully for what we can learn from that”.


“Before Columbia, the foam’s main purpose was to add insulation, to keep propellants cold and protect the external tank from air frictional heating during ascent,” added Gilbrech. “After Columbia, we learned that we needed to treat foam as a structure”.


The twenty-seventh Columbia mission ended in tragedy on February 1, 2003, resulting in the loss of all seven of its crew, and a nearly two and a half year setback for the shuttle program. An initial investigation revealed that a piece of foam, which broke off the vehicle during liftoff, had struck the left wing, damaging temperature sensors there. A seven month long investigation of the Columbia disaster revealed that a 1.6 pound piece of foam broke from the external tank at liftoff and collided with the spaceship’s left wing, cracking it. During reentry, heated gas flowed into the damaged wing, disintegrating the orbiter.


Responding to the suspicion that worker negligence was a factor in the foam problem on STS-114, Gilbrech insisted, “I want to make it clear that we found no negligence on the part of the workers.”


Post-Columbia procedures require more human handling of the foam, which may crush the fragile material. Gilbrech’s team is evaluating new techniques for applying the foam to the structure, lessening the risk of mishandling it.


Gilbrech pointed out that handling the foam without damaging it is difficult, as it is largely filled with air. In rethinking the foam as a structure, those applying it must keep in mind that it’s primary function is protect the tank from the stresses of ascent and the large temperature fluctuations experienced throughout the flight. The foam must remain stable and remain adaptable to the heat and humidity of the air at launch, and the extreme cold of the liquid fuel carried in the external tank.


STS-114 was the first mission which used a new foam known as BX265. Gilbrech’s investigation discovered that an older type of spray used to fasten an older foam to the tank may have left “weak spots” between the pieces of the new foam. It was also confirmed that workers had entered the intertank flange area of the tank to carry out work.


Compounding the foam problem, is the devastation wreaked by hurricane Katrina on the gulf coast region. New Orleans is the location of the Michoud Assembly Facility, where the external tank is constructed and tested before being shipped by barge to the Kennedy Space Center.


Hale acknowledged hurricane Katrina’s impact on the External Tank operations at Michoud, saying that “the infrastructure damage equals the loss of three months of work”, but added “our amazing workforce is coming back to work and they are making amazing progress”. Nearly one-fourth of Michoud’s 2,000 workers have returned to work, and most are anticipated to rejoin their colleagues by December 1.


STS-1, the Shuttle program’s first mission, was flown by Columbia in April 1981. The first operational mission in November 1982, designated STS-5, was also flown aboard Columbia, which launched two communications satellites from its payload bay.


The Shuttle program was put on hold following the Challenger disaster in January 1986, when an O-ring on the right booster failed just 73 seconds after launch.


One memorable moment of the Shuttle program was STS-82, a ten day mission flown in February 1997 aboard Discovery to upgrade the Hubble Space Telescope.


If all goes as planned, the shuttle fleet will resume flights in May 2006, beginning with mission STS-121, the first of nineteen flights planned before retiring the orbiter at the end of 2010. Of those flights, eighteen will take the orbiter to the International Space Station, completing construction, while one will service the Hubble Space Telescope.

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