Shuttle set to launch with lingering safety issues amid safety questions

The space shuttle Discovery is surrounded by early morning fog at the Kennedy Space Center in Cape Canaveral on Friday. The crew of STS-121 is scheduled for launch aboard the space shuttle Discovery today.

Photos by The Associated Press
Published: Saturday, July 1, 2006 at 6:01 a.m.
Last Modified: Saturday, July 1, 2006 at 12:00 a.m.
WASHINGTON - The space shuttle Discovery is poised for launch today for what NASA engineers hope will be an uneventful mission, knowing that another mishap, even a minor one, could doom the shuttle program and deflate President Bush's ambitions for future space exploration.
Countdown for the flight began late Wednesday afternoon, but the shuttle is flying without the approval of NASA's top safety officer. He voted "no-go" for the mission at the final flight readiness review because of concerns that unacceptably large pieces of foam insulation could break away from the external fuel tank during launch and damage the orbiter.
Still, chief safety officer Bryan O'Connor and a fellow dissenter, NASA chief engineer Chris Scolese, agreed in the end with the judgment of NASA Administrator Michael Griffin that the hazard did not pose an unacceptable risk to the crew - which, if necessary, could take "safe haven" on the international space station to await a rescue flight.
The "window" at Kennedy Space Center's Launch Pad 39B lasts through July 19. Once aloft, Discovery will rendezvous with the space station for a 12-day mission that could be extended for an extra day to test in-flight repair techniques. Barring engineering glitches or bad weather, Discovery should lift off today at 3:49 p.m. Eastern time.
The flight is only the second since Columbia disintegrated over Texas on Feb. 1, 2003, because of damage caused by insulating foam breaking away from the external fuel tank. Further foam loss during Discovery's first post-Columbia flight last summer prompted NASA to ground the shuttles again until now.
As it shifts priorities to undertake Bush's "Vision for Space Exploration" - sending humans back to the moon and eventually to Mars - NASA intends to fly the shuttle 17 more times to finish assembly of the space station before retiring it in 2010. That unforgiving schedule requires the aging fleet of three orbiters to make more than four flights a year.
The post-Columbia delays have sharply curtailed the number of flights and have caused NASA to plunder its budget to address the shuttle's now-notorious flaws, even as the agency tries to develop a new spaceship for the moon-Mars initiative.
Another prolonged grounding could finish the shuttle program and force a radical revamping, or even abandonment, of the "Vision," but shuttle project manager N. Wayne Hale told reporters earlier this month that "all indications are" that Discovery's flight will "demonstrate that we can launch again quickly." Shuttle Atlantis is scheduled for liftoff on Aug. 28.
Still, there is little illusion that the fixes put in place during the past year, just like those made in the aftermath of Columbia, have made the shuttle safe. "This is a dangerous business," said Steven W. Lindsey, Discovery's soft-spoken mission commander. "We pound the risks as flat as we can, but they're still out there."
Discovery will use an external tank that for the first time will not have "protuberance air-load," or "PAL," ramps, the ridges of foam that served as windbreaks to protect exterior cables and fuel lines from launch turbulence.
A one-pound chunk of PAL ramp - big enough to cause critical damage to the orbiter - broke off Discovery's external tank during last year's launch, but it tumbled into the void without hitting anything.
After exhaustive wind tunnel tests and computer analysis, engineers determined that "we are safe to fly structurally" without the PAL ramps, Hale said, and they were removed. Getting rid of the ramps, he added, is "the largest aerodynamic change that has ever been made in the history of the shuttle."
What engineers did not do, however, was find a satisfactory way to redesign foam insulation for 34 metal brackets - known as "ice frost ramps" - that hold the fuel pressure lines and electrical cables in place. Without PAL ramps to shield them, they will be exposed to different aerodynamic forces than in previous flights.
"We know that pieces (of foam) can come off (the brackets) and can be harmful," Hale said. "It's a hazard we know we need to fix," he added, but planners decided to go ahead with the current launch and redesign the brackets later.
This was not a decision either taken lightly or quickly. Mission planners first came to an impasse at a meeting in late April, with dissenters arguing that "as-is" brackets were too dangerous and that the shuttle should fly only after engineers had redesigned the brackets and tested them.
Griffin carried the day at that meeting by pointing out that only one major change - removing the PAL ramps - should be flight tested before undertaking a second.
But the impasse reappeared during subsequent meetings, culminating in the O'Connor-Scolese dissent at Discovery's Flight Readiness Review on June 17. Again Griffin cast the deciding vote, this time arguing that the crew would not be in danger because they could make on-orbit repairs, or, if that proved impossible, take refuge on the space station.
O'Connor appeared to accept this judgment, suggesting that he had maintained his opposition because he wanted Griffin to be put on record: "If the administrator could accept it," O'Connor told a news conference last week, "I felt I was not going to throw my badge down."
The lingering dilemma, described by External Tank Project Manager John Chapman, is that the ramps must be aerodynamically sound without the PAL ramps while at the same time insulating the metal brackets to keep ice from forming on them as they are cooled by the liquid hydrogen and liquid oxygen inside the tank. Having ice fall from the tank during launch could be even more hazardous to the orbiter than shedding foam.
"You always want to guard against unintended consequences," Chapman told reporters at Johnson Space Center. "You want to make sure you understand fully (what is happening) before you make any change at all." When redesigned bracket insulation performed worse in wind tunnel tests than the existing version, engineers decided to stay with the original.
Discovery's upcoming mission is the second of what NASA has deemed "test flights" to evaluate post-Columbia safety upgrades, but it also resumes the shuttle's main task - assembling and operating the space station.
Since Columbia, the station has been in something of a caretaker state, with the two crew members - one American and one Russian - spending much of their time keeping vital operating systems in running order with minimal resupply from Russia's Progress cargo spacecraft.
This will change when Discovery delivers European Space Agency astronaut Thomas Reiter to join Commander Pavel Vinogradov and Flight Engineer Jeffrey Williams, bringing the station crew back up to its normal pre-Columbia complement. Reiter, a German national and veteran spacewalker aboard Russia's former Mir space station, will stay aloft for about six months, returning to Earth aboard a later shuttle flight.
Besides Reiter and Lindsey, who has flown the shuttle twice before as pilot and once as mission commander, Discovery's crew includes pilot Mark E. Kelly, flying his second shuttle mission, and spacewalker Piers J. Sellers, a British-born astronaut also on his second mission.
Three rookies round out the crew: Lisa M. Nowak and Stephanie D. Wilson, who will handle cargo and operate "robotic arm" cranes during damage surveys and spacewalks; and the second spacewalker, Michael E. Fossum.
The mission includes two scheduled 61/2-hour spacewalks for Sellers and Fossum, focusing on equipment testing and repair, and will add a third if there is enough fuel and other consumables for an extra day in orbit.
If a third spacewalk takes place, Sellers and Fossum will test the effectiveness of a black adhesive called "Non-Oxide Adhesive Experimental," or "NOAX," in repairing cracks to the reinforced carbon-carbon heat shielding.

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