Discovery's Goal: A Quiet Trip
Thursday, June 29, 2006
The space shuttle Discovery is poised for launch Saturday 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 yesterday afternoon, but the shuttle is flying without approval by 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 D. Griffin that the hazard does not pose an unacceptable risk to the crew -- who, if necessary, could find "safe haven" on the international space station while awaiting a rescue flight.
The launch 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 a day to test in-flight repair techniques. Barring engineering glitches or bad weather, Discovery should lift off Saturday 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 the shuttle 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 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 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.