June 18, 2006 — Despite lingering safety concerns about the shuttle's fuel tank, NASA managers cleared Discovery for launch on July 1, for what is expected to be the second and final test flight following the 2003 Columbia disaster.
The agency's top safety official and chief engineer voted to wait until additional repairs could be made on the fuel tank, which shed debris that led to Columbia's demise and the deaths of seven astronauts.
NASA redesigned the tank, but large pieces of insulating foam also fell off during the first post-Columbia flight in July 2005.
A second redesign was done, but some engineers feel the work did not go far enough. They want to hold off flights until engineers come up with a new design for foam shields covering 34 metal brackets on the outside of the tank.
NASA administrator Michael Griffin acknowledged that more work needs to be done to keep potentially dangerous debris from flying off the tank, but because of other safety improvements, the shuttle crew is not at risk — even in a worst-case scenario.
"I do not see the situation we're in as being a crew-loss situation," Griffin said at a press conference Saturday following a two-day meeting to review Discovery's flight preparations.
"If we are unlucky and we have a debris event, it will not impede the ascent. The crew will arrive safely on orbit, and then we will begin to look at our options," Griffin said.
Since Columbia, the shuttle has flown with a sensor-laden boom for inspections as well as some materials for heat shield repairs.
The space station also is equipped to serve as a safe haven for the entire shuttle crew until a rescue mission by another shuttle or Russian Soyuz rockets could be dispatched. The Columbia crew had none of these options.
"We're not in the situation that we were in with Columbia where we didn't know we had a problem," Griffin said.
While another shuttle accident likely would end the program, Griffin said that accepting a small risk to the vehicle now will help alleviate schedule pressure in three years, when the shuttle is finishing up space station assembly and has just one year left before its retirement.
"This president's budget will not carry funding for shuttle vehicles beyond 2010," Griffin said. "So if we're going to fly, we need to accept some programmatic risks and get on with it."
The shuttle's July 1 liftoff is planned for about 3:43 p.m. In addition to supplies, the shuttle is ferrying equipment to repair the station's mobile external crane, which is needed for future assembly tasks.
Also aboard will be German astronaut Thomas Reiter, who will join two crewmembers already living aboard the station.
After the Columbia accident, the space station crew was cut from three to two people to save on supplies.
The shuttle crew is led by veteran astronaut Steven Lindsey. The other crewmembers are pilot Mark Kelly, flight engineer Lisa Nowak, Stephanie Wilson and spacewalkers Piers Sellers and Michael Fossum.
