June 28, 2006 —After more than three years and $1.3 billion, NASA is ready for a second — and likely last — attempt to recover from the 2003 Columbia disaster and resume construction of the half-built International Space Station.
The countdown begins today for launch of space shuttle Discovery at 3:49 p.m. ET Saturday.
"Everyone's been excited and kind of anxious to get into a launch countdown," NASA test director Jeff Spaulding said at a press conference on Wednesday. "They've worked hard to get us to this point."
With 16 missions on the shuttles' manifest and just four years to finish the job, NASA's chief says it's time to move, despite objections from key safety and engineering officials who unsuccessfully argued for additional modifications before Discovery flies.
NASA administrator Mike Griffin acknowledges he is taking a chance, but not with the lives of the astronauts, who could stay aboard the station for nearly three months while they wait for a new ride home if Discovery should suffer Columbia-like damage during its liftoff.
A Troubled Past
Columbia was struck by a 1.67-pound chunk of foam that fell off its external fuel tank and smashed into its left wing.
The damage was undetected until after the shuttle broke apart as it flew through the atmosphere for landing 16 days later. All seven astronauts aboard died.
Last year, NASA flew its first mission since the accident, testing not only a new tank design, but also a myriad of inflight inspection techniques, heat shield repair materials and other safety improvements.
Large pieces of foam insulation again fell off the tank and the fleet was grounded again.
NASA still expects some foam loss, particularly from areas that cover metal brackets holding pressurization lines and a box of cables to the outside of the tank. But any flyaway foam is expected to be too small to do damage, shuttle managers said.
With the fleet's 2010 retirement date looming and plans to build a new vehicle to transport crews and cargo to the station and eventually the moon, NASA has neither the time nor money to handle more serious shuttle problems.
"If we have another major incident in launching the space shuttle, I would not wish to continue with the program," Griffin said.
Mission Possible
Launching will be only the beginning. The shuttle is scheduled to dock at the station two days later to deliver more than 5,000 pounds of equipment and supplies, as well as a new crewmember, European astronaut Thomas Reiter.
The station has been operating with just two-man crews since Columbia's demise to save on supplies while the shuttle, which delivers the bulk of the station's cargo, was grounded.
The most critical equipment includes replacement parts for the station's mobile transporter, which was shut down after it inadvertently severed a set of cables that provide power, video and data.
Without the transporter, which is a small cart that runs along tracks on the outside the station to move equipment to various work sites, station assembly cannot continue.
One of up to three spacewalks planned during the flight is devoted to repairing the transporter.
Astronauts Piers Sellers and Michael Fossum also are scheduled to test an extension to the shuttle's 50-foot-long robotic arm to see if it is stable enough to serve as a work platform for emergency in-flight heat shield repairs on currently inaccessible parts of the shuttle.
Discovery will also deliver a new oxygen generator, needed to eventually expand the station crew size to six; a European experiment rack to grow plants in space; a sub-zero freezer to store life science and biological samples; and a spare pump for the station's cooling system.
