Discovery at Kennedy Space Center's Launch Pad 39A. Photo Credit/NASA's Kim Shiflett
Shuttle Discovery, after a near four-month delay to troubleshoot external fuel tank cracks, is ready to lift off for the International Space Station on Feb. 24 at 4:50 p.m., EST.
NASA formally set the previously anticipated launch date and time following a Flight Readiness Review at NASA’s Kennedy Space Center on Friday.
During an 11 to 12-day mission, Discovery’s six astronauts will deliver an equipment storage module, an external platform for spare parts and other supplies. Two spacewalks are planned as well to retrieve a failed cooling system pump motor that was temporarily attached to the station’s long solar power system truss in August.
The mission will be the 39th and final flight for NASA’s fleeting leading orbiter. The new equipment is intended to sustain the space station long after NASA’s final shuttle mission later this year.
The countdown is scheduled to get under way on Monday at 3 p.m., EST.
The flight was stalled on Nov. 5 by a launch pad hydrogen leak. Subsequently, technicians discovered a long crack in the insulating foam of the external tank. Underneath the cracked foam, technicians found the first of several cracks ultimately discovered on the metal stringer section of the external tank.
The propellant leak was traced quickly to a Ground Umbilical Carrier Plate, which was replaced. The alignment of the GUCP was refined as well.
The cracks took longer to resolve. Ultimately, engineers determined the damage was caused by combination of factors.
They included a weaker than believed aluminum-lithium alloy in the fabrication of 77 of the 108 stringers, resident forces from the assembly of tank components and the very low temperatures of the liquid hydrogen and oxygen propellants that flowed into Discovery’s fuel tank on Nov. 5.
The cracked stringer sections were cut away and replaced. Doublers were added to give the repaired stringers more strength. Most of the rest of the stringers were equipped with “radius blocks,” small metal fixtures designed to blunt the contractions forces of the cold propellants as well as the aerodynamic forces of the climb to orbit.
Discovery commander Steve Lindsey leads a crew that includes pilot Eric Boe and mission specialists Mike Barrett, Nicolle Stott, Steve Bowen and Alvin Drew. Bowen replaced astronaut Tim Kopra, who was injured in a January bicycle accident.
Bowen will team with Kopra for the spacewalks.
The shuttle will reach the station while European and Japanese as well as Russian spacecraft are docked.
On Friday, the station’s crew moved Japan’s H-II Automated Transfer Vehicle from the bottom to the top of the Harmony module. The transfer using the station’s Canadian robot arm provided clearance for Discovery’s docking on Feb. 26.
Two days ago, the European Space Agency launched the Johannes Kepler, another unmanned cargo ship that is on a course to dock with the station on Feb. 24, several hours ahead of Discovery’s scheduled lift off.
U. S. and Russian space agency officials are discussing a possible “photo op” in which three of the station’s crew would board one of two Soyuz capsules docked to the station and back away a little over 600 feet. The Soyuz crew would then use cameras and a high definition camcorder to photograph the station at a rare moment — when each of the major international partners has a spacecraft parked at the orbiting science laboratory.
The photo shoot would take about 75 minutes.
