Spacewalk 'quite a ballet'
2006-07-10 12:31
Houston, Texas - Two Discovery shuttle astronauts prepared for a tricky second spacewalk on Monday to conduct maintenance work on the International Space Station, as Nasa declared their spaceship fit to fly home.
Astronaut Mike Fossum, who will float out of the ISS with colleague Piers Sellers, said the second of three planned spacewalks would be "quite a ballet".
"The most challenging thing tomorrow is going to be just the choreography," he said from the ISS in an interview with international media.
The astronauts will have to move "back and forth" in the shuttle's payload bay and move a spare pump module up to the ISS. Discovery docked at the ISS on Thursday.
The duo will also replace a cable on the ISS's mobile transporter, a sort of railcar that moves the ISS's robotic arm along a truss for construction and maintenance work on the unfinished orbiting laboratory.
They will venture out of the ISS again on Wednesday to try out shuttle repair techniques deemed crucial for Nasa's efforts to increase space flight safety.
They will test repairs on pre-damaged samples of reinforced carbon-carbon (RCC), a composite material used on the shuttle's wing leading edges as a heat shield.
"This is our chance to really test out in a zero gravity vacuum the repair material that might be used," Fossum said.
In their first spacewalk on Saturday, Sellers and Fossum tested a boom extension on the shuttle's robotic arm as a possible work platform for future repairs. Nasa described the test as a success.
The US space agency has striven to improve shuttle safety since seven astronauts died in the Columbia disaster in February 2003.
Nasa administrator Michael Griffin wants to conduct 16 more flights to complete the ISS by 2010, when the 25-year-old shuttle fleet is scheduled to be retired.
In addition to testing in-orbit repair techniques, Nasa has made several modifications to foam insulation on the shuttle's external fuel tank to prevent debris from striking the spacecraft during lift-off.
Such debris pierced Columbia's heat shield, dooming its return to Earth.
Nasa analysts who reviewed images of the shuttle's heat shield found no damage that could prevent Discovery from coming home on July 17.
"We are absolutely clear and ready to bring this vehicle home when our mission is accomplished," Steve Poulos, the orbiter programme manager, told reporters.
Discovery will get a final check-up at the end of the mission, however, to make sure it was not hit by micrometeorites while in orbit.