Belly-side-up: The shuttle does a back flip relative to the International Space Station so its heat tiles can be examined for damage.
Credit: NASA
WASHINGTON: NASA specialists have begun analysing a gash in the shuttle Endeavour's heat shield to decide if it needs repair. The agency also added three days to the mission to continue work on the International Space Station.
The prolongation of the mission means that the Endeavour, launched Wednesday from Cape Canaveral, Florida, will now return to Earth on 22 August 22, a U.S. space agency spokesman said.
The extra time will allow a fourth, additional spacewalk to the mission to continue construction work on the orbiting laboratory. On Saturday the station was expanded with a new truss segment attached by two astronauts.
Heat shield hole
Endeavour's tour was initially planned for 11 days, with three space walks. NASA however said from the start said it would extend the mission after testing a new system that transfers electricity from the ISS to the shuttle.
The system, which prolongs the life of the shuttle's batteries and allows it to remain aloft longer, was tested successfully on Sunday, NASA said.
Meanwhile NASA engineers at mission control in Houston, Texas, were poring over three-dimensional images of a gouge in the shuttle's heat shield. The images were taken Sunday by a camera, and measurements by a laser, both of which trained on the shuttle's underbelly.
The examination took about three hours as the imaging devices atop a 30-meter-long robotic arm coupled with the Orbiter Boom Sensory System (OBSS) scanned five areas on the shuttle underside that may have been damaged during Wednesday's launch from Cape Canaveral, Florida, NASA said.
Earth-based tests
The gouge, 30.5 x 25.5 mm – smaller than initially reported – and 28.5-mm-deep, was made near a landing gear hatch by a piece of foam, possibly covered with ice, that broke off the shuttle's external fuel tank shortly after blastoff.
Mission management team chairman John Shannon said an exact mould of the gash would be reproduced in thermal tiles and tested in a laboratory that simulates the extreme heat and friction the shuttle encounters on re-entry to Earth.
NASA engineers will be able to "do a thermo analysis model ... to understand what the actual heating impact of re-entry will be for a damage of this type," he said.
The tests, to be carried out "in the next 24 to 48 hours," should provide engineers enough data to determine whether repairs are needed to the damaged heat shield before the shuttle undocks from the ISS on 20 August, he said. "If it comes back that a repair is desirable to do… we have three different methods of doing that."
Without explaining what the repairs entail, Shannon said he had "a lot of confidence if a repair is required that they will be executed."
The foam came off the shuttle's fuel tank, which holds super-cold liquid hydrogen fuel for the takeoff and is jettisoned before orbit is reached. An insulation layer on the tanks is supposed to prevent icing.
Preventing a second Columbia
The NASA keeps a watchful eye on the thermal tiles that cover the shuttle since the Columbia disaster of February 2003.
Columbia's protective heat shield was pierced by a piece of insulating foam that peeled off its external fuel tank during lift-off. The breach resulted in the shuttle disintegrating as it re-entered Earth's atmosphere, killing all seven astronauts on board.
After the examination of Endeavour's underside was completed at 7:00pm GMT Sunday (4:00am Monday, Sydney time), preparations began for the mission's second spacewalk, due to start at 3:31pm GMT Monday, during which astronauts Dave Williams and Rick Mastracchio will replace a faulty ISS control gyroscope.
On Saturday, Mastracchio, of the U.S. and Canadian, Dave Williams, spent six hours and 17 minutes installing and activating a new, 1.58-ton segment for the ISS that the Endeavour had delivered.
Endeavour docked on Friday with the ISS bringing seven astronauts, including 55-year-old Morgan, the first schoolteacher in space.
Morgan's space mission came 21 years after the shuttle Challenger launch explosion in 1986 killed another woman intended to become the first teacher-astronaut, Christa McAuliffe.
