Discovery sails away from space station

[Guest Glenn]

Sourc: http://www.smh.com.au/news/World/Discov ... 96181.html

 

Space shuttle Discovery sailed away from the International Space Station, leaving behind a third full-time crewmember on the station and high hopes that NASA can quickly resume construction of half-built outpost.

 

The shuttle, which arrived at the station nine days ago, is due back on Earth Monday to conclude only the second mission since the 2003 Columbia accident.

 

"Have a safe journey back, soft landings and we'll see you on the ground in a few months," space station astronaut Jeff Williams told the Discovery crew as the shuttle slipped out of its docking port.

 

The primary purpose of Discovery's flight was to demonstrate the successful redesign of the shuttle's fuel tank, return the space station to full staff for the first time in three years and repair the station's mobile rail cart so that assembly of the $US100 billion ($A132.85 billion) complex can resume.

 

All goals were met, as well as a host of other objectives including tests to repair shuttle heat shield damage and the delivery of more than 2.5 tons of new equipment and supplies to the outpost.

 

"Our (goals) won't be completely accomplished until we have the crew safely on the ground," said flight director Tony Ceccacci.

 

Touchdown at the Kennedy Space Center in Florida is scheduled for 9:14am EDT (23:14 AEST) Monday.

 

In addition to packing up their cabin for landing, the Discovery astronauts on Saturday completed a second inspection of their ship's wings to check for damage from micrometeoroid impacts.

 

Analysis was under way but so far engineers have seen nothing to prevent Discovery's planned touchdown on Monday.

 

NASA ordered extensive in-flight inspections as part of $US1.3 ($A1.73) billion in safety upgrades since the Columbia disaster.

 

Inspections earlier in the flight, conducted with the same cameras and sensors on a robot arm used during Saturday's survey, found no damage from launch debris impacts, such as what triggered the breakup of Columbia and the deaths of seven astronauts on Feb. 1, 2003.

 

The only problem nagging at NASA engineers is a small chemical leak in one of the shuttle's three power units used during landing.

 

NASA plans to test the unit on Sunday and if the leak worsens, it may be shut down, forcing the shuttle to land with just two of the power units for the first time in the program's history.

 

While NASA said that would not be a problem, it would mean explosive bolts instead of hydraulic power would be used to release the shuttle's landing gear so it can drop into position for touchdown, deputy shuttle program manager John Shannon said.

 

Also, to minimise risk, the space agency might decide to land the shuttle at Edwards Air Force Base in California where the weather is more stable and the landing area larger than at the Kennedy Space Center.

 

NASA has said this mission was critical to the future of the shuttle program as it tries to recover from the Columbia accident.

 

Columbia's wing heat shield was cracked during launch by falling fuel tank foam but because there were no in-flight inspections at the time, the damage went undetected.

 

Columbia disintegrated while returning to Earth 16 days later when hot gases penetrated its structure.

 

NASA plans to fly 16 shuttle missions to complete the space station. Its next flight is scheduled for launch around August 28.