Shuttle not in the clear yet

[Guest Glenn]

Source: http://www.news.com.au/story/0,10117,19 ... 09,00.html

 

THE Discovery crew have used a boom-mounted digital camera to re-inspect six areas on the shuttle's heat shield, and appear confident problems that led to the 2003 Columbia disaster have been resolved.

 

The most serious area of concern is Discovery's carbon-tipped nose, which must withstand temperatures hot enough to melt steel when the shuttle plunges back into the atmosphere prior to landing.

 

?That's the main thing we're looking at,? flight director Tony Ceccacci said today.

 

Program manager John Shannon said visible discoloration detected on the nose could be anything from bird droppings to damage from some sort of object, NASA's deputy space shuttle .

 

The shuttle's external fuel tank, which has been the US space agency's top safety concern since it triggered the Columbia disaster, did not appear to have shed large enough pieces of its foam insulation to damage Discovery's heat shield, officials said.

 

Foam insulation falling off Columbia's fuel tank during launch smashed into the ship's wing and allowed superheated atmospheric gases to blast through as Columbia flew through the atmosphere for landing.

 

The spacecraft disintegrated over Texas, killing the seven astronauts aboard.

 

The tank design was modified after the accident, but the one flown during NASA's first post-Columbia mission last year shed large foam chunks during launch.

 

Discovery's launch on Tuesday was the second since the accident.

 

Originally planned for 12 days, NASA today extended Discovery's mission by one day to add a third spacewalk to test a heat-shield repair technique.

 

Astronauts said they were happy with the spacecraft's performance ? good news for NASA since more trouble could force the space agency to scrap the shuttle program.

 

?At this point we're really satisfied. We haven't had many problems with Discovery,? pilot Mark Kelly said during an in-flight interview.

 

NASA has spent $US1.3 billion ($1.7 billion) on two fuel tank redesigns and other safety upgrades. Based on Discovery's performance, NASA is gaining confidence the work was successful.

 

Of the six areas targeted for follow-up inspections, three have been cleared, Mr Shannon said.

 

But he said the jury was still out on potential risks in the other areas. ?We don't rule anything out until the analysts come in and say we don't have a problem,? he said.

 

Besides the nosecap, engineers were still assessing blemishes on the right wing and a protruding bit of cloth near the rear of the shuttle. The concern is the strip of semi-rigid fabric, which is among thousands placed between the shuttle's ceramic belly tiles, could cause Discovery to overheat during re-entry.

 

A second protruding strip near the nose of the shuttle was cleared as a potential flight risk, Mr Shannon said.

 

During Discovery's flight last year, astronauts plucked out two protruding strips that could have triggered a heat shield failure.

 

NASA needs to resume regular shuttle flights to complete construction of the half-built International Space Station before the fleet is retired in 2010.

 

Today, Discovery attached an Italian-built cargo module carrying more than 2272 kg of equipment and supplies to the space station.

 

The module holds food, clothing, a freezer for experiment samples, a European Space Agency incubator to grow plants in space and a new oxygen generator so the station's crew size can eventually be doubled to six.

 

Discovery also brought German astronaut Thomas Reiter to the station, where he will stay for six months.