Science News
Shuttle fuelling begins in Florida despite weather threat
By Pat Reber
Dec 7, 2006, 20:21 GMT

Washington - Fuelling began Thursday morning for the planned Discovery shuttle launch later in the evening, but bad weather threatened with a 60 per cent certainty to postpone take-off, NASA officials said.

The weather outlook was also uncertain over the next two days, and officials were eyeing Sunday and Monday as the next possible launch window.

A cold front could bring low cloud cover over Cape Canaveral, Florida, which could delay launch, NASA weather officials said. In addition, there were weather worries at three Transatlantic landing sites that serve as backup in case the mission is aborted after takeoff.

The Discovery and its crew of seven astronauts are headed on one of its most 'complex' construction flights to date on the International Space Station that orbits 400 kilometres above Earth, NASA Associate Administrator for Space Operations Bill Gerstenmeier has said.

On board will be Swedish astronaut Christer Fugelsang, the first Nordic national in space, whose mission has gripped his country with space fever. A running count-down clock in the left-hand corner of a television screen on a Swedish morning television programme measured the enthusiasm with which the mission is being followed there.

The 12-day shuttle mission will also deliver astronaut Sunita Williams, who will take up residence on the space station, and pick up German astronaut Thomas Reiter, who is ending his five-and-a- half-month-long stay in space.

The go-ahead for fuelling came after several small technical problems were resolved. The night launch at 9:35 pm (0235 GMT) from Florida's Cape Canaveral is the first night take-off in many years.

The Discovery flight - with a launch window that extends to December 17 - marks the second working shuttle trip to the ISS since NASA returned to flight in the summer of 2005 after the Columbia shuttle disintegrated in 2003 upon re-entry to Earth's atmosphere. NASA spent most of the past year testing new safety systems, and only resumed carrying heavy loads for space station construction with September's Atlantis flight.

The main task for this mission is to hook up the station's permanent electricity generating system to replace the temporary system that has been in place since the space station went into orbit in 1998.

In September, the Atlantis transported and installed two solar collectors outside the station to boost its power supply. When completed in 2010, the station's capacity is to double to at least six people.

The US shuttle programme, the workhorse that has done most of the heavy lifting to build the space station, is to be retired after the ISS is completed.

During the current mission, astronauts will take two spacewalks, each devoted to rewiring half of the station. Power will have to be shut down inside the half of the station being hooked up.

But the issue that most worries NASA engineers is folding up half of the temporary solar array to make room for the two new solar panels installed in September to rotate. The older array's condition is unpredictable after being exposed for six years to extreme temperature changes every 45 minutes as the station rotates - from minus 128 to plus 93 degrees Celsius.

'It's like a map ­ if you keep a map out in your car for six years and then you decide to fold it up again, you may get some waves in it or it may not fold back the same way at all,' said lead space station flight director John Curry in a press statement.

The mission is the 33rd for Discovery and the 117th space shuttle flight since the programme began in the 1980s.

Discovery's orange external tank contains 500,000 gallons of liquid oxygen and hydrogen when full.

Earlier this week, Russian scientists performed a last minute manoeuvre to raise the orbit of the space station days after a so- called correction of its orbit failed when an engine was prematurely turned off. The orbit must routinely be modified to correct for slight changes.