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Shuttle readies for night launch Shuttle night lift-off postponed
(20 minutes later)
Nasa is preparing to launch its third space shuttle mission in six months despite a poor weather outlook. Nasa has called off the launch of its third space shuttle mission in six months because of poor weather.
The crew are now seated inside space shuttle Discovery and carrying out the final checks ahead of the scheduled launch time of 2135 (0235 GMT). The crew were seated inside the space shuttle Discovery at the scheduled launch time of 2135 (0235 GMT), but low clouds prevented lift-off.
If successful it will be the first night launch of the orbiter since the Colombia accident in 2003. The launch was scheduled to be the first night launch of the orbiter since the Colombia accident in 2003.
Nasa is racing to finish work on the International Space Station (ISS) before the fleet is retired in 2010.Nasa is racing to finish work on the International Space Station (ISS) before the fleet is retired in 2010.
A British-born astronaut, Nicholas Patrick, will fly aboard Discovery. A British-born astronaut, Nicholas Patrick, is due to fly aboard Discovery.
But there are fears that bad weather could scupper the launch, with Nasa's shuttle weather officer Kathy Winters saying a cold front would bring low clouds into central Florida on Thursday evening. A cold front was forecast to bring low clouds into central Florida on Thursday evening.
Nasa has put the prospects for favourable weather conditions at just 40%. The forecast is worse for Friday, with only a 30% chance of favourable weather. A launch appeared possible until the last moment of the launch window despite weather conditions putting the chances at just 40%.
The forecast is worse for Friday, with only a 30% chance of favourable weather.
'Complex mission''Complex mission'
Nasa has described the construction mission as one of the most complex to date.Nasa has described the construction mission as one of the most complex to date.
On the previous shuttle flight in September, astronauts delivered new solar arrays to provide power for additional modules scheduled to be installed next year.On the previous shuttle flight in September, astronauts delivered new solar arrays to provide power for additional modules scheduled to be installed next year.
Kathy Winters said the weather could worsenThe tricky task of wiring the arrays into the ISS power grid falls to the crew of shuttle Discovery. This will need to be done without interrupting the station's life-support and other critical systems. Nasa's Kathy Winters forecast poor weather conditionsThe tricky task of wiring the arrays into the ISS power grid falls to the crew of shuttle Discovery. This will need to be done without interrupting the station's life-support and other critical systems.
Astronauts will also switch the station off its temporary power system, a step Nasa had planned to do in 2003.Astronauts will also switch the station off its temporary power system, a step Nasa had planned to do in 2003.
Half the outpost will be powered down while astronauts make the new electrical connections during two separate spacewalks. It will be a tense time, with little back-up power if other problems arise.Half the outpost will be powered down while astronauts make the new electrical connections during two separate spacewalks. It will be a tense time, with little back-up power if other problems arise.
"Many of us consider this the most challenging flight that the International Space Station will have done since we began the effort of assembling it," said space station manager Mike Suffredini."Many of us consider this the most challenging flight that the International Space Station will have done since we began the effort of assembling it," said space station manager Mike Suffredini.
Station completionStation completion
The only visual change in the outpost will be the addition of a small segment to the space station's exterior truss. But if all goes well, Nasa may have put its biggest construction hurdle behind it.The only visual change in the outpost will be the addition of a small segment to the space station's exterior truss. But if all goes well, Nasa may have put its biggest construction hurdle behind it.
At least 14 more missions are needed to finish the $100bn (£51bn) station.At least 14 more missions are needed to finish the $100bn (£51bn) station.
Mr Patrick, now a US citizen, was born in Saltburn-by-the-Sea, TeessideDiscovery's flight is scheduled to last 12 days, with landing targeted for 19 December at the Kennedy Space Center in Florida.Mr Patrick, now a US citizen, was born in Saltburn-by-the-Sea, TeessideDiscovery's flight is scheduled to last 12 days, with landing targeted for 19 December at the Kennedy Space Center in Florida.
Discovery's crew consists of commander Mark Polansky, pilot William Oefelein and mission specialists Robert Curbeam, Joan Higginbotham, Nicholas Patrick, Sunita Williams and the European Space Agency astronaut Christer Fuglesang.Discovery's crew consists of commander Mark Polansky, pilot William Oefelein and mission specialists Robert Curbeam, Joan Higginbotham, Nicholas Patrick, Sunita Williams and the European Space Agency astronaut Christer Fuglesang.
Sunita Williams will be making a one-way trip. She is to remain aboard the space station, replacing Germany's Thomas Reiter, who will return with the rest of the Discovery crew.Sunita Williams will be making a one-way trip. She is to remain aboard the space station, replacing Germany's Thomas Reiter, who will return with the rest of the Discovery crew.
Night time launchesNight time launches
The US space agency says it would prefer to launch Discovery during the daytime. Daytime launches give cameras a better view of the tank as the shuttle climbs to orbit.The US space agency says it would prefer to launch Discovery during the daytime. Daytime launches give cameras a better view of the tank as the shuttle climbs to orbit.
But the shuttle would need to be able to fly both night and day if the construction programme on the orbiting platform was to be completed within four years.But the shuttle would need to be able to fly both night and day if the construction programme on the orbiting platform was to be completed within four years.
Managers believe the shuttle's fuel tank has been improved to the point that foam debris shedding from the tank during launch - which triggered the Columbia accident - is no longer a threat.Managers believe the shuttle's fuel tank has been improved to the point that foam debris shedding from the tank during launch - which triggered the Columbia accident - is no longer a threat.
A briefcase-sized chunk of foam damaged Columbia's wing on lift-off, allowing superheated gasses to penetrate the heat shield as it returned to Earth in February 2003. All seven astronauts were killed in the disaster.A briefcase-sized chunk of foam damaged Columbia's wing on lift-off, allowing superheated gasses to penetrate the heat shield as it returned to Earth in February 2003. All seven astronauts were killed in the disaster.