US shuttle Discovery lifts off on the way to space station

Discovery roared into the dark night-time Florida sky at 11:59 pm Friday (0359 GMT Saturday), as scheduled, and reached orbit just a few minutes later.

The shuttle and its crew of seven astronauts -- including one Swede -- is to deliver to the ISS equipment for a new bedroom, a treadmill, a freezer, food and other supplies. It will also be dropping off the newest member of the ISS team -- US astronaut Nicole Stott.

Stott will be taking over from engineer and fellow American Tim Kopra, who has been aboard the ISS since July and is returning to Earth with the Discovery.

The launch had been delayed three times. A first attempt on Tuesday was cancelled shortly before liftoff when weather conditions were deemed too dangerous, and two subsequent attempts were thwarted by problems with a liquid hydrogen fill-and-drain valve.

NASA engineers eventually discovered that the problem was caused by false instrument readings and devised a method of determining if the valve was properly closed in case the instruments malfunction again.

The crew led by astronaut Rick Sturckow will be delivering to the station  6.8 tonnes of cargo transported in a pressurized module called Leonardo that was built by the Italian space agency.

Two astronauts from the team are scheduled to conduct three spacewalks of six and a half hours each during the 13-day mission, which is the fourth of five planned for the shuttle this year. The last is scheduled for November.

One of the key goals of the space walks is the replacement of an old liquid ammonia tank, which will be substituted with a new 800 kilogram replacement brought from Earth aboard the Discovery. The substance is used as a coolant.

The astronauts will also be retrieving experiment equipment from the outside of the ISS and returning it to Earth for processing.

The Discovery team is delivering a freezer and a treadmill. The freezer will store samples of blood, urine and other materials that will eventually be taken back to Earth for study on the effects of zero-gravity.

The COLBERT treadmill, named after popular US comedy talkshow host Stephen Colbert, will be the second aboard the ISS. Exercise is key for astronauts spending long periods of time in space, where zero-gravity can result in muscle atrophy.

The mission will be the 128th for the space shuttle program, and the 30th mission to the ISS.

Once the Discovery mission is complete, just six more shuttle flights remain before NASA's three shuttles are retired in September 2010.

The International Space Station is a project jointly run by 16 countries at a cost of 100 billion dollars -- largely financed by the United States.

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