Shuttle Discovery takes final bow (News Feature)

By Anne K Walters Feb 24, 2011, 22:46 GMT

Washington - After a nearly four-month delay, the space shuttle Discovery blasted off Thursday on its final mission, capping a long career with one last flight to the International Space Station.

The oldest vehicle in the operating space shuttle fleet, construction began in 1979 on Discovery, which blasted off into space for the first time in 1984. Its last flight comes as US space agency NASA retires the ageing shuttles and begins to transition routine flights to commercial providers.

But the craft's final launch was a long time coming. NASA repeatedly delayed the liftoff over several months after cracks were discovered in the shuttle's external fuel tank.

The mission was initially scheduled for liftoff in late October, before several cracks found on brackets on the external tank prompted multiple delays. As part of tests to find the cause of the problem, engineers filled the tank with fuel while monitoring it for strains or cracks.

The problem has since been repaired, and NASA engineers said they were confident the vehicle was safe to fly.

After Discovery's planned 11-day mission, the workhorse of the fleet will have spent a total of nearly a year in orbit, made more flights than any other shuttle and carried more crew members.

Discovery has already made history many times.

It was the first shuttle to return to flight after both the shuttle Challenger and Columbia accidents; launched the trailblazing Hubble Space Telescope; made the first US rendezvous with the Russian Mir space station; and made the first and last shuttle trips to rotate crews on the International Space Station (ISS).

Discovery will now be the first shuttle to officially be retired. A previous trip by Atlantis was billed as a potential final flight, but NASA has since added another flight for the shuttle to its manifest for July. Atlantis will make that flight, unless there is a massive budget cut.

Discovery is to deliver the last major piece of the US part of the ISS along with a host of supplies, including a human-like robot, known as Robonaut 2 (R2), the first-such robot ever sent to space.

Unlike the Star Wars droid character of the same nickname, R2 has arms and a head but no legs, and will be used to learn how robots perform in zero gravity with the goal of eventually using them alongside or in place of humans in complicated activities.

The new room to be installed on the US part of the ISS was built by the Italian Space Agency and has been in space before in a different capacity, as the Leonardo cargo module. NASA, which owns the module, has converted it to become a lasting part of the station, known as the Permanent Multipurpose Logistics Module. It will be delivered full of cargo, and astronauts will eventually use it as an extra room for storage or to conduct experiments.

Discovery is bringing aloft an Express Logistics Carrier, which will be attached to the outside of the station to hold spare parts.

Two spacewalks are planned for the mission. During the first, astronauts Steve Bowen and Alvin Drew will move a failed ammonia cooling pump removed on an earlier mission and install a power extension cable and camera equipment. Bowen replaces Tim Kopra on the mission, after he was injured in a biking accident in January.

On the second spacewalk, they will remove covers from the spare- parts carrier and do repair work.

Once Discovery and its six-member crew return to Earth, NASA won't be quite done with the spacecraft. First, engineers want to take the spacecraft apart and look inside - there are pieces that haven't been examined since they were installed more than 30 years ago.

NASA has long planned to retire the ageing shuttle fleet, and the last flight is currently set for July.

President Barack Obama, however, prompted criticism last year when he scuttled long-term plans to return to the moon and, instead, ordered a change in focus to commercial space flight and sending NASA astronauts to an asteroid and later Mars.

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