The US shuttle Discovery has launched from the Kennedy Space Center for the last time.

美国发现号航天飞机最后一次从肯尼迪太空中心点火起飞。

The orbiter roared into a bright blue Florida sky, leaving the pad at 1653 local time (2153 GMT).

Its 11-day mission will see it deliver a new store room and a sophisticated humanoid robot（人形机器人） to the International Space Station (ISS).

Only two further flights remain by Endeavour and Atlantis, which Nasa is trying to see concluded this year.

The orbiter fleet is then expected to retire to museums.

As usual, huge crowds had gathered on all the approach roads leading to the Nasa facility and on the beaches along Florida's Space Coast - everyone wanting to witness a piece of history.

They all had to wait a little longer than expected - the final countdown was delayed by three minutes as a problem was fixed¹ with the computer system that tracks the shuttle to orbit.

As soon as the issue was resolved, ground controllers restarted the clock and called out to Discovery's crew: "Enjoy the ride". Shuttle Commander Steve Lindsey replied: "We appreciate all your work; and for those watching, get ready to witness the majesty² and the power of Discovery as she lifts off one final time."

Discovery is regarded as the "leader of the fleet", and was entrusted³ with（委托给） both return-to-flight missions following the Challenger and Columbia accidents.

First launched in 1984, this is its 39th outing. When it lands back on Earth in nearly two weeks' time it will have covered a cumulative⁴（累积的） career distance of 230 million km (143 million miles). That's further than the distance from the Earth to the Sun (149 million km).

Once the shuttles are retired⁵, the plan is for US astronauts to fly to the space station on Russian Soyuz rockets until perhaps the middle of the decade.

A number of American companies then hope to be in a position to sell launch services to Nasa on a range of new vehicles.

The intention is that the agency should put its efforts into leading the development of a large rocket - known as the Space Launch System - that can send astronauts beyond the space station to destinations such as asteroids⁶（小行星） .

Congress has set out the broad capabilities⁷ it expects to see in this rocket and has given a deadline of 2016 for its introduction. However, Nasa has said it cannot deliver such a vehicle in the time and with the budget the politicians have specified⁸.