Tim Peake was blasted off to ISS from the Baikonur cosmodrome with two other astronauts.

BAIKONUR (AFP) - Tim Peake, the first Briton to travel to the International Space Station, blasted off on Tuesday from the Baikonur cosmodrome with two other astronauts, to cheers and excitement back home.

Peake, 43, joins Russian space veteran Yury Malenchenko and Tim Kopra of NASA for a six-month mission on the ISS. 

Fire from the boosters of the Soyuz rocket cut a bright light through the overcast sky at the Moscow-operated cosmodrome in Kazakhstan as the spacecraft launched on schedule at 1103 GMT.

"It was great to watch Tim Peake blast off on his mission to join the International Space Station," British Prime Minister David Cameron said on Twitter.

Queen Elizabeth II s official Twitter account @BritishMonarchy retweeted the UK Space Agency saying "We have liftoff! @astro_timpeake is on his way to space! #GoodLuckTim, the #UK is with you!"

Russian space officials said the launch had gone according to plan and that the spacecraft was due to dock at the ISS at about 1724 GMT.

Former army major Peake -- a European Space Agency flight engineer -- begins a mission of more than 170 days or nearly six months at the orbiting research outpost along with Malenchenko, 53, and 52-year-old Kopra.

His two fellow crew members have already spent 641 and 58 days in space respectively.

Peake s mission has generated considerable excitement in Britain.

Crowds gathered in the Science Museum in London to witness the liftoff, with thousands of people including around 2,000 schoolchildren breaking into screams and waving British flags as giant screens set up in the exhibition hall showed the rocket blasting off.

A further party is planned for Tuesday evening, when the museum will stay open late in a special celebration, and the first British citizen in space Helen Sharman will give a talk.

"If just one or two of the school children here decide to be engineers or scientists or test pilots as a result of this mission, then it s going to be worth it," said TV science presenter Brian Cox, who watched the launch at the Science Museum.

In Peake s hometown of Chichester in southeastern England, the launch was shown at his old school.

The Chichester Observer quoted his old physics teacher, Mike Gouldstone, as saying: "This is every physics teachers dream, to have had a future astronaut in front of you.

"It is all quite emotional for me. A lot of children come here because  the astronaut Tim Peake  came here."

Peake himself was relaxed ahead of his first voyage into space, talking about his expectations of a festive season aboad the ISS during a pre-flight news conference at the Cosmonaut Hotel in Baikonur on Monday.

"We ll be enjoying the fantastic view of planet Earth and our thoughts will be with everyone on Earth enjoying Christmas and with our friends and family," he said.

On the eve of Peake s departure, the British government unveiled an ambitious new space policy.

The policy aims to more than triple the value of the sector to the national economy, reaching $40 billion by 2030.

UK Secretary of State for Business Innovation and Skills, Sajid Javid, said the new policy will "turn science fiction into science fact" while helping London increase its share of the global space market from seven to 10 percent.

Space travel has been one of the few areas of international cooperation between Russia and the West that has not been wrecked by the Ukraine conflict.

The Soyuz trio will join up with three astronauts already at the ISS -- Scott Kelly of NASA and Russians Sergei Volkov and Mikhail Kornienko.

Three other astronauts -- NASA s Kjell Lindgren, Japanese astronaut Kimiya Yui and Russian cosmonaut Oleg Kononenko -- returned to Earth on Friday in a rare nighttime landing.

The ISS space laboratory has been orbiting the Earth at roughly 28,000 kilometres (17,500 miles) an hour since 1998.