Major Tim Peake will make history today by becoming the first British astronaut to visit the International Space Station.
The 43-year-old dad-of-two, from Salisbury, will be blasted into space in a Russian rocket from the Baikonur Cosmodrome in Kazakhstan at 11.03am UK time.
No Brit has undertaken such a mission - or even left Earth - in more than two decades.
There are 70 events across the UK where people can watch the launch - including his hometown of Salisbury and at a school in Gloucestershire.
Travelling with him are Russian commander Yuri Malenchenko and Nasa astronaut Tim Kopra.
The trio will be squeezed into the "descent module" of a tiny Soyuz TMA space capsule, which is only about seven feet long.
At launch, the 162 ft rocket generates 422.5 tonnes of thrust - a total of 26 million horsepower.
Before lift off the crew have to endure a tense wait of an hour or more in the capsule, during which they can listen to play lists of selected music.
The three songs Major Peake chose were:
Queen - Don't Stop Me Now
U2 - Beautiful Day
Coldplay - A Sky Full Of Stars
At a press conference Major Peake said what he was looking forward to most was his first glimpse of Earth seen from space:
"I don't think anything can truly prepare you for that moment. "Once we get injected into orbit I'll be able to look out the right window and see the beautiful view of Planet Earth."