Today Tim Peake will become the first every official British astronaut to walk in space when he steps outside the International Space Station (ISS) to carry out vital repairs.
The walk is scheduled to start just before 1pm British time and will last more than six hours.
Major Peake and his Nasa colleague Tim Kopra will walk nearly the entire length of the station to replace a broken power unit.
The British astronaut blasted into space last month with an experiment on board designed by children from Magdalen College School.
Here are six things you need to know about his spacewalk.
1- Why is Tim Peake carrying out the spacewalk?
Astronauts regularly perform spacewalks to carry out repairs on the ISS. This time Major Peake and Colonel Kopra need to replace a broken power unit, fit a new valve and lay dozens of metres of cable.
2- How does it work?
Colonel Kopra will leave the ISS first through the quest airlock and will then lay down anchor points. Major Peake will follow him and the pair will then move along the exterior using their arms, but will be attached to the space station via a tether. Once they get to the site where they need to carry out the repairs they will attach another measure to prevent them drifting off into space.
Tim Peake (second right), with crew members on the ISS.
3- How has Major Peake prepared?
There is nothing quite like walking in space but Major Peake trained underwater to try and replicate the experience of working in zero gravity as closely as possible.
4- What will conditions be like?
Because the ISS takes 90 minutes to orbit the earth the two astronauts will be working in darkness for 45 minutes followed by light for 45 minutes. The repairs can only be carried out in darkness, otherwise an electrical charge could travel through the new power unit. Temperatures will plunge to -270C, but the pair's spacesuits will protect them.
5- Is Major Peake the first Briton to walk in space?
He is the first official British astronaut to do so, but not the first person born in the United Kingdom. Michael Fole, who walked in space in 1995, was born in England but went into space as an American citizen. Piers Sellers, who was born in Sussex, also flew under the United States flag.
Tim Peake's rocket taking off for the ISS last month
6- Who will be supporting the two astronauts during the repairs?
Major Peake and Colonel Kopra will have assistance from ISS commander Scott Kelly and astronat Sergei Volkov, who will help the two men into their suits and the airlock and monitror their progress from inside the station. Nasa astronaut Reid Wiseman will guide them through the spacewalk from here on earth.
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