Watch a dramatic spacewalk live, featuring a historic first for the UK

Major Peake will spend nearly six-and-a-half hours outside the ISS from 12.55pm today as he and Nasa colleague Tim Kopra carry out repairs to a broken power unit.

His spacewalk is expected to last six hours.

Earlier in the spacewalk, Col Kopra reported abnormal carbon dioxide readings from his suit.

NASA tightened its flight rules after a spacesuit worn by Italian astronaut Luca Parmitano leaked during a spacewalk in July 2013, almost causing him to drown.

NASA commentator Rob Navias said the crew “was never in any danger at all”.

Unfortunately, the spacewalk that was scheduled to be held on Friday outside the International Space Station (ISS) by two astronauts Tim Peake and Tim Kopra has been suspended.

While Former British astronaut Michael Foale was the first Brit to walk in space, he had dual American citizenship and did so as a NASA astronaut. Peake, however, is representing Britain as an astronaut under the authority of the European Space Agency.

Down on Earth, 250 miles away, Reid Wiseman was communicating with Peake and Kopra during the fix mission.

To distinguish between the two Tims, Mission Control used both their first and last names when calling out to them.

Writing on his blog, Peake said he had done months of training while on Earth for the mission, including virtual reality sessions to train “for the worst-case scenario of becoming detached from the space station”.

Working in darkness when the solar arrays were not charging, Kopra and Peake removed the failed unit and replaced it with a spare.

“We’re all watching, no pressure!”

Replied Peake: “It’s great to be wearing it, a huge privilege, a proud moment”.

Colonel Kopra offered his thanks to the ground staff for ensuring their safety, a sentiment echoed by Major Peake. The duo will make their way all the way out along the arm of the station – nearly as far on the space station as one can go from the airlock, NASA officials said. NASA added absorbent pads to the helmet and put in place other precautions for future spacewalks.

In an interview on NASA TV, Mr Cassidy called it “a significant concern”.

Engineers will scour the data in the weeks ahead to figure out what happened.

What cut the spacewalker short? This came after the primary objective of replacing the failed voltage regulator had been completed successfully.