'Exhilarated' British astronaut starts first spacewalk

Astronaut Tim Peake today became the first Briton to walk in space, undertaking a tricky mission to replace an electrical unit while under cover of darkness.
Peake and US colleague Tim Kopra switched their spacesuits on to battery power at 7:48 am (1248 GMT), marking the official start of the floating debut for Peake, who is also the first British astronaut to fly to the orbiting International Space Station.
In a blog post on Thursday, Peake said he felt "exhilarated" but had "no time to dwell on these emotions."
The 43-year-old Peake's job is to haul a bulky component called a sequential shunt unit, contained in a white bag as big as a suitcase.

He must carry the unit, which would weigh 200 pounds (90 kilograms) on Earth, to the far end of the space station's truss, about 200 feet (60 meters) from the exit.
Kopra, 52, making his third career spacewalk, will carry the tools needed to remove the old unit and replace it with the new one.

The work must be precisely timed to coincide with a nighttime pass of the space station to avoid any sparks from electrical current that might remain in the solar-powered equipment.
The ISS circles the Earth every 90 minutes, and spends 31 of those minutes in the dark.

The first opportunity to start the nighttime job comes at 8:37 am (1337 GMT), NASA commentator Rob Navias said.
Afterward, they will route some cable and install a vent in a cramped space that spacewalk officer Paul Dum described this week as a "challenging work site."
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."
Each step of the six-and-a-half hour spacewalk has been "meticulously planned," he added.
"But I guess nothing can prepare for the feeling of being outside of a spacecraft in the vacuum of space.