It is a day neither man will ever forget.

American Reid Wiseman and German Alexander Gerst have headed out of the International Space Station for their first ever space walk.

But sightseeing from the stars was not an option with plenty of repairs and maintenance to be carried out, including dealing with a failed cooling pump.

The 15-nation ISS laboratory, which flies at an altitude of about 420 km, is overseen by Russia and the United States.