Nasa was forced to end a spacewalk involving British astronaut Tim Peake earlier than scheduled as fellow astronaut Tim Kopra reported a leak in his spacesuit helmet. Royce Renfrew, flight director said the International Space Station (ISS) suspended the spacewalk as a precautionary measure and the astronauts were not in any danger.

Nevertheless, Peake became the first UK citizen ever to walk in space. According to a Nasa press release, the spacewalk was intended to replace a failed voltage regulator that compromised one of the station's eight power channels last November. The astronauts accomplished the task.

About three hours into the spacewalk, Kopra, 52, reported that his helmet pad was damp and a ball of water had collected in his helmet, prompting Nasa to end the exercise.

Nasa said in its blog: "Astronauts Tim Kopra and Tim Peake ended their spacewalk at 12:31 pm EST with the repressurisation of the US Quest airlock following an early termination of the spacewalk after Kopra reported a small water bubble had formed inside his helmet."

Station commander Scott Kelly, also a Nasa astronaut, helped Kopra out of his space suit and the astronauts collected water from the helmet to try to determine the cause of the leak. The crew reported that the water was "cold", indicating it came from the space suit's backpack.

The blog post added: "The crew was never in any danger and returned to the airlock in an orderly fashion. The astronauts replaced a failed voltage regulator that caused a loss of power to one of the station's eight power channels last November, accomplishing the major objective for this spacewalk."

The 4 hours and 43 minutes spacewalk was the third for Nasa's Kopra and the first for Peake of the European Space Agency.

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