CAPE CANAVERAL, Fla. » Two spacewalking astronauts — including Britain’s first — successfully restored full power to the International Space Station today. But the spacewalk was cut short after water leaked into one of the men’s helmets in a scary repeat of a near-drowning 2½ years ago.

NASA astronaut Timothy Kopra took everyone by surprise when he reported a small water bubble and a few minutes later, a film of water, inside his helmet. Wary of the close call of another spacewalker in 2013, Mission Control terminated the planed six-hour spacewalk at the four-hour and 10-minute mark.

“So far, I’m OK,” Kopra assured everyone. Later, he said the water bubble was 4 inches long and getting thicker. “I’m doing good,” he repeated.

NASA stressed that the situation was not an emergency and insisted neither spacewalker was in danger. Indeed, Kopra took time to thank everyone for their help as the air lock was repressurized.

Their crewmates inside waited anxiously with towels to mop up the water, believed to have leaked from the cooling loop in Kopra’s suit.

Kopra and his spacewalking partner, British spaceman Timothy Peake, completed their No. 1 job early on in the spacewalk. The pair quickly removed the voltage regulator that failed two months ago, slashing station power by one-eighth. The breakdown did not disrupt work 250 miles up, but NASA wanted the power grid fixed as soon as possible in case something else failed.

Working in darkness to avoid electrical shock from the solar power system, the astronauts hurried to remove the bad unit and pop in a spare. They had just 31 minutes to complete the job, the amount of nighttime on that particular swing around the world.

It took a bit longer than expected to install the spare, dubbed Dusty, about the size of a 30-gallon aquarium. The spare had been inside the space station since 1999; newly arrived cables allowed a software update.

Mission Control assured the spacewalkers they had enough time, as the two struggled to bolt down the spare unit. Once it was attached, power tests followed. Mission Control informed the astronauts everything looked good. “Awesome,” replied Kopra.

Engineers suspect the original unit suffered an internal electrical short. Following the failure, the station relied on the seven other power channels.

The action unfolded on the far reaches of the space station. The work site is about 200 feet from the astronauts’ exit, about as far as spacewalkers safely can go.

“Glad to see you both out there together on the tip of the world,” Mission Control radioed.

Peake, in particular, received a bounty of well wishes — from space as well as Earth. He became the first spacewalker to wear the Union Jack on the shoulder of his suit.

“We’re all watching, no pressure!” Former Beatle Paul McCartney said via Twitter. “Wishing you a happy stroll outdoors in the universe.”

Earlier, as Peake floated out, space station commander Scott Kelly called, “Hey Tim, it’s really cool seeing that Union Jack go outside. It’s explored all over the world. Now it’s explored space.”

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

Peake, a helicopter pilot chosen by the European Space Agency, is Britain’s first official astronaut.

A handful of previous spacewalkers held dual U.S.-English citizenship, but flew as Americans for NASA. The first British citizen to fly in space, chemist Helen Sharman, visited Russia’s old Mir space station as part of a private competition in 1991.

Peake and Kopra rocketed into orbit exactly one month ago aboard a Russian spacecraft.

To distinguish between the two Tims, Mission Control used both their first and last names when calling out to them. Ground controllers, at least, didn’t have any problem distinguishing the spacewalkers’ voices. Peake is from West Sussex in southeast England; Kopra is from Austin, Texas.

“Popping outside for a walk,” Peake said in a tweet Thursday. “Exhilarated – but no time to dwell on emotions.”

Another European astronaut — Italy’s Luca Parmitano — almost drowned when his helmet filled with water that leaked from the cooling system of his undergarment in July 2013. NASA added absorbent pads to the helmet and put in place other precautions for future spacewalks. Those pads and safety procedures came in handy today.

Parmitano’s spacewalking partner that day, NASA astronaut Chris Cassidy, rushed into Mission Control and offered assistance today, as soon as he learned what happened.

Online:

NASA: http://www.nasa.gov/mission—pages/station/main/index.html

European Space Agency: http://m.esa.int/ESA