A Russian spacewalker had to rush back inside the International Space Station on Wednesday when the battery voltage in his spacesuit suddenly dropped.

Russian Mission Control ordered Oleg Artemyev, the station commander, to quickly return to the airlock so he could hook his suit to station power. The hatch remained open as his spacewalking partner, Denis Matveev, tidied up outside.

NASA said neither man was ever in any danger. Matveev, in fact, remained outside for another hour or so, before he, too, was ordered to wrap it up. Although Matveev’s suit was fine, Russian Mission Control cut the spacewalk short since flight rules insist on the buddy system.

The cosmonauts managed to install cameras on the European Space Agency’s new robot arm before the trouble cropped up, barely two hours into a planned 6 1/2-hour spacewalk.

“You know, the start was so excellent,” Matveev said as he made his way back inside, with some of the robot arm installation work left undone.

The 36-foot (11-meter) robot arm arrived at the space station last summer aboard a Russian lab.