Two astronauts have struggled to replace failed equipment outside the International Space Station, making the second spacewalk in as many weeks at the 260-mile-high lab.
Nasa's Sunita Williams and Japanese astronaut Akihiko Hoshide had to contend with sticky bolts and metal shavings while removing one of four power-switching units and trying to plug in a new one. The bolts were particularly stubborn.
"It's throwing a wrench in our timeline," Mission Control radioed. Flight controllers asked how the spacewalkers were feeling as the work dragged past the five-hour mark. The astronauts assured everyone they were fine.
Engineering teams on the ground debated the best way to get the new unit installed properly and what tools might work.
Putting in a new switching box is the top priority of the spacewalk. In separate work, the spacewalkers managed to hook up one power cable and get another cable halfway connected. It was questionable whether they would have time to replace a bad camera on the space station's big robotic arm.
It is the second spacewalk in less than two weeks. On August 20, two Russians worked outside the orbiting complex installing shields to protect against micrometeorite strikes.
Williams is the lone woman among the space station's current six-person crew. She and Hoshide arrived at the space station a month ago, launching from Kazakhstan aboard a Russian rocket.