A spacewalking astronaut has successfully replaced a blurry camera outside the International Space Station but had to contend with a baulky jetpack and a frayed safety tether.
Both jetpacks and safety ties are crucial for saving a flyaway astronaut.
NASA said on Friday Joe Acaba was always securely attached to the orbiting outpost and never in any danger during the nearly seven-hour spacewalk.
But one of his tethers had to be replaced shortly after he and station commander Randy Bresnik floated outside.
Mission Control noticed the red lifeline was frayed and worn. Bresnik went back to the air lock to get Acaba a spare.
Then five hours into the spacewalk, Mission Control saw that the right handle on Acaba's emergency jetpack was popped open - again. Bresnik once more went to his crewmate's assistance, even offering some tape to keep it down.
After consulting for several minutes in Houston, flight controllers declared the jetpack unreliable and ordered Acaba back inside, once he was done greasing the new robot arm on the space station's big robot arm. He finished the lube job, then headed in.
Bresnik acknowledged things didn't go as planned, "with all the stuff that happened today and the challenges we had". But he thanked everyone for their hard work and diligence.
In the end, only a couple of minor chores were left undone.
"Great work today," Mission Control radioed as the spacewalk came to a close.
It was the third spacewalk in two weeks for the US astronauts. Bresnik went out on all three; he was accompanied by Mark Vande Hei to install the new robotic hand on October 5 and lubricate it on October 10.
Earlier, Acaba unbolted a blurry camera from the new robotic hand installed two weeks ago. He then popped in a spare, which flight controllers quickly tested from Houston. The replacement provided crisp, clear views.
Sharp focus is essential when the space station's robot hand grabs an arriving supply ship and anchors it. The next delivery is a few weeks away, prompting the quick camera swap-out.
Friday's spacewalk - expected to be the last one for the year - also saw the astronauts installing a high-definition camera, replacing a fuse and removing thermal insulation from spare electronics.
Early next year, astronauts will replace the hand on the opposite side of the 18-metre robot arm, Canada's main contribution to the space station. The original latching mechanisms are showing wear and tear since the arm's launch in 2001.
The complex is currently home to three Americans, two Russians and one Italian.
