This story was updated at 10:10 p.m. EST.
A spacewalking astronaut faced down a grease gun explosion only to lose a tool bag on Tuesday during an ambitious clean-and-grease job outside the International Space Station.
Veteran spacewalker Heide Stefanyshyn-Piper lost her grip on the bag while cleaning up a mess from a leaking grease gun she was carrying to help mop up metal grit from inside a massive gear that turns the space station's starboard solar wings.
"Oh great," Stefanyshyn-Piper said as the backpack-sized bag drifted away. "I guess one of my crew lock bags was not transferred and it's loose."
NASA mission controllers tracked the 30-pound (13-kg) bag's departure with cameras and are discussing the impact of the lost tools it contained for the three remaining spacewalks scheduled while NASA's shuttle Endeavour is docked at the space station. The shuttle launched toward the station last week and will remain until at least Thanksgiving.
"It's floating station aft and starboard," Stefanyshyn-Piper reported.
Mission managers said late Tuesday that the bag was flying ahead and below the space station and moving further away by the minute.
"It is definitely moving away from the station with every orbit," said space station flight director Ginger Kerrick. "No concern whatsoever for recontact at this moment with the data that we have."
The lost bag and leaky grease gun marred what had been until then a smooth spacewalk, with Stefanyshyn-Piper and fellow spacewalker Steve Bowen floating out of the station's Quest airlock at 1:09 p.m. EST (1809 GMT). The six-hour, 52-minute excursion marked the third career spacewalk for Stefanyshyn-Piper and the first for Bowen.
"Welcome to EVA," Endeavour astronaut Shane Kimbrough told Bowen, using NASA's technical term for spacewalks, as he choreographed the excursion from inside the space shuttle.
The two spacewalkers also delivered a spare part for the station's cooling system and retrieved an empty station nitrogen tank for the trip home aboard Endeavour among other maintenance tasks. But the highlight of their spacewalk was the space station gear clean up.
"In spite of our little hiccup, one major hiccup there, I think we did a pretty good job today," Stefanyshyn-Piper said at the end.
"You were all champs," spacecraft communicator Mark Vander Hei added. "You rolled with the punches and made it all happen."
Space gear grease job
Known as a Solar Alpha Rotary Joint, the massive gear is 10 feet (3 meters) wide and designed to spin the space station's starboard solar wings so they always face the sun as the station orbits Earth. While a similar gear on the station's port side has been working fine, the starboard side has ground down its lubricating layer of gold. It's been damaged and hasn't worked properly for more than a year.
"There does seem to be a lot of debris," Stefansyshyn-Piper said as she lifted covers off the delicate mechanism to get a glimpse of its inner workings.
Stefanyshyn-Piper and Bowen removed several of the gear's 11 damaged bearings, used mitt-like wet and dry wipes to clean the gear's metal ring, and used the space version of a caulk gun to squeeze out gray Braycote grease and lubricate the mechanism. They then replaced the old bearings with new ones in work that appeared to be smooth going.
By the end of the four spacewalks planned for Endeavour's 15-day mission, all 11 of the bearings will be replaced and the port side gear will be greased up for good measure, mission managers said.
With today's spacewalk, Stefanyshyn-Piper has an even 20 hours of total spacewalking time, while Bowen ended with six hours, 52 minutes. The mission's next spacewalk is set for Thursday.
While Stefanyshyn-Piper and Bowen worked outside the space station, their crewmates unpacked science equipment, a second kitchen, extra bathroom and new water recycling system designed to turn astronaut urine, sweat and other wastewater back into drinkable water.
The two life support systems are part of more than 14,000 pounds (6,350 kg) of new equipment arrived at the station aboard Endeavour to lay the groundwork for larger, six-person crews. The cargo pod carrying the new gear is also packed with two spare bedrooms and a space cooler that will allow station astronauts the luxury of chilled water and other drinks.
The new additions will turn the space station from a three-bedroom, one-bath, one-kitchen home into five-bedroom, two-kitchen, two-bath research outpost, shuttle astronauts have said.
The astronauts are so far ahead with the move-in work, they may not need an extra day docked at the station to install all the new hardware, Kerrick said.
NASA is providing live coverage of Endeavour's STS-126 mission on NASA TV. Click here for SPACE.com's mission coverage and NASA TV feed.