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Spacewalking astronauts seem to have fixed a leak on the International Space Station by replacing a busted ammonia pump over the weekend, NASA says. This is a good sign, because it could mean the leak was a direct result of the pump, and not an ammonia line pierced by a micrometeoroid.

The station is cooled using ammonia, which cycles through radiators, electrical boxes and heat exchangers to “dump” heat generated by space station experiments and activities. The cooling system has two separate loops with their own pumps, which have experienced problems in the past. NASA still doesn’t know where this leak came from, but it may turn out it was a pretty easy fix.

But other spacewalkers have not been as fortunate. In 13 years and counting, the ISS has required a fair share of repairs, many of which rank as NASA’s most MacGyver-y moments. Click through our gallery to see some examples and to learn how NASA fixed this latest problem.

Fixing A Russian Bracket With Hammer And Chisel

In the station’s early days, back in 2000, a U.S. astronaut and a Russian cosmonaut used brute force and some Stone Age tools to make a key repair. A poorly placed bracket was getting in the way of an electronics bay, and astronauts had to basically smash it off. Daniel Burbank and Boris Morukov were trying to replace batteries in the Russian-built Zarya propulsion module, which is the larger white module in the photo at left. But they couldn’t reach a voltage controller because the bracket was in the way. The bracket was held in place by screws and rivets, which secured four nut plates. “The nut plates inexplicably blocked access to screws that helped hold the bracket in place,” as put it. So the only way to move the bracket was to chisel the rivets out. In the inset, Morukov and astronaut Ed Lu are working on Zvezda’s floor.

Using Cufflinks To Fix A Solar Panel

Back in 2007, a hole in a solar blanket could have threatened the International Space Station’s long-term power supply, but spacewalking astronaut Scott Parazynski patched it up with a homemade solution. The 4B wing of the Port 6 solar array truss snagged and ripped when it was being redeployed to its permanent spot. Mission managers scheduled a nail-biting spacewalk that involved Parazynski riding on the station’s robotic arm to the distant edge of the solar array. He patched it with a makeshift “cufflink” built from spare parts. Also during this mission, spacewalkers committed one of the multiple tool-drops, losing a pair of needle-nose pliers that drifted away as they entered the station’s airlock.

Using A Toothbrush, Frayed Wire And Space Tape To Clean A Bolt

On Wednesday, August 30, 2012, NASA Astronaut Sunita Williams and Japan Aerospace Exploration Agency Astronaut Akihiko Hoshide were scheduled to replace a busted power bus on the center truss of the station. This is one of four 220-pound boxes that route power from the solar panels throughout the station. They were able to retrieve the broken bus, but they couldn’t get the new one in place–a bolt got stuck. While trying to drive the bolt down, the crew noticed the bolt was blocked by metal shavings. They they tried to clean them out, but the bolt still wouldn’t go in. After eight hours and 17 minutes, Williams and Hoshide came back in. How would they lubricate and clean the bolt threads? Back at Johnson Space Center, engineers sat down with whatever tools the team had on station and tried to come up with a solution. Operations support officer Victor Badillo took a 4-gauge jumper lead, sliced off the insulation and frayed its wires, creating a stiff brush. You can see it in the middle picture. Then ground support members tested the two types of toothbrushes astronauts had on board, and found a bargain-basement brand would work well. They snapped off its end, taped the wire bristles on the end with space-ready tape, and then told the crew how to make the same tool. On Wednesday, Sept. 5, Williams and Hoshide went back outside, used the toothbrush to clean and lubricate the bolt, and attached it successfully.

Violently Shaking An Ammonia Pump

This diagram shows the space station’s External Active Thermal Control System, including the system of ammonia lines and pumps that keep the station cool. It’s presented several problems in the past, including the most recent spacewalk over the weekend. On July 31, 2010, one of the ammonia pumps failed, forcing ISS crewmembers Tracy Caldwell-Dyson and Doug Wheelock to venture outside on three spacewalks. On Aug. 7, they tried to disconnect the pump but could not detach it from a pressurized quick-disconnect line. “Wow. That thing is not budging,” Wheelock told Mission Control. As the two astronauts struggled with it, some ammonia leaked out, and Wheels described it as tiny snowflakes. Eventually, he took a hammer to the pump and it finally came off. Mission Control erupted in cheers–but then noticed a stream of ammonia flowing out of the troublesome tubes. They plugged it back in. In a second spacewalk a few days later, Wheelock and Caldwell-Dyson went out to close off the quick disconnect and tackle the broken pump. They observed a few snowflakes, which indicated a small leak, but nothing like the week before. The main problem came when Wheelock tried to remove the QD–it wouldn’t come off. “After being given permission to ‘violently’ shake the QD, in order to remove potential ice from hindering its removal, Wheelock’s brute force resulted in success, as the QD came loose,” according to a report at

Nuking A Mouse, Or Removing An Entire Pump When You Can’t Find Its Leak

On Saturday, May 11, astronauts Chris Cassidy and Tom Marshburn didn’t so much MacGyver a solution as shotgun it–they just took out an entire offending piece of equipment. Last week, astronauts spotted a cloud of tiny snowflakes mushrooming from the station’s backbone, which you can see in this image. Engineers took photos and videos and realized they were ammonia flakes leaking from a pump. NASA decided to quickly schedule a spacewalk so the astronauts could fix it–this was precedent-setting in the history of the ISS, according to Norm Knight, NASA’s chief flight director. A little more than two and a half hours into the spacewalk, Cassidy and Marshburn removed the 260-pound pump controller box from the P6 truss and replaced it with a spare that had been stowed nearby, according to NASA. There was no danger to the crew, but it’s important to fix these pumps just in case another were to fail, which could jeopardize science experiments aboard the orbiting lab. So far, there are no signs of a new leak.