Spacewalk Repairs on the International Space Station
{{#rendered}} {{/rendered}}August 7: In this image taken from video and made available by NASA, astronauts Douglas Wheelock, right, and Tracy Caldwell Dyson begin work on the International Space Station to replace a broken ammonia pump. (AP Photo/NASA)
August 7: In this image taken from video and made available by NASA astronaut Doug Wheelock begins the first of two spacewalks to replace a broken ammonia pump. (NASA)
August 7: In this image taken from video and made available by NASA astronaut Doug Wheelock, foreground begins the first of two spacewalks to replace a broken ammonia pump. (NASA)
August 7: In this image taken from video and made available by NASA, astronauts Douglas Wheelock, top, and Tracy Caldwell Dyson work on the International Space Station to restore a crucial cooling system Their mission was to replace a broken ammonia coolant pump, a job considered so difficult that two spacewalks are required. (NASA)
August 7: In this image taken from video and made available by NASA, astronaut Douglas Wheelock works on the International Space Station to restore a crucial cooling system. The mission was to replace a broken ammonia coolant pump, a job considered so difficult that two spacewalks are required. (NASA)
August 7: In this image taken from video and made available by NASA, the NASA command center is supervising the work being done on the International Space Station to restore a crucial cooling system. (NASA)
This February 19 file photo provided by NASA shows the International Space Station with Earth's horizon as a backdrop. Several power systems have been shut down aboard the International Space Station after a cooling system malfunctioned. NASA says that one of two cooling loops aboard the space station was shut down July 31. (NASA)
In this April 11 file photo, NASA astronaut Rick Mastracchio, STS-131 mission specialist, is on a spacewalk to swap an ammonia tank on the International Space Station. (NASA)