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   A problem with one of the International Space Station's cooling systems may require a repair spacewalk, NASA told NBC News on Wednesday. 
   
   The situation doesn't represent a life-threatening emergency, but it has required a cutback in normal operations on the orbiting outpost, NASA spokesman Josh Byerly said. 
   
   "The crew was never in any danger," he said. "They're fine for the near future." 
   
   The problem is one of the "Big 14" maintenance issues that NASA and its partners expect to face on an occasional basis during space station operations. "This is the kind of thing that they expected to happen, at about the expected rate," NBC News space analyst James Oberg said. 
   
   Shutdown mode 
   
   One of the station's two external cooling loops, known as Loop-A, shut down when it reached a pre-set temperature limit on Wednesday, Byerly told NBC News. That forced NASA to reroute coolant into Loop-B. As a result, the station's six-person crew had to prioritize life support systems, electrical systems and science experiments — including the freezers that preserve scientific samples. Some non-critical systems were turned off in NASA's Harmony node, Japan's Kibo lab and Europe's Columbus lab. 
   
   
   
   The crew "worked to keep the freezers going, " Byerly said. 
   
   Engineers think the problem was caused by a malfunctioning flow control valve for the station's ammonia coolant. Mission managers are trying to determine whether a software fix can get the valve working again, or whether a spacewalk will be required. Sorting through all the issues might take a couple of days, or as much as a couple of weeks. 
   
   Routine maintenance 
   
   It generally takes two weeks to plan for a "Big 14" repair operation, but that depends on the resources at hand and the urgency of the problem. In May, NASA astronauts mounted a spacewalk to replace a leaky coolant pump control box after just two days of planning. Spacewalkers also dealt with coolant system maintenance issues in 2012, 2011, 2010, 2009 and 2007. 
   
   
   
   U.S. spacewalks were temporarily suspended after Italian astronaut Luca Parmitano's spacesuit filled with water during a July outing, but Russian spacewalks have proceeded without problems. And since July, NASA has made significant progress on resolving the spacesuit problem that Parmitano faced. 
   
   "We are cleared for a contingency spacewalk if we need to do one," NASA spokesman Kelly Humphries told NBC News. 
   
   Two Americans, three Russians and a Japanese astronaut are living on the space station, which has been continuously occupied since 2000 by spacefliers who spend tours of duty generally lasting four to six months. The current plan calls for the space station to be maintained through 2020, although the United States and the 14 other countries supporting the $100 billion-plus station project are already considering extending its operating life. 
   
   More about the space station: 
   
   Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds. ||||| Story highlights NASA says the space station and crew were never in any danger 
   
   A cooling pump shut down after hitting a temperature limit 
   
   An emergency spacewalk could be necessary, but it's too soon to tell 
   
   NASA scaled back operations on the International Space Station on Wednesday after discovering a problem with a cooling system. 
   
   A pump on one of the station's two external cooling loops shut down after hitting a temperature limit, NASA said. 
   
   Teams worked to get the cooling loop back up and running, NASA said. Experts suspect a malfunctioning valve may have caused the problem, but they're still trying to figure out how to fix it. 
   
   The station and crew aboard were never in any danger, NASA said. 
   
   Officials could determine that an emergency spacewalk is the best way to fix the failed pump -- something they've done in the past. 
   
   NASA said Thursday that there has been no decision on the spacewalk, and it may be a couple of days before the decision is made, according to Kenny Todd, the ISS mission management team chairman. 
   
   Photos: Notable moments of the International Space Station Photos: Notable moments of the International Space Station The crew of the space shuttle Atlantis took this picture of the International Space Station after leaving it in July 2011. Atlantis was the last shuttle to visit the station, which was first launched in 1998 and built by a partnership of 16 nations. Hide Caption 1 of 13 Photos: Notable moments of the International Space Station The crew of the space shuttle Endeavour initiates the station's first assembly sequence in 1998. The International Space Station includes several large modules, each launched separately and connected in space by astronauts. Hide Caption 2 of 13 Photos: Notable moments of the International Space Station The Zarya control module, on the left with the solar panels, floats above Earth with its newly attached Unity module after the first assembly sequence in December 1998. Hide Caption 3 of 13 Photos: Notable moments of the International Space Station The first crew of the International Space Station, seen on board in December 2000. From the left are cosmonaut Yuri P. Gidzenko, astronaut William M. Shepherd and cosmonaut Sergei K. Krikalev. Hide Caption 4 of 13 Photos: Notable moments of the International Space Station The Endeavour crew installs the first set of U.S. solar arrays on the station in 2000. Hide Caption 5 of 13 Photos: Notable moments of the International Space Station In March 2001, a space shuttle delivered the station's second crew and brought the first one home. It also brought Leonardo, the station's first Multi-Purpose Logistics Module, to the station. Leonardo carried supplies and equipment. Hide Caption 6 of 13 Photos: Notable moments of the International Space Station In September 2006, the space shuttle Atlantis docked with the space station, delivering solar wings and a new truss. Hide Caption 7 of 13 Photos: Notable moments of the International Space Station The space shuttle Discovery leaves the space station in March 2008 after its crew successfully delivered and installed the Japanese-built Kibo lab. Hide Caption 8 of 13 Photos: Notable moments of the International Space Station The unmanned SpaceX Dragon spacecraft connects to the space station in May 2012. It was the first private spacecraft to successfully reach an orbiting space station. Hide Caption 9 of 13 Photos: Notable moments of the International Space Station An unmanned Russian cargo craft disconnects from the space station in April 2013. The station relies heavily on ships to bring up supplies. Hide Caption 10 of 13 Photos: Notable moments of the International Space Station Commander Koichi Wakata of the Japan Aerospace Exploration Agency peers out of the space station's Cupola observatory on April 27. The Cupola is a dome-shaped module that allows station crew members to observe and guide activities outside the station. Hide Caption 11 of 13 Photos: Notable moments of the International Space Station A Russian Soyuz spacecraft is docked with the space station on May 5. Since the U.S. shuttle program ended in 2011, all crew members are ferried to and from the space station on Russian rockets. Hide Caption 12 of 13 Photos: Notable moments of the International Space Station A Soyuz spacecraft is seen on May 13 as it lands in Kazakhstan with Wakata and other members of the his Expedition 39 crew. Hide Caption 13 of 13 
   
   The external cooling loops are systems that circulate ammonia outside the station to keep equipment cool. 
   
   Officials discovered the malfunctioning loop was producing too much ammonia Wednesday morning, NASA spokesman Josh Byerly said. 
   
   Teams have shut down some noncritical systems on the station as a result of the problem, NASA said. 
   
   The space station's life support system is still up and running. 
   
   The current mission of the space station, officially called Expedition 38, is scheduled to go until March 2014. 
   
   The six-person crew consists of NASA astronauts Mike Hopkins and Rick Mastracchio of the United States; Russians Mikhail Tyurin, Sergey Ryazanskiy and Oleg Kotov; and Koichi Wakata of Japan.
target: – NASA is reporting a glitch with one of the two cooling pumps on the International Space Station, but it says none of the six crew members are in danger, reports CNN. The crew shut down some non-essential electrical systems as a precaution while they figure what went wrong and how to fix it. Best case, it's a software glitch and a relatively easy repair. Otherwise, a spacewalk will be necessary, reports NBC News. It will likely take days or perhaps weeks to sort it all out. "They're fine for the near future," says a NASA spokesman.