International Space Station I 20th Anniversary
A Narrative Around the Details ISS Challenges and Anomalies
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t the Johnson Space Center (JSC), and at every other NASA center with a hand in managing the International Space Station (ISS), there are case studies and lessons-learned databases on every significant anomaly that has arisen during the two decades the station has been in operation. They are not simply shortform documents or synopses of a problem faced and resolved. “There’s a narrative around the details,” Brian Derkowski said. Derkowski is the manager of the ISS On-Orbit Engineering Office responsible for the ISS Mission Evaluation Room (MER) and the ISS anomaly resolution and engineering support to the flight control team. The instructive power of the story that goes with the particulars of any anomalous event – large or small – is something NASA has striven to internalize over the 20-year history of the ISS, and indeed across the six decades of the agency’s existence. The ISS has a few stories. At around 10:00 in the morning East Coast time on March 30, 2017, veteran U.S. astronaut Peggy Whitson was on a spacewalk outside the ISS doing some routine maintenance. In this case, Whitson and her spacewalk (or extravehicular activity, EVA) companion, astronaut Shane Kimbrough, were installing a thermal shield on an unused docking port on the ISS. The port needed protection against space debris and radiation. “Peggy, I don’t have a shield,” Kimbrough said over the UHF radio to Whitson. “What?” she replied. “Yeah, I don’t have a shield,” Kimbrough reiterated. “Where is it?” she asked. “It’s right by the radiator,” she said, answering her own question. “It’s moving at about half-a-foot-a-second and it looks like straight away from the radiator angle.” “We copy, and we see it,” said a controller from NASA’s Mission Control Center at JSC.
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With that, the 5-foot shield floated blithely off into space, joining 20,000-plus other pieces of sizable debris orbiting Earth. Whitson and Kimbrough had planned to install a total of four such shields during a 6.5-hour EVA. They now had just a trio. What to do? “Despite the rigor we put into preparation and planning, those types of anomalies occaisionally occur,” Derkowski acknowledged. As with all EVAs, Whitson and Kimbrough had only a few hours of time available to work outside the space station. If a timely solution to the loss of the shield was going to be arrived at and executed, it would have to happen very quickly. “Our team in the control center met and rapidly came up with a work-around,” Derkowski said. “Within an hour or so, they had the procedures defined well enough to call up to the EVA crew in real-time and execute the fix.” The fix was effected by retrieving a thermal blanket that had been removed from a port earlier in the EVA. Whitson and Kimbrough fitted the improvised cover to the final port. It wasn’t a perfect fit, but it would effectively prevent exposure to high temperatures and micrometeoroid debris until a purpose-built replacement could be put on-orbit. “That’s the beauty of having all the ISS teams – engineering, operations, safety – all coming together and working issues in real-time,” Derkowski said.
NASA astronaut Peggy Whitson conducts a spacewalk in support of the International Space Station. During one of the expedition’s EVAs, a thermal and micrometeoroid shield was lost, one of four needed to protect the Tranquility Node port from which the Pressurized Mating Adapter-3 (PMA-3) was moved to a new location. Mission Control and the astronauts effected a temporary replacement for the shield.
NASA photo
BY ERIC TEGLER
