NASA ISS Emergency EVA: Expedition 35 Flight Engineer Chris Cassidy

Expedition 35 Flight Engineers Chris Cassidy (pictured) and Tom Marshburn (out of frame) completed a spacewalk at 2:14 p.m. EDT May 11, 2013. 

The emergency EVA was needed to inspect and replace a pump controller box on the International Space Station’s far port truss (P6) leaking ammonia coolant. 

The two NASA astronauts began the 5-hour, 30-minute spacewalk at 8:44 a.m.

A leak of ammonia coolant from the area near or at the location of a Pump and Flow Control Subassembly was detected on Thursday, May 9, prompting engineers and flight controllers to begin plans to support the spacewalk. 

The device contains the mechanical systems that drive the cooling functions for the port truss.

Image Credit: NASA