Mir was the first continuously inhabited long-term research station in orbit and held the record for the longest continuous human presence in space at 3,644 days, until it was surpassed by the ISS on 23 October 2010. It holds the record for the longest single human spaceflight, with Valeri Polyakov spending 437 days and 18 hours on the station between 1994 and 1995. Mir was occupied for a total of twelve and a half years out of its fifteen-year lifespan, having the capacity to support a resident crew of three, or larger crews for short visits.
Deeply involved in the investigation of the 1967 Apollo 1 fire, Shea suffered a nervous breakdown as a result of the stress that he suffered. He was removed from his position and left NASA shortly afterwards. From 1968 until 1990 he worked as a senior manager at Raytheon in Lexington, Massachusetts, and thereafter became an adjunct professor of aeronautics and astronautics at MIT. While Shea served as a consultant for NASA on the redesign of the International Space Station in 1993, he was forced to resign from the position due to health issues.