He spent two long residencies on the Russian space station Mir as a board engineer (January–July 1994 and February–September 1996). In May 2000 he flew on the Atlantis space shuttle mission to construct the International Space Station (ISS), and became a member of its second resident crew in March 2001, transported to the ISS on Discovery for a four-month stay. He has logged over 670 days in space and taken six space walks. Usachev worked for the Energiya Rocket and Space Complex, involved in extravehicular activity training and space construction techniques. He was selected as a cosmonaut in 1989 and retired in 2004.