Sergei Krikalev is a Russian cosmonaut and mechanical engineer. As a prominent rocket scientist, he is a veteran of six space flights and ranks third to Gennady Padalka and Yuri Malenchenko for the amount of time in space: a total of 803 days, 9 hours, and 38 minutes. He retired from spaceflight in 2007 and is currently working as vice president of Space Corporation Energia.
He enjoys swimming, skiing, cycling, aerobatic flying, and amateur radio operations, particularly from space (callsign U5MIR). He graduated from high school in 1975. In 1981, he received a mechanical engineering degree from the Leningrad Mechanical Institute, now called Baltic State Technical University.
After graduation in 1981, he joined NPO Energia, the Russian industrial organization responsible for manned space flight activities. He tested space flight equipment, developed space operations methods, and participated in ground control operations. When the Salyut 7 space station failed in 1985, he worked on the rescue mission team, developing procedures for docking with the uncontrolled station and repairing the station's on-board system.