Sergei Konstantinovich Krikalev (Russian: Серге́й Константинович Крикалёв, also transliterated as Sergei Krikalyov; born August 27, 1958) 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.