Soviet cosmonaut Valery Polyakov, best known for setting the record for the longest single trip to space, has died aged 80, Russia’s space agency announced Monday. On January 8, 1994, Polyakov launched to the Mir space station where he orbited the Earth over 7,000 times before returning after 437 days in space on March 22, 1995. The trained physician previously spent 288 days in space during a single mission in 1988-89. After his record-breaking flight, Polyakov refused to be carried out of the Soyuz capsule—as was the customary practice to help cosmonauts to deal with the effects of returning to gravity—in order to prove how the human body could deal with being in space for long periods of time. The announcement from space agency Roscosmos did not disclose a cause of death.