Soyuz 11 launched 1971

Soyuz 11 crew: Dobrovolsky, Volkov, Patsayev

Soyuz 11, launched June 6, 1971, was manned by Commander Georgy Dobrovolsky, Flight Engineer Vladislav Volkov and Test Engineer Viktor Patsayev.  They docked with Salyut 1 but had to replace part of the ventilation system before they could board her.

Upon re-entry, the capsule depressurized too early, killing the crew.  They are the only known humans to have died in space.