June 30

Georgy Dobrovolsky (1928–1971) was a Soviet pilot and cosmonaut selected for the Soyuz space program. As commander of Soyuz 11, he became part of the first crew to board the Salyut 1 space station in 1971. During reentry, his spacecraft suffered cabin depressurization, leading to the tragic death of Dobrovolsky and his two crewmates. He was posthumously awarded the title Hero of the Soviet Union for his pioneering contributions to human spaceflight. His sacrifice led to critical improvements in spacecraft safety protocols. Dobrovolsky's mission marked a milestone in long-duration space habitation.

Viktor Ivanovich Patsayev (1933–1971) was a Soviet engineer and cosmonaut selected in 1965 for spaceflight. As flight engineer on Soyuz 11, he helped the crew become the first to inhabit the Salyut 1 space station. Patsayev conducted scientific experiments and maintained the station's technical systems during their 23-day mission. Tragically, the Soyuz 11 capsule depressurized during reentry, resulting in the death of Patsayev and his two crewmates. He was posthumously awarded the Hero of the Soviet Union for his pioneering contributions to space exploration. His work influenced long-duration mission planning and spacecraft design.

Vladislav Nikolaevich Volkov (1935–1971) was a Soviet engineer and cosmonaut selected in 1965 as part of the Soyuz program. On the Soyuz 11 mission, he and his crewmates became the first humans to board and live aboard the Salyut 1 space station. Volkov conducted important orbital experiments and maintained life support systems during the crew's 23-day stay. During reentry, a cabin valve malfunction led to the tragic depressurization that claimed the lives of Volkov and his fellow cosmonauts. He was posthumously honored as a Hero of the Soviet Union for his bravery and dedication. His sacrifice led to enhanced safety measures in spacecraft design.