After Apollo 11 and four catastrophic N1 rocket failures, the Soviet Union abandoned the Moon and pivoted to a new finish line: the first space station. Salyut 1, internally DOS-1, was adapted from the classified Almaz military platform and shipped to Baikonur in about a year. This episode explores the 18,000 kilogram, 20 meter cylinder with its apple green and light yellow walls, a deliberate medical countermeasure to give disoriented cosmonauts a visual up and down when their inner ear otoliths stopped working in weightlessness.

We break down the SSVP probe and drogue docking system that still connects vehicles to the Russian segment of the ISS, the Orion 1 ultraviolet observatory designed by Grigor Gurzadyan, and the classified payloads that used astrophysics to characterize rocket exhaust plumes. Soyuz 10 achieved only a soft dock and had to return home, but Soyuz 11 succeeded in June 1971, and Dobrovolsky, Patsayev, and Volkov spent a record 23 days aboard, surviving an electrical fire in zero gravity. On reentry, pyrotechnic separation bolts jarred a pressure equalization valve open at 168 kilometers altitude, and the crew, flying without pressure suits because three suited men could not fit, asphyxiated within a minute. Salyut 1 was deorbited on October 11, 1971 after 175 days, but its architecture led directly to Mir and to the Zvezda module of the ISS.

• Why the 30 engine N1 shook itself apart and how that failure birthed the Soviet space station program
• How Almaz spy hardware became the civilian Durable Orbital Station in roughly a year
• Green and yellow paint as survival gear: hacking the visual cortex when the vestibular system fails
• The probe and drogue docking mechanics behind Soyuz 10’s failed hard dock and Soyuz 11’s success
• The valve failure above the Karman line, the mandate for pressure suits, and the Soyuz redesign to a two person crew