DOS-2 (Salyut backup, s/n 122), the intended second civilian Soviet long-duration orbital station after Salyut 1. Proton-K from Baikonur Site 81/23 failed at T+162 s when the second stage malfunctioned on 29 July 1972; the ~18 t station never reached orbit and fell into the Pacific.
- Outcome
- Failure
- Orbit
- LEO
- Low Earth orbit
- Payload to orbit
- Did not reach orbit
- Flight
- 3rd
- of 29 Proton-K flights
- Date and time
- 29 July 1972, 03:20 UTC
- Rocket
- Proton-K
- Builder
- Khrunichev
- Launch site
- 81/23 (81L), Baikonur Cosmodrome, Republic of Kazakhstan
- Payload
- Human Exploration
- Launches in 1972
- 63rd of 113