Soyuz 7K-TM
The 1975 Apollo–Soyuz Test Project version of the Soyuz spacecraft served as a technological bridge to the third generation Soyuz-T spacecraft.
The Soyuz ASTP spacecraft was designed for use during the Apollo Soyuz Test Project as Soyuz 19. It featured design changes to increase compatibility with the American craft. The Soyuz ASTP featured new solar panels for increased mission length, an APAS-75 docking mechanism instead of the standard male mechanism, and modifications to the environmental control system to lower the cabin pressure to 0.68 atmospheres prior to docking with Apollo. The ASTP Soyuz backup craft flew as the Soyuz 22 mission, replacing the docking port with a camera.
Missions
There are only five spaceflights of the Soyuz 7K-TM spacecraft, mostly in support for the joint US-Soviet Apollo–Soyuz mission. Excess hardware that flew on its final flight were sometimes referred to its own unique configuration called the Soyuz 7K-MF6| Mission | Crew | Launch | Landing | Duration | Notes |
| Kosmos 638 | None | 3 Apr 1974 | 13 Apr 1974 | First test flight of the APAS-75 docking system | |
| Kosmos 672 | None | 12 Aug 1974 | 18 Aug 1974 | Second test flight of the APAS-75 docking system | |
| Soyuz 16 |  |