China's "Androgynous Peripheral Assembly System" (APAS) for docking in the space

The Chinese "Androgynous Peripheral Assembly System" (APAS), used for the Shenzhou space ship and Tian Gong space module, is compatible with the original Russian APAS-98. This APAS is installed on the ISS for docking with the Space Shuttle.

APAS History

APAS-75

The first APAS-75 docking system was developed by the former U.S.S.R. for the Apollo-Soyuz Test Project (ASTP). Unlike previous docking systems, both units could assume the active or passive roles as required. For docking, the spade-shaped guides of the extended active unit and the retracted passive unit interacted for gross alignment. The ring holding the guides shifted to align the active unit latches with the passive unit catches. After these caught, shock absorbers dissipated residual impact energy in the American unit; mechanical attenuators served the same function on the Soviet side. The active unit then retracted to bring the docking collars together. Guides and sockets in the docking collars completed alignment. Four spring push rods drove the spacecraft apart at undocking.

The Soviets built five Soyuz spacecraft that used APAS-75. The first three flew as test systems (Kosmos 638, Kosmos 672 and Soyuz 16). One was used active for the Apollo-Soyuz Test Project (Soyuz 19/AS-210), and the last one flew as Soyuz 22.

APAS-89 (MIR)
The modified second APAS-89 docking system was installed in 1990 on the front side of the Mir-module "Kristall". In 1993, the system was used for the first time by Soyuz TM-16 for coupling. Soyuz TM-16 was so far the only Soyuz spacecraft with a compatible APAS-89 adapter.

Following the decision the U.S. American and Russian space program to coordinate was planned flights of the Space Shuttle to the Mir-station. For the mission STS-71, the first docking of the Space Shuttle at the Mir-station, had to laboriously the Kristall-module on the radial position of the Mir-coupling adapter implemented so that the space shuttle Atlantis the Mir not damaged. After that the Kristall-module was restored to its original position, to clear the radial docking of Soyuz and Progress spacecraft.
To circumvent the complex action, American and Russian experts agreed the development of a special docking module (SDM), which should be connected with the Kristall-module. The construction took place in Russia at RKK Energia.
In 1995, the SDM launched as a payload of Space Shuttle Atlantis (STS-74). The coupling of the SDM was performed on the axial APAS docking adapter of the Kristall-module. As a result, seven more Shuttle-Mir missions were carried out (STS-76, STS-79, STS-81, STS-84, STS-86, STS-89 and STS-91).

APAS-89 (ISS)
The fixed coupled Russian basic modules Zarya and Zvesda of the new Space Station ISS have total 5 docking ports. Only one, the front axial port of the FGB (Zarya) is equipped with an APAS-89 docking system. Here was docked the module Node-1 (Unity) with a compatible active APAS, the Pressurized Mating Adapter (PMA-1).
PMA-1 connects permanently the aft hatch of Node-1 with the Zarya module. PMA-2 was delivered with Node-1 and was located at first at the forward hatch of this module.When STS-98 delivered module Destiny, PMA-2 was moved to the forward hatch of Destiny. When STS-120 delivers the Node-2 to its temporary berthing at the port hatch of Node-2, PMA-2 was first moved to the front hatch of Node-2 and then with this module to the front hatch of Destiny.