ISS docking systems

• Probe-and-drogue
• Hybrid
• APDS
• Links
• Photo gallery

The ISS has four types of docking systems; this page briefly describes the three Russian ones.

Probe-and-drogue

The “classic” probe-and-cone (or probe-and-drogue) docking system is used on the Soyuz and Progress ships. The ships carry the active “probe” section which dock to the receptive cone or drogue part attached to the module. The active part (АСА, ASA) has a probe (СШ, SSh) with a capture latch at the tip, and alignment pins, hooks, and shock absorbers. The probe fits into the drogue of the receiving cone (СК, SK) on the passive docking assembly (ПСА, PSA). The capture latch is activated after the probe enters the drogue, then the shock absorbers dampen out any vibrations. This phase is the “soft dock”. The probe retracts, bringing the two halves together and the hooks on the ASA mate it with the structural ring on the PSA. It is “hard docked” at this point. A one-hour leak check is completed by the crew before hatches are opened. The crew later remove the probe-and-cone docking system (StM) in the Progress to clear the passage for cargo transfer operations.

This system is used on the rear port of Zvezda, and the nadir ports of Zarya and Pirs.

Hybrid

A larger and stronger version of the classic system, the Hybrid Docking System, is used to join the Russian modules together. It has more hooks, a larger diameter hatch, and a larger structural ring to withstand the increased forces on the joints between the docked modules. The larger hatch also means that larger cargo can be passed through.

APDS

The Androgynous Peripheral Docking System (APDS) has its origins in the Apollo-Soyuz program, and a version (Androgynous Peripheral Docking System, APDS-89) was used for the Shuttle-Mir program (the bright orange docking port was originally intended to enable the Buran orbiter to dock to Mir). Each APDS is identical and can act as the passive or active half. The system can dock active-to-active or active-to-passive, but not passive-to-passive. The front port of Zarya has the APDS system; it is docked with Pressurized Mating Adapter-1 (PMA-1). PMA-2 and PMA-3 also have an APDS to which the Space Shuttle can dock.

The Russian name is АСПП, Агрегат Стыковочный Пассивный Периферийный – ASPP, peripheral passive docking assembly

Links

• Capcom Espace: Les docking system d’ISS (ISS docking system). I used this as a starting point for my page; he also has a copy of the NASA ISS Familiarization Manual, from which I got the diagrams and information.
• ISS Alpha: EVA Capabilities and Docking Compartments for International Space Station Alpha
• NASASpaceflight.com forum: Russian docking mechanisms difference?

~ Page last updated: 11 February 2008

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