page_title: Common Berthing Mechanism
section_title: Opportunities
hierarchical_section_title: Common Berthing Mechanism / Operations / Opportunities
caption_attribution_description: English: Original Caption: iss061e147761 (Jan. 30, 2020) --- NASA astronaut and Expedition 61 Flight Engineer Jessica Meir poses in front of the closed hatch of the Cygnus space freighter from Northrop Grumman. Attached to the hatch is the SlingShot small satellite deployer loaded with eight CubeSats that were deployed into Earth orbit for communications and atmospheric research several hours after Cygnus departed the orbiting lab on Jan. 31, 2019.
context_page_description: The Common Berthing Mechanism connects habitable elements in the US Orbital Segment of the International Space Station. The CBM has two distinct sides that, once mated, form a cylindrical vestibule between modules. The vestibule is about 16 inches long and 6 feet across. At least one end of the vestibule is often limited in diameter by a smaller bulkhead penetration.
  The elements are maneuvered to the berthing-ready position by a Remote Manipulator System. Latches and bolts on the Active CBM side pull fittings and floating nuts on the Passive CBM side to align and join the two.
  After the vestibule is pressurized, crew members clear a passage between modules by removing some CBM components. Utility connectors are installed between facing bulkheads, with a closeout panel to cover them. The resulting tunnel can be used as a loading bay, admitting large payloads from visiting cargo spacecraft that would not fit through a typical personnel passageway.
context_section_description: The original design of the ISS called for a Habitat element to be installed on the Nadir-facing port of Node 1 (Unity), and bulkhead penetrations were designed accordingly.  As the station matured through the first phases of assembly, Node 3 was planned for that location.  It later became apparent that installation on the port-side bulkhead would confer significant operational advantages.  Unfortunately, the original routing of utilities inside Node 1 required significant re-work on orbit to enable the change.  The large CBM diameter permitted the use of PMA3 as a pressure-containing closeout during the effort, so that feed-throughs could be removed and replaced without EVA.  PMA3 was moved during Expedition 21 to the port-side CBM, and "...Potable Water, ISL & 1553 data cabling, and installing IMV [Inter-Modular Ventilation] ducting, cables and hoses..." were connected in preparation for the arrival of Node 3.  The reconfigured bulkhead was tested for leakage before moving PMA3 back to its storage location, and Node 3 was installed in the newly prepared location on STS-130.
  The depth, diameter, and accessibility of the CBM have also been exploited in support of dispensing CubeSats from the SlingShot deployment system.  The framework mounts into the PCBM's interior envelope on logistics vehicles (e.g., Cygnus).  The Bishop Airlock Module will also take advantage of the robust interface between the ACBM and PCBM to repeatedly berth and deberth a "bell" hosting similar capability.
caption: Expedition 61 Flight Engineer Jessica Meir poses in front of the SlingShot small satellite deployer loaded with eight CubeSats.
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