Common Berthing Mechanism
The Common Berthing Mechanism (CBM) is a berthing mechanism primarily used to connect pressurized elements within the US Orbital Segment of the International Space Station. It roughly corresponds to the docking ports that are used to join such elements within the Russian Orbital Segment. It was developed by Boeing at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama under contract NAS15-10000 from the National Aeronautics and Space Administration (NASA).
The CBM system is a combination of structural, mechanical and control components that perform the capture, closure, and passive structural connection between two pressurized modules. The total CBM system is composed of two distinct sets of equipment: the active and passive halves. The active half [ACBM] supports the mechanical and control elements which effect the actual capture and closure functions of the berthing operations. The passive half [PCBM] contains the inert elements required to complete the berthing and closure action. It also contains the seals effecting pressurized capability at the Module/Module interface.
The ACBM was developed in response to specification S683-29902 (CAGE 3A768). The PCBM was developed under specification S683-28943 (CAGE 3A768). According to the specifications, the CBM provides a Module/Module clear passage diameter of 50", which is large enough to accommodate a standard hatch and allow International Standard Payload Racks to be passed between modules. Using such racks, payloads can be pre-configured and transported to the station aboard a variety of logistics modules. Once the hatches have been opened and the Module/Module vestibule configured, electrical, data, and fluid lines can be manually connected by the crew in a "shirt-sleeve" environment.
In addition to Module/Module attachment locations, the CBM is also used as a structural/mechanical/utility interface (e.g., for the base of the Z1 truss) and for docking adapters at various locations.
On radial ports, the 4 covers ('petals') on the ACBM open to expose the 4 sets of latches and alignment guides. For any ACBM location, the PCBM is aligned with ACBM using a tele-robotic device (of which several varieties exist). Latches engage and retract. When fully latched, 16 bolts are driven (under remote control) from the active side into the passive side. Bolts are tightened in multiple stages, allowing the temperatures to equalise as necessary. Bolt loads are sensed by a load cell within each of the 16 units.
Uses on the ISS
Uses of the CBM (as of late 2018) are tabulated below.
(1) Timeframes for the factory mates of PMA-1 and PMA-2 to Node 1 are approximate.
(2) A few major non-CBM matings are included here for context.
(3) NP-2015-05-022-JSC: "Reference Guide to the International Space Station", NASA Johnson Space Center, Houston, TX (2015). Retrieved from http://www.nasa.gov/sites/default/files/atoms/files/np-2015-05-022-jsc-iss-guide-2015-update-111015-508c.pdf
(4) “The International Space Station – Operating an Outpost in the New Frontier”, NASA Johnson Space Center, Houston, TX (2018). Retrieved from http://www.nasa.gov/sites/default/files/atoms/files/iss-operating_an_outpost-tagged.pdf
Closing of an active CBM's covers
|Wikimedia Commons has media related to Common Berthing Mechanism.|
- Honeywell (2001). "The common berthing mechanism (CBM) for International Space Station" (PDF). (923 KiB)
- CAGE 3A768: T683-13850-3, "Common Berthing Mechanism Assembly Qualification Test Report (Revision New)" (8 October 1998)
- CAGE 3A768: S683-28943C: "Passive Common Berthing Mechanism Critical Item Development Specification" (21 July 1995).