Community hub
Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Common Berthing Mechanism
The Common Berthing Mechanism (CBM) connects habitable elements in the US Orbital Segment (USOS) of the International Space Station (ISS). The CBM has two distinct sides that, once mated, form a cylindrical vestibule between modules. The vestibule is about 16 inches (0.4 m) long and 6 feet (1.8 m) 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 (RMS). Latches and bolts on the active CBM (ACBM) side pull fittings and floating nuts on the passive CBM (PCBM) 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.
All CBM types feature an aluminum ring that is bolted onto the pressure shell during fabrication of the parent module. The bolted joint compresses two concentric o-ring seals: one is silicone (for better temperature performance), and the other is fluorocarbon (for better resistance to scrubbing). A mated pair of rings is primary structure for life-critical pressure loads, so the rings and seals were engineered to the same standards as the module shells. If the primary seals deteriorate, they can be augmented by secondary seals that were designed and qualified as part of the CBM. The secondary seals can be installed as an intravehicular activity (IVA).
Most of the vestibule's volume is reserved for crew passage, and a closeout is typically installed around the perimeter of the hatch as a boundary for the passageway. In most locations, volume is reserved for utility connections outboard of the closeout. The set of utilities is specific to each pair of mated modules.
In addition to its structural characteristics, the ACBM performs and reverses the basic functions associated with berthing:
Two functional types were specified for the ACBM. The Type I ACBM, with a complement of 24 independent mechanisms, can be found either axially or radially oriented on the parent module. It can face any of the six orbital orientations, so can be anywhere within a wide range of temperatures at the start of berthing operations.
The Type II ACBM augments the design of the Type I with components to protect its parent module when nothing is berthed on a port. Four of the components are mechanisms that can be deployed to get out of the incoming module's way. Others are removed by the crew after the vestibule is pressurized. The Type II is used where ports would otherwise be exposed for long periods of time, or in directions that experience aggressive pre-berth conditions. The Type II ACBM is found on the radial ports of resource nodes, and can face in any orbital orientation.
Hub AI
Common Berthing Mechanism AI simulator
(@Common Berthing Mechanism_simulator)
Common Berthing Mechanism
The Common Berthing Mechanism (CBM) connects habitable elements in the US Orbital Segment (USOS) of the International Space Station (ISS). The CBM has two distinct sides that, once mated, form a cylindrical vestibule between modules. The vestibule is about 16 inches (0.4 m) long and 6 feet (1.8 m) 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 (RMS). Latches and bolts on the active CBM (ACBM) side pull fittings and floating nuts on the passive CBM (PCBM) 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.
All CBM types feature an aluminum ring that is bolted onto the pressure shell during fabrication of the parent module. The bolted joint compresses two concentric o-ring seals: one is silicone (for better temperature performance), and the other is fluorocarbon (for better resistance to scrubbing). A mated pair of rings is primary structure for life-critical pressure loads, so the rings and seals were engineered to the same standards as the module shells. If the primary seals deteriorate, they can be augmented by secondary seals that were designed and qualified as part of the CBM. The secondary seals can be installed as an intravehicular activity (IVA).
Most of the vestibule's volume is reserved for crew passage, and a closeout is typically installed around the perimeter of the hatch as a boundary for the passageway. In most locations, volume is reserved for utility connections outboard of the closeout. The set of utilities is specific to each pair of mated modules.
In addition to its structural characteristics, the ACBM performs and reverses the basic functions associated with berthing:
Two functional types were specified for the ACBM. The Type I ACBM, with a complement of 24 independent mechanisms, can be found either axially or radially oriented on the parent module. It can face any of the six orbital orientations, so can be anywhere within a wide range of temperatures at the start of berthing operations.
The Type II ACBM augments the design of the Type I with components to protect its parent module when nothing is berthed on a port. Four of the components are mechanisms that can be deployed to get out of the incoming module's way. Others are removed by the crew after the vestibule is pressurized. The Type II is used where ports would otherwise be exposed for long periods of time, or in directions that experience aggressive pre-berth conditions. The Type II ACBM is found on the radial ports of resource nodes, and can face in any orbital orientation.