Pressurized Mating Adapter

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Pressurized Mating Adapter
STS-111 PMA-2 view.jpg
PMA-2 attached to the forward port of Destiny, where it was located between 2001 and 2007
Module statistics
Part ofInternational Space Station
Launch date
  • PMA-1 & 2: December 4, 1998
  • PMA-3: October 11, 2000
Launch vehicleSpace Shuttle
  • PMA-1 & 2: December 7, 1998
  • PMA-3: October 13, 2000

The Pressurized Mating Adapter (PMA) is a class of spacecraft adapters that convert the Common Berthing Mechanism (CBM) used on the US Orbital Segment to APAS-95 docking ports. There are three PMAs located on the International Space Station (ISS); the first two were launched with the Unity connecting module in 1998 aboard STS-88, and the third was launched in 2000 aboard STS-92.


Its origins lie in Boeings design for the Pressurized Docking Adapter then later part of the Pressurized Berthing Adapter assembly that appeared in Boeings designs for Space Station Freedom 1987, Fred[1] 1991 and Space Station Alpha 1993-1995.

Fabrication completed in 1995 with tests and mating tests with Node STA throughout 1996-97[2].

Space Station Fred configuration 1991


Expedition 58 crew member Anne McClain inside PMA-1, with the interior of Zarya in the background. PMA-1 has served as the bridge between Zarya and Unity since the modules were berthed in 1998.

The three PMAs are identical,[3] but they have slightly different uses. All three perform the same basic function of connecting a CBM port of an ISS module to an APAS-95 docking port of another module or visiting spacecraft.[4] For this purpose, the PMAs carry a passive CBM port and a passive APAS port. The PMAs are pressurized and heated from the inside, and they allow for power and data communications transfer through docking rings and external connections.[5]


This was one of the first components of the International Space Station. PMA-1 joins the Russian side of the station with the US side. On STS-88, the crew used the shuttle's robotic arm to attach the Zarya control module to PMA-1, which was already connected to the aft berthing port of Unity. These first two station components are permanently connected by PMA-1.


Locations of PMA-2 and PMA-3 on the forward and zenith ports of Harmony, with International Docking Adapters attached to convert the APAS-95 ports to IDSS

PMA-2 is mounted on the forward port of the Harmony connecting node, and was used when Space Shuttle orbiters docked at the ISS. It was outfitted with Station-to-Shuttle Power Transfer System (SSPTS) hardware to allow the shuttles to stay docked longer to the space station.[6]

PMA-2 has been moved several times as part of the ongoing space station assembly process. It was originally connected to the forward hatch of Unity, but when STS-98 delivered the Destiny module in February 2001, PMA-2 was moved to the berthing ring of the Z1 truss so that Destiny could be berthed to the forward hatch of Unity. PMA-2 was finally moved to the forward hatch of Destiny.[7] (The removal of PMA-2 from Unity was the first time the CBM had been used to disconnect two ISS components.)[8] After STS-120 had delivered Harmony to the space station in October 2007, Canadarm2 repositioned PMA-2 at the forward port of Harmony on November 12, 2007. Two days later, the combined package of Harmony and PMA-2 was moved to its final location, the forward hatch of Destiny. As of 2020, PMA-2 is expected to stay berthed at the forward port of Harmony for the remaining duration of the ISS.

When a shuttle docked with the station, its "final approach [was] at a relative velocity of one-tenth of a foot per second. [As it made] contact with Pressurized Mating Adapter 2 [latches] automatically attached the two spacecraft together. Once relative motion between the spacecraft stopped, [a Shuttle astronaut retracted] the docking ring on [the Shuttle's] mechanism, closing latches to firmly secure the shuttle to the station."[9]

On July 18, 2016, International Docking Adapter-2 was launched on SpaceX CRS-9.[10] It was attached and connected to PMA-2 during a spacewalk on August 19, 2016.[11]


PMA-3 was brought to the ISS by STS-92 in October 2000, mounted on a Spacelab pallet.[12] It was initially attached to the nadir (bottom, or Earth-facing) hatch of Unity. About six weeks later, when STS-97 delivered the P6 solar array truss structure, Endeavour docked at PMA-3.[13] When STS-98 moved PMA-2 from Unity to Destiny via the Z1 truss in February 2001, Atlantis was docked at PMA-3.[7] For the remainder of the shuttle's operation, PMA-3 was not used for shuttle dockings. PMA-3 was moved in March 2001 to Unity's port hatch by the crew of STS-102 to make room for the docking of a Multi-Purpose Logistics Module (MPLM).[14]

On August 30, 2007, PMA-3 was returned to the nadir port of Unity to make room for the temporary docking of the new Harmony (Node 2) module that was delivered by STS-120.[15] Harmony was transferred to the forward port of Destiny, while PMA-3 was moved back to the port berthing mechanism of Unity on August 7, 2009, to accommodate reconfiguration of the Unity port bulkhead by crew members in a pressurized environment.[16] On January 25, 2010, PMA-3 was moved from the port berthing mechanism of Unity to the zenith (space-facing) port of Harmony to make room for the new Tranquility (Node 3) module which was added to the station during STS-130. After activation of Tranquility, PMA-3 was moved again on February 16, 2010, to the port location on Tranquility where the Cupola observatory module had been docked for launch.[17]

PMA-3 was robotically removed from Tranquility on March 26, 2017, and attached to Harmony after being prepared during a successful spacewalk on March 24, 2017. A second spacewalk was conducted on March 30, 2017, to finalize the PMA-3 cable connections on Harmony. PMA-3 received International Docking Adapter-3 in August 2019.[18]


  1. ^
  2. ^
  3. ^ – Elements
  4. ^ "Human Space Flight – Space Fact". NASA. July 4, 2002. Retrieved January 17, 2007.
  5. ^ "STS-92 Press Release Kit: Payload section". NASA. October 10, 2000. Retrieved October 27, 2007.
  6. ^ "International Space Station Status Report #07-08". NASA.
  7. ^ a b STS-98, Mission Control Center (February 10, 2001). "Status Report # 07". NASA. Retrieved January 18, 2007.
  8. ^ Harwood, William (February 10, 2001). "Atlantis crew to attach Destiny lab to station today". Spaceflight Now. Retrieved January 15, 2007.
  9. ^ STS-102, Mission Control Center (March 9, 2001). "Status Report # 03". NASA. Retrieved January 18, 2007.
  10. ^ Jason Rhian (July 18, 2016). "SpaceX Conducts Second Ground Landing After Launch Of CRS-9 Dragon To ISS". Spaceflight Insider.
  11. ^ Harwood, William (August 19, 2016). "Spacewalkers attach docking adapter to space station for commercial vehicles". Spaceflight. Retrieved August 20, 2016.
  12. ^ STS-92, Mission Control Center (October 16, 2000). "Status Report # 10". NASA. Retrieved January 18, 2007.
  13. ^ STS-97, Mission Control Center (December 2, 2000). "Status Report # 05". NASA. Retrieved January 18, 2007.
  14. ^ STS-102, Mission Control Center (March 11, 2001). "Status Report # 07". NASA. Retrieved January 18, 2007.
  16. ^ "NASA - 08-07-2009 ISS On-Orbit Status". Retrieved June 3, 2017.
  17. ^ STS-130, Mission Control Center (February 16, 2010). "Status Report # 17". NASA. Retrieved February 16, 2010.
  18. ^ Pietrobon, Steven (August 20, 2018). "United States Commercial ELV Launch Manifest". Retrieved August 21, 2018.

External links[edit]

  • YouTube animation Canadarm2 and Dextre move the PMA-3 between locations, one of the five times it was moved so that modules could use a Common Berthing Mechanism port instead of PMA-3.