The terms Androgynous Peripheral Attach System (APAS), Androgynous Peripheral Assembly System (APAS) and Androgynous Peripheral Docking System (APDS),[1][2] are used interchangeably to describe a Russian family of spacecraft docking mechanisms, and are also sometimes used as a generic name for any docking system in that family. A system similar to APAS-89/95 is used by the Chinese Shenzhou spacecraft.[3]
The name of the system is Russian in origin, and is an acronym, АПАС, in the Cyrillic alphabet, from the Russian Андрогинно-периферийный агрегат стыковки (Androginno-periferiynyy agregat stykovki). The English acronym was designed to be just the same letters but in the Latin alphabet, for which the first two words are direct counterparts of those in the original. The third word in Russian comes from the German Aggregat, meaning "complicated mechanism", and the last means "docking". The last two words in the English name were picked to begin with the same equivalent letters as in the Russian name.[citation needed]
The idea behind the design is that unlike with the probe-and-drogue docking system, any APAS docking ring can mate with any other APAS docking ring; both sides are androgynous. In each docking there is an active and a passive side, but both sides can fulfill either role. There are three basic variations of the APAS system.
APAS-75
Co-developed by American and Soviet engineers through a series of in-person meetings, letters and teleconferences, APAS-75 was initially planned to be used on an American mission to a Salyut space station which instead became Apollo–Soyuz.[4] There were differences between the American and Soviet version of the docking mechanism, but they were still mechanically compatible. Early on, the Americans called the device both the International Rendezvous and Docking Mission (IRDM) Docking Mechanism and the International Docking System.[5] The device is called the Androgynous Peripheral Docking System (APDS) in the NASA press packet for ASTP.[1]
Design
Unlike previous docking systems, either APAS-75 unit could assume the active or passive role as required. For docking, the spade-shaped guides of the extended active unit (right) and the retracted passive unit (left) interacted for gross alignment. The ring holding the guides shifted to align the active unit latches with the passive unit catches. After these caught, shock absorbers dissipated residual impact energy in the American unit; mechanical attenuators served the same function on the Soviet side. The active unit then retracted to bring the docking collars together. Guides and sockets in the docking collars completed alignment. Four spring push rods drove the spacecraft apart at undocking.[6]
The Americans selected North American Rockwell to construct seven docking mechanisms (two flight, four test, and one spare).[7]
The Soviet Union built five Soyuz spacecraft that used APAS-75. The first three flew as test systems (Cosmos 638, Cosmos 672 and Soyuz 16). One was used for the Apollo-Soyuz Test Project, Soyuz 19 the only Soyuz to actually use the docking system, and the last one flew as Soyuz 22. On the American side the Apollo–Soyuz Docking Module carried one APAS-75 docking collar and one Apollo docking collar.
Development
In April 1970 NASA Administrator Thomas O. Paine suggested, in an informal meeting with Russian academician Anatoli Blagonravov in New York, that the two nations cooperate on astronaut safety, including compatible docking equipment on space stations and spacecraft to permit rescue operations in space emergencies.[8]
Engineer Caldwell Johnson proposed a ring and cone system during a meeting in Moscow during October 1970.[9] Boris N. Petrov rejected the simple adaptation of Apollo and Soyuz as a "space stunt" and had proposed developing a universal docking mechanism, Johnson suggested that the Manned Spacecraft Center (MSC) draw up a "design specifically adequate to requirements of a particular CSM/Salyut mission, the design being representative only of the fundamental form and function of docking gear satisfying the requirements for compatible docking system for future spacecraft."[9]
During a meeting in Houston during June 1971, Soviet docking specialist Valentin N. Bobkov indicated that the Soviets also favored some version of the double ring and cone.[5] Bobkov illustrated through sketches that the overall diameter of the docking system could not exceed 1.3 meters, because any larger system would require a change in the launch shroud.[5] When Johnson raised the question of altering the shroud, the Soviets stressed the major impact that such a modification would have.[5] In addition to having to design a new shroud, they would have to test out the launch aerodynamics of the altered hardware.[5] The Americans had hoped to argue for a larger tunnel, but such a change appeared to be too great for their counterparts.[5]
Drawing of a four-guide docking system that NASA proposed to the Soviets during a November 1971 meeting in Moscow
After the June meetings, Johnson had put Bill Creasy and his mechanical designers to work on the preliminary design of a docking mechanism.[5] By the time the NASA delegation left for Moscow, Creasy's crew had designed and built a 1-meter double ring and cone docking system that had four guide fingers and attenuators on both rings, so either half could be active or passive during docking.[5] The Structures and Mechanics Laboratory at MSC made 16-millimeter movies demonstrating this system in action, which Johnson took to Moscow in November, along with a booklet describing the system and a model of the capture latches.[5] To Johnson's surprise, Vladimir Syromyatnikov had been working on a variation of NASA's ring and cone concept since the previous October.[5] Instead of the four guide fingers in the American proposal, Syromyatnikov suggested three, and in lieu of hydraulic shock-absorbers, he proposed electromechanical attenuators.[5] In essence, the Soviets had accepted the idea of using a set of intermeshing fingers to guide the two halves of the docking gear from the point of initial contact to capture.[5] The concept of using shock absorbing attenuators on the active spacecraft's capture ring to buffer the impact of two spacecraft coming together was also acceptable.[5] Both groups of engineers planned to retract the active half of the docking gear using an electrically powered winch to reel in a cable.[5] Once retracted, structural or body latches would be engaged to lock the two ships together. Three basic issues had to be resolved— the number of guides, the type of attenuators, and the type of structural latches— before the design of a universal system could proceed.[5]
Johnson, Creasy, and the other engineers in the Spacecraft Design Division had wanted to use four guides because they believed that it provided the best geometry when using hydraulic attenuators.[5] As Bill Creasy subsequently explained it, the most probable failure situation using hydraulic attenuators would be a leak that would cause one shock absorber to collapse on impact.[5] A study of various combinations had led the MSC specialists to conclude that four guides and eight shock absorbers was the optimum design.[5] Creasy pointed out too that the most likely trouble with an electromechanical system would be a freeze-up or binding of one of the pairs of attenuators.[5] Thus, the Soviets had sought to minimize the number of pairs in their system for the same reason that the Americans had preferred a larger number to limit the probability of something going wrong.[5]
Since the United States had no significant engineering or hardware equity in its proposed design, and since the USSR had considerable equity in its proposed design, the Soviet design was selected as a baseline for the next phase of study.[5]
By the end of the November–December meeting, the two teams had signed a set of minutes outlining the basic concept for a universal androgynous docking system.[5] The formal statement read, "The design concept includes a ring equipped with guides and capture latches that were located on movable rods which serve as attenuators and retracting actuators, and a docking ring on which are located peripheral mating capture latches with a docking seal."[5] Basic information on shapes and dimensions of the guides were also included in the minutes.[5] They were to be solid and not rodlike; as first proposed by the Soviets, and three in number.[5] As long as the requirement for absorbing docking forces was met, each side was free to execute the actual attenuator design as it best saw fit.[5] The Soviets planned to use an electromechanical approach designed for the Soyuz docking probe, and the Americans proposed to stick with hydraulic shock absorbers similar to those used on the Apollo probe.[5] This proposal also called for developing docking gear that could be used in either an active or passive mode; when one ship's system was active, the other would be passive.[5]
Looking into the detailed design of the mechanism, the two sides had further agreed that the capture latches would follow the design developed at MSC and the structural latches and ring would follow the Soviet pattern.[5] These paired sets of hooks had been successfully used on both Soyuz and Salyut.[5] In addition, the group concurred on details regarding the alignment pins, spring thrusters (to assist in the separation of the spacecraft at undocking), and electrical connector locations.[5] To evaluate the docking system concept and to ensure the establishment of compatibility at an early point in the development, the men planned to build a two-fifths-scale test model, the exact details of which would be decided at the next joint meeting.[5]
Upon his return to Houston, Caldwell Johnson prepared a memorandum to document some of the informal understandings reached in Moscow.[5] He indicated that this reflected "upon the manner in which the two countries will conduct and coordinate the next phase of the engineering studies of those systems... The understandings... were reached more often than not outside of formal meetings, and so are not likely otherwise to be reported."[5] For example, in the area of hatch diameter, he noted that "it became apparent from the beginning... that a hatch diameter greater than about 800 mm could not be incorporated into the Salyut spacecraft without great difficulty," but MSC had "long since reconciled itself" to a test hatch diameter of less than 1 meter.[5] Johnson went on to comment that "the capture ring assembly had variously been called ring and cone, double ring and cone, and ring and fingers.[5] It was agreed henceforth to call the capture ring 'ring' and the fingers 'guides.'"[5]
Bill Creasy and several of his colleagues worked with Yevgeniy Gennadiyevich Bobrov at the drafting table to lay out these first Soviet-American engineering drawings.[10] Larry Ratcliff drew the capture ring and guides on drafting paper, and Robert McElya supplied the details of the structural interface ring, while Bobrov prepared a similar drawing for the structural latches.[10] T.O. Ross then took these drawings and conducted a dimensional analysis to be sure that all items were compatible.[10] Agreement on technical specifications for the docking system cleared the way for NASA to begin discussions with Rockwell about building the docking system.[10]
In April 1972, the Soviets informed NASA that they had chosen to use a Soyuz spacecraft in place of a Salyut space station for cost and technical reasons.[4]
Final official approval of a joint docking mission came in Moscow on 24 May 1972. U.S. President Nixon and U.S.S.R. Premier Aleksey N. Kosygin signed the Agreement Concerning Cooperation in the Exploration and Use of Outer Space for Peaceful Purposes, including development of compatible spacecraft docking systems to improve safety of manned space flight and to make joint scientific experiments possible.[8] The first flight to test the systems was to be in 1975, with modified Apollo and Soyuz spacecraft.[8] Beyond this mission, future crewed spacecraft of the two nations were hoped to be able to dock with each other.[8]
Scale prototypes were constructed to help assist in development
In July 1972, the group concentrated on spelling out more fully specifications for the docking system.[11] Some refinements were made in the guides and other parts of the mechanism; as with the other groups, a schedule for the upcoming months was written, indicating documents to be prepared and tests to be conducted.[11] After the team had a thorough look at the American two-fifths-scale docking system, which helped the designers discuss the operation of the mechanism and decide on refinements, they scheduled joint model tests for December.[11] Then the engineers would be able to see just how the interfacing elements of one country's system mated with those of the other.[11] The Soviets said they would draft the "Test Plan for Scale Models of Apollo/Soyuz Docking System" (IED 50003), while the Americans drew up the dimensions of the model and the test fixtures.[11]
Under the direction of Syromyatnikov, the Soviet team had readied their documentation in both English and Russian and had prepared their two-fifths-scale model of the docking system for the joint meeting.[12] Some of the Americans observed that while the U.S.S.R. mechanism was more complex mechanically than the American one, it was suitable for the mission and "sophisticated" in its execution.[12] The two sides reviewed and signed the two-fifths-model test plan and scheduled the test for December in Moscow.[12]
The Preliminary Systems Review (PSR) was planned to be a "formal configuration review... initiated near the end of the conceptual phase, but prior to the start of detail design" work on the docking mechanism.[12] As part of their presentation to the Preliminary Systems Review Board (the Board being the Technical Directors), Don Wade and Syromyatnikov included all the test data, specifications, and drawings for the docking system, as well as a design evaluation for the mechanism. After hearing their report, Lunney and Bushuyev felt three problem areas needed further study.[12] First, the requirement for a spring thruster designed to help separate the two spacecraft had caught their attention, since the failure of this thruster to compress properly could prevent completion of docking.[12] Second, Lunney and Bushuyev emphasized the importance of an indicator that would verify that the structural latches were properly in place.[12] The American system provided information on the functioning of each latch but did not indicate that the interface seals were compressed, while the Soviet system gave data on compression of the seals but none for the latches.[12] To assure the structural integrity of the transfer tunnel, it was important to know that all eight latches were closed.[12] The third problem area was whether it was possible for the structural latches be inadvertently released.[12] Bushuyev and Lunney called for a thorough re-evaluation of all these issues and advised the group to present their specific recommendations to them in December and January.[12]
The group tests of the two-fifths-scale model and the second part of the Preliminary Systems Review for the docking system was the last joint activity scheduled for 1972.[13] The Americans arrived in Moscow on December 6 and worked through December 15.[13] Testing the scale models occurred at the Institute of Space Research in Moscow.[13]
Tests of the full-scale Soviet and American docking systems began in Houston during October 1973.[14]
APAS-89
Passive
Active
When the USSR started working on Mir they were also working on the Buran shuttle program. APAS-89 was envisioned to be the docking system for Buran with the Mir space station. The APAS-75 design was heavily modified. The outer diameter was reduced from 2030mm to 1550mm and the alignment petals were pointed inward instead of outward. This limited the internal passage diameter of the docking port to about 800mm.[15] The Buran shuttle was finally canceled in 1994 and never flew to the Mir space station, but Mir's Kristall module was outfitted with two APAS-89 docking mechanisms. The Mir Docking Module, basically a spacer module between Kristall and the Shuttle, also used APAS-89 on both sides.
APAS-95
Passive (the geometry of the mating and latching features are still androgynous, but this variant is intended to reduce docking impact with additional position control on one side. either side can still be used together with either side, but mating two active sides would be unnecessary)
Active
APAS was selected for the Shuttle-Mir program and manufactured by Russian company RKK Energiya under a $18 million contract signed in June 1993.[16] Rockwell International, prime contractor for the Shuttle, accepted delivery of hardware from Energiya in September 1994[16] and integrated it onto Space Shuttles' Orbiter Docking System, an add-on that was installed in the payload bay and was originally meant for use with Space Station Freedom.
Although Energia's code for the Shuttle APAS is APAS-95, it has been described as being basically the same as APAS-89.[17] It had a mass of 286kg.[16]
APAS-95 was selected to join the American and Russian modules on the International Space Station (ISS) and to allow the Space Shuttle to dock. The Shuttle's Orbiter Docking System remained unchanged from when it was used for the Shuttle–Mir Program in 1995. The active capture ring that extends outward from the spacecraft captured the passive mating ring on the space station's APAS-95 connection on the Pressurized Mating Adapter. The capture ring aligned them, pulled them together and deployed 12 structural hooks, latching the two systems with an airtight seal. The Pressurized Mating Adapters are permanently passive.
ASA-G/ASP-G
Passive (the geometry of the berthing and latching features are non-androgynous)
Active
It is used only by Nauka Science (or Experiment) Airlock, to berth to nauka forward port on 4 May 2023, 01:00 UTC during VKD-57 spacewalk. The non-androgynous berthing mechanism is a unique hybrid derivative the Russian APAS-89/APAS-95 system as it has 4 petals instead of 3 along with 12 structural hooks and is a combination of an active "probe and drogue" soft-dock mechanism on port and passive target on airlock.[18]
Mir was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. Mir was the first modular space station and was assembled in orbit from 1986 to 1996. It had a greater mass than any previous spacecraft. At the time it was the largest artificial satellite in orbit, succeeded by the International Space Station (ISS) after Mir's orbit decayed. The station served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, physics, astronomy, meteorology, and spacecraft systems with a goal of developing technologies required for permanent occupation of space.
Apollo–Soyuz was the first crewed international space mission, carried out jointly by the United States and the Soviet Union in July 1975. Millions of people around the world watched on television as a United States Apollo spacecraft docked with a Soviet Soyuz capsule. The project, and its handshake in space, was a symbol of détente between the two superpowers during the Cold War.
Soyuz 16 was a December, 1974, crewed test flight for a joint Soviet-United States space flight which culminated in the Apollo–Soyuz mission in July 1975. The two-man Soviet crew, Anatoly Filipchenko and Nikolai Rukavishnikov, tested a docking ring and other systems to be used in the joint flight.
The Apollo command and service module (CSM) was one of two principal components of the United States Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functioned as a mother ship, which carried a crew of three astronauts and the second Apollo spacecraft, the Apollo Lunar Module, to lunar orbit, and brought the astronauts back to Earth. It consisted of two parts: the conical command module, a cabin that housed the crew and carried equipment needed for atmospheric reentry and splashdown; and the cylindrical service module which provided propulsion, electrical power and storage for various consumables required during a mission. An umbilical connection transferred power and consumables between the two modules. Just before reentry of the command module on the return home, the umbilical connection was severed and the service module was cast off and allowed to burn up in the atmosphere.
Soyuz TM-16 was the sixteenth expedition to the Russian Space Station Mir.
Soyuz TM-22 was a Soyuz spaceflight to the Soviet space station Mir. It launched from Baikonur Cosmodrome Launch Pad 1 on September 3, 1995. After two days of free flight, the crew docked with Mir to become Mir Principal Expedition 20 and Euromir 95. Mir 20 was a harbinger of the multinational missions that would be typical of the International Space Station. After 179 days, 1 hour and 42 minutes on orbit, Reiter obtained the record for spaceflight duration by a Western European.
A space rendezvous is a set of orbital maneuvers during which two spacecraft, one of which is often a space station, arrive at the same orbit and approach to a very close distance. Rendezvous requires a precise match of the orbital velocities and position vectors of the two spacecraft, allowing them to remain at a constant distance through orbital station-keeping. Rendezvous may or may not be followed by docking or berthing, procedures which bring the spacecraft into physical contact and create a link between them.
Kosmos 638 was an uncrewed test of the 1975 Apollo–Soyuz Test Project Soyuz. It carried an APAS-75 androgynous docking system.
Glynn Stephen Lunney was an American NASA engineer. An employee of NASA since its creation in 1958, Lunney was a flight director during the Gemini and Apollo programs, and was on duty during historic events such as the Apollo 11 lunar ascent and the pivotal hours of the Apollo 13 crisis. At the end of the Apollo program, he became manager of the Apollo–Soyuz Test Project, the first collaboration in spaceflight between the United States and the Soviet Union. Later, he served as manager of the Space Shuttle program before leaving NASA in 1985 and later becoming a vice president of the United Space Alliance.
Vladimir Sergeevich Syromyatnikov was a Soviet and Russian space scientist best known for designing docking mechanisms for crewed spacecraft; it was his Androgynous Peripheral Attach System which, in the 1970s, linked the Soviet and American space capsules in the Apollo-Soyuz test flight.
The NASA Docking System is NASA's implementation of the International Docking System Standard (IDSS), an international spacecraft docking standard promulgated by the International Space Station Multilateral Coordination Board. NDS is a spacecraft docking and berthing mechanism used on the International Space Station (ISS) and the Boeing Starliner and planned to be used on the Orion spacecraft. The international Low Impact Docking System (iLIDS) was the precursor to the NDS. NDS Block 1 was designed and built by The Boeing Company in Houston, TX. Design qualification testing took place through January 2017.
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. All three of the PMAs are now used to permanently connect parts of the ISS, so they are no longer available as docking ports for visiting spacecraft.
Soyuz 7K-OK was the first generation of Soyuz spacecraft and was flown between 1967 and 1971. The 7K-OK was used for the first ferry flights to the Salyut space station program, beginning a long history of space station service that continues today with the International Space Station (ISS).
The 1975 Apollo–Soyuz Test Project version of the Soyuz spacecraft served as a technological bridge to the third generation Soyuz-T spacecraft (1976–1986).
Docking and berthing of spacecraft is the joining of two space vehicles. This connection can be temporary, or partially permanent such as for space station modules.
The docking mechanism of the Apollo was a "probe and drogue" system designed to allow the Apollo Command/Service Module (CSM) to dock with the Apollo Lunar Module. The same system was later used for the Skylab 2, Skylab 3 and Skylab 4 CSMs to dock with the Skylab space station, and the Apollo–Soyuz Test Project CSM to dock with a Docking Module adapter which allowed docking with the Soyuz 19 spacecraft. There were 12 hard latches.
The International Docking System Standard (IDSS) is an international standard for spacecraft docking adapters. It was created by the International Space Station Multilateral Coordination Board, on behalf of the International Space Station partner organizations; NASA, Roscosmos, JAXA, ESA, and the Canadian Space Agency.
Sistema Stykovki i Vnutrennego Perekhoda, SSVP is a docking standard used by Soviet and Russian spacecraft, sometimes called RDS for Russian Docking System. It has been used on all variants of Soyuz other than the Soyuz 7K-L3 and early flights of the Soyuz 7K-OK, as well as Progress, TKS, ATV, and on all Soviet and Russian space stations.
Soyuz Kontakt(Soyuz Contact) was the docking hardware of the Soviet crewed spacecraft program. The Soviet lunar human program was canceled in 1974 after many failures. Four failures of the N-1 Rocket super heavy-lift launch vehicle and the success of the U.S. Apollo program ended the Soviet crewed moon program.
↑ Bart Hendrickx; Bert Vis (2007). Energiya-Buran: The Soviet Space Shuttle. Chichester, UK: Praxis Publishing Ltd. pp.379–381. ISBN978-0-387-69848-9. Although Energiya's internal designator for the Shuttle APAS is APAS-95, it is essentially the same as Buran's APAS-89
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