Apollo–Soyuz

Apollo-Soyuz was the first crewed internationalspace mission, carried out jointly by theUnited Statesand theSoviet Unionin July 1975. Millions of people around the world watched on television as an AmericanApollospacecraftdockedwith a SovietSoyuzcapsule. The project, and its "handshake" in space, was a symbol ofdétentebetween the two superpowers amid theCold War.
The Americans officially called the mission theApollo–Soyuz Test Project(ASTP) while the Soviets called itExperimental flight "Soyuz"–"Apollo"(Russian:Экспериментальный полёт «Союз»–«Аполлон»,romanized:Eksperimentalniy polyot "Soyuz"–"Apollon") andSoyuz 19. The unnumbered American spacecraft was left over fromcanceled Apollo missionsand was the last Apollo module to fly.
The mission consisted of three American astronauts (Thomas P. Stafford,Vance D. Brand, andDeke Slayton) and two Soviet cosmonauts (Alexei LeonovandValery Kubasov) who performed both joint and separate scientific experiments, including an arrangedeclipse of the Sunby the Apollo module to allow instruments on the Soyuz to take photographs of thesolar corona. The pre-flight work provided useful experience for later joint American–Russian space flights, such as theShuttle–Mirprogramand theInternational Space Station.
Apollo–Soyuz was the last crewed United States spaceflight for nearly six years untilthe first launchof theSpace Shuttleon 12 April 1981, and the last crewed United States spaceflight in aspace capsuleuntilCrew Dragon Demo-2on 30 May 2020.
The purpose and catalyst of Apollo–Soyuz was the policy ofdétentebetween the twoCold Warsuperpowers: the United States and the Soviet Union. Tensions ran high between the two world superpowers while the United States was engaged in theVietnam War. Meanwhile, the Soviet press was highly critical of the Apollo space missions, printing "the armed intrusion of the United States andSaigonpuppets intoLaosis a shameless trampling underfoot of international law" over a photograph of theApollo 14launch in 1971.Although Soviet leaderNikita Khrushchevmade the Soviet Union's policy of détente official in his 1956 doctrine of peaceful coexistence at the20th Congress of the Communist Party of the Soviet Union, the two nations seemed to be in perpetual conflict.
AfterJohn Glenn's 1962orbital flight, an exchange of letters between PresidentJohn F. Kennedyand Soviet PremierNikita Khrushchevled to a series of discussions led by NASA Deputy AdministratorHugh Drydenand Soviet scientistAnatoly Blagonravov. Their 1962 talks led to theDryden-Blagonravov agreement, which was formalized in October of that year, the same time the two countries were in the midst of theCuban Missile Crisis. The agreement was formally announced at the United Nations on 5 December 1962. It called for cooperation on the exchange of data from weather satellites, a study of theEarth's magnetic field, and joint tracking of the NASAEcho II balloon satellite.Kennedy interested Khrushchev in a joint crewedMoon landing,but after the assassination of Kennedy in November 1963 and Khrushchev's removal from office in October 1964, the competition between the two nations' crewed space programs heated up, and talk of cooperation became less common, due to tense relations and military implications.
On 19 April, 1971, the USSR launched the first piloted orbital space station,Salyut 1. Meanwhile, the United States had launched theApollo 14mission several months prior, the third mission to land on the Moon. Each side gave the other little coverage of their achievements.
With the close of theVietnam War, relations between the United States and the USSR began to improve, as did the prognosis for a potential cooperative space mission.Apollo–Soyuz was made possible by the thaw in these relations, and the project itself endeavoured to amplify and solidify the improving relations between the United States and the Soviet Union. According to Soviet leaderLeonid Brezhnev:
Thus, both sides recognized ASTP as a political act of peace.
In October 1970,Soviet Academy of SciencespresidentMstislav Keldyshresponded toNASA AdministratorThomas O. Paine's letter proposing a cooperative space mission, and there was subsequently a meeting to discuss technical details. At a meeting in January 1971, U.S. PresidentRichard Nixon's Foreign Policy AdviserHenry Kissingerenthusiastically espoused plans for the mission, and expressed these views to NASA administratorGeorge Low: "As long as you stick to space, do anything you want to do. You are free to commit—in fact, I want you to tell your counterparts in Moscow that the President has sent you on this mission".
Both sides had severe criticisms of the other side's engineering. Soviet spacecraft were designed with automation in mind; theLunokhod 1andLuna 16were both uncrewed probes, and eachSoyuz spacecrafthad been designed to minimize risk due to human error by having fewer manual controls with which human operators would have to contend during flight. By contrast, the Apollo spacecraft was designed to be operated by humans and required highly trained astronauts to operate. The Soviet Union criticized the Apollo spacecraft as being "extremely complex and dangerous".
The Americans also had their own concerns about Soviet spacecraft.Christopher C. Kraft, director of theJohnson Space Center, criticized the design of the Soyuz:
The American astronauts had a very low opinion for the Soyuz spacecraft as it was a craft that was designed to be controlled from the ground. This was in stark contrast with the  Apollo module that was meant to be flown from the capsule. EventuallyGlynn Lunney, the Manager of the Apollo–Soyuz Test Program, warned them about talking to the press about their dissatisfaction as they had offended the Soviets.NASA was worried that any slight would cause the Soviets to pull out and the mission to be scrapped.
American and Soviet engineers settled their differences for a possible docking of American and Soviet spacecraft in meetings between June and December 1971 inHoustonandMoscow, including Bill Creasy's design of theAndrogynous Peripheral Attach System(APAS) between the two ships that would allow either to be active or passive during docking.
By April 1972, both the United States and the USSR signed anAgreement Concerning Cooperation in the Exploration and Use of Outer Space for Peaceful Purposes,committing both the USSR and the United States to the launch of the Apollo–Soyuz Test Project in 1975.
ASTP was particularly significant for the USSR's policy of keeping the details of their space program secret from the Soviet people and the world at large, especially Americans. The ASTP was the first Soviet space mission to be televised in a live fashion during the launch, while in space, and during the landing.Soyuz 19 was also the first Soviet spacecraft to which a foreign flight crew had access before flight; the Apollo crew were permitted to inspect it and the launch and crew training site, which was an unprecedented sharing of information with Americans about any Soviet space program.
Not all reactions to ASTP were positive. Many Americans fearedthat ASTP was giving the USSR too much credit in their space program, putting them on equal footing with the sophisticated space exploration efforts of NASA. More feared that the apparent peaceful cooperation between the USSR and the United States would lull people into believing there was no conflict at all between the two superpowers.Some Soviet publicists called American critics of the mission "demagogues who stand against scientific cooperation with theUSSR".In general, tensions between the United States and the USSR had softened, and the project set a precedent for future cooperative projects in space.
It was American astronautDeke Slayton's only space flight. He was chosen as one of the originalMercury Sevenastronauts in April 1959, but had been grounded until 1972 for medical reasons.
Jack Swigerthad originally been assigned as the command module pilot for the ASTP prime crew, but he was removed before the official announcement as punishment for his involvement in theApollo 15 postal covers incident.
It was the last space mission for Soviet cosmonautAlexei Leonov, who had become the first person towalk in spaceduring the March 1965Voskhod 2mission.
The ASTP entailed the docking of an AmericanApollo command and service module(CSM) with a SovietSoyuz 7K-TMspacecraft. Although the Soyuz was given a mission designation number (Soyuz 19) as part of the ongoingSoyuz programme, its radio call sign was simply "Soyuz" for the duration of the joint mission. The Apollo mission was not a numbered mission of theApollo program, and similarly bore the call sign "Apollo." Despite this, the press and NASA have referred to the mission as "Apollo 18," but this should not be confused with thecanceled lunar mission.
The Apollo spacecraft was launched with a docking module specially designed to enable the two spacecraft to dock with each other, used only once for this mission. TheSaturn IBlaunch vehicle andCSMwere surplus material. Like theApollo Lunar Module, the docking modulehad to be retrievedfrom theS-IVBupper-stage of theSaturn IBrocket after launch. The docking module was designed as both an airlock — as the Apollo was pressurized at about 5 psi (34 kPa) usingpure oxygen, while the Soyuz used anitrogen/oxygenatmosphere atsea level pressure(about 15 psi (100 kPa)) — and an adapter, since the surplus Apollo hardware used for the ASTP mission was not equipped with theAPASdocking collar jointly developed byNASAand theAcademy of Sciences of the Soviet Unionfor the mission. One end of the docking module was attached to the Apollo using the same "probe-and-drogue" docking mechanism used on the Lunar Module and theSkylabspace station, while its other end had the APAS docking collar, which Soyuz 19 carried in place of the standard Soyuz/Salyut system of the time. The APAS collar fitted onto Soyuz 19 was releasable, allowing the two spacecraft to separate in case of malfunction.
The Apollo flew with a three-man crew on board:Tom Stafford,Vance Brand, andDeke Slayton. Stafford had already flown into space three times, including within eightnautical milesof the lunar surface as Commander ofApollo 10, and was the firstgeneral officerto fly into space. He was abrigadier generalin theUnited States Air Forceat the time of the flight; he would retire with three stars in 1979. Slayton was one of the originalMercury Sevenastronauts selected in 1959, but an irregular heartbeat grounded him until 1972. He became head of NASA's astronaut office and, after a lengthy medical program, selected himself for this mission. At the time, Slayton was the oldest person to fly in space and the one with the longest gap between selection as an astronaut and first flight into space. Brand, meanwhile, had trained with the Apollo spacecraft during his time as a backupApollo 15command module pilot, and had served two stints as a backup Skylab commander. The closest he had come to flying prior to ASTP was as commander for theSkylab Rescuemission mustered to potentially retrieve the crew ofSkylab 3due to a fuel leak on that mission's Apollo CSM.
The Soyuz flew with two men:Alexei LeonovandValery Kubasov. Leonov became the first man towalk in spaceonVoskhod 2in March 1965. Kubasov, who flew onSoyuz 6in 1969, ran some of the earliestspace manufacturingexperiments. Both were to have flown on the ill-fatedSoyuz 11in 1971 (Leonov as commander, Kubasov as the flight engineer), but were grounded because Kubasov was suspected of havingtuberculosis. The two-man crew on the Soyuz was a result of the modifications needed to allow the cosmonauts to wear theSokol space suitduring launch, docking, and reentry.
The ASTP-classSoyuz 7K-TMspacecraft used was a variation of the post-Soyuz 11 two-man design, with the batteries replaced bysolar panelsenabling "solo" flights (missions not docking to one of theSalyutspace stations). It was designed to operate, during the docking phase, at a reduced nitrogen/oxygen pressure of 10.2 psi (70 kPa), allowing easier transfers between the Apollo and Soyuz. Six ASTP-class Soyuz spacecraft were built in total, including the one used. Before the actual mission, two craft were launched uncrewed as Kosmos satellites. The third was launched as the crewedSoyuz 16flight as a rehearsal in order to test the APAS docking mechanism. Another craft was used fully fueled as a "hot backup" at the launch site – later it was disassembled. And the sixth craft was available as a "cold" backup; it was later used on thelast "solo" Soyuz flightin 1976, but with the APAS docking adapter replaced by theMKF-6multispectral camera.
The Soyuz and Apollo flights launched within seven-and-a-half hours of each other on 15 July 1975, and docked on 17 July 1975. Three hours later, the two mission commanders, Stafford and Leonov, exchanged the first international handshake in space through the open hatch of the Soyuz. NASA had calculated that the historic handshake would have taken place over the British seaside resort ofBognor Regis,but a delay resulted in its occurrence being over the city ofMetzin France.During the first crew exchange, the crews were read a statement from SovietGeneral SecretaryLeonid Brezhnev, and received a phone call fromU.S. PresidentGerald Ford.
While the two ships were docked, the three Americans and two Soviets conducted joint scientific experiments, exchanged flags and gifts (including tree seeds which were later planted in the two countries), listened to each other's music (examples include "Tenderness" byMaya Kristalinskayaand "Why Can't We Be Friends?" byWar), signed certificates, visited each other's ships, ate together, and conversed in each other's languages. (Because of Stafford's pronounced drawl when speaking Russian, Leonov later joked that there were three languages spoken on the mission: Russian, English, and "Oklahomski".) There were also docking and redocking maneuvers, during which the two spacecraft reversed roles and the Soyuz became the "active" ship.
American scientists developed four of the experiments performed during the mission. EmbryologistJane Oppenheimeranalyzed the effects of weightlessness on fish eggs at various stages of development.
After 44 hours together, the two ships separated, and maneuvered to use the Apollo to create an artificialsolar eclipseto allow the crew of the Soyuz to take photographs of thesolar corona. Another brief docking was made before the ships went their separate ways. The Soviets remained in space for two more days, and the Americans for five, during which the Apollo crew also conductedEarthobservation experiments.
The mission was considered a great success, both technically and as a public-relations exercise for both nations. The only serious problem was duringreentryandsplashdownof the Apollo craft, during which the crew were accidentally exposed to toxicmonomethylhydrazineandnitrogen tetroxidefumes, caused by unignitedreaction control system(RCS)hypergolic propellantsventing from the spacecraft and reentering a cabin air intake. The RCS was inadvertently left on during descent, and the toxic fumes were sucked into the spacecraft as it drew in outside air. Brand briefly lost consciousness, while Stafford retrieved emergency oxygen masks, put one on Brand, and gave one to Slayton. The three astronauts were hospitalized for two weeks inHonolulu,Hawaii.Brand took responsibility for the mishap; because of high noise levels in the cabin during reentry, he believed he was unable to hear Stafford call off one item of the reentry checklist, the closure of two switches which would have automatically shut off the RCS and begun drogue parachute deployment. These procedures were manually performed later than usual, allowing the ingestion of the propellant fumes through the ventilation system.
The ASTP was the final flight of an Apollo spacecraft. Immediately after the launch of the Apollo spacecraft, preparations began to convertLC-39Band theVehicle Assembly BuildingatKennedy Space Centerfor use by theSpace Shuttle, the United States' next crewed spacecraft program.LC-39Ahad already been closed after the launch ofSkylab.
A derivative (but mechanically incompatible) docking collar,APAS-89, was launched as part of theKristallmodule of the SovietMirspace station. Originally intended as the docking port for the (defunct)BuranSoviet space shuttle, the APAS-89 unit was used for the next Russian-American docking mission,STS-71, twenty years later as part of theShuttle–Mir program(though not before the docking port was tested by the last APAS-equipped Soyuz,Soyuz TM-16, in 1993).
The AmericanSpace Shuttlecontinued to use the same APAS-89 docking hardware through the end of theSpace Shuttle programto dock to Mir and then theInternational Space Station, the latter through thePressurized Mating Adapters(PMAs).
The PMAs are equipped with the laterAPAS-95adapters, which differ from the APAS-89 adapters in that they are no longer androgynous; while compatible with the APAS-89 docking collars, they are not capable of acting as the "active" partner in docking.
The first PMA, PMA-1, remains in use as the interface connecting the Russian-built, NASA-ownedZaryamodule to theUS segment of the ISS(USOS), and so the APAS continues in use to this day (2024).
Apollo–Soyuz was the first joint US–Soviet space mission. At the time it was thought that space would become either more international or competitive as a result, but it became both. The mission became symbolic of each country's goals of scientific cooperation, while their news reports downplayed the technical prowess of the other. Soviet press implied that it was leading the United States in space flight, tying it to theMarxist–Leninistideology, while the United States reported that the Soyuz was technically primitive.High-profile space cooperation declined after the successful mission and became entangled inlinkage politics, but it set a precedent of cooperation that continued in theShuttle–Mir Program.
The American and Soviet commanders, Stafford and Leonov, became lasting friends. Leonov was the godfather of Stafford's younger children.Stafford gave a eulogy at Leonov's funeral in October 2019.
Anasteroid,2228 Soyuz-Apollo, discovered in 1977 by Soviet astronomerNikolai Chernykh, is named after the mission.
To commemorate Apollo–Soyuz, renowned British/Irish bartenderJoe GilmoreofThe Savoy Hotel's American Bar created the 'Link-Up' cocktail. When the astronauts were told the cocktail was being flown out from London to be enjoyed on their return, they said, "Tell Joe we want it up here".
The Apollo craft carried the SAG telescope designed to observe in theextreme ultraviolet.Across several orbits of observing the instrument discovered two ultraviolet sources; HZ 43 and FEIGE 24, both of which wereWhite dwarfs.Other stars observed included,Proxima Centauri(aRed Dwarf),SS Cygni(aBinary star), andSirius(also a Binary star). A third possible discovery was an unknown object in thePavo constellation.The star HD 192273 was later suggested as a candidate for the Pavo observation but further study concluded that the star’s distance and spectral class made this unlikely.
TheApollo command modulefrom the mission is on display at theCalifornia Science CenterinLos Angeles.The descent module of Soyuz 19 is on display at theRKK Energiya museuminKorolyov, Russia.
A display at theNational Air and Space MuseuminWashington, D.C.shows the docked Apollo/Soyuz configuration. The display is made up of the unflown Apollo Command and Service Module 105 (used for vibration testing for theSkylabprogram), the back-up Docking Module, and an unflown Soyuz spacecraft, on loan from the Russian government.
TheUnited States Postal Serviceissued theApollo–Soyuz commemorative stamps, honoring the United States–Soviet link up in space, on 15 July 1975, the day of the launch.
The remaining crew's most recent reunion was on 16 July 2010, when Leonov, Kubasov, Stafford, and Brand met at anOmegatimepiece store inNew York City. All except Leonov participated in a public roundtable that evening. Omega had produced several watches to be used on the mission.
A large Soyuz–Apollo monument was constructed outside the Soviet (now Russian)space control centerRKA Mission Control Center(Russian acronym: TsUP) inMoscow. It consisted of a metal scale model ofEarthoverarched by an arc terminating in the joined Soyuz–Apollo spacecraft. It was damaged when a vehicle collided with it in the late 1990s,and was removed for repairs.
The mission control room that hosted the Americans inKorolyov, Russia, was preserved as a memorial to the Soyuz–Apollo mission.
The United States spent US$245 million (equal to $1,390,000,000 today)on the Apollo–Soyuz project and spacecraft.
The amount of money the Soviet Union spent on the ASTP is unknown but reportedly constituted a "significant portion."