Proton (rocket family)

Proton (Russian: Протон, lit.'proton', formal designation: UR-500, GRAU: 8K82, Sheldon: D-1, DoD: SL-9/-12/-13) is a Soviet and Russian hypergolicexpendableheavy-lift launch vehicle family. Developed by the Soviet space program, its first launch was in 1965. The Proton-K flew 310 missions from 1967 to 2012; the modernized Proton-M, operational since 2001, is flown by Roscosmos for commercial and state payloads, scheduled until 2029.

Components are manufactured in the Khrunichev State Research and Production Space Center, Moscow, and Chemical Automatics Design Bureau, Voronezh, then transported to the Baikonur Cosmodrome, Kazakhstan, where they are assembled at Site 91 to form the launch vehicle. Following payload integration, the rocket is then brought to the launch pad horizontally by rail and raised into vertical position for launch. As with many Soviet rockets, the names of recurring payloads became associated with the launch vehicle itself. The moniker "Proton" originates from a series of similarly named scientific satellites, which were among the rocket's first payloads.

Launch capacity to low Earth orbit is about 22.8 tonnes (50,000 lb). Geostationary transfer capacity is about 6.3 tonnes (14,000 lb). Commercial launches are marketed by International Launch Services (ILS). During the 1970s and 1980s, Proton-K launched every interplanetary probe of the Soviet space program's Venera and Mars missions, using its Blok D fourth stage. In three-stage configuration, it launched the Zond program's circumlunar flights and all seven space stations of the Salyut program. The Soviet program also considered the Proton for launching the TKS crewed spacecraft and LKSspaceplane.

From 1986, Protons launched six of the seven modules of Mir, the first modular space station, and from 1998, launched the Zarya, Zvezda, and Nauka modules of the International Space Station's Russian Orbital Segment. Protons launched the first two generations of GLONASS satellites and various commercial satellites; the Proton-M upgrade first flew in 2001 and uses the Briz family for fourth stages.

In 2013, the rocket was intended to be retired before 2030. Since 2018, Proton has been approaching retirement; Russia's Angara A5, a replacement in the heavy-lift role, conducted four test flights and one operational flight between 2014 and 2025. No new launch service contracts for Proton are likely to be signed; its latest scheduled launches are the Science Power Module 1 to the ISS and an Ekspress satellite, both in 2029.