he "Soyuz"   premiered in 1963. The two-and-one-half-stage launch vehicle burns simple liquid oxygen and a form of kerosene. The first stage consists of a core vehicle powered by a 11D512 (RD-108) main engine (one turbopump with four separate combustion chambers) burning LO2/kerosene fed from stage 1 tanks, generating 167,000 lb of thrust,  and four strap-on boosters with 11D511(RD-107) main engines (one turbopump with four separate combustion chambers) burning LO2/kerosene fed from stage 1 tank, generating a total of 740,000 lb of thrust. The second stage carries a single, 4-nozzle 11D55 (RD-110) main engine burning LO2/kerosene, generating 67,000 lb of thrust. The "Soyuz" Block I provides a considerable increase over Vostok's payload capability to LEO.

Since 1964 all Soviet and Russian human missions have relied on the "Soyuz", but the largest program it supports involves military and civilian recoverable photographic reconnaissance flights. Significant upgrades to the vehicle took place in 1973 and 1982. It is used today for launching manned "Soyuz" spacecraft, "Progress" cargo spacecraft, and biological research satellites, as well as "Kosmos" observation satellites. It also launched the "Voskhod" manned spacecraft. Although the "Soyuz"-class boosters have remained essentially unchanged in external appearance since their inception, their systems have been subjected to a constant stream of modifications over the years. In addition, subtle differences exist between superficially identical components. For example, the basic core stage and strap-on boosters may vary slightly from vehicle to vehicle in such details as propellant loading and main engine thrust, depending on the vehicle version and mission application. "Soyuz" can also employ a number of different payload fairings depending on the mission at hand. The "Soyuz"-class launch vehicles, until recently, have exclusively used LOX and kerosene propellants in all stages. However, this is changing with the recent introduction of the "Ikar" and, soon, "Fregat" upper stages, both of which use UDMH/N2O4 propellant.