RD-108

RD-108. It is a liquid-propellant rocket engine developed in the Soviet Union by the design bureau OKB-456, led by chief designer Valentin Glushko. The engine was developed as a sustainer powerplant for the first stage of the R-7 Semyorka, the world's first intercontinental ballistic missile, and its derivative launch vehicles. Characterized by its four combustion chambers and vernier engines for thrust vector control, it has been a cornerstone of the Soviet space program and its successor, the Russian space program, for over six decades.

Design and development

The design originated from the late 1940s and early 1950s as part of the Cold War competition with the United States. Under the direction of Sergei Korolev at OKB-1, the R-7 required a powerful, reliable engine cluster. Valentin Glushko's team at OKB-456 was tasked with its creation, building upon earlier work with nitric acid and kerosene propellants but ultimately selecting the more efficient combination of liquid oxygen and kerosene. A key innovation was the use of four main combustion chambers fed by a single turbopump assembly, a design choice that enhanced reliability and simplified development compared to a single large chamber. The engine also incorporated two vernier engines for precise thrust vector control, as the main chambers were mounted in a fixed position. This development was supported by extensive testing at facilities like the Scientific Research Institute of Chemical Machine Building.

Technical specifications

The engine operates on a Gas-generator cycle, using liquid oxygen as the oxidizer and a refined form of kerosene known as RG-1 as the fuel. At sea level, it produces a thrust of approximately 941 kilonewtons, with a specific impulse of 257 seconds. Each of its four main combustion chambers operates at a chamber pressure of around 5.85 MPa. The engine is controlled by the KORD system, which monitors its performance. For attitude control and roll control during flight, it relies on the four smaller vernier engines, which are integral to the assembly. The turbopump is driven by a gas generator that burns a small portion of the main propellants.

Operational history

The engine first flew on 15 May 1957, powering the ill-fated maiden launch of the R-7 Semyorka. Its first successful flight occurred later that year, demonstrating the ICBM's capability. Its most historic operational use was on 4 October 1957, when it launched Sputnik 1, the world's first artificial satellite, from Baikonur Cosmodrome. This event marked the beginning of the Space Race. The engine subsequently launched numerous milestone missions, including Vostok 1 carrying Yuri Gagarin, the first human in space. It has served as the core propulsion for the entire R-7 rocket family, including the Vostok, Voskhod, Molniya, and Soyuz launch vehicles. Launches continue from Baikonur Cosmodrome and Guiana Space Centre.

Variants and derivatives

Several improved variants have been developed to increase reliability and performance. The RD-108A, introduced in the 1960s, featured minor improvements for the Voskhod and Soyuz rockets. A significant derivative is the RD-107, which is nearly identical but functions as a strap-on booster engine for the R-7 family, with slight differences in its vernier engine configuration and mounting. The basic design philosophy also influenced later Energomash engines, such as those in the Zenit rocket family. Modernized versions, sometimes designated for specific Soyuz-2 rocket models, incorporate updated materials and manufacturing techniques while retaining the core architecture.

See also

* RD-107 * R-7 Semyorka * Soyuz (rocket) * Valentin Glushko * Sergei Korolev * Liquid oxygen * Kerosene * Baikonur Cosmodrome * Sputnik 1

Category:Rocket engines Category:Soviet inventions Category:Spacecraft propulsion