RD-107

RD-107. The RD-107 is a pioneering liquid-propellant rocket engine developed in the Soviet Union and remains one of the most reliable and long-lived engines in spaceflight history. Designed by the team led by Valentin Glushko at the OKB-456 design bureau, it was the primary powerplant for the R-7 Semyorka ICBM and its derivative launch vehicles. Its robust Gas-generator cycle design, using Liquid oxygen and RP-1 kerosene, has been fundamental to the Soviet space program and its successor, the Russian space program.

Development and design

The development of the engine was initiated in the early 1950s under the direction of chief designer Valentin Glushko at OKB-456 (later NPO Energomash), in response to the state requirement for a powerful ICBM. The design team, which included notable figures like Semyon Kosberg who worked on the injector systems, faced significant challenges in achieving stable combustion and reliable ignition. A key innovation was the use of four main combustion chambers with two vernier chambers for each, all fed by a single turbopump assembly, providing both primary thrust and precise flight control. This configuration was rigorously tested at facilities like the Scientific Research Institute of Chemical Machine Building (NIIkhimmash) to overcome issues of combustion instability that plagued early rocket engine designs. The successful development was a cornerstone of Sergei Korolev's R-7 Semyorka rocket family, enabling the Soviet Union to achieve major milestones in the Space Race.

Technical specifications

The engine operates on a Gas-generator cycle, where a small portion of propellant is burned in a gas generator to drive the turbopump that feeds the main combustion chambers. It uses the propellant combination of Liquid oxygen as the oxidizer and RP-1 kerosene as the fuel. At sea level, it produces a thrust of approximately 821 kilonewtons (kN) with a specific impulse of 257 seconds. The engine features four fixed main chambers and two gimbaled vernier chambers for each main unit, providing three-axis flight control without the need for complex gimbaling of the primary nozzles. The combustion chamber pressure is around 5.85 MPa. Each engine assembly, including its verniers, has a dry mass of about 1,190 kilograms. Its design emphasized simplicity and robustness, contributing to its exceptional reliability record over decades of service with Roscosmos.

Operational history

The engine first flew on 15 May 1957, powering the inaugural launch of the R-7 Semyorka, the world's first operational ICBM. Its most famous early missions included launching Sputnik 1, the first artificial satellite, on 4 October 1957, and propelling Vostok 1 with Yuri Gagarin, the first human in space, on 12 April 1961. It became the foundational engine for the entire R-7 rocket family, including the Vostok, Voskhod, and Molniya launch vehicles. For over six decades, its modernized versions have been exclusively used to launch all Soyuz spacecraft from Baikonur Cosmodrome, Plesetsk Cosmodrome, and Guiana Space Centre, as well as Progress cargo missions to the International Space Station. This unparalleled service history makes it the most-flown liquid-propellant rocket engine in history.

Variants and derivatives

The basic design has been continuously upgraded, leading to several major variants. The RD-107A, introduced in the 1960s, featured improvements to the combustion chamber and turbopump for higher performance and reliability. The RD-107AM was a further modernization used on later Soyuz-FG rockets. A closely related design is the RD-108, which powers the core stage of the R-7 family and shares the same core architecture but operates at higher altitude. Derivatives of the technology and design philosophy influenced many later Energomash engines, including those used on the Zenit rocket and elements of the Energia super-heavy lift launch vehicle. The engine's legacy continues with the RD-107A/RD-108A engines used on the current Soyuz-2 launch vehicle family.

See also

* RD-108 * R-7 Semyorka * Soyuz (rocket family) * Valentin Glushko * NPO Energomash * Liquid rocket propellant * Gas-generator cycle

Category:Rocket engines Category:Soviet inventions Category:1950s in the Soviet Union