Energia (Russian: Энергия, Energiya, "Energy") was a Soviet rocket that was designed by NPO Energia to serve as a heavy-lift expendable launch system as well as a booster for the Buran spacecraft. Control system main developer enterprise was the NPO "Electropribor". The Energia used four strap-on boosters each powered by a four-chamber RD-170 engine burning kerosene/LOX, and a central core stage with 4 one-chamber RD-0120 (11D122) engines fueled by liquid hydrogen/LOX.
The launch system had two functionally different operational variants: Energia-Polyus, the initial test configuration, in which the Polyus system was used as a final stage to put the payload into orbit, and Energia-Buran, in which the Buran spacecraft was the payload and the source of the orbit insertion impulse.
The rocket had the capacity to place about 100 tonnes in Low Earth orbit, up to 20 tonnes to geostationary orbit and up to 32 tonnes to a translunar trajectory.
Work on the Energia/Buran system began in 1976 after the decision was made to cancel the unsuccessful N1 (rocket). The cancelled N1 rocket-based Manned Lunar Launch Facilities and Infrastructure were used for Energia (notably the huge horizontal assembly building), just as NASA reused infrastructure designed for the Saturn V in the Space Shuttle program. Energia also replaced the "Vulkan" concept, which was a design based on the Proton (rocket family) and using the same hypergolic propellants, but much larger and more powerful. The "Vulkan" designation was later given to a variation of the Energia which has eight boosters and multiple stages.
The Energia was designed to launch the Russian "Buran" reusable shuttle, and for that reason was designed to carry its payload mounted on the side of the stack, rather than on the top, as is done with other launch vehicles. After design of the Energia-Buran system, it was also proposed that the booster could be used without the Buran as a heavy-lift cargo launch vehicle; this configuration was originally given the name "Buran-T". This configuration required the addition of an upper stage to perform the final orbital insertion. The first launch of the Energia was in the configuration of a heavy launch vehicle, with the large Polyus military satellite as a payload, however Polyus failed to correctly perform the orbital insertion.
Due to the termination of the Buran programme the Energia program was concluded after only two launches, and further the payload on the first launch didn't perform the final boost properly. The legacy of Energia/Buran project manifests itself most visibly in form of the RD-170 family of rocket engines, and the Zenit launcher, with the first stage roughly the same as one of the Energia first-stage boosters.
The Energia was first test-launched on 15 May 1987, with the Polyus spacecraft as the payload. A FGB ("Functional Cargo Block") engine section originally built as a cancelled Mir module was incorporated into the upper stage used to inject the payload into orbit, similarly to Buran and the US Space Shuttle performing the final orbital insertion, since the planned "Buran-T" upper stage had not yet progressed beyond the planning stage. The intended orbit was altitude 280 km (170 mi), inclination 64.6°.
The Soviets had originally announced that the launch was a successful sub-orbital test of the new Energia booster with a dummy payload, but some time later it was revealed that the flight had, in fact, been intended to orbit the Polyus, a UKSS (Russian: Универсальный Комплекс Стенд-Старт, Universal Complex Stand-Start) military payload. The two stages of the Energia launcher functioned as designed, but due to a software error in its attitude control system, Polyus' orbital insertion motor failed to inject the payload into orbit. Instead, the Polyus reentered the atmosphere over the Pacific Ocean.
The second flight, and the first one where payload successfully reached orbit, was launched on 15 November 1988. This mission launched the unmanned Soviet Shuttle vehicle, Buran. At apogee, the Buran spacecraft made a 66.7 m/s burn to reach a final orbit of 251 km x 263 km.
Production of Energia rockets ended with the fall of the Soviet Union and the end of the Buran shuttle project. Ever since, there have been persistent rumors of the renewal of production, but given the current political realities, that is highly unlikely. While the Energia is no longer in production, the Zenit boosters are still in production and in use. The four strap-on liquid-fuel boosters, which burned kerosene and liquid oxygen, were the basis of the Zenit rocket which used the same engines. The engine is the four combustion chamber RD-170. Its derivative, the RD-171, is still used on the Zenit rocket. A half-sized derivative of the engine, the two-chamber RD-180, powers Lockheed Martin's Atlas V rocket, while the single-chamber derivative, the RD-191, has been used to launch the Korean Naro-1 (as a reduced-thrust variant named the RD-151) and the Russian Angara rocket.
In August 2016, plans were announced to develop a super heavy-lift launch vehicle from existing Energia components instead of pushing the less-powerful Angara A5V project. This would allow Russia to launch missions towards establishing a permanent Moon base with simpler logistics, launching just one or two 80–160-ton super-heavy rockets instead of four 40-ton Angara A5Vs implying quick-sequence launches and multiple in-orbit rendez-vous.
Three major variants were conceptualized after the original configuration, each with vastly different payloads.
The Energia M was the smallest design configuration. The number of Zenit boosters was reduced from four to two, and instead of four RD-0120 engines in the core, it had only one. It was designed to replace the Proton rocket, but lost the 1993 competition to the Angara rocket.
Energia II, named Uragan (Russian: Ураган, Hurricane), was a rocket proposed to be fully reusable with the design feature to land on a conventional airfield. Unlike the Energia, which was planned to be semi-reusable (like that of the U.S. Space Shuttle), the Uragan concept was to have allowed the complete recovery of all Buran/Energia elements, like that of the original totally reusable Orbiter/Booster concept of the U.S. Shuttle. The Energia II core as proposed would be capable of re-entering and gliding to a landing, presumably using technology developed for the Buran.
The final unflown configuration was also the largest. With eight Zenit booster rockets and an Energia-M core as the upper stage, the "Vulkan" (which was the same name of another Soviet heavy lift rocket that was cancelled years earlier) or "Hercules" (which is the same name designated to the N-1 rockets) configuration could have launched up to 175 tonnes into orbit.
The development of rocket-carrier "Vulcan" and the refurbishment of the "Energia" launch pad for its launches was in progress in 1990-1993. But later on the work on this project was cancelled due to lack of funds and the collapse of the Soviet Union.