chamber RD-170. Its derivative, the RD-171, was 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. The RD-181, based on the RD-191, is used on the Antares rocket. In August 2016, Roscosmos announced conceptual plans 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 rendezvous. Tests of RD-171MV engine, an updated version of the engine used in Energia, were completed in September 2021 and may potentially be used in the successor Soyuz-5 rocket. Proposed variants Three major design variants were conceptualized after the original configuration, each with vastly different payloads. Energia M The Energia M was an early-1990s design configuration, and the smallest of the three. The number of Zenit boosters was reduced from four to two, and instead of four RD-0120 engines in the core, it was to have had only one. It was designed to replace the Proton rocket, but lost a 1993 competition to the Angara rocket. A non-functional prototype ("structural test vehicle") of the Energia M still exists in a seemingly abandoned hangar at Baikonur Cosmodrome. Energia-2 (Uragan) Energia-2, named Uragan (, Hurricane), was a rocket design proposed in the late 1980s to be fully reusable with the capability to land on a conventional airfield. Unlike the Energia-Buran, which was planned to be semi-reusable (like the U.S. Space Shuttle), the Uragan concept was to have allowed the complete recovery of all Buran/Energia elements, like 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. Vulkan The final never-built design concept 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) configuration was initially projected to launch up to 200 metric tonnes into 200 km orbit with inclination 50.7°. The development of rocket-carrier