The RD-180 () is a rocket engine designed and built in Russia. It features a dual combustion chamber, dual-nozzle design and is fueled by a RP-1/LOX mixture. The RD-180 is derived from the RD-170/RD-171 line of rocket engines, which were used in the Soviet Energia launch vehicle and are still in use in the Ukrainian Zenit launch vehicles. RD-180 engines are also used for the first stage of the American Atlas V launch vehicle, which is being phased out due to the national security implications of being reliant on foreign parts which became of concern after the Russian invasion of Crimea. , Russian supplies and maintenance have been discontinued as the result of trade sanctions caused by the 2022 Russian invasion of Ukraine. History The roots of the RD-180 rocket engine extend back into the Soviet Energia launch vehicle project. The RD-170, a four-chamber engine, was developed for use on the strap-on boosters for this vehicle, which ultimately was used to lift the Buran orbiter. This engine was scaled down to a two-chamber version by combining the RD-170's combustion devices with half-size turbomachinery. After successful performances in engine tests on a test stand and high-level agreements between the US government and the Russian government, the engines were imported to the US for use on the Lockheed Martin Atlas III, with first flight in 2000. The engine is also used on the United Launch Alliance Atlas V, the successor to the Atlas III. The engine has similar design features to the NK-33, which was developed by a different bureau (Kuznetzov) nearly a decade prior. 2014–2015 availability concerns Doubts about the reliability of the supply chain for the RD-180 arose following the Russian military intervention in Ukraine in March 2014. For over 13 years since the engine was first used in the Atlas III launch vehicle in 2000, there was never any serious jeopardy to the engine supply, despite an uneven record of US–Russian relations since the Cold War. But worsening relations between the West and Russia after March 2014 have led to several self inflicted blockages, including a short-lived judicial injunction from the US courts that were unclear on the scope of the US sanctions on importing the Russian engine. On 13 May 2014, Russian Deputy Prime Minister Dmitry Rogozin announced that "Russia will ban the United States from using Russian-made rocket engines for military launches"—a frequent payload of the ULA