Atlas V is being phased out due to the national security implications of reliance on the Russian-built engine,[1] which became a concern after the Russian annexation of Crimea.

The thermodynamics of the cycle allow an oxygen-rich preburner to give a greater power-to-weight ratio, but with the drawback that high-pressure, high-temperature gaseous oxygen must be transported throughout the engine.

However, worsening relations between the West and Russia after March 2014 led to several self-imposed blockages, including a short-lived judicial injunction from the US courts that was unclear whether the scope of the US sanctions covered importing the Russian engine.

[6] 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"[7]—a frequent payload of the ULA Atlas V launch vehicle, which powers its first stage with a single RD-180 engine that is expended after each flight.

[8] In response, the US Air Force asked the Aerospace Corporation to evaluate alternatives for powering the Atlas 5 booster with non-RD-180 engines.

Early estimates in 2014 were that it would require five or more years to replace the RD-180 on the Atlas V.[9] Even though the Russian government could cut off the supply to ULA of imported RD-180 engines, the US Congress, with emerging support from the Air Force, came to the view that it would not be advantageous to build a US production line for the RD-180, mainly because it would need a license from the Russian government.

It was not clear when or if the RD-180 would be replaced, and the RFI asked for several options including similarity to the Russian engine, whether it would come in a new configuration and the use of "alternative launch vehicles" for the EELV mission.

[13] In January 2015, Orbital Sciences Corporation received all the necessary permissions from government bodies for the delivery of 60 engines from NPO Energomash.

According to a 2005 GAO Assessment of Selected Major Weapon Programs, Pratt & Whitney planned to start building the RD-180 in the United States in 2008 with a first military launch by 2012,[15] but this did not occur.

United Launch Alliance (ULA) announced in February 2015 that it was considering undertaking US production of the Russian RD-180 engine at the Decatur, Alabama, rocket stage manufacturing facility.

[18] In an interview on August 26, 2021, ULA's CEO Tory Bruno said that three or four RD-180s were installed on Atlas V rockets for upcoming missions, and the rest were sitting in a warehouse.

[20] As a result of the geopolitical and US political considerations, United Launch Alliance considered a possible replacement for the Russian RD-180 engine used on the first-stage booster of the ULA Atlas V. Formal study contracts were issued in June 2014 to a number of US rocket-engine suppliers.

During the early 1990s, General Dynamics Space Systems Division (later purchased by Lockheed Martin) acquired the rights to use the RD-180 in the Evolved Expendable Launch Vehicle (EELV) and the Atlas program.

An additional development program was undertaken to certify the engine for use on the modular Common Core Booster primary stage of the Atlas V rocket.

For those who might be concerned about too much reliance on Russia, he pointed out that RD Amross was "very close to producing a U.S.-built version of the RD-180, and with some infusion of NASA funding could be manufacturing that engine (and perhaps even a 1,700,000 lbf or 7.6 MN thrust equivalent of the RD-170) in a few years".