United Launch Alliance (ULA) is changing its schedule for receiving the Russian-made RD-180 rocket engine from an annual shipment to twice-per-year, according to a company spokeswoman.

ULA spokeswoman Jessica Rye said Wednesday there are deliveries of engines scheduled in August and October instead of just one for 2014.  Rye said the engines will be shipped once they are completed instead of once per year. Rye did not provide further details on the reason for the delivery schedule change.

ULA's Atlas V launch vehicle uses the Russian made RD-180. Photo: ULA.
ULA’s Atlas V launch vehicle uses the Russian made RD-180. Photo: ULA.

ULA uses the RD-180 first stage rocket engine for United States national security space launches in an Air Force program called the Evolved Expendable Launch Vehicle (EELV) program. The RD-180 is controversial as it is used to provide a critical U.S. national security capability. It is also used by a firm, ULA, that holds a monopoly on EELV, which has rapidly increasing program costs.

The engine is developed by the Russian firm

NPO Energomash and is distributed in the United States by RD AMROSS, a joint venture of NPO Energomash and United Technologies Corp.– [UTX] subsidiary Pratt & Whitney. ULA is a joint venture of Lockheed Martin [LMT] and Boeing [BA].