From the Introduction: "The National Security Space Launch (NSSL) is a U.S. government program that enables acquisition of launch services, aimed at ensuring continued access to space for critical national security missions. The U.S. Air Force oversaw NSSL's predecessor program, the Evolved Expendable Launch Vehicle (EELV), and awarded four companies contracts to design a cost-effective launch vehicle system. The Department of Defense (DOD) acquisition strategy was to select one company to ensure national security space (NSS) launches were affordable and reliable. The EELV effort was prompted by significant increases in launch costs, procurement concerns, and the lack of competition among U.S. companies. Today, the NSSL program's main priority is mission success. A RAND study released April 2020 identified a magnitude of risk associated with assured access to space. As Congress continues its oversight of NSSL, it may consider examining DOD's plan on the prioritization of the launch-related risks to ensure continued access to space and 100% mission success. A major concern in Congress and elsewhere over U.S. reliance on a Russian rocket engine (RD-180), used on one of the primary national security rockets for critical national security space launches, was exacerbated by the Russian backlash over the 2014 U.S. sanctions against its actions in Ukraine. Moreover, significant overall NSSL program cost increases and unresolved questions over individual launch costs, along with legal challenges to the Air Force contract awards by space launch companies, prompted legislative action."
CRS In Focus, IF11531
Congressional Research Service: https://crsreports.congress.gov/