The 2010 Joint Space Communication Layer (JSCL) Initial Capabilities Document (ICD) forecasts a large demand increase for US MILSATCOM in contested environments during the 2020–2025 timeframe. In response, the US Air Force in 2012 commenced the MILSATCOM Design for Affordability Risk Reduction (DFARR) effort to develop prototypes for a new protected tactical communications system. MIT Lincoln Laboratory (MIT LL) was tasked with building a test bed for this effort that would enable demonstration of prototype user terminals and space segment designs provided by DFARR contractor teams. This paper describes the test bed implementation and its use throughout the DFARR, which culminated in system-level over-the-air demonstrations, and risk-reduction demonstrations for a terminal End Cryptographic Unit (ECU) prototype.