REP NASA's Rocket Engine Prototype (REP) effort seeks to deliver a large-scale, prototype liquid-oxygen/kerosene engine system that will enable development of full-scale, flight-ready engines for a next generation reusable booster. IPD The Integrated Powerhead Demonstrator (IPD) project — which seeks to double the capability of booster engines providing access to space — is contributing new engine technologies for NGLT and Department of Defense propulsion research. X-43A The first demonstrator vehicle in NASA's "Hyper-X" series of experimental hypersonic ground and flight test vehicles, the X-43A will demonstrate "air-breathing" engine technologies for future hypersonic aircraft and/or reusable space launch vehicles, achieving speeds above Mach 5, or five times the speed of sound. TBCC/RTA The Turbine-Based Combined Cycle (TBCC) engine project seeks to deliver a Mach 4+ hypersonic propulsion system in this decade. Prime among its enabling technologies: the Revolutionary Turbine Accelerator (RTA), intended to demonstrate high mach turbine and TBCC propulsion for space access. RBCC/ ISTAR NASA is developing a Rocket-Based Combined Cycle (RBCC) engine system for ground demonstration in this decade. The Integrated System Test of an Air-breathing Rocket (ISTAR) project is NASA's first flight-type system development and ground test of an RBCC propulsion system.