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​The Defense Advanced Research Projects Agency (DARPA) has launched a program seeking to close the critical gap in the performance of conventional turbine jet engines and the scramjet or ramjet engines necessary to achieve hypersonic speeds. The goal of the project is a hybrid system “that would combine and improve upon the best of off-the-shelf turbine and ramjet/scramjet technologies,” said Christopher Clay, DARPA program manager. DARPA is calling the hybrid system the Advanced Full Range Engine (AFRE). It is a continuation of a decades-long effort to produce reusable aircraft capable of Mach 5, or about 3,300 miles per hour. The problem the AFRE program is attacking is that turbine jet engine performance currently tops out at about Mach 2.5, while hypersonic engines cannot provide effective thrust at speeds much below Mach 3.5, DARPA explained in a release. AFRE hopes to produce a turbine-based combined cycle engine, which would use a turbine engine for low-speed operations and a dual-mode ramjet—which would work efficiently with either subsonic or supersonic airflow —for high-speed operations. To provide information on the program and receive input, DARPA has scheduled a Proposers Day on July 13 and 14 at its Conference Center in Arlington, Va. (See also: Beyond the Hypersonic.)