Intended to explore the possibilities of high-speed flight and high-efficiency hover beyond the capabilities of aircraft like the V-22 Osprey, DARPA’s Disc-Rotor Compound Helicopter program may ultimately develop a helicopter-like aircraft with a rotating circular wing and retractable blades. Boeing Thursday was announced as the expected recipient of a Sole Source contract for ongoing development of the program, beginning with small-scale model testing, and will be supported with $3 million in 2008 and $6 million in ’09. According to an unclassified DARPA report, “the enabling technologies are disc-rotor configuration, circulation control, seamless reversible transition between hover and wing borne flight, and loading/center-of-pressure control.” Following wind-tunnel tests of scale models, a full-scale demonstrator aircraft would be built to establish the concept’s feasibility with hopes of evolving it into an aircraft capable of cruise speeds in the 300-400 knot range. That aircraft could provide vertical takeoff and landing plus hover capability for troop and cargo insertion.
Such designs have previously been studied by NASA and some suspect that through development of the disc-rotor concept, a compound helicopter could theoretically be capable of supersonic flight. In the near term, the Disc-Rotor Compound Helicopter program will explore the “flowfield environment” created by a disc-rotor in transition from blade-hover to disc-wing flight. According to one source, “the circular disk has similar aerodynamic abilities as a delta wing,” with “no bad habits” throughout its flight envelope and with characteristics well-suited to high-speed flight.
