Get out your propelling pencils, slide rules and find the back of an envelope. The US Air Force Research Laboratory and Defense Advanced Research Projects Agency have a couple new programs in the pipeline.
INVENT - Integrated Vehicle Energy Technology demonstration (AFRL), two platform teams, each led by an airframer, are to demonstrate a new aircraft subsystem architecture including: adaptive power and thermal management; robust electrical management; and high-performance electrical actuation - near-term applications include subsonic long-range strike, unmanned and tactical aircraft. This sounds like the next big step on from the JAST Integrated Subsystems Technology demo that led into JSF.
VULCAN - DARPA program to demonstrate a propulsion system capable of accelerating a full-scale hypersonic vehicle from rest to Mach 4+. VULCAN will integrate a current production turbine engine (F100, F110, F119 or F414) into a constant volume combustion (CVC) engine so they share the same inlet and exhaust. The turbine would operate from rest to its upper limit, around Mach 2, where the CVC would take over and the turbine would be "cocooned". Examples of a CVC include the pulsed-detonation engine and continuous-detonation engine. DARPA has other irons in this fire, including the FACET turbine/scramjet combined-cycle engine demonstration.
DARPA, meanwhile, is celebrating its 50th year, and has produced this video to commemorate some of its achievements: