The good Monsignor Norris regretted in his August 6 report that there was no model of the USAF's HEETE (Highly Efficient Embedded Turbofan Engine) on show at the Joint Propulsion Conference in Denver.
Bill Sweetman photos
FTFY. This masterpiece of sterolithography was visible last week at the Association for Unmanned Vehicle Systems International (AUVSI) show in DC.
HEETE is associated with USAF ideas for an ultra-long-endurance, high-altitude, stealthy UAV called SensorCraft. There are two challenges: packing a high-bypass engine internally and delivering a lot of electrical power at a point where the engine really wants to be loafing along with minimal fuel burn. HEETE clearly has an aggressively three-dimensional fan with lots of sweep and twist, to handle a lot of air in the smallest possible diameter, and the core runs at a mindboggling 70:1 pressure ratio for small size and high tolerance of auxiliary power offtake.
However, it wasn't the most unusual propulsive device on show. Teledyne Continental showed a half-scale model of an experimental device produced for the Versatile Advanced Affordable Turbine Engines (VAATE) initiative:
It's not en engine. It's a propulsor driven by an external gas generator, feeding it with hot air through the ducts radiating from its casing. One application could be a cruise fan for a VTOL vehicle like Lockheed Martin's Various UAV. It could also be connected to multiple gas generators, in a system designed to provide high power for take off and optimized power for cruise. Alternatively, a single gas generator could power multiple small fans, making it easier to embed the engines in a stealthy vehicle.