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Advanced Propulsion and Power Concepts for Large Size Class Unmanned Aerial Systems (UAS)


OBJECTIVE: Develop and demonstrate more efficient and reliable propulsion and power systems for large (10,000 lb class) RPAs to improve capability over existing conventional propulsion and power generation systems. DESCRIPTION: Tactical requirements for unmanned aerial systems (UASs) exceed current capabilities for performance, reliability, maintainability, and supportability. Mission requirements such as extended endurance, increased power for auxiliary/sensor systems, and low altitude, low speed maneuverability are becoming paramount. Specifically, in the 10,000 lb class of vehicles, which usually includes only ground launched systems, these capabilities are not currently optimized with either electrochemical energy storage-based propulsion concepts, or with existing petrochemical engine-based propulsion concepts. Electrical power required for advanced payloads has increased dramatically. The objective of this topic is to investigate advanced propulsion and power concepts that span the potential spectrum from pure petrochemical to full electrical that can meet the current and projected future needs of large RPAs. Current RPA propulsion and power systems are sized to provide enough power and speed for takeoff requirements, leading to systems which operate inefficiently at other operating conditions. In addition, current systems can be noisy, which may limit RPA operational effectiveness. Fully electric based systems are quiet, but have issues with power density and energy storage capacity. Fuel cell-based systems could provide a very efficient energy source, but tend to be limited in the amount of power provided for larger RPAs. Batteries are limited by their energy storage capacity, unless they can be charged during operation by another energy source. A hybrid approach could enable users to take advantage of the quiet, efficient operation of electric-based propulsion while also taking advantage of the power density of current engines. All concepts will have to meet the different operational conditions of large RPAs, which should include full power takeoff and dash modes for 10 percent of mission duration and part-power cruise and loiter conditions for 80 percent of mission time as an example. Loiter mode should include segments of quiet operation (e.g., 10 to 30 percent of total mission duration) and segments of increased electric payload power draw. Key capabilities include the ability of systems to operate with heavy-fuel (JP-8, diesel); possible dual operation of electrical and petrochemical engine components to additively produce peak propulsive power; the ability to regenerate a rechargeable electrical power storage system during cruise conditions; the ability to shut-down the engine and run in electric-only quiet propulsion mode, if applicable; the ability to restart the engine as applicable; and the ability to provide electric power to a number of payloads. During the Phase I effort, concepts should be developed that provide adequate power for propulsion and sensor payloads, as well as have a decreased weight over present single-power concepts. Key capabilities will be to achieve mission loiter equivalent to present systems, i.e., mission endurance of 12 to 16 hours as a minimum. Phase II will develop, fabricate, and demonstrate the system in a ground test environment. Phase III options should plan to integrate the enhanced propulsion system into an airframe and demonstrate the performance of the system with flight testing in a RPA mission environment or demonstrate the capabilities in a ground test environment that can simulate mission conditions such as altitude and temperature differentials. PHASE I: Demonstrate the feasibility of an innovative approach for advanced power and propulsion concepts through modeling, empirical, and pragmatic analysis. The analysis should include the effects or requirements driven by vehicle, subsystems, payloads, and all other ancillary components of the power and propulsion system. PHASE II: The Phase II effort will fully develop and fabricate the system design from Phases I and II and demonstrate the system in, at least, a fully representative ground-based environment. PHASE III: Military Application: Performing intelligence, surveillance and reconnaissance, targeting and target acquisition missions. Commercial Application: Law enforcement, Homeland Security and emergency service RPA performing intelligence, surveillance, search and rescue, and disaster relief missions. REFERENCES: 1."Hybrid Engine Concept from Flight Design,"AVweb, v15n30d, July 30, 2009, 2."Meyer Nutating Disk Engine, a New Concept in Internal Combustion Engine Technology,"43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 8-11 July 2007, Cincinnati, OH. 3. Frederick G. Harmon, Andrew A. Frank, and Jean-Jacques Chattot,"Conceptual Design and Simulation of a Small Hybrid-Electric,"University of CaliforniaDavis, Davis, California 95616-5294, Remotely Piloted Aircraft.
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