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Innovative Hybrid Power System for Increased Endurance Rapid Response Small Unmanned Aerial Systems (SUAS)


OBJECTIVE: Develop a hybrid electric propulsion system to support a Rapid Response Small SUAS (<30lb) capability. This requires fast dash (>150mph) while maintaining extended endurance (>15 hrs) on station and low acoustic noise operation. DESCRIPTION: United States Forces currently have a need for a SUAS (<30 lbs gross take-off weight (GTOW) in remote areas for a variety of functions, such as reconnaissance, surveillance, targeting and acquisition (RSTA) in support of convoy operations due to the capabilities that these systems offer. For non-military use, this type of SUAS can fulfill multiple roles where there is currently a significant need, such as for border patrol and emergency responders, quick assessment of forest fires in remote areas, intercept/surveillance of suspicious boats approaching the coastline, etc. Unfortunately, for quick response applications, currently-fielded SUASs in this size class either do not have both the fast response times or the on-station endurance necessary to complete the mission (i.e., 44 lbs GTOW SUAS with dash speed limited to 90 mph, endurance limited to 10 hrs time-on-station @ 60 mph). Industry is working to develop all-electric SUASs that can achieve cruise speeds in excess of 150 mph; however, much research is still needed to extend their endurance (with integrated payload) and to demonstrate the system's utility for both military and non-military applications. The goal of this topic is to develop an all-electric (i.e. fuel cell hybrid with turbogenerator, etc.) propulsion system to support a rapid response (55+ mph loiter speed; 150+ mph dash speed)<30 lbs GTOW SUAS capable of providing"eyes-on-target"within 2-3 minutes over a 6-mile flight radius with low acoustic noise operation. The SUAS propulsion system should enable an endurance of at least 15 hours (>15hr threshold,>25hr objective) and support a 2+ lb payload, which could include (but is not limited to) a gimbal-mounted stabilized EO/IR camera, with sufficient power reserved to operate the payload during loiter. User requirements sometimes dictate that SUASs operate in environments with high winds (35 knots threshold, 50 knots objective) and/or low temperatures (down to -30oF) at high altitudes (up to 12,000 ft Mean Sea Level (MSL) threshold, 25,000 ft MSL objective). Additionally, the operation of the propulsion system requires a low acoustic signature (i.e. acoustically non-detectable at the AV mission altitude, typically no greater than 1,000 ft AGL). The SUAS propulsion system designed under this topic shall demonstrate a path to operate in these environments. Furthermore, since the SUAS of this size class will be directed towards small team operations with portability and transportability in mind, the power system should operate on a fuel consistent with a low logistics footprint. A sample mission may include: Take-off/dash to target area, loiter for an extended duration (>15 hrs) while providing sufficient power for payload operation (e.g. 10% loiter power reserved for payload), return/dash to initial launch position. In addition to the design, key technical challenges/performance limitations shall be outlined. A plan shall be proposed as to how technical challenges can be overcome and requirements met to achieve flight objectives. PHASE I: Design an advanced power system (e.g. fuel cell/turbogen hybrid) capable of operation on a SUAS with the payload, achieving total GTOW<30 lbs. Define performance parameters/interface constraints. Demonstrate feasibility through modeling & simulation and/or bench tests that the system has sufficient power/energy-density to meet design metrics, using above sample mission as baseline. PHASE II: Develop advanced power system with a focus on integration into SUAS. Obtain baseline data from selected platform to verify power system sizing and use as performance comparison. Demonstrate that SUAS system is capable of producing sufficient power-to-weight ratios for adequate climb and dash performance, and able to attain program endurance metrics in a simulated operational environment (threshold). Flight test the SUAS to verify performance in an actual operating environment (objective). PHASE III: Military applications include intelligence, surveillance, and reconnaissance (ISR), target tracking and acquisition. Commercial applications include border patrol and search and rescue for emergency responders. REFERENCES: 1. Defense Technology Area Plan for 2005; DoD Key Technology Areas (#1); AFSOC/A5ZU Key Technology Areas Increased Power. 2. FY2009-2034 Unmanned Systems Integrated Roadmap, 3. A. Himansu, et al.; Hybrid Solid Oxide Fuel Cell / Gas Turbine System Design for High-Altitude Long Endurance Aerospace Missions; Proceedings from 4th International ASME Conference on Fuel Cell Science, Engineering, & Technology; Irvine, CA; (2006).
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