TECHNOLOGY AREA(S): Air Platform, Space Platforms, Weapons

ACQUISITION PROGRAM: PMA 263 Navy and Marine Corp Small Tactical Unmanned Air Systems

OBJECTIVE: Develop a lightweight, compact, drop-in and highly efficient integrated fuel cell-based hybrid propulsion and power system.

DESCRIPTION: Navy energy action goals, as released by SECNAV [Ref 1], include developing more efficient systems, reducing greenhouse emissions, eliminating/reducing fossil-fuel usage, and increasing the use of alternative green energy sources in the fleet.� Therefore, future power sources must extend operational range and lower maintenance cycles [Ref 2].

Currently, combustion engines that use petroleum fuels are relied upon to provide thrust and drive motors to propel the aircraft.� The fuel-to-power conversion efficiency of the combustion process is low (i.e., can be as low as 15%), resulting in high fuel consumption and harmful gas emissions.� The use of batteries is attractive as an alternative energy source for unmanned aircraft systems (UAS), where geometric limitations prohibit the use of combustion engines.� However, their low energy density (less than 200 Watt-Hour/Kilogram) prevents the widespread use of battery power sources as the primary mover for the aircraft.

Fuel cell technologies (FCT) allow the reformation of jet fuel into hydrogen-rich gas, resulting in usable electric power with high conversion efficiencies (i.e., 60-70%).� FCTs are solid-state devices with the following characteristics: high energy-density; clean fuel burn resulting in water, heat, and air as byproducts; contain no movable parts which enable quiet operations; maintenance free over the lifecycle; and are scalable.� These characteristics translate to improved mission performance and warfighting capabilities, including potentially doubling endurance time to 44 hours in some cases, and reduced weight (<135 pounds) [Ref 3].

There are four key components in a fuel cell system: (1) reformer converting logistic fuel (i.e., JP-5/JP-8) into usable hydrogen (H2) gas; (2) fuel cell stack that produces electrical power output upon receiving a fuel such as H2 gas as an input; (3) balance-of-plant consisting of burners and heaters for combined heat and power to improve efficiency; and (4) electronic firmware with hardware components and software algorithms along with controls.� There is a need for integrating the above key components to develop an integrated fuel cell system (IFCS) to leverage the full potential of fuel cell technologies.� The current market lacks such IFCS that are highly dense (i.e., power and energy density), and operationally suitable for aircraft applications.

The goal is to develop a baseline IFCS that produces a minimum electrical power output of 0.5-1 kilowatt (kW).� The design concept must be scalable up to 5-10 kW as well as be modular and plug-and-play in nature.� Based on the fuel source, a polymer membrane (PEM) fuel cell or solid-oxide fuel cell stack can be used.�� The fuel cell stack must be fully compatible with current industry and state-of-the-art onboard (e.g., reformer and H2 storage system) and off-board hydrogen technologies (i.e., electrolysis).� The developed IFCS must have a total weight threshold of 35 pounds (lbs) {15.9 kilograms (Kg)} with an objective of 19lbs (8.6Kg).� The IFCS must also be fully compatible for Groups I-IV UAS vehicles [Ref 4].

The developed IFCS must be compatible with all current operational aircraft, electrical and environmental requirements [Ref 2, Ref 3], and must meet other requirements that include (but are not limited to) the following: sustained operation over a wide ambient temperature range (e.g., -40�C to +71�C), capability to withstand carrier-based shock and vibration loads, altitude range up to 65,000 feet per MIL-STD-810G [Ref 5], electromagnetic inference (EMI) up to 200V/m per MIL-STD-461F [Ref 6], and electrical power quality per MIL-STD-704 [Ref 7].

PHASE I: Develop a baseline IFCS that produces a minimum of 0.5-1 kW of electric power.� Leverage modeling and simulation tools for proof-of-concept.� Show feasibility for air vehicle integration to unmanned aircraft system.� The Phase I effort includes the development of prototype plans for Phase II.

PHASE II: Build a prototype system that is compact and lightweight, and then demonstrate the functionality of the IFCS suitable for a UAS meeting its propulsion and power needs.� Demonstrate the scalability of the IFCS to 10kW.

PHASE III DUAL USE APPLICATIONS: Fully develop a functional and airworthy IFCS with performance specifications satisfying the targeted acquisition requirements coordinated with Navy technical points of contacts.� Complete testing per military performance specifications and transition to appropriate platforms.

Commercialize the fuel -cell and IFCS technologies.� Leverage the advantage of scalable manufacturing processes to develop a cost-effective manufacturing process for technology transition to various system integrations for both DoD and civilian applications. The potential for commercial application and dual use is high.� Beyond the Navy application, there are applications for electric vehicle, consumer portable electronics, and commercial aviation sectors.

REFERENCES:

1. Paige, Paula. �SECNAV Outlines Five Ambitious Energy Goals.� Navy News Service. 16 Oct 2009. Story Number: NNS091016-30. Corporate Communications ONR. http://www.navy.mil/submit/display.asp?story_id=49044

2. FY15 Navy Programs. RQ-21A Blackjack Unmanned Aircraft System (UAS). http://www.dote.osd.mil/pub/reports/FY2015/pdf/navy/2015rq21a_blackjack.pdf

3. Naval Air Systems Command-Small Tactical Unmanned Aircraft Systems. �RQ-21A Blackjack�. http://www.navair.navy.mil/index.cfm?fuseaction=home.displayPlatform&key=5909B969-2077-41C2-9474-C78E9F60798C

4. �Unmanned Aircraft System Airspace Integration Plan�, Version 2.0. Department of Defense UAS Task Force, Airspace Integration Integrated Product Team. March 2011. http://www.acq.osd.mil/sts/docs/DoD_UAS_Airspace_Integ_Plan_v2_(signed).pdf

5. MIL-STD-810G. �Department of Defense Test Method Standard: Environmental Engineering Considerations Laboratory Tests�. 31 Oct 2008. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35978

6. MIL-PRF-461F. �Department of Defense Interface Standard: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment�. 10 Dec 2007. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35789

7. MIL-STD-704F. �Department of Defense Aircraft Electrical Power Characteristics� 30 Dec 2008. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35901

KEYWORDS: Compact; Lightweight; Power Dense; Integrated Fuel Cell System; Propulsion and Power; Unmanned Aircraft System