Aircraft Electric/Hybrid-Electric Power and Propulsion Workshop Perspective of the V/STOL Aircraft Systems Tech Committee

Aircraft Electric/Hybrid - Electric Power &

Propulsion Workshop Perspective of the

V/STOL Aircraft Systems Tech Committee

th Workshop to be held July 28 , 2016 at the Hilton Salt Lake City Center in Salt Lake City, Utah Schedule 0700 – 0800 Check - in and Continental Breakfast 0800 – 0 830 Introduction and welcome by AIAA Speakers from adjacent research 0830 – 0930 Large Scale Batteries, by R. Chamberlain (invited) and Extreme Electric Machines by Kiruba Haran 0930 – 1030 Panel: Visions of the Future Featuring John Nairus (AFRL), Cheryl Bowman (NASA) and Dr. Babu Chalamala (Sandia National Lab, invited) 1030 – 1100 Coffee Break 1100 – 1205 Panel: Activities from AIAA Committees Featuring Ilan Kroo (Aircraft Design TC, invited), Craig Hange ( V/STOL Aircraft Systems TC, invited) , Andrew Gibson (Green Engineering PC, invited), John Nairus (Energy Optimized Aircraft and Equipment Systems PC ) 1205 – 1305 Lunch 1300 – 1515 Breakout session introduction and rotation through discussion breakout sessions (technology, systems integration, standards, certification, and role of AIAA 1515 – 1545 Coffee Break 1545 – 1630 Reports from breakout sessions 1630 – 1700 Wrap - Up and Next Steps 1700 – 1715 Closing Comments by AIAA Vertical Short Take - Off Landing (V/STOL) Aircraft Systems Technical Committee • We are advocates for the use of powered - lift technology to provide enhanced capability to new aircraft concepts to promote improvements to the Air Transportation System  Military – Includes austere basing where access to airfields may be denied. Permits dispersion of assets for protection from attack, deployment of assets closer to the front  Civilian – Increasing throughput by opening up unused or underutilized airports and runways. Access to austere areas in the event of emergency or catastrophe  UAV – Permit take - off and landing at or near areas of operational interest.

Permit low - speed / hovering operations in certain scenarios (Power line inspection for example)  Rotorcraft and Helicopter – Access to austere locations, thin haul routes, urban commuting, rescue and medical evacuation  Personal Air Vehicle – True “point - to - point” service Technical & Operational Issues Endemic to V/STOL • Powered – Lift, Using thrust to provide lift when aerodynamics are insufficient due to low - speed (low dynamic pressure)  Maintaining lift greater than weight  Sufficient control power and authority to maintain flight path • Flow Field Effects  In - ground - effect induced forces caused by thrust entrainment  Thrust impingement and recirculation – Hot gases and their influence on aircraft and environment • Noise and Acoustics – On aircraft, near field, and far field Technical & Operational Issues Endemic to V/STOL • Aircraft balance issues  Keeping the thrust at the center - of - gravity (CG)  Ability to provide control moments about the CG • Internal plumbing and routing  Moving air to other areas of the airframe to provide thrust where it will maintain balance. Takes up important volume in the aircraft.

 Vectoring nozzles or vectoring engines. Both introduce complexity, weight, and cost.

 Lift augmentation – Using favorable interactions of the flow to create additional lift – Upper surface blowing, circulation control, ejector nozzles • Mission integration issues – What other requirements are contrary to V/STOL performance e.g. – Supersonic performance for F - 35B Technical & Operational Issues Endemic to V/STOL • One engine inoperative (OEI) for 2 or more engines  Loss in thrust that is countering drag and providing lift  Inability to provide restoring moments  The promise of a slower take - off and landing should improve safety, not diminish it • Mechanical solutions to OEI or critical engine inoperative (CEI) are complex, hard to maintain, and expensive • A wide operating range of airflow momentum requirements to generate the most efficient thrust beg for the use of true variable bypass ratio  US / UK, CALF, JAST, X - 32, X - 35, F - 35 all incorporate variable bypass in one form or another Addressing Technical & Operational Issues Endemic to V/STOL • Distributed propulsion is a potential revolutionary answer  More propulsors means smaller impact of OEI (ref 2004 study)  Smaller propulsors can be integrated on other locations on the aircraft improving effectiveness, freeing up volume, and reducing induced jet effects  On / off “binary” throttle settings may be viable (Engine runs “on - design” only) • However….

 Mechanical complexity associated with ‘n’ turbo - machinery based units is increased dramatically  Propulsion sub - systems also went from 2 to ‘n’. There is very little benefit from being used on smaller thrust engines  Economies of scale works against DP in turbomachinery efficiency, weight, and manufacturability (Bypass ratio becomes smaller) Distributed Propulsion • RSCA Studies 2004 – 2005, EMAX Concept used 22 engines Addressing Technical & Operational Issues Endemic to V/STOL • Distributed Electric / Hybrid Electric Propulsion is a potentially a better answer for V/STOL operations  Gas generator performance is potentially decoupled from fan performance  The number of potential systems architectures increases, but this permits better mission tailoring Addressing Technical & Operational Issues Endemic to V/STOL • Transfer of power accomplished via electricity through (relatively) small wiring, not hot air pipes or mechanical rotating shafts • Power transfer not confined to certain areas due to volume constraints (e.g. Piping fan air across the fuselage is impractical) • Hot air energy is created and expended in the turboshaft only.

There is very little hot air exiting the aircraft • Fans are used for all thrust • Fans can be dissimilar in size and momentum • Does not need to be turboshaft powered. Could be diesel • Very high bypass ratio. True variable - bypass ratio capability • An overspeed capability, and a battery augmentation capability • Electric is really the only way to go for small UAV Addressing Technical & Operational Issues Endemic to V/STOL • Issues and concerns  Large amounts of sensors, actuators, and data transfer required  Integrated airframe & propulsion is required and is complex  Cooling systems for embedded components and electrical inefficiencies distributed in the airframe. Active cooling potentially needed for low - speed or hover.

 Cryogenic and superconducting may be needed to get better efficiencies  Existing generator / motor industry not accustomed to working to aircraft power - to - weight goals Schematic of Distributed Turbo - Electric STOL Aircraft