Electrified Aircraft Propulsion Development

Electrified Aircraft Propulsion

Development

AIAA Propulsion and Energy Forum “Powering the Game Changers” 11 July 2018 Dr. Rubén Del Rosario Director of Aeronautics NASA Glenn Research Center

Electrified Aircraft Propulsion Concepts

• Electrified Aircraft Propulsions systems use electrical motors to provide some or all of the thrust for an aircraft – Turboelectric systems use a turbine driven generator as the power source. Partially turboelectric systems split the thrust between a turbo fan and the motor driven fans – Hybrid electric systems use a turbine driven generator combined with electrical energy storage as the power source.

Many configurations exist with difference ratios of turbine to electrical power and integration approaches – All Electric systems use electrical energy storage as the only power source.

Benefits of Electrified Aircraft Propulsion

• Improvements to highly optimized aircraft like single aisle transports – Potential fuel burn reduction estimated using turbo electric distribution to BLI thruster in addition to other benefits from improved engine cores or airframe efficiencies. Later developments could be more advanced electrical distribution and power storage.

• Enabling new configurations of VTOL aircraft – The ability to widely distribute electric motor driven propulsors operating from one or two battery or turbine power sources, enable new VTOL configurations with potential to transform short and medium distance mobility through 3x-4x speed improvement.

• Revitalizing the economic case for small short range aircraft services – The combination of battery powered aircraft with higher levels of autonomous operation to reduce pilot requirements could reduce the operating costs of small aircraft operating out of community airports resulting in economically viable regional connectivity with direct, high- speed aircraft services.

Subsonic Transport Technology Strategy

Ensuring U.S. technological leadership

Prove out Prove out Energy usage Harmful Objectionable transformational transformational reduced by more noise reduced emissions reduced propulsion technologies airframe technologies than by more than by more than

60% 90% 65%

Current Next Generation Future Generations Generation -Transitional- -Transformational- Image Credit: Denis Fedorko Image Credit: pjs2005 from Hampshire, UK Image Credit: Weimeng Image Credit: Don-vip 4

Transforming Propulsion – A Breakthrough Opportunity

Turbo-Electric Propulsion Architecture Boundary-Layer Ultra-Efficient “Small Ingesting Propulsor(s) Core” Turbofan In whole or in part, transformational propulsion enables the next generation transitional subsonic transport configuration and enables future generation transformational subsonic transports

Transforming Propulsion – A Breakthrough Opportunity

Turbo-Electric Propulsion Architecture • UTRC, RR hybrid electric studies • U of I Electric Machine showed feasibility for 3X • New Boeing and RR 150 PAX studies increase in power density • STARC tailcone thruster series – in-house and • GE inverter outpacing original plans Aurora • Customizing soft magnetic alloys for component st • NEAT – Running 1 powertrain test improvements • Small Core Compressor work with P&W • Successful completion of BLI2DTF and GE progressing well. Testing on • Fan inlet distortion studies in W-8 schedule for late FY18 • Planning test in Wind Tunnel (ARC 11ft) • N+3 Combustor test with UTRC scheduled Tailcone BLI for FY19 Boundary-Layer Ultra-Efficient “Small Ingesting Propulsor(s) Core” Turbofan In whole or in part, transformational propulsion enables the next generation transitional subsonic transport configuration and enables future generation transformational subsonic transports

Electrified Aircraft Propulsion Strategy for Commercial Transport

Initial focus on turboelectric aircraft Concept Definition and System analysis Novel integration and BLI Impact Regional Market MW flightweight electrical Flight and Single Aisle Class component development demonstration by 2030s Integrated systems testing Advanced cores with large power extraction Hybrid electric option to be considered with advances in battery technology

Studies Targeting Regional Jets and Single Aisle Markets

• Partially and Fully Distributed Turboelectric Concepts

NASA STARC - ABL Boeing/NASA SUGAR - FREEZE NASA N3-X ECO-150

• Parallel Hybrid Concepts

Low Spool R-R LW EVE High Spool UTRC hGTF Boeing/NASA SUGAR - VOLT

Electrified Aircraft Propulsion

NASA Electric Aircraft Testbed (NEAT)

Development and Testing of MW Class Power System

High Power Density Electric Motor Development NASA research (power density at electromagnetic level), 1 – 3 MW, >96 % efficiency Various claims (100 – 200 kW) Siemens (200 kW) System level, 95 % efficiency Single-aisle Turboelectric Aircraft with Aft Power Density, kW/kg Boundary Layer Ingestion (STARC – ABL) Current electric vehicles • Conventional single aisle tube-and-wing Current industrial configuration • Twin underwing mounted turbine engines with

NASA Electric

attached generators on fan shaft

Aircraft Testbed

• Ducted, electrically driven, boundary layer

(NEAT) for testing

ingesting tailcone propulsor • Projected 7 – 12 % fuel burn savings for 1300 nm

multi MW level

mission

power system

NEAT: From Concept to Operation in Three Years

“Aft Thruster In Altitude Chamber”  125 kW Single String Tests  500 kW STARC-ABLE • MW-Scale STARC-ABL • Full-scale EAP Powertrain Commencement of Testing for 500 kW STARC-ABL 500 kW STARC-ABL Configuration

NEAT: Status and Results for 500 kW Testing

Long-term Objective : Mature Electrified Aircraft Power (EAP) powertrain technologies and validate at the system level including Powertrain architectures EMI mitigation Fault and thermal management DC bus stability Flight-efficiency, and high power, high voltage component verification FY18 Objective : Establish subscale STARC-ABL powertrain w/ COTS equipment and run complete flight-profiles w/ turbine and ducted fan emulation “Aft Thruster In Altitude Chamber” Configuration : 600 V, 500 kW multi-bus, ARINC 664 communication, power regeneration, facility thermal mgt.

Results:  Successfully operated at 600V, 460 kW (500 kW by March 2018)  informing next design  Validated emulation scheme  Quantified system communication choke points and power transients  Measured important issues with load balance and control response  Continuing to refine and add fidelity throughout year Commencement of Testing for 500 kW STARC-ABL Learning significant amount, results will be presented summer 2018

NASA Technology Investment Strategy

Enable a broad expansion of vertical lift applications Overarching • Improve current configuration cost, speed, payload, safety, and noise Vertical Lift • Open new markets with new configurations and capability Strategy • Capitalize on convergence of technology in electric propulsion, autonomy and flight controls

NASA technology emphasis

Technology applicability scales up and down in many areas www.nasa.gov

NASA-developed Concept Vehicles for UAM

Objective: Identify NASA vehicles to serve as references to openly discuss

technology challenges common to multiple concepts in the UAM community (Choose one feature from each column to arrive at a vehicle to study)  Open, publicly- Passengers 50 nm trips Market Type Propulsion available per full configurations charge/  Provide focus for trade refuel studies and system 1 1 x 50 nm Air Taxi Multicopter Battery analysis 2 x 37.5 nm  Push farther than 2 2 x 50 nm Commuter Side by Side Parallel current market trends Scheduled (no tilt) hybrid  Provide a range of 4 4 x 50 nm Mass Transit (multi-) Tilt Turboelectric configurations wing  Cover a wide range of 6 8 x 50 nm Air Line (multi-) Tilt Turboshaft technologies and rotor missions that are being 15 Lift + cruise Hydrogen proposed fuel cell www.nasa.gov

NASA-developed Concept Vehicles for UAM

NOT “BEST” DESIGNS; NO INTENT TO BUILD AND FLY

Passengers 50 nm trips Market Type Propulsion Quadrotor “Air Taxi” per full charge/ refuel 1 1 x 50 nm Air Taxi Multicopter Battery 2 x 37.5 nm Side by Side “Vanpool” 2 2 x 50 nm Commuter Side by Side Parallel Scheduled (no tilt) hybrid 4 4 x 50 nm Mass Transit (multi-) Tilt Turboelectric wing Lift+Cruise Air Taxi 6 8 x 50 nm Air Line (multi-) Tilt Turboshaft rotor 15 Lift + cruise Hydrogen fuel cell • Aircraft designed through use of NASA conceptual design and sizing tool for vertical Tilt wing “Airliner” lift, NDARC.

• Concepts described in detail in publications “Concept Vehicles for Air Taxi Operations,” by Johnson, Silva and Solis. AHS Aeromechanics Design for Transformative Vertical Lift, San Francisco, Jan. 2018 and ”VTOL Urban Air Mobility Concept Vehicles for Technology Development,” by Silva, Johnson, Antcliff and Patterson. AIAA Aviation 2018, Atlanta, GA, June 2018.

06 Feb 2018

Relevant Research Areas for UAM

PERFORMANCE

ROTOR-ROTOR

aircraft optimization

INTERACTIONS

rotor shape optimization performance, vibration, handling qualities hub and support drag minimization

PROPULSION EFFICIENCY

aircraft arrangement airframe drag minimization high power, lightweight battery vibration and load alleviation light, efficient, high-speed electric motors power electronics and thermal management light, efficient diesel engine light, efficient small turboshaft engine

ROTOR-WING

efficient powertrains

INTERACTIONS

conversion/transition interactional aerodynamics Tiltwing + TurboElectric

SAFETY and

Quadrotor + Electric flow control

AIRWORTHINESS

FMECA (failure mode, effects, and Side-by-side + Hybrid criticality analysis)

STRUCTURE AND

component reliability and life cycle crashworthiness

AEROELASTICITY

propulsion system failures structurally efficient wing and rotor support Lift+Cruise + high voltage operational safety rotor/airframe stability TurboElectric crashworthiness durability and damage tolerance

OPERATIONAL

NOISE AND ANNOYANCE

EFFECTIVENESS

AIRCRAFT DESIGN

low tip speed disturbance rejection (control rotor shape optimization weight, vibration bandwidth, control design) flight operations for low noise handling qualities aircraft arrangement/ interactions all-weather capability active control cumulative noise impacts from fleet ops passenger acceptance cost (purchase, maintenance, DOC) active noise control cabin noise Red = primary focus metrics and requirements www.nasa.gov Blue = secondary focus

Summary

NASA RVLT is focused on • Overcoming significant barriers to the use of vertical lift vehicles in expanded missions • Providing technology leadership – Technologies and tools to enable low noise design and operations and reduce annoyance – Efficient configuration concepts that reduce fuel burn – Technologies that improve safety, mobility, payload and speed • Developing vision of the future for vertical lift; identifying technical challenges for new markets – Methods to assess advanced innovative concepts – Pathfinder for next gen emerging market technologies

Concept Vehicles to Focus Urban Air Mobility Research

• Open, publicly-available reference vehicle configurations

− Cover a wide range of technologies and missions

− Provide focus for trade studies and system analysis

− Assess failure modes and hazards of concept vehicle EAP

architectures

- Fifteen passengers (3000-lb payload) - 8x50 = 400-nm range - One passenger (250-lb payload) - turbo-electric tiltwing - 50-nm range - electric quadrotor - Six passengers (1200-lb payload) - Six passengers (1200-lb payload) - 2x37.5 = 75nm range - 4x50 = 200-nm range - turbo-electric Lift+Cruise VTOL - hybrid side-by-side helicopter • Aircraft designed using NASA conceptual design and sizing tool, NDARC.

• References – “Concept Vehicles for Air Taxi Operations,” by W. Johnson, C. Silva and E. Solis. AHS Aeromechanics Design for Transformative Vertical Lift, San Francisco, CA Jan. 2018 and ”VTOL Urban Air Mobility Concept Vehicles for Technology Development,” by Silva, Johnson, Antcliff and Patterson.

AIAA Aviation 2018, Atlanta, GA, June 2018.

Back up

Thin Haul Commuter (Conventional Takeoff and Landing)

Commercial (9-10 passenger) NASA Flight Testing – X57 Aircraft X-57 “Maxwell” • Cruise-sized wing: enabled by DEP system for takeoff/landing performance • High-efficiency cruise propellers: electric motors mounted at wingtips Zunum Aero Current Effort: • All-electric propulsion system: 40+ (Hybrid electric) • Demonstration of kWh battery, 240 kW across 14 technologies and advanced motors concepts through flight tests • Fully redundant powertrain • Develop technologies to extend the range Eviation (all electric) 9-10 passenger, commercial introduction planned for 2022 – 25 time frame

Urban Air Mobility – Vertical Takeoff and Landing (VTOL)

Move people inside congested urban areas from point to point using a vertical takeoff air vehicle Technologies UberElevate • Electric & hybrid -Electric distributed electric propulsion UberElevate Significant (~300-400 kw HEP) commercial • Fault tolerant propulsion, flight interest, initial systems commercial • Low-noise/annoyance introduction • Small ground/air footprint in low- likely to be in visibility Airbus - Vahana 2022 timeframe • 300 Wh/kg battery pack • Battery integration and safety • High-speed charging • Autonomous system capability • All weather operation • High speed interoperable digital communications network NASA strategy under development – will • Higher efficiency small gas turbine influence initial and subsequent generations for hybrid electric

Hybrid Electric Integrated Systems Testbed (HEIST)

• The HEIST is being developed to study power management and transition complexities, modular architectures, and flight control laws for turboelectric distributed propulsion technologies using representative hardware and piloted simulations • The HEIST is configured in the fashion of an iron bird to provide realistic interactions, latencies, dynamic responses, fault conditions, and other interdependencies for turboelectric distributed aircraft, but scaled to the 200 kW level.

• HEIST has power and voltage levels that would be considered subscale for a commercial transport, but test capability extends to the entire airplane system and can exercise all aspects of flight control, including cockpit operations.