X-57 Technical Papers

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2023

X-57 Cruise Motor and High-Lift Motor Mission Profile Power Analysis (Acquired October 31, 2023)
Author: Franklin “Keith” Harris, Axient/AFRC
Abstract: The X-57 Mission Profile Power Analysis was developed to evaluate the X-57 traction battery’s performance against Mod II, Mod III and Mod IV generic flight mission profiles. Traction battery system performance acceptance testing requirements were developed using data generated by this analysis. This analysis was also used to define the maximum power requirements for the traction system components.

X-57 Mod II Avionics Power Analysis (Acquired October 31, 2023)
Author: Franklin “Keith” Harris, Axient Corp/AFRC
Abstract: The X-57 Mod II Avionics Power Analysis was developed to provide the design requirements for the X-57 Avionics Power System. In the Mod II configuration, the two stock Tecnam P2006T Rotax engines are replaced with two electric motors. A high voltage traction battery (460 VDC nominal) supplies power for the motors. The Mod II avionics power design uses the stock Tecnam avionics power architecture as a baseline. The stock Tecnam power system utilizes three 12 VDC power sources, a battery and two alternators, to provided redundant avionics power. This redundancy was preserved in the X-57 avionics power architecture. A block diagram of the X-57 avionics system can be found in the “Mod II Architecture” worksheet of this documents. Since the X-57 electric motors do not have alternators or generators, two 13.8V DC Converters were added to replace the stock Tecnam alternators. Input power to these DC Converters is provide by the high voltage traction battery. The Tecnam stock lead acid battery was replaced with a Lithium Iron Phosphate (LiFePO4) battery. The Mod II Avionics Power Analysis provided the power requirements for the two 13.8V DC converters and the Lithium Iron Phosphate battery. Power requirement estimates for each subsystem used in this analysis were provided by manufacturer specifications, measured in the laboratory or provided by the subsystem design engineer. Typical power requirements and maximum power requirements were provided for each subsystem.

The Mod II Avionics Power Systems consists of seven 13.8 VDC buses, two 28 VDC Buses and two 23 VDC buses.

The avionics power requirements for Mod III configuration are the same as Mod II. The Mod III configuration replaces the stock Tecnam wing with a carbon fiber wing that is optimized for cruise conditions. The motors are located on the wingtips. The Mod IV Avionics Power Analysis is a separate analysis and is document number ANLYS-CEPT-032.

X-57 Mod IV Avionics Power Analysis (Acquired Date: October 2, 2023)
Author: Franklin “Keith” Harris, Axient/AFRC
Abstract: The X-57 Mod IV Avionics Power Analysis was developed to provide the design requirements for the X-57 Mod IV Avionics Power System. In the Mod IV configuration, twelve 13kW high lift motors and motor controllers are distributed along the leading edge of the Mod III carbon fiber wing to assist with lift during takeoff and landing. These motors are turned off during the cruise phase of the flight. A high voltage traction battery (460 VDC nominal) supplies power for the high lift motors. The Mod IV avionics power design uses the Mod II and Mod III power architecture as a baseline. Please see the Mod II Avionics Power Analysis (ANLYS-CEPT-020) for a description of the Mod II and Mod III avionics power design.

Structural Validation Testing for X-57 Airworthiness (Acquired: August 3, 2023)
Author: Wesley Li, AFRC
Abstract: Presented at the Air Vehicles Technology Symposium, Goal was to demonstrate and validate the structural integrity of the Mod III wing for flight. Presentation discusses: composite wing airworthiness approach, proof and loads calibration test success criteria, Mod II wing test article, load cases, predicted displacements from FEM, test setup, instrumentation, testing, test results, and lessons learned.

X-57 Maxwell Aircraft EMI/EMC Integration Lessons Learned (Acquired June 7, 2023)
Author: Sean Clarke (AFRC)
Abstract: This brief discusses some of the EMI/EMC integration lessons learned with regards to inverter and battery compatibility, conducted interference from inverter/motor, and tolerating residual radiated interference.

Cruise Propulsion System Thermal Analysis for NASA’s X-57 “Maxwell” Mod II Configuration (Acquired May 4, 2023)
Authors: Nicholas K. Borer (LaRC), Trong Bui (AFRC), Andrews D. Smith (GRC)
Abstract: The X-57 “Maxwell” is NASA’s flight demonstrator for distributed electric propulsion technologies. The X-57 Mod II configuration is designed to test the electric cruise propulsion system for X-57 and features an electric cruise motor mounted in an integral nacelle on each wing. The electric motors and associated control equipment for X-57 Mod II are air-cooled; therefore, they require adequate cooling airflow to stay within temperature limits set by the X-57 project in all relevant flight conditions. A computational flow analysis was conducted to estimate the internal flow properties of the X-57 Mod II cruise nacelles in three critical flight conditions. These flow properties were then used to determine the boundary conditions for individual component thermal models, which were used to estimate individual component operating temperatures. 

X-57 Cruise Motor Controller Design and Testing (Acquired: May 4, 2023)
Authors: Jacob Terry, AFRC; Susanah Kowalewski, GRC; David Avanesian, GRC; Sean Clarke, AFRC
Abstract: Presented at the AIAA Electric Aircraft Technology Symposium. This presentation provides a high level overview of the Mod II X-57 cruise motor controllers (CMCs) to include the CMC design requirements;  the CMC redesign effort; prototype hardware overview; initial CMC dyno testing and performance; CMC acceptance test program; CMC vibration and thermal testing; and lessons learned.

Computational Analysis on the Effects of High-lift Propellers and Wingtip Cruise Propellers on X-57 (Acquired May 1, 2023)
Authors: Seung Yoo, AFRC;. Jared Duensing, STC; Karen Deere, LaRC; Jeff Viken, LaRC; Michael Frederick, AFRC
Abstract: Demonstrate technologies intended to improve aerodynamic efficiency and reduce carbon footprint. Study focused on effects of high-lift propellers and wingtip mounted cruise propellers; high-lift propellers and wingtip mounted cruise propellers modeled separately;  understanding of the aerodynamics of the vehicle computational model for wingtip mounted cruise propeller analysis; and performance benefit.

X-57 Electromagnetic Interference Design, Integration and Test Consideration (Acquired April 24, 2023)
Authors: David Avanesian (GRC), Matthew Granger (GRC), Michael Garrett (GRC), Sean Clarke (AFRC)
Abstract: X-57 is NASA’s first all electric aircraft that utilizes existing airframe of Tecnam 2006P GA aircraft integrated with new all electric power train. The objective of the project was to deliver high performing distributed electric propulsion system while developing US industry in the area of EAP. The project was divided into three distinct flight mods, each serving as a risk reduction efforts to final mod where full distributed power train with highly modified wing structure would be tested in flight.

Flight weight, efficient power electronics are enablers for distributed, electric aircraft propulsion systems, and GRC team has developed high power and highly efficient SiC based converters for both cruise and high lift systems on the aircraft. Both controller’s development efforts demonstrate a means to achieve an in-the-nacelle controller with purely passive cooling while maintaining high efficiency. This paper describes the lessons learned on design, integration, and testing challenges that X-57 faced while developing these novel technologies.

X-57 Whirl Flutter  Propeller Stability Assessments (Acquired: April 21, 2023)
Authors: Josiah Waite, LaRC: Andrew Kreshosk, U.S. Army Research Laboratory Adelphi; Jinwei Shen, University of Alabama; Kyle Nelson, University of Alabama
Abstract: Presented for the Aerospace Flutter and Dynamics Council. Presentation included X-57 whirl flutter analysis overview, the limitations, assumptions and challenges; whirl flutter analysis workflow and parameter variation; flight and trim conditions; whirl flutter cases such as windmilling; high lift propeller rotor stability; low speed aeroacoustics wind tunnel tests; damping estimation; predicted high lift propeller stability; and overall conclusions.

X-57 High Lift Motor Controller Design and Testing (Acquired: April 18, 2023)
Authors: Jacob Terry, AFRC; Susanah Kowalewski, GRC; David Avanesian, GRC; Sean Clarke, AFRC
Abstract: Presented at the AIAA Electric Aircraft Technology Symposium. This presentation provides a high level overview of the X-57 high lift motor controller (HLMC) design and testing to include: distributed electronic propulsion (DEP) architecture; HLMC key objectives; HLMC electrical and mechanical design; HLMC thermal and mechanical design; HLMC power and efficiency testing; HLMC qualification testing; wind tunnel testing; and conclusions.

X-57 Cockpit Display System Development and Features (Acquired April 11, 2023)
Authors: Adam Curry, AFRC; Sean Clarke AFRC; Aamond Samuel, AFRC
Abstract: The X-57 Maxwell airplane [1,2] cockpit display system includes multiple, pilot-selectable pages in a multifunction display with detailed statuses of critical parameters from each of the cruise motors (CMs), cruise motor controllers (CMCs), and battery control modules (BCMs), as well as air temperature measurements at reference locations in the passive ram-air cooling ducts for the motors, controllers, and auxiliary equipment. The user (pilot or ground-test crew) can select overview pages that are part of the standard instrument panel scan pattern or switch to a series of detail or debug pages as the system is operating using a rotary position switch in the cockpit. This paper presents and describes each of these displays, and gives an overview of the development and verification process. The critical data condensed for cockpit handling from each of the major electric propulsion and traction power systems are discussed.

Development of the Mod II X-57 Piloted Simulator and Flying Qualities Predictions (Acquired March 29, 2023)
Authors: Ryan Wallace, AFRC; James Reynolds, AFRC; Mike Frederick, AFRC; Dana Mcminn, LaRC; Dave Cox, LaRC and Nick Borer Larc
Abstract: This paper discusses the development of the X-57 Mod II piloted simulator along with the predicted flight dynamics of the airplane. The piloted simulator models were initially based on data published by Tecnam on a P2006T airplane but were further improved upon through parameter identification of flight data as well as modeling tools such as computational fluid dynamics. In addition to having accurate flight models, a realistic cockpit was constructed to aid pilot training. From the piloted simulator, an understanding of how the airplane will behave throughout the flight envelope using established FAR and MIL standards is discussed. Using the simulation results, this paper will show that the airplane is predicted to be statically and dynamically stable as well as having Level 1 flying qualities.

X-57 Maxwell Aircraft – Certification Pathfinder (Acquired January 19, 2023)
Authors: Heather Maliska (AFRC) and Sean Clarke (AFRC)
Abstract: X-57 Project Need – Advance the Nation’s ability to design, test, and determine airworthiness of distributed electric and aero-propulsive coupling technologies, which are a critical enabler of emerging, advanced air mobility markets. The value of X-57 lies in advancing the Nation’s ability to design, test, and certify electric aircraft, which will enable entirely new markets. The Mod II flight test program is a pathfinder for the experimental propulsion system performance and reliability to reduce the risk in the X-57 configuration.

2022

Application of Framework for Estimating Performance and Uncertainty for Modified Aircraft Configurations Using NASA’s X-57 Maxwell (Acquired November 23, 2022)
Authors: Casey L. Denham (LaRC), Mayuresh Patil (Georgia Institute of Technology) Christopher J. Roy (Virginia Tech Blacksburg), Natalie Alexandrov (LaRC)
Abstract: A framework to estimate the performance and associated uncertainty of modified configurations of certified aircraft is applied to the X-57 Maxwell aircraft. In previous theoretical studies, the framework was shown to predict performance and uncertainty bounds accurately. The X-57 Maxwell is an experimental aircraft designed to demonstrate the benefits of distributed electric propulsion through a series of four incremental modifications to a Tecnam P2006T aircraft. The available models and data are first shown to be within the application domain of the framework. We then apply the framework to two X-57 Maxwell modifications. We compare the estimated performance and associated uncertainties against the airworthiness criteria. The results indicate that the framework is a promising tool for the certification by analysis workflow. We expect the framework to reduce and supplement the flight testing required to show compliance to airworthiness certification criteria for a modified configuration.

X-57 Maxwell Airworthiness Validation Plan (Acquired October 5, 2022)
Authors: Herbert Schlickenmaier (HS Advanced Concepts), Mark Anderson (Flight Test Solutions, LLC), Evan Harrison (Georgia Institute of Technology) Edwin Hooper (Aviation Consultant, Inc.), Jeff Knickerbocker (Sunrise Certification and Consulting, Inc.)
Abstract: This report is a Final Airworthiness Validation Plan (AVP) and describes how an aircraft like X-57 does (and does not) meet current airworthiness standards. The objective of this report is to create an example certification basis, associated means of compliance (MoC), and method of compliance for a distributed electric propulsion airplane under 14 Code of Federal Regulations (CFR) Part 21, “Certification Procedures for Products and Articles,” and its associated relevant sections of 14 CFR for “Airworthiness Standards” of Part 23, “Normal Category Airplanes,” Part 33 “Aircraft Engines,” and Part 35 “Propellers.”

OPS-CEPT-001 X-57 Maxwell Mod II Go/No Go (Publish Date: September 27, 2022)
OPS-CEPT-001 X-57 Maxwell Mod II Go/No Go (ADA-compliant)
Author: Ethan Baumann, NASA AFRC
Abstract: This document formally documents the Go/No-Go Parameter List for the X57 Mod II Flights. This document will be updated as necessary to properly reflect and capture project needs. This document applies only to the X-57 Mod II flights. Only Safety of Flight, Safety of Test, and Mission Critical parameters are tracked as part of the Go/No-Go Parameter List.

OPS-CEPT-002 X-57 Maxwell Mission Operations Plan (Publish Date: July 12, 2022)
OPS-CEPT-002 X-57 Maxwell Mission Operations Plan (ADA-compliant)
Author: Ethan Baumann, NASA AFRC
Abstract: This document formally documents the X-57 Mod II Mission Operations plan. This plan encompasses the Mission Rules, Mission Limits, Communication Plan, Control Room Operations Plan, and the Control Room Training Plan in effect for all X-57 mission operations, which require control room support conducted with the X-57 Maxwell aircraft (tail number NASA 857) in the Mod II configuration.

X-57 “Maxwell” High-Lift Propeller Test For Improved Thrust Measurements And Slipstream Velocities (Acquired: April 27, 2022; Presented: June 28, 2022)
Authors: Brandon Litherland, Nicholas Borer, Nikolas Zawodny, Zachery Frederick  (NASA Langley Research Center, Hampton, Virginia)
Abstract: NASA’s X-57 “Maxwell” concept uses distributed electric propulsion technology that includes 12 high-lift propellers (HLPs). The HLPs are designed to augment lift at low speeds, and are otherwise turned off and passively fold against nacelles in cruise flight. The HLPs enable increased aerodynamic efficiency in the cruise configuration by allowing for a much more highly-loaded wing without sacrificing low-speed capabilities. The HLPs have been extensively analyzed, and full-scale prototypes have been tested at NASA Langley’s Low Speed Aeroacoustic Wind Tunnel (LSAWT) in 2020 and 2022. This presentation presents the results of the LSAWT tests.

Computational Analysis Of The X-57 Maxwell Airplane At Unpowered Conditions (Preliminary Fuselage) (Acquired: March 8, 2021, Publication Date: April 1, 2022)
Authors: Karen A. Deere, Jeffrey K. Viken, Sally A. Viken and Melissa B. Carter, NASA Langley Research Center, Hampton, Virginia, Michael R. Wiese and Norma L. Farr Craig Technologies, Hampton, Virginia
Abstract: The X-57 Maxwell is an all-electric airplane that implements a distributed electric propulsion system to demonstrate that high-efficiency electric propulsion can be integrated with aerodynamics to increase the performance of an airplane. To this end, distributed electric fans were installed on the wing to provide increased flow over the wing at the low takeoff and landing speeds of the X-57. The low-speed lift augmentation allows for a reduction in wing area for cruise optimization. The X-57 wing area was reduced to 42 percent of the wing area of the baseline aircraft, a Tecnam P2006T. With this reduced wing area and the electric propulsion system, it is estimated that the X-57 will cruise on less than one-third the total energy compared to the baseline aircraft. To meet the cruise performance goal at a Mach number of 0.233 at an altitude of 8000 feet, the X-57 has a cruise lift coefficient of 0.7516 and needs to have a cruise drag coefficient of 0.05423 or less. Based on specific criteria addressed in this paper, the X-57 Maxwell is estimated to meet its powered landing goal of a maximum lift coefficient of 4.0.

X-57 Ground Dynamics Modeling and Analysis (Acquired: April 7, 2022)
Authors: Loren J. Newton, Ryan D. Wallace, NASA Armstrong Flight Research Center, Edwards, CA
Abstract: This paper presents simulation work to assess the ground handling behavior of the X-57 airplane, prior to its first flight under electric propulsion. A tire deformation model was  fit to manufacturer ground testing data to develop a detailed simulation model of previously unmodeled rolling drag forces on the tires. A special modeling effort corrected for a difference  between the runway surface in the manufacturer data (grass) and in intended X-57 surface operations (asphalt/concrete). Analysis based on variation in the test conditions of the  manufacturer test data showed that uncertainty in the new estimated rolling drag model should lead to no more than 1.5-percent uncertainty in the takeoff acceleration. Another batch simulation series swept across ground operating conditions and airplane configurations, characterizing turning radii and roll angles experienced for different open-loop steering commands in these various situations. This simulation allowed the identification of ground handling characteristics even beyond the regime of normal operations.

2021

X-57 “Maxwell” High-Lift Propeller Testing and Model Development (Presented August 4, 2021)
Authors: Brandon Litherland, Nicholas K. Borer, Nikolas Zawodny
Abstract: NASA’s X-57 “Maxwell” distributed electric propulsion flight demonstrator has a high-lift system that includes 12 fixed-pitch high-lift propellers located upstream of the wing leading edge for lift augmentation at low speeds. These high-lift propellers are not required at higher speeds and are folded conformally along the nacelles to reduce drag when not in operation. Aircraft performance models and flight simulations incorporate propeller performance to predict thrust, moments, and power consumption and propeller model accuracy is important in identifying safe operating regimes for this aircraft. Current high-lift propeller performance models have been verified and calibrated against numerous computational fluid dynamics analyses under a variety of flight conditions. We performed a series of full-scale wind tunnel tests at the NASA Langley Research Center Low Speed Aeroacoustic Wind Tunnel to further validate these models, to identify any adverse operating conditions for these propellers, and to assess the accuracy of the facility’s new Propeller Test Stand. The results indicate that the models accurately predicted performance and that the right-handed propeller showed lower torque and thrust for a given propeller speed compared to the left-handed version. Acoustic data support these measurements, showing higher tonal noise for the left versus right propeller. We suspect this is due to slight differences in the material properties between the early production (right) and more recent (left) blade sets leading to greater detwisting in the right-handed blades under load. Both propellers demonstrated very stable operation throughout the test including during deployment, stowing, and windmilling.  This Slide Show was presented at AIAA Aviation Forum 2021.

X-57 “Maxwell” High-Lift Propeller Indicator and Control Requirements (Published: June 17, 2021)
Author: Claudia Sales
Abstract: This document establishes the interface requirements for the X-57 High Lift Propeller Control (HiPC) and the High Lift Propeller Indicator (HiPI) subsystems. The HiPI and HiPC shall follow the A/B system architecture for the X-57 aircraft. The A/B architecture is utilized by flight critical systems including the high lift propulsors (high lift propeller, high lift motor and high lift motor controller). This architecture provides redundancy in the event of an A system failure or a B system failure. The A and B high lift propulsors are distributed across the left and right wing so that a failure of an A system or B system will not produce an abrupt asymmetric thrust event and cause an adverse yaw condition for the aircraft. The HiPI and HiPC provide the indication and control interfaces between the X-57 cockpit and the 12 High lift motor controllers (HLMCs).

X-57 “Maxwell” High-Lift Propeller Testing and Model Development (Acquired June 2, 2021)
Authors: Brandon Litherland, Nicholas K. Borer, Nikolas Zawodny
Abstract: NASA’s X-57 “Maxwell” distributed electric propulsion flight demonstrator has a high-lift system that includes 12 fixed-pitch high-lift propellers located upstream of the wing leading edge for lift augmentation at low speeds. These high-lift propellers are not required at higher speeds and are folded conformally along the nacelles to reduce drag when not in operation. Aircraft performance models and flight simulations incorporate propeller performance to predict thrust, moments, and power consumption and propeller model accuracy is important in identifying safe operating regimes for this aircraft. Current high-lift propeller performance models have been verified and calibrated against numerous computational fluid dynamics analyses under a variety of flight conditions. We performed a series of full-scale wind tunnel tests at the NASA Langley Research Center Low Speed Aeroacoustic Wind Tunnel to further validate these models, to identify any adverse operating conditions for these propellers, and to assess the accuracy of the facility’s new Propeller Test Stand. The results indicate that the models accurately predicted performance and that the right-handed propeller showed lower torque and thrust for a given propeller speed compared to the left-handed version. Acoustic data support these measurements, showing higher tonal noise for the left versus right propeller. We suspect this is due to slight differences in the material properties between the early production (right) and more recent (left) blade sets leading to greater detwisting in the right-handed blades under load. Both propellers demonstrated very stable operation throughout the test including during deployment, stowing, and windmilling.  This Conference Paper was presented at AIAA Aviation Forum 2021.

X-57 “Maxwell” High-Lift Propeller Testing and Model Development (Acquired June 2, 2021) 
Authors: Brandon L. Litherland, Borer, Nicholas K., and Nikolas S. Zawodny
Abstract: This conference paper was presented at the AIAA Aviation Conference (Virtual) Forum 2021.  NASA’s X-57 “Maxwell” distributed electric propulsion flight demonstrator has a high-lift system that includes 12 fixed-pitch high-lift propellers located upstream of the wing leading edge for lift augmentation at low speeds. These high-lift propellers are not required at higher speeds and are folded conformally along the nacelles to reduce drag when not in operation. Aircraft performance models and flight simulations incorporate propeller performance to predict thrust, moments, and power consumption and propeller model accuracy is important in identifying safe operating regimes for this aircraft. Current high-lift propeller performance models have been verified and calibrated against numerous computational fluid dynamics analyses under a variety of flight conditions. We performed a series of full-scale wind tunnel tests at the NASA Langley Research Center Low Speed Aeroacoustic Wind Tunnel to further validate these models, to identify any adverse operating conditions for these propellers, and to assess the accuracy of the facility’s new Propeller Test Stand. The results indicate that the models accurately predicted performance and that the right-handed propeller showed lower torque and thrust for a given propeller speed compared to the left-handed version.

2020

X-57 High-Lift Propeller Control Schedule Development (Acquired November 17, 2020)
Authors: Nicholas K. Borer, Michael D. Patterson
Abstract: The NASA X-57 distributed electric propulsion flight demonstrator uses a high-lift propeller system to maintain low-speed capability with a highly loaded, cruise-efficient wing. Previous research showed that the control scheme for the high-lift propellers was a crucial factor to enable an adequate balance between stabilized glideslope control and appropriate lift margin during the approach-to-landing phase of flight. This paper expands the high-lift propeller control considerations to include all phases of low-speed flight, including preflight, taxi, takeoff, initial climb, approach, and landing.

All-Electric X-Plane, X-57 Mod II Ground Vibration Test (Acquired August 28, 2020)
Authors: Natalie Dawn Spivey, Samson Truong, Roger Truax
Abstract: As part of the National Aeronautics and Space Administration New Aviation Horizons initiative to demonstrate and validate future high-impact concepts and technologies, the X-57 Maxwell airplane–the first all-electric X-plane–was conceived to advance research in the area of electric propulsion to show the feasibility of minimizing fuel use, reducing emissions, and lowering noise during flight. Through several configuration modifications to the X-57 airplane, validation of electrical-powered flight with increasing efficiency between each modification when compared to the baseline original airplane is anticipated. In the case of the X-57 Modification II airplane, a ground vibration test was needed to identify the airplane structural modes and use them to update and validate the finite element model.  This paper will highlight the testing performed to acquire the modal data as well as the results.

A Performance Analysis of Folding Conformal Propeller Blade Designs (Acquired May 18, 2020)
Authors: Litherland, Brandon L.; Derlaga, Joseph M.
Abstract: NASA’s X-57 Maxwell flight demonstrator has a high-lift system that includes 12 fixed pitch high-lift propellers located upstream of the wing leading edge for lift augmentation at low speeds. The method of designing the high-lift blades permits several variations of blade cross-section placement along the nacelle surface and a comparative performance analysis was needed to determine if any particular design showed significant benefits. This conference paper analyzes the performance of three conformal high-lift propeller designs and compared them to that of a non-conformal baseline propeller to establish both the benefit of stowable blades and the value of each variation.

X-57 Maxwell NASA’s First Electric X-Plane (Acquired May 4, 2020)
Authors: Sydney Schnulo, Dustin Hall
Abstract: This presentation was made at COSI Science Fest 7, 9 May 2020, Columbus, OH.  NASA’s first all-electric experimental airplane! Some primary goals the X-57 has include reducing the energy required in flight; Use existing state-of-the-art technology; Learn about the integration challenges of electric aircraft.

Status Report on Aeroelasticity in the Vehicle Development for X-57 Maxwell (Publication Date: June 25, 2018, Acquired April 13, 2020)
Authors: Heeg, Jennifer; Stanford, Bret K.; Wieseman, Carol D.; Massey, Steven J.; Moore, James; Truax, Roger; Miller, Kia
Abstract: Risk reduction is the objective of the X-57 Maxwell aeroelasticity team. The X-57, NASA’s experimental electric propulsion aircraft, has a long thin wing with primary propulsion systems located at the wing tips and high lift motors distributed along the span. Many of the classical aeroelastic concerns associated with such a configuration were addressed through early design decisions. The as-designed intermediate flight vehicle configurations show flutter mechanisms associated with flexible models of control surface systems –the stabilator, flaps and ailerons. Improvements to the analytical models, based on ground test data and project decisions about flight operations, show improved prospects of the vehicle being aeroelastically stable throughout the flight envelope. On-going ground testing and further analyses will lend credibility to the flutter predictions and vehicle safety.  This paper was presented at AIAA Aviation 2018 and Aeronautics Forum and Exposition (AIAA AVIATION 2018).

X-57 Wing Structural Load Testing (Acquired April 13, 2020)
Authors: Eric J. Miller, Wesley Li, Ashante Jordan, Shun-Fat Lung
Abstract: This conference paper was presented at the Aviation 2020 (Reno NV) Conference.  The X-57 flight project will provide an opportunity to assess the benefits of distributed electric propulsion. The plan is to use a TECNAM P2006T twin-engine light aircraft (Aeronautiche TECNAM S.p.A., Capua, Italy) as the baseline aircraft, but design and fabricate a new wing to test the technology. The wing when fully integrated onto the X-57 TECNAM P2006T fuselage will incorporate two wingtip cruise electric motors and 12 high-lift electric motors along the wing span. The testing described in this paper confirmed the strength of the X-57 wing for flight and provided an opportunity to calibrate the wing flight strain gages for monitoring loads in flight. The X-57 wing was qualification tested in the National Aeronautics and Space Administration Armstrong Flight Research Center Flight Loads Laboratory. This paper documents the airworthiness approach, test setup, instrumentation, and preliminary results. The X-57 ground load testing lessons learned are also discussed.

Development of a Thermal Management System for Electrified Aircraft (Published March 01, 2020, Acquired March 18, 2020)
Authors: Jeff Ryes W. Chapman, Sydney L. Schnulo, and Michael P. Nitzsche
Abstract: This Technical Memorandum covers the refinement of thermal models from design estimates to actual fabricated performance. Matching the experimental data of the first fully electrified version of the X-57 Maxwell experimental vehicle requires high fidelity thermal analysis to sufficiently capture the electric motor and inverter temperature profiles.  The methods and experiments described are a snapshot of on-going work and include challenges encountered during motor performance verification.

An Experimental Approach to a Rapid Propulsion and Aeronautics Concepts Testbed (Acquired February 4, 2020)
Authors: McSwain, Robert G.; Geuther, Steven C.; Howland, Gregory; Patterson, Michael D.; Whiteside, Siena K.; North, David D. (Principal Investigator); Glaab, Louis J. (Editor); Rhew, Ray D. (Editor)
Abstract: Modern aircraft design tools have limitations for predicting complex propulsion-airframe interactions. The demand for new tools and methods addressing these limitations is high based on the many recent Distributed Electric Propulsion (DEP) Vertical Take-Off and Landing (VTOL) concepts being developed for Urban Air Mobility (UAM) markets. This paper proposes that low cost electronics and additive manufacturing can support the conceptual design of advanced autonomy-enabled concepts, by facilitating rapid prototyping for experimentally driven design cycles.

eVTOL Passenger Acceptance (Publication date: January 1, 2020)
Authors: Thomas Edwards, George Price
Abstract: With the expected introduction of electric vertical takeoff and landing (eVTOL) aircraft for urban air mobility (UAM) services, passenger acceptance has become an issue of interest to manufacturers and operators. This study took an initial look at what passengers expect from an eVTOL UAM flight experience – what aspects matter most, what might be acceptable, and where there are gaps in our understanding.  The analysis included a literature search and interviews with experts from the aviation community to identify passenger concerns and potential mitigations. Passenger concerns were found to fall into six general categories: perceived safety, noise and vibration, availability and access, passenger well-being, concern for the environment, and vehicle motion.

2019

Using CFD to Develop NASA’s X-57 Maxwell Flight Simulator (Published November 17, 2019, Acquired December 20, 2019)
Authors: Duensing, Jared; Housman, Jeffrey; Jensen, James; Maldonado, Daniel; Kiris, Cetin; Fredrick, Michael; Yoo, Seung; Bui, Trong;
Abstract: This is a slide presentation from a conference showing graphs, charts, and illustrations depicting various CFD simulation processes and a high level background on the X-57.

Design and Performance of a Hybrid-Electric Fuel Cell Flight Demonstration Concept (Published June 25, 2018, Acquired December 09, 2019)
Authors: Borer, Nicholas K., Geuther, Steven C., Litherland, Brandon L., Kohlman, Lee
Abstract: As electric powertrain and propulsion-airframe integration technologies advance, airborne electric propulsion concepts appear to be on the cusp of disrupting or transforming aviation markets. One of the many challenges to this transformation lies within the onboard energy storage and generation technologies. State-of-the-art battery technology is heavy and lacks support infrastructure; purely combustion-based solutions to electrical power generation suffer from increased inefficiency as compared to a traditional combustion powertrain. This paper explores another alternative: a hybrid-electric, solid oxide fuel cell power system.

Flight Performance Maneuver Planning for NASA’s X-57 “Maxwell” Flight Demonstrator – Part 1: Power-Off Glides (Published June 17, 2019, Acquired December 09, 2019)
Authors: Borer, Nicholas K., Cox, David E., Wallace, Ryan D.
Abstract: Distributed Electric Propulsion technology is expected to yield up to a fivefold increase in high-speed cruise efficiency for NASA’s X-57 “Maxwell” flight demonstrator when compared to a combustion-powered general aviation baseline. A portion of this increased efficiency is due to beneficial aero-propulsive interaction inherent to the distributed propulsion architecture.  The measure of the relative increase in efficiency between a conventional and distributed propulsion wing will be extracted from comparisons between flight test data from the electrically powered X-57 Mod II configuration with a conventional wing, and from the electrically powered X-57 Mod III/IV configuration with a distributed propulsion wing.

X-57 60kW Permanent Magnet Synchronous Cruise Motor Finite Element Electromagnetic Modeling (Published 2019, Acquired November 27, 2019)
Authors: Marrufo, Marco; Kloesel, Kurt
Abstract: This is a poster with X-57 Technical Data and information about the software used to model 2 and 3 dimensional models of the cruise motors on the X-57.

Certification Gap Analysis (Published Sep 01, 2019, Acquired Nov 27, 2019)
Authors: Herbert Schlickenmaier, Mark G. Voss, Ronald E .Wilkinson
Abstract: This report describes a generic method for addressing any new technology to its associated set of regulations and certification criteria. The result is a framework under which a detailed assessment can be conducted. Using just such a framework, the report maps the detailed updated regulations and evolving ASTM standards to the particular technology planning and tests. As a result, a roadmap of NASA technology is documented that shows clear transfer of technology data to industry (standards developers, as well as technology developers) and the FAA regulatory policy and certification staff upon whom certification and policy will be data-driven. A clear description of benefits and gaps are identified, as well.

Certification Rules and Standards Review (Published Sep 01, 2019, Acquired Nov 27, 2019)
Authors: Herbert Schlickenmaier, Mark G. Voss, Ronald E .Wilkinson
Abstract: This report characterizes the certification practices for electric propulsion systems by modeling changes to current engine and propeller certification practices (14 CFR 23, 33 and 35 and means of compliance in standards developed by ASTM Committee F39 and F44). Industry technology paths are varied, so this report focuses on insights from the NASA X-57 Maxwell Distributed Electric Propulsion flight demonstrator system technology project. There are 122 sections of the regulation reviewed, where 28 needed tailoring or revision. A second report will examine the regulations to the X-57 system development products. A final report will describe a general regulatory gaps method for new vehicle concepts.

Certification Coordination Roadmap (Published Sep 01, 2019, Acquired Nov 27, 2019)
Authors: Herbert Schlickenmaier, Mark G. Voss, Ronald E .Wilkinson
Abstract: Innovative technology has to prove itself in the context of legacy regulations. The knowledgeable technologist must engage standards process and regulating authorities to understand their roles and to advise the effect of new technology, and with manufacturers to demonstrate technology benefit. A model for Innovative Technology Environment relating NASA to industry, standards and regulation is described. The needs of the standards community of the X-57 are identified, and a NASA standards structure is described. No NASA project works with standards and regulatory organizations like the X-57.

Design and Test of a Structurally-Integrated Heat Sink for the Maxwell X-57 High Lift Motor Controller (Published 2019, Acquired November 22, 2019, Presented Aug. 26-30, 2019)
Authors: Edwards, Ryan; Smith, Andrew.
Abstract: An innovative thermal management solution was conceptualized, built and tested for the X57 Maxwell electric airplane. A combination of commercial CFD codes and bespoke thermal modeling tools were employed to rapidly develop a structurally-integral power electronics heat sink. A structurally-integrated heat sink was devised for the GIMC-SCEPTOR high lift motor controller. The nacelle-conforming sink is designed to dissipate heat from the power electronics assembly while simultaneously acting as the mechanical load path between the wing structure and high lift motor.  This was a presentation presented at TFAWS at LaRC in August 2019.

X-57 Mod 2 Motor Thermal Analysis (Acquired November 07, 2019)
Authors: Chin, Jeffrey C.; Tallerico, Thomas F.; Smith, Andrew D.
Abstract: This work covers the refinement of thermal models from design estimates to actual fabricated performance. Matching the experimental data of the first fully electrified version of the X-57 Maxwell experimental vehicle requires high fidelity thermal analysis to sufficiently capture the electric motor and inverter temperature profiles.  The methods and experiments described are a snapshot of on-going work and include challenges encountered during motor performance verification.

NASA Electrified Aircraft Propulsion Efforts (Publication date: October 07, 2019, Acquired November 06, 2019)
Authors: Jansen, Ralph H., Bowman, Cheryl L., Clarke, Sean C., Avanesian, David, Dempsey, Paula J., Dyson, Rodger W.
Abstract: NASA’s broad investments in Electrified Aircraft Propulsion (EAP) are reviewed in this paper. NASA investments are guided by an assessment of potential market impacts, technical key performance parameters, and technology readiness attained through a combination of studies, enabling fundamental research, and flight research. NASA has determined that the impact of EAP varies by market and NASA is considering three markets: national/international, on-demand mobility, and short haul regional air transport.  This paper focuses on the vehicle related activities, however there are related NASA activities in air space management and vehicle autonomy activities as well as a breakthrough technology project called the Convergent Aeronautics Solutions Project.

Further Development of the NASA X-57 Maxwell Mission Planning Tool for Mods II, III, and IV (Acquired August 27, 2019)
Authors: Sydney L. Schnulo, Dustin L. Hall, Andrew D. Smith
Abstract: This paper details the continued development of the X-57 Mission Planning Tool and demonstrates its capability to assess the effect of subsystem performance on the integrated aircraft system.  The tool can also analyze how the aircraft will react if performance goals, such as electric component efficiencies, are either not met or exceeded.  The results presented achieve maximum cruise duration of the X-57 through each stage in development as well as trajectory analyses predicting component efficiency limits and energy consumption.

Development of a Maxwell X-57 High Lift Motor Reference Design (Acquired August 26, 2019)
Authors: Dustin L. Hall, Jeffrey C. Chin, Aaron D. Anderson, Jerald T. Thompson, Andrew D. Smith, Ryan D. Edwards, Kirsten P. Duffy
Abstract: This report covers the design and development process taken to create an open reference model representative of the 12 lift augmenting motors. A combined worst case scenario was used as the design point, which represents the simultaneously occurring worst case aspects of thermal, static stress, electromagnetic, and rotor dynamic conditions. This work also highlights the tightly coupled nature of aerospace electric motor design, requiring constant iteration between all disciplines involved.

Battery Evaluation Profiles for X-57 and Future Urban Electric Aircraft (Published August 17, 2020)
Authors: Jeff Chin, Eliot Aretskin-Hariton, Daniel Ingraham, Dustin Hall, Sydney L. Schnulo, Justin Gray and Eric S. Hendricks
Abstract: Battery energy density is one of the most critical design parameters for sizing all-electric aircraft, but it’s easily overestimated. Establishing the effective, usable energy density is confused by varying degrees of margin needed to account for structural and thermal management between different cell chemistry and pack designs. A better methodology is needed to fairly compare emerging battery technologies for electric aircraft. This paper serves to better inform battery development, and, similarly, provide aircraft designers with more realistic assumptions for applying knockdown margins in their designs.

Overview of the X-57 Structure Requirements, Modifications, and Airworthiness (Published June 21, 2019)
Author: Li, Wesley
Abstract: This presentation is an overview of the X-57 structural design requirements for the propeller systems hide and power systems, modifications to the existing Tecnam aircraft, as well as the structural airworthiness process which includes the analysis and ground testing of the composite wing.

Computational Analysis of the External Aerodynamics of the Unpowered X-57 Mod-III Aircraft (Presentation date June 21, 2019)
Authors: Seung Y. Yoo, Jared C. Duensing
Abstract: Investigations of the external aerodynamics of the unpowered X-57 using computational fluid dynamics are presented.

Computational Analysis of the External Aerodynamics of the Unpowered X-57 Mod-III Aircraft (Conference Paper) (Published June 17, 2019)
Authors: Seung Y. Yoo, Jared C. Duensing
Abstract: Investigations of the external aerodynamics of the unpowered X-57 Mod-III configuration using computational fluid dynamics are presented. Two different Reynolds-averaged Navier-Stokes flow solvers were used in the analysis: the STAR-CCM+ unstructured solver using polyhedral grid topology, and the Launch Ascent Vehicle Aerodynamics (LAVA) structured curvilinear flow solver using structured overset grid topology. A grid refinement study was conducted and suitable grid resolution was determined by examining the forces and moments of the aircraft. Code-to-code comparison shows that STAR-CCM+ and LAVA are in good agreement both in quantitative values and trends.

Computation Simulations of Electric Propulsion Aircraft: The X-57 Maxwell (Presented June 13, 2019)
Authors: Seung Y. Yoo, Jared C. Duensing, Jeffrey A. Housman, Daniel Maldonado, James C. Jensen, Cetin C. Kiris
Abstract: Outline – Introduction: X-57 CFD task overview; Motivation. Part I, Computational simulations without propulsion: Establishing CFD (Computational Fluid Dynamics) Best Practices – Grid generation – Mesh refinement study – Numerical methods – Wind tunnel validation study; Power-Off Aerodynamic Database Results. Part II, Computational simulations with propulsion: Cruise Power-On Database; High-Lift Power-On Database. Summary.

Gradient-Based Propeller Optimization with Acoustic Constraints, (Published Jan 07, 2019, Acquired May 03, 2019)
Authors: Ingraham, Daniel; Gray, Justin; Lopes, Leonard V.
Abstract: This  paper looks at combining a blade element momentum theory tool with an acoustic prediction tool to optimize a propeller subject to both aerodynamic and acoustic constraints.

An Overview of the Layered and Extensible Aircraft Performance System (LEAPS) Development, (Published 2018, Acquired Feb 12, 2019)
Authors: Welstead, Jason R.; Caldwell, Darrell; Condotta, Ryan; Monroe, Nerissa.
Abstract: The Layered and Extensible Aircraft Performance System (LEAPS) is a new sizing and synthesis tool being developed within the Aeronautics Systems Analysis Branch (ASAB) at NASA Langley Research Center.  This paper examines the five challenge problems for LEAPS that includes an analysis of the X-57 Maxwell distributed electric propulsion aircraft.

Establishing Best Practices for X-57 Maxwell CFD Database Generation, (Published Jan 07, 2019, Acquired Feb 11, 2019)
Authors: Jared C. Duensing, Seung Y. Yoo, Daniel Maldonado, Jeffrey A. Housman, James C. Jensen, and Cetin C. Kiris.
Abstract: This paper examines the comparisons made between CFD solutions and experimental data collected in the 12-foot Low-Speed Wind Tunnel at NASA Langley Research Center in order to validate predictions.

Exploring the Effects of Installation Geometry in High-Lift Propeller Systems (Publication Date: January 8, 2018, Acquired February 5, 2019)
Authors: Fei, Xiaofan; Patterson, Michael D.; German, Brian J.
Abstract: A high-lift propeller system is a distributed electric propulsion technology which dedicates an array of wing-mounted tractor propellers to actively augment wing lift during takeoff and landing. This paper describes the results of a wind tunnel experiment dedicated to investigating the effects of high-lift propeller installation geometry on lift generation. Variables investigated include propeller height, offset, and inclination. Results show that propeller height is the most critical variable and that the height for maximum lift depends highly on the angle of attack and flap deflection. In addition, a relationship between optimal propeller height and the wing’s unblown lift coefficient is discovered.  This conference paper was presented at AIAA SciTech 2018.

Battery Performance Modeling on Maxwell X-57 (Published January 6, 2019)
Authors: Jeffrey C. Chin, Sydney L. Schnulo, Thomas B. Miller, Kevin Prokopius, and Justin Gray
Abstract: Accurate battery thermal estimation, state-of-charge (SOC), and voltage response estimates are essential for mission planning of battery powered electric aircraft. Numerous works exist that outline simulation of lithium-ion battery cells with thermal considerations, so this paper serves to expand the experimentally validated regime into higher temperatures and to Li-ion batteries in the 18650 form factor.

2018

Development of a Multi-Phase Mission Planning Tool for NASA X-57 Maxwell (Published 6/23/2018, Acquired Oct 05, 2018)
Authors: Schnulo, Sydney L.; Chin, Jeffrey C.; Falck, Robert D.; Gray, Justin S.; Papathakis, Kurt V.; Clarke, Sean C.; Reid, Nickelle; Borer, Nicholas K.
Abstract: The physical design and operation of electric aircraft like NASA Maxwell X-57 are significantly different than conventionally fueled aircraft. Operational optimization will require close coupling of aerodynamics, propulsion, and power. To address the uncertainty of electric aircraft operation, a system level Mission Planning Tool is developed to simulate all aircraft trajectory phases: taxi, motor run-up, takeoff, climb, cruise, and descent. The Mission Planning Tool captures performance parameters at each point of the trajectory including battery state of charge, the temperatures of components in the electrical system, and propulsion system thrust.

Computational Component Build-Up for the X-57 Distributed Electric Propulsion Aircraft (Published 07/27/2018)
Authors: Deere, Karen A.; Viken, Jeffery K.; Viken, Sally A.; Carter, Melissa B.; Cox, Dave; Wiese, Michael R.; Farr, Norma
Abstract: A computational study of the wing for the distributed electric propulsion X-57 Maxwell airplane configuration at cruise and takeoff/landing conditions was completed. Three unstructured-mesh, Navier-Stokes computational fluid dynamics methods, FUN3D, USM3D and Kestrel, were used to predict the performance buildup of components to the full X-57 configuration. The goal of the X-57 wing and distributed electric propulsion system design was to meet or exceed the required lift coefficient of 3.95 for a stall speed of 58 knots.

X-57 Maxwell Battery from Cell Level to System Level Design and Testing [STUB] (Published 07/13/2018)
Authors: Hernandez Lugo, Dionne; Clarke, Sean; Miller, Tom; Redifer, Matt; Foster, Trevor
Abstract: This presentation will cover a breakout of X-57 battery specifications, battery design and lessons learned when designing a high voltage battery system to power electrified aircrafts.

Integration Concept for a Hybrid-Electric Solid-Oxide Fuel Cell Power System into the X-57 “Maxwell” [STUB] (Published 06/26/2018)
Authors: Deere, Karen A.; Viken, Jeffery K.; Viken, Sally A.; Carter, Melissa B.; Cox, Dave; Wiese, Michael R.; Farr, Norma
Abstract: A computational study of the wing for the distributed electric propulsion X-57 Maxwell airplane configuration at cruise and takeoff/landing conditions was completed. Three unstructured-mesh, Navier-Stokes computational fluid dynamics methods, FUN3D, USM3D and Kestrel, were used to predict the performance buildup of components to the full X-57 configuration. The goal of the X-57 wing and distributed electric propulsion system design was to meet or exceed the required lift coefficient of 3.95 for a stall speed of 58 knots.

Optimization of an Air Core Dual Halbach Array Axial Flux Rim Drive for Electric Aircraft, (Published Jun 23, 2018, Acquired Oct 05, 2018)
Authors: Tallerico,Thomas F.; Chin, Jeffrey C.; Cameron, Zachary A.
Abstract: This paper represents initial steps in the development of an electric propulsion system design code.  NASA’s all electric aircraft X-57,  is  used  as  a  case  study  for  this  design  code.

X-57 and Whirl Flutter Discussion (Published 5/4/2018)
Authors: Miller, Kia: Truax, Roger
Abstract: A look at challenges involving whirl flutter and the X-57. Includes whirl flutter background and the X-57 approach.

Distributed Propulsion Aircraft with Aeroelastic Wing Shaping Control for Improved Aerodynamic Efficiency (Publication Date: December 22, 2017, Acquired February 20, 2018)
Authors: Nguyen, Nhan T.; Reynolds, Kevin; Ting, Eric; Nguyen, Natalia
Abstract: This study presents an aeroelastic wing shaping control concept for distributed propulsion aircraft. By leveraging wing flexibility, wing-mounted distributed propulsion can be used to re-twist wing shapes in-flight to improve aerodynamic efficiency. A multidisciplinary approach is used to develop an aero-propulsive-elastic model of a highly flexible wing distributed propulsion transport aircraft. The conceptual model is used to evaluate the aerodynamic benefit of the distributed propulsion aircraft. The initial conceptual analysis shows that an improvement in the aerodynamic efficiency quantity of lift-to-drag ratio L/D is possible with the proposed aeroelastic wing shaping control for distributed propulsion aircraft. Two concepts are studied: single-generator configuration and dual-generator configuration with four propulsors per wing. The baseline aircraft model is NASA Generic Transport Model. A fan performance analysis is developed for propulsion sizing. Cruise performance analysis is conducted to evaluate the potential improvement in the cruise range for the configurations under study. A flutter analysis is performed to address the potential flutter issue as the propulsors are placed toward the wing tip which would cause a reduction in the wing natural frequencies. Flight control considerations are addressed in the context of the engine-out requirement, yaw and roll controls, and yaw damping augmentation using differential thrust.  This Accepted Manuscript was published on the Journal of Aircraft Volume: 55, Issue: 3.

2017

Distributed Electric Propulsion Portfolio, & Safety and Certification Considerations (Published 10/24/2017)
Author: Kurt V. Papathakis
Abstract: This presentation is an overview of the current Air Mobility programs being studied by NASA.

Trajectory Optimization of Electric Aircraft Subject to Subsystem Thermal Constraints (Date Acquired: 10/5/2017)
Authors: Falck, Robert D.; Chin, Jeffrey C.; Schnulo, Sydney L.; Burt, Jonathan M.; Gray, Justin S.
Abstract: Trajectory optimization with thermal constraints.  Electric aircraft pose a unique design challenge in that they lack a simple way to reject waste heat from the power train. While conventional aircraft reject most of their excess heat in the exhaust stream, for electric aircraft this is not an option. To examine the implications of this challenge on electric aircraft design and performance, we developed a model of the electric subsystems for the NASA X-57 electric testbed aircraft. We then coupled this model with a model of simple 2D aircraft dynamics and used a Legendre-Gauss-Lobatto collocation optimal control approach to find optimal trajectories for the aircraft with and without thermal constraints. The results show that the X-57 heat rejection systems are well designed for maximum-range and maximum-efficiency flight, without the need to deviate from an optimal trajectory.

Steady State Thermal Analyses of SCEPTOR X-57 Wingtip Propulsion (Published June 4, 2017, Acquired Aug 25, 2017)
Authors: Schnulo, Sydney L. and Chin, Jeffrey C. and Smith, Andrew D. and Dubois, Arthur
Abstract: This is a Conference paper that that explores Electric aircraft concepts that enable advanced propulsion airframe integration approaches that promise increased efficiency as well as reduced emissions and noise. This work focuses on the high and low fidelity heat transfer analysis methods performed to ensure that the wingtip motor inverters do not reach their temperature limits. It also explores different geometry configurations involved in the X-57 development and any thermal concerns.

A Method for Designing Conforming Folding Propellers (Date Acquired: 7/21/2017)
Authors: Litherland, Brandon L.; Patterson, Michael D.; Derlaga, Joseph M.; Borer, Nicholas K.
Abstract: Folding design for high-lift props. As the aviation vehicle design environment expands due to the influx of new technologies, new methods of conceptual design and modeling are required in order to meet the customer’s needs. In the case of distributed electric propulsion (DEP), the use of high-lift propellers upstream of the wing leading edge augments lift at low speeds enabling smaller wings with sufficient takeoff and landing performance. During cruise, however, these devices would normally contribute significant drag if left in a fixed or windmilling arrangement. Therefore, a design that stows the propeller blades is desirable. In this paper, we present a method for designing folding-blade configurations that conform to the nacelle surface when stowed. These folded designs maintain performance nearly identical to their straight, non-folding blade counterparts.

High-Lift Propeller Noise Prediction for a Distributed Electric Propulsion Flight Demonstrator (Date Acquired: 7/13/2017)
Authors: Nark, Douglas M.; Buning, Pieter G.; Jones, William T.; Derlaga, Joseph M.
Abstract: High-lift prop noise prediction. Over the past several years, the use of electric propulsion technologies within aircraft design has received increased attention. The characteristics of electric propulsion systems open up new areas of the aircraft design space, such as the use of distributed electric propulsion (DEP). In this approach, electric motors are placed in many different locations to achieve increased efficiency through integration of the propulsion system with the airframe. Under a project called Scalable Convergent Electric Propulsion Technology Operations Research (SCEPTOR), NASA is designing a flight demonstrator aircraft that employs many “high-lift propellers” distributed upstream of the wing leading edge and two cruise propellers (one at each wingtip).

Computational Analysis of a Wing Designed for the X-57 Distributed Electric Propulsion Aircraft (Published 7/11/2017)
Authors: Deere, Karen A. and Viken, Jeffrey K. and Viken, Sally A. and Carter, Melissa B. and Wiese, Michael R. and Farr, Norma L.
Abstract: This is a Conference paper with a computational study of the wing for the distributed electric propulsion X-57 Maxwell airplane configuration at cruise and takeoff/landing conditions.

A NASA Approach to Safety Considerations for Electric Propulsion Aircraft Testbeds (Published 07/10/2017)
Authors: Papathakis, Kurt V., Sessions, Alaric M., Burkhardt, Phillip A., Ehmann, David W.
Abstract: Electric, hybrid-electric, and turbo-electric distributed propulsion technologies and concepts are beginning to gain traction in the aircraft design community, as they can provide improvements in operating costs, noise, fuel consumption, and emissions compared to conventional internal combustion or Brayton-cycle powered vehicles. NASA is building multiple demonstrators and testbeds to buy down airworthiness and flight safety risks for these new technologies, including X-57 Maxwell, HEIST, Airvolt, and NEAT.

Computational Analysis of Powered Lift Augmentation for the LEAPTech Distributed Electric Propulsion Wing (Published 7/10/2017)
Authors: Deere, Karen A.; Viken, Sally A.; Carter, Melissa B.; Viken, Jeffrey K.; Wiese, Michael R.; Farr, Norma L.
Abstract: A computational study of a distributed electric propulsion wing with a 40deg flap deflection has been completed using FUN3D. Two lift-augmentation power conditions were compared with the power-off configuration on the high-lift wing (40deg flap) at a 73 mph freestream flow and for a range of angles of attack from -5 degrees to 14 degrees. The computational study also included investigating the benefit of corotating versus counter-rotating propeller spin direction to powered-lift performance.

Approach Considerations in Aircraft with High-Lift Propeller Systems (Date Acquired: 7/10/ 2017)
Authors: Patterson, Michael D.; Borer, Nicholas K.
Abstract: Approach path design & analysis with high lift props. NASA’s research into distributed electric propulsion (DEP) includes the design and development of the X-57 Maxwell aircraft. This aircraft has two distinct types of DEP: wingtip propellers and high-lift propellers. This paper focuses on the unique opportunities and challenges that the high-lift propellers–i.e., the small diameter propellers distributed upstream of the wing leading edge to augment lift at low speeds–bring to the aircraft performance in approach conditions.

X-57 Power and Command System Design (Published 5/2/2017, Acquired 7/6/2017)
Authors: Clarke, Sean; Redifer, Matthew; Papathakis, Kurt; Samuel, Aamod; Foster, Trevor
Abstract: This paper describes the power and command system architecture of the X-57 Maxwell flight demonstrator aircraft.  Findings from this paper were presented at an AIAA Conference June 5-9, 2017 in Denver Colorado.  See the conference presentation which is a separate document.

Annoyance to Noise Produced by a Distributed Electric Propulsion High-Lift System (Publication Date: June 5, 2017, Acquired June 26, 2017)
Authors: Rizzi, Stephen A.; Palumbo, Daniel L.; Rathsam, Jonathan; Christian, Andrew; Rafaelof, Menachem
Abstract: A psychoacoustic test was performed using simulated sounds from a distributed electric propulsion aircraft concept to help understand factors associated with human annoyance. A design space spanning the number of high-lift leading edge propellers and their relative operating speeds, inclusive of time varying effects associated with motor controller error and atmospheric turbulence, was considered. It was found that the mean annoyance response varies in a statistically significant manner with the number of propellers and with the inclusion of time varying effects, but does not differ significantly with the relative RPM between propellers. An annoyance model was developed, inclusive of confidence intervals, using the noise metrics of loudness, roughness, and tonality as predictors.  This conference paper was presented at AIAA Aviation 2017.

X-57 Power and Command System Design (Published: 6/7/2017)
Authors: Clarke, Sean and Redifer, Matthew and Papathakis, Kurt and Samuel, Aamod and Foster, Trevor
Abstract: This presentation provides an overview of the X-57 Power and Command System Design to include the Avionics Power System, Traction Power System, and the Command System.

Update on the Current State of Electric Propulsion Research Design (Published 6/6/2017)
Authors: Clarke, Sean; Redifer, Matthew; Papathakis, Kurt; Samuel, Aamod; Foster, Trevor
Abstract: This paper describes the power and command system architecture of the X-57 Maxwell flight demonstrator aircraft. The X-57 is an experimental aircraft designed to demonstrate radically improved aircraft efficiency with a 3.5 times aero-propulsive efficiency gain at a “high-speed cruise” flight condition for comparable general aviation aircraft. These gains are enabled by integrating the design of a new, optimized wing and a new electric propulsion system.

Comparison of High-Fidelity Computational Tools for Wing Design of a Distributed Electric Propulsion Aircraft (Published 6/5/2017)
Authors: Deere, Karen A., Viken, Sally A., Carter, Melissa B., Viken, Jeffrey K., Derlaga, Joseph M., Stoll, Alex M.
Abstract: A variety of tools, from fundamental to high order, have been used to better understand applications of distributed electric propulsion to aid the wing and propulsion system design of the Leading Edge Asynchronous Propulsion Technology (LEAPTech) project and the X-57 Maxwell airplane.  Results from these computational tools for the high-lift wing tested on the Hybrid-Electric Integrated Systems Testbed truck and the X-57 high-lift wing presented compare reasonably well.

Transient Thermal Analyses of Passive Systems on SCEPTOR X-57 (Published 6/5/2017)
Authors: Chin, Jeffrey C. and Schnulo, Sydney L. and Smith, Andrew D.
Abstract: This paper summarizes the thermal analyses of X-57 vehicle subsystems that don’t employ externally air-cooled heat sinks.

Whirl Flutter Stability and Its Influence on the Design of the Distributed Electric Propeller Aircraft X- 57 (Published 6/5/2017)
Authors: Hoover, Christian B. and Shen, Jinwei and Kreshock, Andrew R. and Stanford, Bret K. and Piatak, David J. and Heeg, Jennifer
Abstract: This paper studies the whirl flutter stability of the NASA experimental electric propulsion aircraft designated the X-57 Maxwell.

Design of the Cruise and Flap Airfoil for the X-57 Maxwell Distributed Electric Propulsion Aircraft, (Published 6/5/2017)
Authors: Jeffrey K. Viken, Sally A. Viken, Karen A. Deere, Melissa B. Carter. 
Abstract: This paper is a computational and design study on an airfoil and high-lift flap for the X-57 Maxwell Distributed Electric Propulsion (DEP) testbed aircraft.

Cooling of Electric Motors Used for Propulsion on SCEPTOR (Published 5/17/2017)
Authors: Christie, Robert J.; Dubois, Arthur; Derlaga, Joseph M.
Abstract: This paper discusses the options evaluated for cooling the motors on SCEPTOR (Scalable Convergent Electric Propulsion Technology and Operations Research): a project that will demonstrate Distributed Electric Propulsion technology in flight.

Comparison of Aero-Propulsive Performance Predictions for Distributed Propulsion Configurations (Date Acquired: 2/6/2017)
Authors: Borer, Nicholas K.; Derlaga, Joseph M.; Deere, Karen A.; Carter, Melissa B.; Viken, Sally A.; Patterson, Michael D.; Litherland, Brandon L.; Stoll, Alex M.
Abstract: Aero-propulsion predictions & validations. This paper discusses the rapid, “design-order” toolchains developed to investigate the large, complex tradespace of candidate geometries for the X-57. Due to the lack of an appropriate, rigorous set of validation data, the results of these tools were compared to three different computational flow solvers for selected wing and propulsion geometries. The comparisons were conducted using a common input geometry, but otherwise different input grids and, when appropriate, different flow assumptions to bound the comparisons. The results of these studies showed that the X-57 distributed propulsion wing should be able to meet the as-designed performance in cruise flight, while also meeting or exceeding targets for high-lift generation in low-speed flight.

2016

X-57 Critical Design Review (Published 11/15/2016)
Day 1 Package
Day 2 Package
Authors: Various authors from the NASA-various contractors team.
Abstract: This document contains the presentation slides used for the CDR presentation made by the SCEPTOR X-57 team on Nov 15-17, 2016.  The presentation addresses program requirements, solutions, and analysis approaches as planned as of the presentation date.

Spiral Development of Electrified Aircraft Propulsion from Ground to Flight (Published 11/10/2016)
Author: Starr Ginn
Abstract: This presentation is the first in a series of demonstrators showcasing electric propulsion technologies in aircraft.

Spiral Development of Electrified Aircraft Propulsion from Ground to Flight (Published 10/24/2016)
Author: Starr Ginn
Abstract: This presentation is an overview of the current Air Mobility programs being studied by NASA.

Convergent Aeronautics Solutions Project – SCEPTOR – Scalable Convergent Electric Propulsion Technology and Operations Research (Published 09/08/2016)
Authors: Moore, Mark; Clarke, Sean
Abstract: A presentation on the SCEPTOR project and using Distributed Electric Propulsion (DEP) to achieve ultra-high efficiency, low carbon emissions, and low operating costs at high-speed.

High-Lift Propeller System Configuration Selection for NASA’s SCEPTOR Distributed Electric Propulsion Flight Demonstrator (Date Acquired: 8/10/2016)
Authors: Patterson, Michael D.; Derlaga, Joseph M.; Borer, Nicholas K.
Abstract: High-lift propeller design.  Although the primary function of propellers is typically to produce thrust, aircraft equipped with distributed electric propulsion (DEP) may utilize propellers whose main purpose is to act as a form of high-lift device. These \high-lift propellers” can be placed upstream of wing such that, when the higher-velocity ow in the propellers’ slipstreams interacts with the wing, the lift is increased. This technique is a main design feature of a new NASA advanced design project called Scalable Convergent Electric Propulsion Technology Operations Research (SCEPTOR).

Perceived Annoyance to Noise Produced by a Distributed Electric Propulsion High Lift System (Publication Date: June 13, 2016, Acquired August 4, 2016)
Authors: Palumbo, Dan; Rathsam, Jonathan; Christian, Andrew; Rafaelof, Menachem
Abstract: Results of a psychoacoustic test performed to understand the relative annoyance to noise produced by several configurations of a distributed electric propulsion high lift system are given. It is found that the number of propellers in the system is a major factor in annoyance perception. This is an intuitive result as annoyance increases, in general, with frequency, and, the blade passage frequency of the propellers increases with the number of propellers. Additionally, the data indicate that having some variation in the blade passage frequency from propeller-to-propeller is beneficial as it reduces the high tonality generated when all the propellers are spinning in synchrony at the same speed. The propellers can be set to spin at different speeds, but it was found that allowing the motor controllers to drift within 1% of nominal settings produced the best results (lowest overall annoyance). The methodology employed has been demonstrated to be effective in providing timely feedback to designers in the early stages of design development. 

The LEAPTech Experiment, Approach, Results, Recommendations (Published 8/1/2016)
(You must be logged into NTRS site in order to view this paper.)
Authors: Murray, James; Lechniak, Jason
Abstract: TA presentation on the approach, results, and recommendations for the The LEAPTech Experiment.  The LEAPTech experiment was an ambitious initial foray into Airframe-Propulsion Interaction (API) analysis, design, and testing.  Approach was akin to George Mueller’s Apollo “All-Up Testing” philosophy.  “All-Up Testing” carries inherent risk.  Failure is an option.

Design and Development of a 200-kw Turbo-Electric Distributed Propulsion Testbed (Published 7/25/2016)
Authors: Papathakis, Kurt V., Kloesel, Kurt J., Lin, Yohan, Clarke, Sean, Ediger, Jacob J., Ginn, Starr
Abstract: This test bench represents a significant risk mitigation for creating the turbo-electric flying demonstrator.  The presentation looks at Strategic Thrusts 3 Ultra Efficient Commercial Vehicles, and strategic Thrust 4: Transition to Low Carbon Propulsion.  Also covered are Armstrong Electric and Hybrid-Electric Propulsion Roadmap, Turbo-Electric Distributed Propulsion (TeDP), and Hybrid Electric Integrated Systems Testbed Objectives, Project Timeline, System Architecture, System Hierarchy, Communication Architecture, and Architecture Description / Interconnect Diagram.

Design of an Electric Propulsion System for SCEPTOR (Published 6/23/2016)
Authors: Dubois, Arthur; van der Geest, Martin; Bevirt, JoeBen; Clarke, Sean; Christie, Robert J.; Borer, Nicholas K.
Abstract: The rise of electric propulsion systems has pushed aircraft designers towards new and potentially transformative concepts. As part of this effort, NASA is leading the SCEPTOR program which aims at designing a fully electric distributed propulsion general aviation aircraft. This article highlights critical aspects of the design of SCEPTOR’s propulsion system conceived at Joby Aviation in partnership with NASA, including motor electromagnetic design and optimization as well as cooling system integration.

Design of an Electric Propulsion System for SCEPTOR (Date Acquired: 6/23/2016)
Authors: Dubois, Arthur; van der Geest, Martin; Bevirt, JoeBen; Clarke, Sean; Christie, Robert J.; Borer, Nicholas K.
Abstract: Cruise motor design. The rise of electric propulsion systems has pushed aircraft designers towards new and potentially transformative concepts. As part of this effort, NASA is leading the SCEPTOR program which aims at designing a fully electric distributed propulsion general aviation aircraft. This article highlights critical aspects of the design of SCEPTOR’s propulsion system conceived at Joby Aviation in partnership with NASA, including motor electromagnetic design and optimization as well as cooling system integration. The motor is designed with a finite element based multi-objective optimization approach. This provides insight into important design tradeoffs such as mass versus efficiency, and enables a detailed quantitative comparison between different motor topologies.

A Simple Method for High-Lift Propeller Conceptual Design (Published 6/22/2016)
Authors: Michael Patterson, Nick Borer, and Brian German
Abstract: In this paper, we present a simple method for designing propellers that are placed upstream of the leading edge of a wing in order to augment lift. Because the primary purpose of these “high-lift propellers” is to increase lift rather than produce thrust, these props are best viewed as a form of high-lift device; consequently, they should be designed differently than traditional propellers. We present a theory that describes how these props can be designed to provide a relatively uniform axial velocity increase, which is hypothesized to be advantageous for lift augmentation based on a literature survey.

A Simple Method for High-Lift Propeller Conceptual Design (Date Acquired: 6/22/2016)
Authors: Patterson, Michael; Borer, Nick; German, Brian
Abstract: How to size high-lift propellers. In this paper, we present a simple method for designing propellers that are placed upstream of the leading edge of a wing in order to augment lift. Because the primary purpose of these “high-lift propellers” is to increase lift rather than produce thrust, these props are best viewed as a form of high-lift device; consequently, they should be designed differently than traditional propellers. We present a theory that describes how these props can be designed to provide a relatively uniform axial velocity increase, which is hypothesized to be advantageous for lift augmentation based on a literature survey.

SCEPTOR Power System Design: Experimental Electric Propulsion System Design and Qualification for Crewed Flight Testing (Published 6/22/2016)
Author: Clarke, Sean
Abstract: This presentation is the first in a series of demonstrators showcasing electric propulsion technologies in aircraft.

Design and Performance of the NASA SCEPTOR Distributed Electric Propulsion Flight Demonstrator (Publication date:6/13/2016)
Authors: Borer, Nicholas K., Patterson, Michael D., Viken, Jeffrey K., Moore, Mark D., Clarke, Sean, Redifer, Matthew E., Christie, Robert J., Stoll, Alex M., Dubois, Arthur, Bevirt, JoeBen Gibson, Andrew R.; Foster, Trevor J.; Osterkamp, Philip G.
Abstract: Distributed Electric Propulsion (DEP) technology uses multiple propulsors driven by electric motors distributed about the airframe to yield beneficial aerodynamic-propulsion interaction. The NASA SCEPTOR flight demonstration project will retrofit an existing internal combustion engine-powered light aircraft with two types of DEP: small “high-lift” propellers distributed along the leading edge of the wing which accelerate the flow over the wing at low speeds, and larger cruise propellers co-located with each wingtip for primary propulsive power.

Aircraft Electric Propulsion Systems: Applied Research at NASA (Publication date:04/21/2016)
Author: Clarke, Sean
Abstract: Researchers at NASA are investigating the potential for electric propulsion systems to revolutionize hide the design of aircraft from the small-scale general aviation sector to commuter and transport-class vehicles. Electric propulsion provides new degrees of design freedom that may enable opportunities for tightly coupled design and optimization of the propulsion system with the aircraft structure and control systems. This could lead to extraordinary reductions in ownership and operating costs, greenhouse gas emissions, and noise annoyance levels. We are building testbeds, high-fidelity aircraft simulations, and the first highly distributed electric inhabited flight test vehicle to begin to explore these opportunities.

2015

Distributed Electric Propulsion (DEP) Aircraft (Publish Date: October 13, 2015)
Author: Mark D. Moore, LaRC
Abstract: This paper attempts to answer some questions related to Distributed Electric Propulsion (DEP) Aircraft.  Can electric propulsion impact aviation over the next decade, or is battery specific energy too constraining?  What value does electric propulsion offer aviation in the near-term in terms of carbon emissions, and how can low carbon solutions be incentivized in the aviation market without dependency on carbon taxing?  If electric propulsion is a ‘disruptive technology’ enabling low carbon aviation, what is the likely evolutionary technology path?

LEAPTech HEIST Power Architecture and Testing (Published 12/9/ 2015)
Authors: Clarke, Sean; Lin, Yohan; Papathakis, Kurt; Samuel, Aamod
Abstract: LEAPTech HEIST Power Architecture and Testing presentation including a roadmap, Power System Architecture Overview and components, and lessons learned.

X-57 Preliminary Design Review (Published 11/12/2015)
Day 1 Package
Day 2 Package
Authors: Various authors from the NASA-various contractors team.
Abstract: This document contains the presentation slides used for the PDR presentation made by the X-57 team on Nov 12-13, 2015.  The presentation addresses program requirements, solutions, and analysis approaches as planned as of the presentation date.

Enabling Electric Propulsion for Flight (Published 6/3/2015)
Author: Ginn, Starr Renee
Abstract: Team Seedling project AFRC and LaRC 31ft distributed electric propulsion wing on truck bed up 75 miles per hour for coefficient of lift validation. Convergent Aeronautic Solutions project, sub-project Convergent Electric Propulsion Technologies AFRC, LaRC and GRC, re-winging a 4 passenger Tecnam aircraft with a 31ft distributed electric propulsion wing.

Enabling Electric Propulsion for Flight (Published 01/08/2015)
Author: Ginn, Starr
Abstract: Description of current ARMD projects; Team Seedling project AFRC and LaRC 31ft distributed electric hide propulsion wing on truck bed up 75 miles per hour for coefficient of lift validation. Convergent Aeronautic Solutions project (new ARMD reorg), sub-project Convergent Electric Propulsion Technologies AFRC, LaRC and GRC, re-winging a 4 passenger Tecnam aircraft with a 31ft distributed electric propulsion wing. Advanced Air Transport Technologies (Fixed Wing), Hybrid Electric Research Theme, developing a series hybrid ironbird and flight sim to study integration and performance challenges in preparation for a 1-2 MW flight project.

2014

Enabling Electric Propulsion for Flight – Hybrid Electric Aircraft Research at AFRC (Published 11/13/2014)
Authors: Clarke, Sean; Lin, Yohan; Kloesel, Kurt; Ginn, Starr
Abstract: Advances in electric machine efficiency and energy storage capability are enabling a new alternative to traditional propulsion systems for aircraft. This has already begun with several small concept and demonstration vehicles, and NASA projects this technology will be essential to meet energy and emissions goals for commercial aviation in the next 30 years.

Drag Reduction Through Distributed Electric Propulsion (Date Acquired: 10/9/2014)
Authors: Stoll, Alex M.; Bevirt, JoeBen; Moore, Mark D.; Fredericks, William J.; Borer, Nicholas K.
Abstract: Early look at conceptual design.  One promising application of recent advances in electric aircraft propulsion technologies is a blown wing realized through the placement of a number of electric motors driving individual tractor propellers spaced along each wing. This configuration increases the maximum lift coefficient by providing substantially increased dynamic pressure across the wing at low speeds. This allows for a wing sized near the ideal area for maximum range at cruise conditions, imparting the cruise drag and ride quality benefits of this smaller wing size without decreasing takeoff and landing performance.

Tradespace Exploration of Distributed Propulsors for Advanced On-Demand Mobility Concepts (Date Acquired: 10/8/2014)
Authors: Borer, Nicholas K.; Moore, Mark D.; Turnbull, Andrew R.
Abstract: Propeller design.  This paper explores the design space of fixed-pitch propellers for use as (1) lift augmentation when distributed about a wing’s leading edge, and (2) as fixed-pitch cruise propellers with significant thrust at reduced tip speeds for takeoff. A methodology is developed for evaluating the high-level trades for these types of propellers and is applied to the exploration of a NASA Distributed Electric Propulsion concept. The results show that the leading edge propellers have very high solidity and pitch well outside of the empirical database, and that the cruise propellers can be operated over a wide RPM range to ensure that thrust can still be produced at takeoff without the need for a pitch change mechanism.