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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

COBRA-DDP: Trajectory Generation and Collision Avoidance Augmentations for eVTOL Vehicles

This paper presents a receding horizon model predictive control variation of the combined Bernstein polynomial optimal reciprocal collision avoidance (ORCA) differential dynamic programming (COBRA-DDP) algorithm for AAM vehicles. Collision avoidance in combination with effective trajectory replanning are expected to be core components of AAM vehicles operating within a crowded airspace. This environment necessitates the use of real-time trajectory planning algorithms that are capable of planning around large amounts of stationary and moving obstacles. Previous work on COBRA-DDP demonstrated the capability of the algorithm to produce dynamically feasible trajectories for AAM vehicles and general collision avoidance. This paper improves upon the previous work by increasing the number of stationary and moving obstacles, implementing a variation of COBRA-DDP that lends itself to real-time application. These advancements are demonstrated on a vertical takeoff and landing (VTOL) vehicle simulation with highly nonlinear vehicle dynamics.

COBRA-DDP↗
NASA NTRSDate not supplied

COBRA-DDP: Trajectory Generation and Collision Avoidance Augmentations for eVTOL Vehicles

This paper presents a receding horizon model predictive control variation of the combined Bernstein polynomial optimal reciprocal collision avoidance (ORCA) differential dynamic programming (COBRA-DDP) algorithm for AAM vehicles. Collision avoidance in combination with effective trajectory replanning are expected to be core components of AAM vehicles operating within a crowded airspace. This environment necessitates the use of real-time trajectory planning algorithms that are capable of planning around large amounts of stationary and moving obstacles. Previous work on COBRA-DDP demonstrated the capability of the algorithm to produce dynamically feasible trajectories for AAM vehicles and general collision avoidance. This paper improves upon the previous work by increasing the number of stationary and moving obstacles, implementing a variation of COBRA-DDP that lends itself to real-time application. These advancements are demonstrated on a vertical takeoff and landing (VTOL) vehicle simulation with highly nonlinear vehicle dynamics.

COBRA-DDP↗
NASA NTRSDate not supplied

GlennICE Simulation of 24, 28 and 36 Inch Diameter eVTOL Propellers in Forward Flight

Flow solutions and water collection results are presented for three different propeller sizes. Flow solutions were generated using the NASA FUN3D software, and water collection was simulated using NASA GlennICE software. The geometries considered represent experimental articles that have been tested in the NASA Icing Research Tunnel. Each configuration has four blades. For the experiment, the same spinner centerbody is used for each propeller size. The different sized blades are similar for radii larger than about 40% of total span. Operating conditions were chosen to match operating points where experimental data was collected. Results are presented for both single bin simulations, as well as 7-bin Langmuir D distributions. For 80 microns MVD the Langmuir D distribution showed small differences compared to the single bin. For 15 microns MVD the Langmuir D distribution had a larger impact, especially on the spinner. In the experiment, the centerbody was unchanged as propeller size was changed. In this paper, additional simulations were completed with the 36 inch case perfectly scaled down to 24 and 28 inch. The perfect geometric scaling allows for an assessment of the effect of constant centerbody size on the results. While slight differences in pressure distribution on the propeller are visible between scaled and non-scaled centerbody, the effect seems quite minimal regarding water collection. All simulations were run very cold to ensure rime ice, since handling runback water in the non-inertial frame is beyond the scope of the present work. Ice shapes were generated using a single time step growth. The total mass on the blade and spinner was generally underpredicted for 15 microns MVD, and overpredicted for 80 microns MVD. When comparing ice shapes at operating conditions the numerical results produce very similar ice shapes.

Aircraft Icing↗
NASA NTRSDate not supplied

GlennICE Simulation of 24, 28 and 36 Inch Diameter eVTOL Propellers in Forward Flight

Flow solutions and water collection results are presented for three different propeller sizes. Flow solutions were generated using the NASA FUN3D software, and water collection was simulated using NASA GlennICE software. The geometries considered represent experimental articles that have been tested in the NASA Icing Research Tunnel. Each configuration has four blades. For the experiment, the same spinner centerbody is used for each propeller size. The different sized blades are similar for radii larger than about 40% of total span. Operating conditions were chosen to match operating points where experimental data was collected. Results are presented for both single bin simulations, as well as 7-bin Langmuir D distributions. For 80 microns MVD the Langmuir D distribution showed small differences compared to the single bin. For 15 microns MVD the Langmuir D distribution had a larger impact, especially on the spinner. In the experiment, the centerbody was unchanged as propeller size was changed. In this paper, additional simulations were completed with the 36 inch case perfectly scaled down to 24 and 28 inch. The perfect geometric scaling allows for an assessment of the effect of constant centerbody size on the results. While slight differences in pressure distribution on the propeller are visible between scaled and non-scaled centerbody, the effect seems quite minimal regarding water collection. All simulations were run very cold to ensure rime ice, since handling runback water in the non-inertial frame is beyond the scope of the present work. Ice shapes were generated using a single time step growth. The total mass on the blade and spinner was generally underpredicted for 15 microns MVD, and overpredicted for 80 microns MVD. When comparing ice shapes at operating conditions the numerical results produce very similar ice shapes.

Aircraft Icing↗
NASA NTRSDate not supplied

Transition Aero-Propulsive Analysis of a Tilt-Wing eVTOL Aircraft Using a Surface-Vorticity Solver

This work uses FlightStream, a surface-vorticity solver, to perform an aero-propulsive analysis on the NASA LA-8 aircraft through the transition flight regime. Aerodynamic force and moment coefficient predictions for forward and transition flight of the airframe without propulsors are compared with wind tunnel data. Powered transition cases are simulated using Conway actuator disks to model the propellers and results are compared with response surface equations derived from wind tunnel data. The approach described in the paper provides mid-fidelity solutions at a reduced computational cost compared to volumetric CFD, which allows for rapid transition flight analyses and optimization in the early design stages. The best prediction results were observed in forward flight and high-speed transition. Mid-transition results were not as close in magnitude but the trends exhibited reasonable agreement with experimental data.

Advanced Air Mobility↗
NASA NTRS2025

A Summary of Results from Vertical Drop Testing of Hybrid III and WIAMan ATDs

With the development and maturation of the Urban Air Mobility (UAM) market, many new types of electric vertical take-off and landing (eVTOL) vehicles will be flying in the national airspace carrying goods, people or conducting operations for a variety of missions. These types of vehicles are unlike current aircraft due to their novel design and operational profile. Several considerations must be examined in areas including noise, comfort and safety in order for these vehicles to be utilized and accepted into the current airspace system. Researchers at NASA Langley Research Center (LaRC) have conducted sub-scale and full-scale tests on representative eVTOL airframes and seats under a variety of dynamic impact conditions. These tests were conducted to generate data necessary to inform the development of standards in the areas specific to crashworthiness of eVTOL vehicle systems and safety. The data in this report relates to occupant responses obtained during a test campaign utilizing various makes, models, and sizes of Anthropomorphic Test Devices (ATD’s, a.k.a. crash test dummies) undergoing vertical impacts in a variety of seats. The data is intended to provide occupant behavior response and injury metrics for several anticipated impact scenarios that may occur in eVTOL operations. This report will present test data highlighting the effects of several variables on the test results. Discussions on the ATD sizes, along with comparisons between different ATD makes and types will be included. The performance of an in-house developed energy absorbing seat will be detailed, and discussions pertaining to the applicability in various loading conditions will be presented. Finally, a discussion as to the applicability of the tested results to eVTOL full-scale conditions will be included.

Dynamic Drop Testing↗
NASA NTRSDate not supplied

Wind Tunnel-Based Aerodynamic Model Identification for a Tilt-Wing, Distributed Electric Propulsion Aircraft

This paper describes the methodology used to develop a high-fidelity aerodynamic model for the Langley Aerodrome No. 8 (LA-8) tandem tilt-wing, distributed electric propulsion, vertical takeoff and landing aircraft. Electric vertical takeoff and landing (eVTOL) vehicle configurations exhibit aerodynamic characteristics of both fixed-wing and rotary-wing aircraft as well as complex vehicle-specific phenomena, such as propeller-wing interactions and high incidence angle propeller aerodynamics. Consequently, conventional aircraft aerodynamic modeling strategies require modification when applied to eVTOL aircraft. Two novel system identification-based approaches are used to develop an aerodynamic model for the LA-8 aircraft configuration using wind tunnel data collected with design of experiments techniques. The modeling strategies are compared by assessing their predictive performance for validation data acquired separately from the data used to identify the model and are shown to have sufficient predictive capability. Research findings are presented with a discussion of unique eVTOL aerodynamic modeling characteristics and practical strategies to inform future aerodynamic modeling efforts for eVTOL aircraft.

Urban Air Mobility↗
NASA NTRSDate not supplied

System Identification for Propellers at High Incidence Angles

Propellers used for electric vertical takeoff and landing (eVTOL) aircraft propulsion systems experience a wide range of aerodynamic conditions, including large incidence angles relative to oncoming airflow. In oblique flow, propellers exhibit deviations in thrust and torque oriented along the propeller axis of rotation, as well as significant off-axis forces and moments. Although important for modeling eVTOL aircraft aerodynamics, sparse experimental data or mathematical models exist for propellers at incidence. This paper describes a propulsion system modeling methodology for the Langley Aerodrome No. 8 (LA-8) tandem tilt-wing, eVTOL aircraft. System identification methods are applied to isolated propeller wind tunnel data gathered across the vehicle's flight envelope to develop a mathematical model of the propulsion system, including a static motor model, dynamic motor model, and propeller aerodynamic model. Modeling results validated against data withheld from the modeling process indicate good predictive capability and agree with theoretical expectations. The results are followed by a discussion of model implementation strategies into high-fidelity eVTOL aircraft simulations.

system identification↗
NASA NTRS2021

System Identification for Propellers at High Incidence Angles

Propellers used for electric vertical takeoff and landing (eVTOL) aircraft propulsion systems experience a wide range of aerodynamic conditions, including large incidence angles relative to oncoming airflow. In oblique flow, propellers exhibit deviations in thrust and torque oriented along the propeller axis of rotation, as well as significant off-axis forces and moments. Although important for modeling eVTOL aircraft aerodynamics, sparse experimental data or mathematical models exist for propellers at incidence. This paper describes a propulsion system modeling methodology for the LA-8 tandem tilt-wing, eVTOL aircraft. System identification methods are applied to isolated propeller wind tunnel data gathered across the vehicle's flight envelope to develop a mathematical model of the propulsion system, including a static motor model, dynamic motor model, and propeller aerodynamic model. Modeling results validated against data withheld from the modeling process indicate good predictive capability and agree with theoretical expectations. The results are followed by a discussion of model implementation strategies into high-fidelity eVTOL aircraft simulations.

system identification↗
NASA NTRSDate not supplied

Advancing Electric Propulsion Aircraft Evaluation for Urban Air Mobility: Insights from NASA Ames

This presentation delves into a recent evaluation conducted at NASA-Ames on the Vertical Motion Simulator, focusing on the handling qualities of Distributed Electric Propulsion VTOL (eVTOL) aircraft, specifically tailored for Urban Air Mobility (UAM) applications. The presentation will focus on the recent effort to adapt and refine use of the Aeronautical Design Standard -33 (ADS-33) rotorcraft handling qualities developed by the U.S. Army and NASA to meet the diverse needs of civilian (eVTOL) concept evaluation. A brief discussion of the author’s personal test pilot insights in the early development of military Fly-By-Wire evaluation methods will also be provided. The emergence of innovative eVTOL designs with unique lift capabilities and flight control systems, present both opportunities and challenges, particularly in ensuring safety amidst technological complexity. To navigate these challenges, our investigation examined evaluation criteria designed to accommodate the varied configurations and advanced automation systems inherent in modern eVTOL aircraft. By establishing a standardized approach to evaluation, our research not only fosters innovation but also upholds safety standards in the dynamic landscape of urban air mobility. Through this endeavor, we help to facilitate the seamless integration of novel aircraft capabilities into new operations, contributing to a new era of safe and efficient aerial transportation.

eVTOL↗
NASA NTRSDate not supplied

Training the Powered-Lift Evaluation Pilot

This poster describes a project to prepare pilots for a study assessing novel aircraft automation concepts for electric Vertical Takeoff and Landing (eVTOL) aircraft using NASA’s Vertical Motion Simulator (VMS). By exploring the operational and learning challenges related to transitioning between forward flight and vertical landing, we seek to establish baselines of pilot workload and aircraft handling qualities across varying atmospheric conditions and automation states. The simulated eVTOL design differentiates flight control allocations as a function of airspeed across four speed ranges as the vehicle transitions between fully thrust-borne lift and wing-borne lift. As speed increases, side stick controls command: translational ground speeds, vertical and lateral acceleration, vertical rate, vertical flight path angle, and bank angle. This novel approach to flight control allocation creates a significant learning challenge for pilots. Since initial eVTOL aircraft may have limitations on hover capabilities, automation and flight guidance cues also vary with airspeed to provide efficient landing profiles while still providing cues suitable for cruise flight. The NASA team prepared the study pilots to follow these flight guidance cues along curved Required Navigation Performance (RNP) approaches and along 6o and 12o glide paths to energy-efficient assistive-hover landing and goarounds. The pre-VMS preparation sought to prepare pilots from diverse levels of experience and background. To do this, NASA researchers designed and developed a fixed-based, large field-ofview simulator with terrain, structures, and air traffic. With one day of combined classroom learning and skill development in the fixedbase simulator, pilots were largely able to fly the simulated eVTOL in the VMS with sufficient mastery to provide handling quality assessments using the Cooper-Harper Handling Qualities Rating and workload assessments through the Bedford Workload Scale.

AAM↗
NASA NTRSDate not supplied

Advancing Electric Propulsion Aircraft Evaluation for Urban Air Mobility: Insights from NASA-Ames

This presentation delves into a recent evaluation conducted at NASA-Ames on the Vertical Motion Simulator, focusing on the handling qualities of Distributed Electric Propulsion VTOL (eVTOL) aircraft, specifically tailored for Urban Air Mobility (UAM) applications. The presentation will focus on the recent effort to adapt and refine use of the Aeronautical Design Standard -33 (ADS-33) rotorcraft handling qualities developed by the U.S. Army and NASA to meet the diverse needs of civilian (eVTOL) concept evaluation. A brief discussion of the author’s personal test pilot insights in the early development of military Fly-By-Wire evaluation methods will also be provided. The emergence of innovative eVTOL designs with unique lift capabilities and flight control systems, present both opportunities and challenges, particularly in ensuring safety amidst technological complexity. To navigate these challenges, our investigation examined evaluation criteria designed to accommodate the varied configurations and advanced automation systems inherent in modern eVTOL aircraft. By establishing a standardized approach to evaluation, our research not only fosters innovation but also upholds safety standards in the dynamic landscape of urban air mobility. Through this endeavor, we help to facilitate the seamless integration of novel aircraft capabilities into new operations, contributing to a new era of safe and efficient aerial transportation.

Loran Allen Haworth↗
NASA NTRSDate not supplied

Multidisciplinary Systems Analysis of a Six Passenger Quadrotor Urban Air Mobility Vehicle Powertrain

There is a high degree of research interest in the design space for electric vertical takeoff and landing (eVTOL) vehicles, because these vehicles are seen as key enablers for urban air mobility (UAM). This work further explores the eVTOL design space, by presenting analysis of a six-passenger eVTOL quadrotor powertrain, with integrated power, propulsion, and thermal management systems modeled using the Numerical Propulsion System Simulation (NPSS) and the NPSS Power System Library. Four architectures are modeled at the same design point and compared over a design mission. Results from an architecture comparison study show that a hybrid architecture performs best in terms of cruise range, however, the hybrid needs batteries with high specific energy and specific power in order to obtain a benefit vs turboelectric architectures. Sensitivity studies are conducted to show correlations between component parameters and system metrics. This data provides useful indicators for further technological improvement. Lastly, an initial TMS model is presented, and sensitivity studies on TMS design parameters are presented as well, to show high level TMS design trends.

evtol↗
NASA NTRSDate not supplied

Simulation of Lift plus Cruise Vehicle Models to Define a Full-Scale Crash Test Campaign

A series of dynamic simulations were completed on the National Aeronautics and Space Administration(NASA) Lift plus Cruise (LPC) concept electric Vertical Take-off and Landing (eVTOL) vehicle in preparation for an anticipated future full-scale crash-test campaign. The crash test campaign is envisioned as a data gathering exercise with an intent generating full-scale test data to inform eVTOL crashworthiness regulations, evaluate the use of energy absorbing concepts within vehicle design, and validate finite element modeling techniques used in crashworthiness predictions. This report discusses the two main objectives for the simulation efforts: the development of a structural cabin section, and a series of analyses utilized to determine the sensitivities of impact variables. A structural cabin section was created based from previous research efforts involving the LPC vehicle utilized for occupant response. To refine for the structural modifications, the wing and tail sections of the vehicle were removed. The tail was replaced with a representative mass at the aft of the fuselage. The overhead wing was replaced with a beam structure sized to approximate the bending response of the wing under crash loading conditions. The beam structure was fixed to the fuselage similar to the original Wingbox design in order to properly capture effects of this overhead mass on survivable volume within the vehicle. The fidelity of the fuselage frame structure within the FEM was increased to quantify the effect of frame sizing on structural response. From this an eVTOL test article design was developed, which satisfied basic crashworthiness requirements, was reconfigurable to assess the effect of various design avenues on structural response and optimized to improve manufacturability. The impact variable sensitivity results primarily show the orientation of the impact vector played a major role in types of injuries sustained, along with their severity. The vehicle was largely insensitive to small variations in pitch attitude but highly sensitive to both impact surface at certain angles and landing gear location.

eVTOL↗
NASA NTRSDate not supplied

Full-Envelope Aero-Propulsive Model Identification for Lift+Cruise Aircraft Using Computational Experiments

This paper describes a process utilizing computational fluid dynamics experiments to develop a reduced-order, integrated propulsion-airframe aerodynamic model for a lift+cruise electric vertical takeoff and landing (eVTOL) reference aircraft concept. eVTOL configurations exhibit aerodynamic characteristics of both fixed-wing and rotary-wing aircraft as well as complex phenomena, such as propulsion-airframe interactions. Consequently, conventional aircraft aerodynamic modeling strategies require modification when applied to these unique aircraft. A novel aero-propulsive modeling approach using design of experiments techniques and computational fluid dynamics simulations is postulated for modeling a lift+cruise aircraft configuration. Aero-propulsive models are developed throughout the operational flight envelope to enable continuous flight dynamics simulations from hover through forward flight. The model adequacy is assessed using validation data acquired separately from data used to identify the model and indicates that the models have sufficient predictive capability. Research findings are presented with a discussion of unique lift+cruise aircraft aerodynamic characteristics and practical strategies to inform future aero-propulsive modeling and simulation efforts for eVTOL aircraft.

lift+cruise↗
NASA NTRS2026

A Summary of Test and Analysis Results from a Second Lift+Cruise Full-Scale Drop Test

The realization of advanced air mobility markets is enabling new forms of transportation to take shape in the United States and around the world. Though currently in development, as these markets mature, new types of vertical take-off and landing (VTOL) vehicles have been undergoing development for use. There are many factors which must be addressed prior to these types of vehicles becoming viable alternative forms of transportation in these markets. These factors include incorporation into the existing airspaces, the logistics of operating in urban environments, along with numerous factors associated with safety and reliability. To address some of the safety aspects associated with the development of these new types of vehicles, NASA has been conducting research into the performance of an example electric VTOL (eVTOL) aircraft as a part of the Revolutionary Vertical Lift Technology (RVLT) project. Over the course of this research, many aspects including the development of energy absorbing components, the evaluation of seating systems, the development of advanced finite element material model systems and the acquisition of full-scale vehicle impact data were investigated. The report will discuss aspects related to the acquisition of full-scale vehicle data which occurred in the form of a full-scale impact test conducted in the Summer of 2025. This test was on a NASA designed Lift+Cruise composite cabin test article and represented a partial capstone in the entirety of previous eVTOL research conducted for the project. In this test, a variety of experiments were included in order to investigate the effect of a full-scale environment on the experiment results. In parallel, the development of a computational impact model to simulate the full-scale test will be discussed in this report. A model of the Lift+Cruise test article was developed utilizing data collected from previous sub- and full-scale test data and then simulated in the current test environment. The model development, its use in pre-test predictions, and its use in post-test correlation will all be presented. This report will present the test data acquired from the Lift+Cruise test and document several of the results obtained. One intended result is to determine the effect of a complex full-scale crash impact on the identification of occupant injury risk within seat and vehicle designs. A second intended result is to determine whether high-fidelity models can be used with some confidence in the prediction of test events and can allow for additional test cases to be simulated without the need of having to conduct additional tests. The overall goal of the test is to provide the community with data that can be used for design, development or certification efforts, along with providing data on what an example eVTOL crash incident could entail.

energy storage systems↗