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NASA NTRS2022

Yuma 2022 Rotorcraft Acoustic Flight Test

A cooperative flight test campaign between U.S. Navy, Army, Marine Corps, and NASA was performed at Marine Corps Air Station (MCAS) Yuma from 19 January to 15 February 2022. The primary purpose of testing military vehicles was to characterize the acoustic signature of the MV-22 rotorcraft and Stalker unmanned aerial system for typical mission gross weight, configuration, and for a range of typical mission operating conditions. Additionally, a civilian MD530 vehicle was tested to characterize the acoustic emissions for both legacy blades and S411 main rotor blades. This report provides an overview of the test, documents the data acquired, and describes the formats of the stored data.

Acoustics↗
NASA NTRSDate not supplied

Acoustic Flight Test of the Joby Aviation Advanced Air Mobility Prototype Vehicle

An extensive acoustic flight test was performed on the Joby Aviation pre-production all-electric vertical takeoff and landing prototype. With the design intent of carrying a pilot and four passengers a maximum range of 150 miles, this vehicle utilizes distributed propulsion and vectored thrust via six tilting propellers. As part of the Advanced Air Mobility (AAM) National Campaign, this is the first full-scale AAM aircraft tested by NASA over representative conditions for all phases of a typical mission profile. A 58- channel distributed microphone array was used to acquire acoustic measurements on more than 100 test points (31 unique conditions). The measurements were postprocessed with synchronously sampled vehicle position and state data to form ground noise contours of departures and approaches at various flight path angles and accelerations. Comparing ground areas of 75 dBA isolines, approaches consistently exhibit higher noise levels rela- tive to departures. Directivity maps were generated for constant airspeed level flyovers. Examples comparing the differences in a semi-thrust borne and full wing-borne mode are given, with full wing-borne mode representing the quietest phase of the flight envelope tested. Measurements for hover in and out of ground effect are given and found to have 2 to 5 dB variation over a single run, and more significant variation between back-to-back runs. Finally, initial analysis of acoustic symmetry about the longitudinal vehicle axis and repeatability over several test days are presented.

Acoustics↗
NASA NTRSDate not supplied

Communication Network Awareness Machine System Phase I Development: The Intelligent Party-Line Schema

As NextGen continues toward the full implementation of a Net-Centric Architecture (N-CA)it will inherently provide a continuous increase to the Three-Vs components (Volume, Velocity, and Variety) of big data . This will create an insurmountable environment for direct-action aviation personnel (DAAP)as the DAAP’s natural abilities to manage and process data into actionable information will be overmatched by the Three-Vs. Therefore, conducting operations within a N-CA requires that new tools and applications be researched and developed to aid the DAAP’s ability to understand and manage data, mitigate non-normals, create contingency plans and actions. This paper will describe a research area at NASA Langley Research Center known as the Intelligent Party-Line (IPL).

Intelligent Party-Line↗
NASA NTRSDate not supplied

EVALUATION OF ACOUSTIC SNAPSHOT ARRAYS FOR ROTORCRAFT SOURCE NOISE CHARACTERIZATION

Historical development of acoustic hemispheres has required steady flight of a rotorcraft vehicle across a large linear array of microphones. The US Army, NASA, and Navy recently conducted a rotorcraft acoustics flight test in which multiple “snapshot” microphone arrays were used alongside a traditional linear microphone array. The snapshot arrays allow for a near instantaneous capture of rotorcraft acoustic emissions, without the need for steady flight. Development of the snapshot array is contained herein, and an evaluation of effectiveness of the array during adverse weather conditions. The snapshot arrays captured significant variation in acoustic emissions throughout a single run and between multiple runs of similar conditions. Hemispheres were created and modelled in land-use planning software and an investigation of A-weighted Sound Exposure Level (SEL [dBA]) was conducted. Sideline predictions of SEL compared well (within 0.1 dBA) between traditional and snapshot arrays, while centre line locations were less favourable with a difference of 1.6 dBA. Future refinement is required for the snapshot array technique, including advanced design of microphone placement and employing a semiempirical method to interpolate between measurement points, instead of the linear frequency weighting conventionally employed.

Rotorcraft↗
NASA NTRSDate not supplied

A Preliminary Development of The Intelligent Change Detection System (ICDS): Using Machine Learning to Combat Change Blindness in Remote Operation Environments

The emergence of Advance Air Mobility (AAM) will increase the number and types of aerial vehicles operating in shared airspaces, which will subsequently affect the amount of actionable data that ground control station operators (GCSOs) will be expected to manage. In this environment, GCSOs are particularly susceptible to the visual perceptual phenomenon known as change blindness, in which a stimulus undergoes a change without the change being noticed by its observer. A machine agent designed to detect change blindness and mitigate the effects could improve human agent performance in a data-saturated remote operations environment. The objective of this paper is to describe a proof-of-concept system architecture that integrates real-time eye tracking and vehicle telemetry data to prevent human-agent errors resulting from change blindness while operating aircraft from a remote ground control station (GCS).

Real-Time Streaming Data Architecture↗
NASA NTRSDate not supplied

Foundational Human-Autonomy Teaming Research and Development in Scalable Remotely Operated Advanced Air Mobility Operations: Research Model and Initial Work

To achieve the scalability envisioned for many Advanced Air Mobility (AAM) applications, uncrewed aerial system (UAS) concepts are being pursued with the goal of enabling fewer human operators to manage more increasingly autonomous vehicles. NASA’s Transformational Tools and Technologies – Revolutionary Aviation Mobility (T3-RAM) subproject has identified human-autonomy teaming (HAT) as a critical area of research required to support these operations. Under T3-RAM, the HAT Foundational Research Activity has been tasked with providing basic research to identify HAT and human-automation interaction (HAI) principles that can be used to achieve scalable multi-vehicle UAS operations. This paper first outlines a research model to produce ecologically relevant basic research, then contextualizes completed and planned research and development activities within this model. Proposed research threads are presented, along with their practical and theoretical implications.

Human-Autonomy Teaming↗
NASA NTRSDate not supplied

A Preliminary Development of The Intelligent Change Detection System (ICDS): Using Machine Learning to Combat Change Blindness in Remote Operation Environments

The emergence of Advance Air Mobility (AAM) will increase the number and types of aerial vehicles operating in shared airspaces, which will subsequently affect the amount of actionable data that ground control station operators (GCSOs) will be expected to manage. In this environment, GCSOs are particularly susceptible to the visual perceptual phenomenon known as change blindness, in which a stimulus undergoes a change without the change being noticed by its observer. A machine agent designed to detect change blindness and mitigate the effects could improve human agent performance in a data-saturated remote operations environment. The objective of this paper is to describe a proof-of-concept system architecture that integrates real-time eye tracking and vehicle telemetry data to prevent human-agent errors resulting from change blindness while operating aircraft from a remote ground control station (GCS).

Real-Time Streaming Data Architecture↗
NASA NTRSDate not supplied

Evaluation of Acoustic Propagation in Layered Media Using Wave Confinement

A comprehensive method for propagation of sound in layered media is discussed that involves dividing the domain into two regions, source field and far field. The source field is provided using experimentally collected data from full-scale rotorcraft acoustic flight tests, which consists of short waveforms that cannot be directly simulated on the grid without numerical errors. Instead, grid based computational waves are used to carry the details of these waveforms, including amplitude, arrival time and location of origin on source sphere. This is done by solving the scalar wave equation using the Wave Confinement (WC) method, which involves adding an extra term to produce converged solutions. WC is used to study wave propagation in two different atmospheric conditions, and the results are compared to the flight test data. Overall, WC can accurately capture the propagation effects and there is a good agreement with the flight test data.

rotorcraft acoustics↗
NASA NTRSDate not supplied

Evaluation of Acoustic Propagation in Layered Media Using Wave Confinement

A comprehensive method for propagation of sound in layered media is discussed that involves dividing the domain into two regions, source field and far field. The source field is provided using experimentally collected data from full-scale rotorcraft acoustic flight tests, which consists of short waveforms that cannot be directly simulated on the grid without numerical errors. Instead, grid based computational waves are used to carry the details of these waveforms, including amplitude, arrival time and location of origin on source sphere. This is done by solving the scalar wave equation using the Wave Confinement (WC) method, which involves adding an extra term to produce converged solutions. WC is used to study wave propagation in two different atmospheric conditions, and the results are compared to the flight test data. Overall, WC can accurately capture the propagation effects and there is a good agreement with the flight test data.

rotorcraft acoustics↗
NASA NTRS2023

The Lifetime Surveillance of Astronaut Health Newsletter

Welcome to the October 2023 issue of the Lifetime Surveillance of Astronaut Health (LSAH) Newsletter! This issue will showcase our Space Radiation Analysis Group (SRAG), highlighting their contributions towards keeping our astronauts safe during spaceflight.

Ronnie Rafanan↗
NASA NTRSDate not supplied

Acoustic Characterization of the NASA Langley 14- by 22-Foot Subsonic Tunnel Using Single-Microphone Analysis Techniques

An experimental campaign was conducted to assess recent acoustic modifications to the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel. This effort was undertaken in preparation for future rotorcraft, Advanced Air Mobility, and airframe noise acoustic tests. The tunnel is a closed circuit and typically operates in an open-jet configuration for acoustic studies. A vertical linear array of microphones and a phased array were placed on traverses outside of the core flow. Pole-mounted acoustic sources with known waveforms were used to identify reflective surfaces under static conditions with no tunnel flow. A similar process was replicated with more compact sources in an aerodynamic fairing for flow speeds up to Mach 0.16. This enabled investigation of the test section core flow and bounding shear layer impacts on the acoustic measurements. Periodic averaging was employed and was shown to be capable of isolating periodic acoustic signals even for poor signal-to-noise ratio conditions. Benefits and limitations of single-microphone processing methods are identified. A companion paper utilizes a phased array in an effort to address the identified limitations to more traditional single-microphone data collection.

Acoustic Characterization↗
NASA NTRSDate not supplied

Acoustic Characterization of the NASA Langley 14- by 22-Foot Subsonic Tunnel using a Phased Array

A characterization test was conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel to assess recent acoustic modifications in the facility. Test section reflectivity, background noise and shear layer effects were evaluated by taking measurements of known noise sources. Both conventional speakers and a high-pressure air source were employed as noise generation mechanisms. These were mounted to a pole or fairing at a consistent location in the test section. The source waveforms were used to represent the expected frequency content of scaled Urban Air Mobility vehicles. Acoustic measurements were taken using two unique microphone arrays placed outside the core flow, one of which was a 54-element streamwise-traversing phased array. The other was an 11-element linear tower array. The applicability of phased array acoustic beamforming techniques to mitigate shear layer effects and reject background noise is presented. Additionally, beamforming results are compared to results from single-microphone processing techniques. Flow speeds investigated ranged from Mach 0.00 (static) to Mach 0.12. The tunnel has been partially acoustically treated but still exhibits flow noise, reducing the signal-to-noise ratio of the source under investigation. Conventional beamforming was able to capture high frequency content passing through the shear layer better than single microphone measurements. CLEAN deconvolution improves source mapping at low frequencies.

phased array↗
NASA NTRSDate not supplied

Reflectivity characterization of in-flow acoustic floor treatment for the NASA Langley 14- by 22-Foot Subsonic Tunnel

An experimental campaign was performed to assess acoustic modifications to the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel. Recent acoustic test campaigns in this facility have emphasized the reduction of aerodynamic noise due to flow scrubbing across acoustically treated floor baskets. However, the measures implemented to address this noise contaminant have resulted in the installation of floor basket coverings of high acoustic reflectivity. Therefore, a controlled test campaign was performed to identify a suitable acoustic basket configuration in terms of both acoustic absorptivity and reduced flow scrubbing noise. This test campaign was conducted in two phases: the first in an anechoic chamber facility on a single acoustic basket panel to identify a notional configuration of acceptable absorptivity, and the second in a complete floor basket installation checkout test in the NASA Langley 14- by 22-Foot Subsonic Tunnel. Results show that the newly implemented floor treatment exhibits suitable performance in both desired categories of acoustic absorptivity and reduced flow scrubbing noise. This campaign has also validated the effectiveness and usefulness of the anechoic chamber test configuration as a means of assessing acoustic reflections at oblique angles of incidence.

Nikolas S Zawodny↗
NASA NTRSDate not supplied

Investigation of Speed and Altitude Effects on Sound Exposure Level Calculations for Multiple Helicopters

International and United States Federal regulations evaluate helicopter acoustic emissions for certification purposes as well as community noise impact assessments. The Sound Exposure Level (SEL) is a commonly used metric that represents the loudness of a single event, with a penalty for duration. For example, a flyover lasting ten seconds can have the same SEL as a five-second duration flyover that is 3 dB higher in peak level. Ten helicopters spanning the light and medium weight classes were modeled using flight test data. They were then virtually flown using the Advanced Acoustic Model at multiple speeds and altitudes. SEL and A-weighted SEL (SELA) were calculated at ground-based observer locations for each condition. Scaling laws with altitude are determined, and cruising airspeeds which result in the minimum SEL are found. Implications for future land-use planning will be discussed, and the relationships are reduced to general or vehicle-specific operational guidance for pilots.

community noise↗
NASA NTRSDate not supplied

Acoustic Characterization of the NASA Langley 14- by 22-Foot Subsonic Tunnel Using Single-Microphone Analysis Techniques

An experimental campaign was conducted to assess recent acoustic modifications to the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel. This effort was undertaken in preparation for future rotorcraft, Advanced Air Mobility, and airframe noise acoustic tests. The tunnel is a closed circuit and typically operates in an open-jet configuration for acoustic studies. A vertical linear array of microphones and a phased array were placed on traverses outside of the core flow. Pole-mounted acoustic sources with known waveforms were used to identify reflective surfaces under static conditions with no tunnel flow. A similar process was replicated with more compact sources in an aerodynamic fairing for flow speeds up to Mach 0.16. This enabled investigation of the test section core flow and bounding shear layer impacts on the acoustic measurements. Periodic averaging was employed and was shown to be capable of isolating periodic acoustic signals even for poor signal-to-noise ratio conditions. Benefits and limitations of single-microphone processing methods are identified. A companion paper utilizes a phased array in an effort to address the identified limitations to more traditional single-microphone data collection.

Acoustic Characterization↗