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At least 307 records · Page 17

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NASA NTRS2011

TPSAS-NF1676L-12284-DND

A much desired capability for conceptual design of aircraft is the ability to rapidly and accurately evaluate new concepts to avoid adverse trade decisions that can hinder the development in the later stages of design. For the conceptual design of supersonic aircraft, it is important to evaluate the robustness of a new low-boom concept. Here, robustness means that the aircraft configuration has low-boom ground signatures at both under-track and off-track locations. An integration process for off-track boom analysis is developed to facilitate robust design of low-boom supersonic aircraft. The integrated off-track analysis can also be used to study sonic boom impact on flight corridors where flight conditions and ground elevation might have a significant effect on ground signatures. The key for off-track sonic boom analysis is accurate solutions for off-body pressure distribution along the lower region of a cylinder cut around the aircraft. To ensure the numerical accuracy of the off-body pressure distribution, a mesh study is performed to determine the mesh requirements for off-track analysis as well as comparisons between Cart3D and USM3D off-track sonic boom results for various low-boom concepts. The integrated and automated process makes it possible to study the environmental impact of future supersonic concepts in the early design phases and support the planning of future flight corridors to mitigate sonic boom effects.

Irian Ordaz↗

NASA NTRS1999

High Speed Civil Transport Design Using Collaborative Optimization and Approximate Models

The design of supersonic aircraft requires complex analysis in multiple disciplines, posing, a challenge for optimization methods. In this thesis, collaborative optimization, a design architecture developed to solve large-scale multidisciplinary design problems, is applied to the design of supersonic transport concepts. Collaborative optimization takes advantage of natural disciplinary segmentation to facilitate parallel execution of design tasks. Discipline-specific design optimization proceeds while a coordinating mechanism ensures progress toward an optimum and compatibility between disciplinary designs. Two concepts for supersonic aircraft are investigated: a conventional delta-wing design and a natural laminar flow concept that achieves improved performance by exploiting properties of supersonic flow to delay boundary layer transition. The work involves the development of aerodynamics and structural analyses, and integration within a collaborative optimization framework. It represents the most extensive application of the method to date.

Manning, Valerie Michelle↗

NASA NTRS2010

Analysis of Nozzle Jet Plume Effects on Sonic Boom Signature

An axisymmetric full Navier-Stokes computational fluid dynamics (CFD) study was conducted to examine nozzle exhaust jet plume effects on the sonic boom signature of a supersonic aircraft. A simplified axisymmetric nozzle geometry, representative of the nozzle on the NASA Dryden NF-15B Lift and Nozzle Change Effects on Tail Shock (LaNCETS) research airplane, was considered. The highly underexpanded nozzle flow is found to provide significantly more reduction in the tail shock strength in the sonic boom N-wave pressure signature than perfectly expanded and overexpanded nozzle flows. A tail shock train in the sonic boom signature, similar to what was observed in the LaNCETS flight data, is observed for the highly underexpanded nozzle flow. The CFD results provide a detailed description of the nozzle flow physics involved in the LaNCETS nozzle at different nozzle expansion conditions and help in interpreting LaNCETS flight data as well as in the eventual CFD analysis of a full LaNCETS aircraft. The current study also provided important information on proper modeling of the LaNCETS aircraft nozzle. The primary objective of the current CFD research effort was to support the LaNCETS flight research data analysis effort by studying the detailed nozzle exhaust jet plume s imperfect expansion effects on the sonic boom signature of a supersonic aircraft. Figure 1 illustrates the primary flow physics present in the interaction between the exhaust jet plume shock and the sonic boom coming off of an axisymmetric body in supersonic flight. The steeper tail shock from highly expanded jet plume reduces the dip of the sonic boom N-wave signature. A structured finite-volume compressible full Navier-Stokes CFD code was used in the current study. This approach is not limited by the simplifying assumptions inherent in previous sonic boom analysis efforts. Also, this study was the first known jet plume sonic boom CFD study in which the full viscous nozzle flow field was modeled, without coupling to a sonic boom propagation analysis code, from the stagnation chamber of the nozzle to the far field external flow, taking into account all nonisentropic effects in the shocks, boundary layers, and free shear layers, and their interactions at distances up to 30 times the nozzle exit diameter from the jet centerline. A CFD solution is shown in Figure 2. The flow field is very complicated and multi-dimensional, with shock-shock and shockplume interactions. At the time of this reporting, a full three-dimensional CFD study was being conducted to evaluate the effects of nozzle vectoring on the aircraft tail shock strength.

Bui, Trong↗

NASA NTRS1976

Preliminary Sizing and Performance Evaluation of Supersonic Cruise Aircraft

The basic processes of a method that performs sizing operations on a baseline aircraft and determines their subsequent effects on aerodynamics, propulsion, weights, and mission performance are described. The input requirements of the associated computer program are defined and its output listings explained. Results obtained by applying the method to an advanced supersonic technology concept are discussed. These results include the effects of wing loading, thrust-to-weight ratio, and technology improvements on range performance, and possible gains in both range and payload capability that become available through growth versions of the baseline aircraft. The results from an in depth contractual study that confirm the range gain predicted for a particular wing loading, thrust-to-weight ratio combination are also included.

Fetterman, D. E., Jr.↗

NASA NTRS2012

Recent Progress on Sonic Boom Research at NASA

Sonic boom research conducted at NASA through the Supersonics Project of the Fundamental Aeronautics Program is oriented toward understanding the potential impact of sonic boom noise on communities from new low-boom supersonic aircraft designs. Encompassing research in atmospheric propagation, structural response, and human response, NASA research contributes to knowledge in key areas needed to support development of a new noise-based standard for supersonic aircraft certification. Partnerships with several industry, government, and academic institutions have enabled the recent execution of several acoustic field studies on sonic booms. An overview of recent activities funded by NASA includes: focus boom model development and experimental validation, field experiments of structural transmission of sonic booms into large buildings, and low boom community response testing.

Loubeau, Alexandra↗

NASA NTRSDate not supplied

Experiment Design and Visualization Techniques for an X-59 Low-boom Variability Study

This presentation outlines the design of experiments approach and data visualization techniques for a simulation study of sonic booms from NASA’s X-59 supersonic aircraft. The X-59 will soon be flown over communities across the contiguous USA as it produces a low-loudness sonic boom, or low-boom. Survey data on human perception of low-booms will be collected to support development of potential future commercial supersonic aircraft noise regulatory standards. The macroscopic atmosphere plays a critical role in the loudness of sonic booms. The extensive sonic boom simulation study presented herein was completed to assess climatological, geographical, and seasonal effects on the variability of the X-59’s low-boom loudness and noise exposure region size in order to inform X-59 community test planning. The loudness and extent of the noise exposure region make up the “sonic boom carpet.” Two spatial and temporal resolutions of atmospheric input data to the simulation were investigated. A Fast Flexible Space-Filling Design was used to select the locations across the USA for the two spatial resolutions. Analysis of simulated X-59 low-boom loudness data within a regional subset of the northeast USA was completed using a bootstrap forest to determine the final spatial and temporal resolution of the countrywide simulation study. Atmospheric profiles from NOAA’s Climate Forecast System Version 2 database were used to generate over one million simulated X-59 carpets at the final selected 138 locations across the USA. Effects of aircraft heading, season, geography, and climate zone on low-boom levels and noise exposure region size were analyzed. Models were developed to estimate loudness metrics throughout the USA for X-59 supersonic cruise overflight, and results were visualized on maps to show geographical and seasonal trends. These results inform regulators and mission planners on expected variations in boom levels and carpet extent from atmospheric variations. Understanding potential carpet variability is important when planning community noise surveys using the X-59.

X-59↗

NASA NTRS2015

Experimental and Computational Sonic Boom Assessment of Lockheed-Martin N+2 Low Boom Models

Flight at speeds greater than the speed of sound is not permitted over land, primarily because of the noise and structural damage caused by sonic boom pressure waves of supersonic aircraft. Mitigation of sonic boom is a key focus area of the High Speed Project under NASA's Fundamental Aeronautics Program. The project is focusing on technologies to enable future civilian aircraft to fly efficiently with reduced sonic boom, engine and aircraft noise, and emissions. A major objective of the project is to improve both computational and experimental capabilities for design of low-boom, high-efficiency aircraft. NASA and industry partners are developing improved wind tunnel testing techniques and new pressure instrumentation to measure the weak sonic boom pressure signatures of modern vehicle concepts. In parallel, computational methods are being developed to provide rapid design and analysis of supersonic aircraft with improved meshing techniques that provide efficient, robust, and accurate on- and off-body pressures at several body lengths from vehicles with very low sonic boom overpressures. The maturity of these critical parallel efforts is necessary before low-boom flight can be demonstrated and commercial supersonic flight can be realized.

Cliff, Susan E.↗

NASA NTRS1974

Cold-flow performance of several variations of a ram-air-cooled plug nozzle for supersonic-cruise aircraft

Experimental data were obtained with a 21.59 cm (8.5 in.) diameter cold-flow model in a static altitude facility to determine the thrust and pumping characteristics of several variations of a ram-air-cooled plug nozzle. Tests were conducted over a range of nozzle pressure ratios simulating supersonic cruise and takeoff conditions. Primary throat area was also varied to simulate afterburner on and off. Effect of plug size, outer shroud length, primary nozzle geometry, and varying amounts of secondary flow were investigated. At a supersonic cruise pressure ratio of 27, nozzle efficiencies were 99.7 percent for the best configurations.

Harrington, D. E.↗

NASA NTRS1992

Experimental investigation of wing installation effects on a two-dimensional mixer/ejector nozzle for supersonic transport aircraft

Experimental results from a wind tunnel test conducted to investigate propulsion/airframe integration (PAI) effects are presented. The objectives of the test were to examine rough order-of-magnitude changes in the acoustic characteristics of a mixer/ejector nozzle due to the presence of a wing and to obtain limited wing and nozzle flow-field measurements. A simple representative supersonic transport wing planform, with deflecting flaps, was installed above a two-dimensional mixer/ejector nozzle that was supplied with high-pressure heated air. Various configurations and wing positions with respect to the nozzle were studied. Because of hardware problems, no acoustics and only a limited set of flow-field data were obtained. For most hardware configurations tested, no significant propulsion/airframe integration effects were identified. Significant effects were seen for extreme flap deflections. The combination of the exploratory nature of the test and the limited flow-field instrumentation made it impossible to identify definitive propulsion/airframe integration effects.

Anderson, David J.↗

NASA NTRS1973

Internal performance of a wedge nozzle for a supersonic cruise aircraft with a multispoke primary for noise suppression

Nozzle performance was obtained with cold primary and secondary flows over a range of nozzle pressure ratio from 2 to 31 and corrected secondary-to primary-flow ratio from 0 to 11 percent. Several fixed shroud positions were tested to simulate a translating outer cylindrical shroud to provide data for both supersonic cruise and takeoff configurations. The addition of 14 spokes in the primary nozzle for noise suppression reduced the thrust efficiency 3 percent at supersonic cruise and 4.5 percent at takeoff.

Johns, A. L.↗

NASA NTRSDate not supplied

Single-Stream Empirical Jet-Noise Models Based on Scale-Model Data

Accurate single-stream jet-noise models for hot jets in flight are necessary for predicting noise of future commercial supersonic aircraft at takeoff. Previous comparisons between flight data and existing models have shown unacceptably large errors in the predictive tools. In the current effort, acoustic data were acquired in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center for a single-stream hot jet with a range of operating conditions and simulated flight speeds that include those expected at takeoff of commercial supersonic aircraft. Models are presented for the resulting shape functions used to estimate the average spectra derived from the appropriate scaling of the jet-noise data.

Acoustics↗

NASA NTRSDate not supplied

Single-Stream Empirical Jet Noise Models Based on Scale-Model Data

Acoustics↗

NASA NTRS2019

Multipoint Variable Cycle Engine Design Using Gradient-based Optimization

Supersonic aircraft are challenging to optimally design due to the widely varying constraints and flight conditions they experience. Additionally, a large number of disciplinary subsystems must be considered due to highly complex design requirements. One subsystem that has a major effect on overall performance is the engine. In this work, we construct a supersonic mixed-flow variable cycle engine and perform multipoint gradient-based optimization using this model. We see that the operational variables allow the optimizer to tailor performance at each individual flight condition, leading to better overall performance. To simulate airframe integration constraints, we run successive optimizations with increasingly restrictive inlet areas and see decreases in engine performance. This work is part of a larger effort to incorporate engine design into aero-thermal-mission optimization of a supersonic aircraft.

Cycle analysis↗

NASA NTRSDate not supplied

TPSAS-NF1676L-20030-DND

Sonic booms from recently proposed supersonic aircraft designs developed with advanced tools are predicted to be quieter than those from previous designs. The possibility of developing a low-boom flight demonstration vehicle for conducting community response studies has attracted international interest. These studies would provide data to guide development of a preliminary noise certification standard for commercial supersonic aircraft. An affordable approach to conducting these studies suggests the use of a sub-scale experimental aircraft. Due to the smaller size and weight of the sub-scale vehicle, the resulting sonic boom is expected to contain spectral characteristics that differ from that of a full-scale vehicle. To determine the relevance of using a sub-scale aircraft for community annoyance studies, a laboratory study was conducted to verify that these spectral differences do not significantly affect human response. Indoor annoyance was evaluated for a variety of sonic booms predicted for several different sizes of vehicles. Previously reported results compared indoor annoyance for the different sizes using the metric Perceived Level (PL) at the exterior of the structure. Updated results include analyses with other candidate noise metrics, nonlinear regression, and specific boom duration effects.

Alexandra Loubeau↗

NASA NTRSDate not supplied

Review of Noise Metric Sensitivities for Analysis of Quiet Supersonic Overflight

Six different noise metrics (PL, ASEL, BSEL, DSEL, ESEL, and ISBAP) are currently used to quantify sonic boom levels from overflight of supersonic aircraft. A previous meta-analysis using laboratory subjective data identified these metrics, each of which correlated well with human perception of low-boom sounds both indoors and outdoors. Because the analysis did not identify a single metric that was significantly superior, no internationally agreed-upon metric has been chosen for the quiet supersonic aircraft noise certification procedures currently under development. Other analyses of metric sensitivities using existing empirical and simulation datasets, however, have shown significant differences between metrics. Variability of metrics due to macro-atmospheric effects and atmospheric turbulence perturbations have been explored, as well as variability in measurements due to microphone setup configurations, array layouts, and ambient noise effects. This paper reviews these prior studies, summarizes the current understanding of metric sensitivities, and discusses how they may impact future downselection of metrics for certification procedures.

sonic boom↗

NASA NTRS2023

Estimating the Noise Dose Range of the NASA X-59 Aircraft in Supersonic Cruise Using PCBoom Propagation Simulations

PCBoom propagation simulations of the NASA X-59 low-boom in supersonic cruise were conducted using near-field CFD pressure waveforms as inputs to estimate the noise dose range. Low-booms were propagated through realistic atmospheric profiles from the Climate Forecast System Version 2 across the USA, and loudness statistics of the low-booms are presented. The near-field waveforms correspond to aircraft configurations expected to produce minimum- and maximum-loudness levels on the ground. The simulations show that the practical Perceived Level noise dose range is 72 to 86.7 dB. Dose ranges for other single event and cumulative sonic boom metrics of interest are also provided.

X-59↗

NASA NTRS1996

Active Sonic Boom Control

A theory and simulation code are developed to study nonsteady sources as means to control sonic booms of supersonic aircraft. A key result is that the source of sonic boom pressure is not confined to the length of the aircraft but occupies an extensive segment of flight path. An aircraft in nonsteady flight functions as a synthetic aperture antenna, generating complex acoustic waves with no simple relation to instantaneous volume or lift distributions. The theory applies linear acoustics to slender nonsteady sources but requires no far field approximation. The solution for pressure contains a term not seen in Whitham's theory for sonic booms of distant supersonic aircraft. The term describes a pressure field that decays algebraically behind the Mach cone and, in the case of steady flight, integrates to a ground load equal to the weight of the aircraft. The algebraic term is separate from those that describe the sonic boom. Two nonsteady source phenomena are evaluated: periodic velocity changes (surge), and periodic longitudinal lift redistribution (slosh). Surge can attenuate a sonic boom and convert it into prolonged weak reverberation, but accelerations needed to produce the phenomenon seem too large for practical use. Slosh may be practical and can alter sonic booms but does not, on the average, result in boom attenuation. The conclusion is that active sonic boom abatement is possible in theory but maybe not practical

Crow, Steven C.↗

NASA NTRSDate not supplied

Predicting Supersonic Noise at the Airport—Tech Challenge Wrapup

NASA has completed a Technical Challenge to reduce uncertainty of predicting the noise of future commercial supersonic aircraft around the airport. Noise prediction models being used to guide manufacturers and regulators have previously been based on conventional aircraft configurations. Aircraft configurations required for supersonic flight are not predicted well by these models. NASA used physics-based simulations along with some historical data to extend noise prediction models to cover aircraft designs typical of near-term market concepts. The presentation gives an overview of this work and its lasting accomplishments.

supersonic↗