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At least 1,333 records · Page 74
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NASA NTRS2015

Acoustic Liner Drag: A Parametric Study of Conventional Configurations

Interest in the characterization of the aerodynamic drag performance of acoustic liners has increased in the past several years. This paper details experiments in NASA Langley's Grazing Flow Impedance Tube to quantify the relative drag of several conventional perforate-over-honeycomb liner configurations. For a fixed porosity, facesheet hole diameter and cavity depth are varied to study the effect of each. These configurations are selected to span the range of conventional liner geometries used in commercial aircraft engines. Detailed static pressure and acoustic measurements are made for grazing flows up to M=0.5 at 140 dB SPL for tones between 400 and 2800 Hz. These measurements are used to calculate a resistance factor (λ) for each configuration. Analysis shows a correlation between perforate hole size and the resistance factor but cavity depth seems to have little influence. Acoustic effects on liner drag are observed to be limited to the lower Mach numbers included in this investigation.

Howerton, Brian M.↗
NASA NTRS2013

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel: 6-Ply In-Autoclave Facesheets - Part 2

Four honeycomb sandwich panel types, representing 1/16th arc segments of a 10-m diameter barrel section of the Heavy Lift Launch Vehicle (HLLV), were manufactured and tested under the NASA Composites for Exploration program and the NASA Constellation Ares V program. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.000 in. honeycomb core. Additionally, two separate carbon fiber/epoxy material systems were chosen for the facesheets: in-autoclave IM7/977-3 and out-of-autoclave T40-800b/5320-1. Smaller 3- by 5-ft panels were cut from the 1/16th barrel sections. These panels were tested under compressive loading at the NASA Langley Research Center (LaRC). Furthermore, linear eigenvalue and geometrically nonlinear finite element analyses were performed to predict the compressive response of each 3- by 5-ft panel. This manuscript summarizes the experimental and analytical modeling efforts pertaining to the panels composed of 6-ply, IM7/977-3 facesheets (referred to as Panels B-1 and B-2). To improve the robustness of the geometrically nonlinear finite element model, measured surface imperfections were included in the geometry of the model. Both the linear and nonlinear models yield good qualitative and quantitative predictions. Additionally, it was correctly predicted that the panel would fail in buckling prior to failing in strength. Furthermore, several imperfection studies were performed to investigate the influence of geometric imperfections, fiber angle misalignments, and three-dimensional (3-D) effects on the compressive response of the panel.

Pineda, Evan J.↗
NASA NTRS1990

High-Reynolds-Number Test of a 5-Percent-Thick Low-Aspect-Ratio Semispan Wing in the Langley 0.3-Meter Transonic Cryogenic Tunnel: Wing Pressure Distributions

A high Reynolds number test of a 5 percent thick low aspect ratio semispan wing was conducted in the adaptive wall test section of the Langley 0.3 m Transonic Cryogenic Tunnel. The model tested had a planform and a NACA 64A-105 airfoil section that is similar to that of the pressure instrumented canard on the X-29 experimental aircraft. Chordwise pressure data for Mach numbers of 0.3, 0.7, and 0.9 were measured for an angle-of-attack range of -4 to 15 deg. The associated Reynolds numbers, based on the geometric mean chord, encompass most of the flight regime of the canard. This test was a free transition investigation. A summary of the wing pressures are presented without analysis as well as adapted test section top and bottom wall pressure signatures. However, the presented graphical data indicate Reynolds number dependent complex leading edge separation phenomena. This data set supplements the existing high Reynolds number database and are useful for computational codes comparison.

Chu, Julio↗
NASA NTRS1992

A study of the influence of the data acquisition system sampling rate on the accuracy of measured acceleration loads for transport aircraft

A research effort was initiated at National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC), to describe the relationship between the sampling rate and the accuracy of acceleration loads obtained from the data acquisition system of a transport aircraft. An accelerometer was sampled and digitized at a rate of 100 samples per second onboard a NASA Boeing 737 (B-737) flight research aircraft. Numerical techniques were used to reconstruct 2.5 hours of flight data into its original input waveform and then re-sample the waveform into rates of 4, 8, 16, and 32 samples per second. Peak-between-means counting technique and power spectral analysis were used to evaluate each sampling rate using the 32 samples per second data as the comparison. This paper presents the results from these methods and includes in appendix A, the peak-between-means counting results used in a general fatigue analysis for each of the sampling rates.

Whitehead, Julia H.↗
NASA NTRS1997

Filmless Radiography

Technology initially prototyped under a Small Business Innovation Research contract between Quantex Corporation and Langley Research Center was licensed to Liberty Technology and incorporated into RADView, a new filmless radiography technology. The NASA-sponsored work involved the investigation of Electron Trapping, which led to a solid-state film that uses a special class of photoluminescent materials to capture radiographic images. RadView is a total imaging solution for the conversion of radiographic film records to digital format and digital acquisitions of radiographs. With the RADView technology, there is a reduction of exposure times and errors; film waste is eliminated; and the efficiency of data management and precise image analysis is boosted. The solid-state film can be exposed, read, erased, and re- exposed indefinitely until mechanical replacement is required. Digital images can be stored to optical media for up to 100 years and beyond without information loss.

Source record↗
NASA NTRS1953

Wind-Tunnel Investigation at Low Speed of the Rolling Stability Derivatives of a 1/9-Scale Powered Model of the Convair XFY-1 Vertically Rising Airplane, TED No. NACA DE 373

An experimental investigation has been conducted in the Langley stability tunnel at low speed to determine the rolling stability derivatives of a 1/9-scale powered model of the Convair XFY-1 vertically rising airplane. Effects of thrust coefficient were investigated for the complete model and for certain components of the model. Effects of control deflections and of propeller blade angle were investigated for the complete model. Most of the tests were made through an angle-of-attack range from about -4deg to 29deg, and the thrust coefficient range was from 0 to 0.7. In order to expedite distribution of these data, no analysis of the data has been prepared for this paper.

Queijo, M. J.↗
NASA NTRS2023

Development of a Field-Deployable Microphone Phased Array for Airframe Noise Flyover Measurements

This technical memorandum describes in detail the construction and use of a large channel-count, field-deployable microphone phased array designed for airframe noise flyover measurements for a range of aircraft types and scales. The array incorporated 185 hardened, weather-resistant sensors suitable for outdoor use. A custom 4-mA current loop receiver circuit with temperature compensation was developed to power the sensors over extended cable lengths with minimal loss of signal-to-noise. Extensive calibrations and performance testing of the sensors were conducted to verify the design specifications. A compact data system combining sensor power, signal conditioning, and digitization was assembled for use with the array. Complementing the data system was a robust analysis system capable of near real-time presentation of beamformed and deconvolved contour plots and integrated spectra obtained from data acquired during flyover passes of the array. Additional instrumentation systems needed to process the array data were also developed, including a commercial 10-meter weather station comprised of a sonic anemometer, aspirated temperature/humidity probe and pressure sensor. Unique methods for assessing the health of the array in-situ were developed and demonstrated. A detailed mock-up of the instrumentation suite (phased array, weather station, and data processor) was performed in the NASA Langley Acoustic Development Laboratory in 2014 to vet the system performance. Issues with the sensors and electronics were identified during the mock-up and subsequently corrected. The array was then deployed for preliminary field testing at Fort A.P. Hill in Virginia in 2015 followed by the array being utilized in three separate full-scale airframe noise test campaigns at Edwards Air Force Base in California from 2016 to 2018 where the system was used to characterize the noise generated by both baseline and treated flaps and main landing gear on a commercial transport-sized vehicle.

Phased Array↗
NASA NTRS2001

Analysis of the Performance Characteristics of the Five-Channel Microtops II Sun Photometer for Measuring Aerosol Optical Thickness and Precipitable Water Vapor

Five Microtops II sun photometers were studied in detail at the NASA Goddard Space Flight Center (GSFC) to determine their performance in measuring aerosol optical thickness (AOT or Tau(sub alphalambda) and precipitable column water vapor (W). Each derives Tau(sub alphalambda) from measured signals at four wavelengths lambda (340, 440, 675, and 870 nm), and W from the 936 nm signal measurements. Accuracy of Tau(sub alphalambda) and W determination depends on the reliability of the relevant channel calibration coefficient (V(sub 0)). Relative calibration by transfer of parameters from a more accurate sun photometer (such as the Mauna-Loa-calibrated AERONET master sun photometer at GSFC) is more reliable than Langley calibration performed at GSFC. It was found that the factory-determined value of the instrument constant for the 936 nm filter (k= 0.7847) used in the Microtops' internal algorithm is unrealistic, causing large errors in V(sub 0(936)), Tau(sub alpha936), and W. Thus, when applied for transfer calibration at GSFC, whereas the random variation of V(aub 0) at 340 to 870 nm is quite small, with coefficients of variation (CV) in the range of 0 to 2.4%, at 936 nm the CV goes up to 19%. Also, the systematic temporal variation of V(sub 0) at 340 to 870 nm is very slow, while at 936 nm it is large and exhibits a very high dependence on W. The algorithm also computes Tau(sub alpha936) as 0.91Tau(sub alpha870), which is highly simplistic. Therefore, it is recommended to determine Tau(sub alpha936) by logarithmic extrapolation from Tau(sub alpha675) and Tau(sub alpha 870. From the operational standpoint of the Microtops, apart from errors that may result from unperceived cloud contamination, the main sources of error include inaccurate pointing to the Sun, neglecting to clean the front quartz window, and neglecting to calibrate correctly. If these three issues are adequately taken care of, the Microtops can be quite accurate and stable, with root mean square (rms) differences between corresponding retrievals from clean calibrated Microtops and the AERONET sun photometer being about +/-0.02 at 340 nm, decreasing down to about +/-0.01 at 870 nm.

Ichoku, Charles↗
NASA NTRS1979

Aircraft Design Analysis

The helicopter pictured is the twin-turbine S-76, produced by Sikorsky Aircraft division of United Technologies, Stratford, Connecticut. It is the first transport helicopter ever dey n e d purely as a commercial vehicle rather than an adaptation of a military design. Being built in large numbers for customers in 16 countries, the S-76 is intended for offshore oil rig support, executive transportation and general utility service. The craft carries 12 passengers plus a crew of two and has a range of more than 450 miles-yet it weighs less than 10,000 pounds. Significant weight reduction was achieved by use of composite materials, which are generally lighter but stronger than conventional aircraft materials. NASA composite technology played a part in development of the S-76. Under contract with NASA's Langley Research Center, Sikorsky Aircraft designed and flight-tested a helicopter airframe of advanced composite materials.

Source record↗
NASA NTRS1965

Shielding requirements for manned orbiting space stations

A detailed parametric investigation of radiation shielding requirements was performed for first generation manned orbiting space stations. Two specific space station designs were studied; the results of the shielding analysis are based on the actual geometry of the vehicles, onboard equipment, and supplies. Results are presented for circular orbits ranging from 100 to 600 nautical miles and from 29° to 90° inclination. The effects of the geometry of the space stations, the use of personal shielding, and the use of particular shielding materials are discussed.

MANNED ORBITAL SPACE STATION /MOSS/↗
NASA NTRS1980

Preliminary evaluation of time and distance spacing cues using a cockpit displayed target

A simulator evaluation was conducted to compare time and distance selfspacing cues wherein a pilot establishes and maintains separation from a cockpit displayed target. Langley's terminal configured vehicle simulator which represents an advanced aircraft employing cathode ray tubes for primary flight displays and highly augmented flight control modes was used. Three tasks, two in trail rendezvous tasks (target straight and level and target turning) and one merge task were utilized. Three pilots flew each task twice, once with a time predictor cue and once with a distance predictor. Both time and distance spacing methods are operationally acceptable to the pilots. A slight preference was indicated by the pilots for the distance based predictor in performing rendezvous and merging tasks. Analysis of the recorded data showed the spacing performance with both predictors was essentially the same.

Kelly, J. R.↗
NASA NTRS1995

NASA Multidisciplinary Design and Analysis Fellowship Program

This report is a Year 1 interim report of the progress on the NASA multidisciplinary Design and Analysis Fellowship Program covering the period, January 1, 1995 through September 30, 1995. It summarizes progress in establishing the MDA Fellowship Program at Georgia Tech during the initial year. Progress in the advertisement of the program, recruiting results for the 1995-96 academic year, placement of the Fellows in industry during Summer 1995, program development at the M.S. and Ph.D. levels, and collaboration and dissemination of results are summarized in this report. Further details of the first year's progress will be included in the report from the Year 1 Workshop to be held at NASA Langley on December 7-8, 1995.

Source record↗
NASA NTRS1953

Wind-Tunnel Investigation at Low Speed of the Yawing Stability Derivatives of a 1/9-Scale Powered Model of the Convair XFY-1 Vertically Rising Airplane, TED No. NACA DE 373

An experimental investigation has been conducted in the Langley stability tunnel at low speed to deter+nine the yawing stability derivatives of a 1/9-scale powered model of the Convair XFY-1 vertically rising airplane. Effects of thrust coefficient were investigated for the complete model and for certain components of the model. Effects of control deflections and of propeller blade angle were investigated for the complete model. Most of the tests were made through an angle-of-attack range from about -4deg to 29deg, and the thrust coefficient range was from 0 to 0.7. In order to expedite distribution of these data, no analysis of the data has been prepared for this.

Queijo, M. J.↗
NASA NTRS2013

Trip-Induced Transition Measurements in a Hypersonic Boundary Layer Using Molecular Tagging Velocimetry

Measurements of mean streamwise velocity, fluctuating streamwise velocity, and instantaneous streamwise velocity profiles in a hypersonic boundary layer were obtained over a 10-degree half-angle wedge model. A laser-induced fluorescence-based molecular tagging velocimetry technique was used to make the measurements. The nominal edge Mach number was 4.2. Velocity profiles were measured both in an untripped boundary layer and in the wake of a 4-mm diameter cylindrical tripping element centered 75.4 mm downstream of the sharp leading edge. Three different trip heights were investigated: k = 0.53 mm, k = 1.0 mm and k = 2.0 mm. The laminar boundary layer thickness at the position of the measurements was approximately 1 mm, though the exact thickness was dependent on Reynolds number and wall temperature. All of the measurements were made starting from a streamwise location approximately 18 mm downstream of the tripping element. This measurement region continued approximately 30 mm in the streamwise direction. Additionally, measurements were made at several spanwise locations. An analysis of flow features show how the magnitude, spatial location, and spatial growth of streamwise velocity instabilities are affected by parameters such as the ratio of trip height to boundary layer thickness and roughness Reynolds number. The fluctuating component of streamwise velocity measured along the centerline of the model increased from approximately 75 m/s with no trip to +/-225 m/s with a 0.53-mm trip, and to +/-240 m/s with a 1-mm trip, while holding the freestream Reynolds number constant. These measurements were performed in the 31-inch Mach 10 Air Tunnel at the NASA Langley Research Center.

Bathel, Brett F.↗
NASA NTRS2019

Buckling Testing and Analysis of Honeycomb Sandwich Panel Arc Segments of a Full-Scale Fairing Barrel Part 4: Six-ply Out-of-Autoclave Facesheets

Four honeycomb sandwich panel types, representing 1/16th arc segments of a 10-m diameter barrel section of the Heavy Lift Launch Vehicle (HLLV), were manufactured and tested under the NASA Composites for Exploration program and the NASA Constellation Ares V program. Two configurations were chosen for the panels: 6-ply facesheets with 1.125 in. honeycomb core and 8-ply facesheets with 1.000 in. honeycomb core. Additionally, two separate carbon fiber/epoxy material systems were chosen for the facesheets: in-autoclave IM7/977-3 and out-of-autoclave T40-800b/5320-1. Smaller 3 ft. by 5 ft. panels were cut from the 1/16th barrel sections. These panels were tested under compressive loading at the NASA Langley Research Center (LaRC). Furthermore, linear eigenvalue and geometrically nonlinear finite element analyses were performed to predict the compressive response of each 3 ft. by 5 ft. panel. This manuscript summarizes the experimental and analytical modeling efforts pertaining to the panels composed of 6-ply, T40-800b/5320-1 facesheets (referred to as Panels D). To improve the robustness of the geometrically nonlinear finite element model, measured surface imperfections were included in the geometry of the model. Both the linear and nonlinear models yield good qualitative and quantitative predictions. Additionally, it was correctly predicted that the panel would fail in buckling prior to failing in strength. Furthermore, three-dimensional (3D) effects on the compressive response of the panel were studied.

David E Myers↗
NASA NTRS1982

Investigation of effects of microphone position and orientation on near-ground noise measurements

Three ground level microphone mounting techniques (flush mounting, inverting the microphone over a plate, and lying the microphone on a plate) were compared over a frequency range from 315 Hz to 20 kHz and over a wide range of incidence angles in the Langley Jet-Noise Laboratory anechoic room. The flush mounted microphone, when compared with a free field microphone, exhibited approximate pressure doubling up to a frequency of 10 kHz. At frequencies less than 4 kHz, the inverted and lying microphones were in good agreement with the flush mounted microphone, and their 1/3-octave-band response spectra were fairly insensitive to the position of the microphone. At higher frequencies, the geometry of the microphone and its mounting became important. The inverted microphone 0.5 times the diameter above the plate gave the flattest response compared with the flush mounted microphone. Nondimensional analysis of the inverted and lying results showed that for Kappa H cos theta 0.7 the response of the microphones approached that of the flush mounted microphone.

Willshire, W. L., Jr.↗
NASA NTRS2004

Performance and Reliability Optimization for Aerospace Systems subject to Uncertainty and Degradation

This report summarizes work performed by the Space Systems Laboratory (SSL) for NASA Langley Research Center in the field of performance optimization for systems subject to uncertainty. The objective of the research is to develop design methods and tools to the aerospace vehicle design process which take into account lifecycle uncertainties. It recognizes that uncertainty between the predictions of integrated models and data collected from the system in its operational environment is unavoidable. Given the presence of uncertainty, the goal of this work is to develop means of identifying critical sources of uncertainty, and to combine these with the analytical tools used with integrated modeling. In this manner, system uncertainty analysis becomes part of the design process, and can motivate redesign. The specific program objectives were: 1. To incorporate uncertainty modeling, propagation and analysis into the integrated (controls, structures, payloads, disturbances, etc.) design process to derive the error bars associated with performance predictions. 2. To apply modern optimization tools to guide in the expenditure of funds in a way that most cost-effectively improves the lifecycle productivity of the system by enhancing the subsystem reliability and redundancy. The results from the second program objective are described. This report describes the work and results for the first objective: uncertainty modeling, propagation, and synthesis with integrated modeling.

Miller, David W.↗