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At least 523 records · Page 29

Application of ERTS-1 imagery to the study of caribou movements and winter dispersal in relation to prevailing snowcover

The author has identified the following significant results. Habitat differentiation was determined feasible using output from MSS band 6 because of apparent high correlations between surface moisture and habitat type on the test area. Progressive early snow distribution was readily determined from MSS outputs, particularly bands 4 and 5. Approximately thirty thousand caribou migrated into the test area during the reporting period, and aerial reconnaissance data on distribution were obtained for selected areas within several days of satellite overflight.

Lent, P. C.↗

Experimental probability density distributions for optical and infrared cross-beam units

A series of cross beam experiments for measuring meteorological parameters was conducted. Both optical and infrared sensors were tested for comparison. The test configuration and experiment identification are provided. A data report is presented for an approximate analysis of the probability density distributions of the signals from both the optical and the infared units. Two runs representing each of the two types of cross-beam units were selected for analysis. Probability density functions are also presented for the instantaneous product of the signals for each of the runs.

Huff, L. L.↗

Experimental investigation of a double-diffused MOS structure

Self-aligned polysilicon gate technology was applied to double-diffused MOS (DMOS) construction in a manner that retains processing simplicity and effectively eliminates parasitic overlap capacitance because of the self-aligning feature. Depletion mode load devices with the same dimensions as the DMOS transistors were integrated. The ratioless feature results in smaller dimension load devices, allowing for higher density integration with no increase in the processing complexity of standard MOS technology. A number of inverters connected as ring oscillators were used as a vehicle to test the performance and to verify the anticipated benefits. The propagation time-power dissipation product and process related parameters were measured and evaluated. This report includes (1) details of the process; (2) test data and design details for the DMOS transistor, the load device, the inverter, the ring oscillator, and a shift register with a novel tapered geometry for the output stages; and (3) an analytical treatment of the effect of the distributed silicon gate resistance and capacitance on the speed of DMOS transistors.

Lin, H. C.↗

AIFTDS stand-alone RMDU flight test report

The remote multiplexer/digitizer unit for the airborne integrated flight test data system was subjected to a flight test environment in order to study its dynamic response and that of its associated instrumentation circuitry during an actual flight test. The shielding schemes and instrumentation used are described and the data obtained are analyzed.

Wilner, D. O.↗

Radar-Data-Processing System

Report describes radar data system at NASA Western Aeronautical Test Range. System provides real-time and recorded data about flightpaths of research aircraft and Space Shuttle. Called RADATS, processes data from three radars simultaneously; interacts with system operator; enhances data by introducing corrections and smoothing; controls range, azimuth, and elevation of radars; and automatically calibrates itself before and after missions. Software classified into three kinds of programs: utility, real-time, and calibration. Equipment exhibited exceptional reliability. Software matured to become virtually trouble-free.

Anderson, Karl F.↗

Reduction of blade-vortex interaction noise using higher harmonic pitch control

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.

Brooks, Thomas F.↗

Reduction of blade-vortex interaction noise through higher harmonic pitch control

An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.

Brooks, Thomas F.↗

FPCAS2D user's guide, version 1.0

The FPCAS2D computer code has been developed for aeroelastic stability analysis of bladed disks such as those in fans, compressors, turbines, propellers, or propfans. The aerodynamic analysis used in this code is based on the unsteady two-dimensional full potential equation which is solved for a cascade of blades. The structural analysis is based on a two degree-of-freedom rigid typical section model for each blade. Detailed explanations of the aerodynamic analysis, the numerical algorithms, and the aeroelastic analysis are not given in this report. This guide can be used to assist in the preparation of the input data required by the FPCAS2D code. A complete description of the input data is provided in this report. In addition, four test cases, including inputs and outputs, are provided.

Bakhle, Milind A.↗

A longitudinal aerodynamic data repeatability study for a commercial transport model test in the National Transonic Facility

A high Reynolds number investigation of a commercial transport model was conducted in the National Transonic Facility (NTF) at Langley Research Center. This investigation was part of a cooperative effort to test a 0.03-scale model of a Boeing 767 airplane in the NTF over a Mach number range of 0.70 to 0.86 and a Reynolds number range of 2.38 to 40.0 x 10(exp 6) based on the mean aerodynamic chord. One of several specific objectives of the current investigation was to evaluate the level of data repeatability attainable in the NTF. Data repeatability studies were performed at a Mach number of 0.80 with Reynolds numbers of 2.38, 4.45, and 40.0 x 10(exp 6) and also at a Mach number of 0.70 with a Reynolds number of 40.0 x 10(exp 6). Many test procedures and data corrections are addressed in this report, but the data presented do not include corrections for wall interference, model support interference, or model aeroelastic effects. Application of corrections for these three effects would not affect the results of this study because the corrections are systematic in nature and are more appropriately classified as sources of bias error. The repeatability of the longitudinal stability-axis force and moment data has been accessed. Coefficients of lift, drag, and pitching moment are shown to repeat well within the pretest goals of plus or minus 0.005, plus or minus 0.0001, and plus or minus 0.001, respectively, at a 95-percent confidence level over both short- and near-term periods.

Wahls, R. A.↗

Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: METSAT A1 Signal Processor (P/N 1331670-2, S/N F03)

This report presents a description of tests performed, and the test data, for the A1 METSAT Signal Processor Assembly PN: 1331679-2, S/N F03. This assembly was tested in accordance with AE-26754, "METSAT Signal Processor Scan Drive Test and Integration Procedure." The objective is to demonstrate functionality of the signal processor prior to instrument integration.

Lund, D.↗

Elemental Water Impact Test: Phase 2 36-Inch Aluminum Tank Head

Spacecraft are being designed based on LS-DYNA simulations of water landing impacts. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. EWIT Phase 2 featured a 36-inch aluminum tank head. The tank head was outfitted with one accelerometer, twelve pressure transducers, three string potentiometers, and four strain gages. The tank head was dropped from heights of 1 foot and 2 feet. The focus of this report is the correlation of analytical models against test data. As a measure of prediction accuracy, peak responses from the baseline LS-DYNA model were compared to peak responses from the tests.

Vassilakos, Gregory J.↗

Elemental Water Impact Test: Phase 1 20-Inch Hemisphere

Spacecraft are being designed based on LS-DYNA simulations of water landing impacts. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. Phase 1 of the EWIT series featured water impact tests of a 20-inch hemisphere dropped from heights of 5 feet and 10 feet. The hemisphere was outfitted with an accelerometer and three pressure gages. The focus of this report is the correlation of analytical models against test data.

Vassilakos, Gregory J.↗

Helicopter Acoustic Flight Test with Altitude Variation and Maneuvers

A cooperative flight test campaign between NASA and the U.S. Army was performed from September 2014 to February 2015. The purposes of the testing were to: investigate the effects of altitude variation on noise generation, investigate the effects of gross weight variation on noise generation, establish the statistical variability in acoustic flight testing of helicopters, and characterize the effects of transient maneuvers on radiated noise for a medium-lift utility helicopter. This test was performed at three test sites (0, 4000, and 7000 feet above mean sea level) with two aircraft (AS350 SD1 and EH-60L) tested at each site. This report provides an overview of the test, documents the data acquired and describes the formats of the stored data.

Watts, Michael E.↗

Space-Cent: Studying the Physiological and Anatomical Effects of Centrifugation and Head Down Tilt: 2021 Update

BACKGROUND The objective of this study was to evaluate the cerebral and ocular physiological and anatomical effects of head-down tilt bedrest (HDBR) with and without daily artificial gravity (AG) in healthy subjects to provide novel insights into possible countermeasures for the Spaceflight Associated Neuro-ocular Syndrome (SANS). Previous long-term studies using the spaceflight analog of strict 6° HDBR for 30 days revealed changes in ocular structure, including optic disc edema. The effects of an AG countermeasure using intermittent centrifugation to restore upright hydrostatic gradients and reduce the ocular and brain anatomical effects has not been explored. METHODS The effects of 60-day exposure to simulated microgravity (6° HDBR) on the cerebral, ocular and vestibular systems with and without the intervention of daily 30 minute exposure to AG (short-arm centrifugation) was evaluated in 24 healthy subjects. Non-invasive measurements of cerebral blood flow, intracranial blood volume (near infrared spectroscopy, NIRS), cerebral and ocular structure (MRI and optical coherence tomography), internal jugular vein area (ultrasound), lateral ventricular volumes (MRI), intraocular pressure, and sensorimotor/vestibular (i.e. balance and coordination) systems were made during various time-points during the bedrest study. Additional measures with ultrasound and NIRS were made during centrifugation. RESULTS The study began in Spring 2019 and all 24 subjects completed the testing by end of 2019. Data analysis continues. We report the following updated results for 2021. MRI showed significant decreases in carotid artery flow, increases in brain and CSF volumes, and aqueductal flow velocities in all subjects in HDT compared to baseline supine, but no effects of the short duration AG. All groups showed increased posterior globe flattening during bedrest compared to baseline, without protection from AG. As previously reported we observed chorioretinal folds for the first time in a bedrest analog, as well as optic disc edema, with no protection from the short-term AG. Data from the study is now being transmitted to the NASA LSDA which will allow for future research. CONCLUSIONS The 6 degree HDBR analog produced significant changes in the anatomical and physiological functions of the brain and eye in healthy subjects. Daily 30 minute exposure to AG with short-arm centrifugation had significant transient effects on physiology of the cerebrovascular system, but was not sufficient to prevent the anatomical effects of HDBR on the brain and eye.

E M Bershad↗

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↗

Flight Wing Surface Pressure and Boundary-Layer Data Report from the F-111 Smooth Variable-Camber Supercritical Mission Adaptive Wing

Flight tests were conducted using the advanced fighter technology integration F-111 (AFTI/F-111) aircraft modified with a variable-sweep supercritical mission adaptive wing (MAW). The MAW leading- and trailing-edge variable-camber surfaces were deflected in flight to provide a near-ideal wing camber shape for the flight condition. The MAW features smooth, flexible upper surfaces and fully enclosed lower surfaces, which distinguishes it from conventional flaps that have discontinuous surfaces and exposed or semi-exposed mechanisms. Upper and lower surface wing pressure distributions were measured along four streamwise rows on the right wing for cruise, maneuvering, and landing configurations. Boundary-layer measurements were obtained near the trailing edge for one of the rows. Cruise and maneuvering wing leading-edge sweeps were 26 deg for Mach numbers less than 1 and 45 deg or 58 deg for Mach numbers greater than 1. The landing wing sweep was 9 deg or 16 deg. Mach numbers ranged from 0.27 to 1.41, angles of attack from 2 deg to 13 deg, and Reynolds number per unit foot from 1.4 x 10(exp 6) to 6.5 x 10(exp 6). Leading-edge cambers ranged from O deg to 20 deg down, and trailing-edge cambers ranged from 1 deg up to 19 deg down. Wing deflection data for a Mach number of 0.85 are shown for three cambers. Wing pressure and boundary-layer data are given. Selected data comparisons are shown. Measured wing coordinates are given for three streamwise semispan locations for cruise camber and one spanwise location for maneuver camber.

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