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  • AERODYNAMICS
  • EARTH RESOURCES AND REMOTE SENSING
  • 1995-1999  (59)
  • 1
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    Measurements of scramjet thrust in shock tunnels (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: By using results obtained in tests on supersonic combustion of hydrogen in air, the conditions governing model size and operating pressure levels for shock tunnel experiments on models of flight vehicles with scramjet propulsion are established. It is seen that large models are required. The development of the stress wave force balance is then described, and its use as a method of measuring thrust/drag on such models is discussed. Test results on a simple, fully integrated scramjet model, with intakes, combustion chambers, thrust surfaces and exterior surfaces, using a 13 percent silane 87 percent hydrogen fuel mixture, showed that a steady state with thrust generation could be achieved within the shock tunnel test time, and the thrust could be measured. Results are presented for a range of stagnation enthalpies, and show that the scramjet model produces net positive thrust at velocities up to 2.4 km/sec.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 94-2516 , AIAA Aerospace Ground Testing Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States|Shock Tunnel Studies of Scramjet Phenomena 1994; 11 p
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    NASA TECHNICAL REPORTS
  • 2
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    Using foreground/background analysis to determine leaf and canopy chemistry (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Spectral Mixture Analysis (SMA) has become a well established procedure for analyzing imaging spectrometry data, however, the technique is relatively insensitive to minor sources of spectral variation (e.g., discriminating stressed from unstressed vegetation and variations in canopy chemistry). Other statistical approaches have been tried e.g., stepwise multiple linear regression analysis to predict canopy chemistry. Grossman et al. reported that SMLR is sensitive to measurement error and that the prediction of minor chemical components are not independent of patterns observed in more dominant spectral components like water. Further, they observed that the relationships were strongly dependent on the mode of expressing reflectance (R, -log R) and whether chemistry was expressed on a weight (g/g) or are basis (g/sq m). Thus, alternative multivariate techniques need to be examined. Smith et al. reported a revised SMA that they termed Foreground/Background Analysis (FBA) that permits directing the analysis along any axis of variance by identifying vectors through the n-dimensional spectral volume orthonormal to each other. Here, we report an application of the FBA technique for the detection of canopy chemistry using a modified form of the analysis.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL, Summaries of the Fifth Annual JPL Airborne Earth Science Workshop. Volume 1: AVIRIS Workshop; p 129-132
    Format: application/pdf
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  • 3
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    Passive measurement and interpretation of polarized microwave brightness temperatures (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The goal of this project is to develop satellite-based observational techniques for measuring both oceanic and atmospheric variables using passive polarimetric radiometry. Polarimetric radiometry offers a potential alternative to radar scatterometry in observing global ocean surface wind direction from satellites. Polarimetric radiometry might also provide a means of detecting cell-top ice in convective storms by virtue of the polarizing properties of oriented ice particles, and thus facilitate estimation of the phase of the storm. The project focuses on the development of polarimetric microwave radiometers using digital cross-correlators for obtaining precise measurements of all four Stokes' parameters. As part of the project a unique four-band polarimetric imaging radiometer, the Polar Scanning Radiometer (PSR), is being designed for use on the NASA DC-8 aircraft. In addition to providing an aircraft-based demonstration of digital correlation technology the PSR will significantly enhance the microwave imaging capability of the existing suite of DC-8 instruments. During the first grant year excellent progress has been made in the following areas: (1) demonstrating digital correlation radiometry, (2) fabricating aircraft-qualified correlators for use in the PSR, and (3) modeling observed SSM/I brightness signatures of ocean wind direction.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-CR-199288 , NAS 1.26:199288
    Format: application/pdf
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  • 4
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    The acoustic characteristics of turbomachinery cavities (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Internal fluid flows are subject not only to self-sustained oscillations of the purely hydrodynamic type but also to the coupling of the instability with the acoustic mode of the surrounding cavity. This situation is common to turbomachinery, since flow instabilities are confined within a flow path where the acoustic wavelength is typically smaller than the dimensions of the cavity and flow speeds are low enough to allow resonances. When acoustic coupling occurs, the fluctuations can become so severe in amplitude that it may induce structural failure of engine components. The potential for catastrophic failure makes identifying flow-induced noise and vibration sources a priority. In view of the complexity of these types of flows, this report was written with the purpose of presenting many of the methods used to compute frequencies for self-sustained oscillations. The report also presents the engineering formulae needed to calculate the acoustic resonant modes for ducts and cavities. Although the report is not a replacement for more complex numerical or experimental modeling techniques, it is intended to be used on general types of flow configurations that are known to produce self-sustained oscillations. This report provides a complete collection of these models under one cover.
    Keywords: AERODYNAMICS
    Type: NASA-CR-4671 , M-778 , NAS 1.26:4671
    Format: application/pdf
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  • 5
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    Flow visualization studies of VTOL aircraft models during Hover in ground effect (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A flow visualization study of several configurations of a jet-powered vertical takeoff and landing (VTOL) aircraft model during hover in ground effect was conducted. A surface oil flow technique was used to observe the flow patterns on the lower surfaces of the model. There were significant configuration effects. Wing height with respect to fuselage, the presence of an engine inlet duct beside the fuselage, and nozzle pressure ratio are seen to have strong effects on the surface flow angles on the lower surface of the wing. This test was part of a program to improve the methods for predicting the hot gas ingestion (HGI) for jet-powered vertical/short takeoff and landing (V/STOL) aircraft. The tests were performed at the Jet Calibration and Hover Test (JCAHT) Facility at Ames Research Center.
    Keywords: AERODYNAMICS
    Type: NASA-TM-108860 , A-95025 , NAS 1.15:108860
    Format: application/pdf
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  • 6
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    Design and development of an F/A-18 inlet distortion rake: A cost and time saving solution (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An innovative inlet total pressure distortion measurement rake has been designed and developed for the F/A-18 A/B/C/D aircraft inlet. The design was conceived by NASA and General Electric Aircraft Engines personnel. This rake has been flight qualified and flown in the F/A-18 High Alpha Research Vehicle at NASA Dryden Flight Research Center, Edwards, California. The eight-legged, one-piece, wagon wheel design of the rake was developed at a reduced cost and offered reduced installation time compared to traditional designs. The rake features 40 dual-measurement ports for low- and high-frequency pressure measurements with the high-frequency transducer mounted at the port. This high-frequency transducer offers direct absolute pressure measurements from low to high frequencies of interest, thereby allowing the rake to be used during highly dynamic aircraft maneuvers. Outstanding structural characteristics are inherent to the design through its construction and use of lightweight materials.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4722 , NAS 1.15:4722 , H-2078 , AIAA PAPER 94-2132 , NIPS-95-05907 , Biennial AIAA Flight Test Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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  • 7
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    Lift, drag and thrust measurement in a hypersonic impulse facility (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper reports the extension of the stress wave force balance to the measurement of forces on models which are non-axisymmetric or which have non-axisymmetric load distributions. Recent results are presented which demonstrate the performance of the stress wave force balance for drag measurement, for three-component force measurement and preliminary results for thrust measurement on a two-dimensional scramjet nozzle. In all cases, the balances respond within a few hundred microseconds.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 94-2596 , AIAA Aerospace Ground Testing Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States|Shock Tunnel Studies of Scramjet Phenomena 1994; 9 p
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  • 8
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    Hypersonic aerodynamics test facility using the external propulsion accelerator (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The use of the External propulsion Accelerator (EPA) for launching models of hypersonic aerodynamic configurations into an instrumented ballistic range is discussed. The aerodynamic model is encased inside an axisymmetric projectile designed to be accelerated to high speed in the EPA. Accelerator lengths required to achieve hypersonic speeds are estimated to vary from 10 meters for Mach 7, 40 meters for Mach 10, 150 meters for Mach 15, and 700 meters for Mach 30, assuming a limit of 50,000 g's acceleration. For a model span of 10 cm to 25 cm, the launch tube diameters are 40 cm and 100 cm, respectively. Using this EPA launcher will enable exact simulation of hypersonic flight in ground facilities where both the gas composition and pressure can be controlled in the ballistic range.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 95-6138 , AIAA, Aerospace Planes and Hypersonics Technologies Conference; Apr 03, 1995 - Apr 07, 1995; Chattanooga, TN; United States|; 5 p.
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  • 9
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    Scramjet thrust measurement in a shock tunnel (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: This note reports tests in a shock tunnel in which a fully integrated scamjet configuration produced net thrust. The experiments not only showed that impluse facilities can be used for assessing thrust performance, but also were a demonstration of the application of a new technique to the measurement of thrust on scramjet configurations in shock tunnels. These two developments are of significance because scramjets are expected to operate at speeds well in excess of 2 km/s, and shock tunnels offer a means of generating high Mach number flows at such speeds.
    Keywords: AERODYNAMICS
    Type: Aeronautical Journal (ISSN 0001-9240); 99; 984; p. 161-163
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  • 10
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    Application of IEM model on soil moisture and surface roughness estimation (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Monitoring spatial and temporal changes of soil moisture are of importance to hydrology, meteorology, and agriculture. This paper reports a result on study of using L-band SAR imagery to estimate soil moisture and surface roughness for bare fields. Due to limitations of the Small Perturbation Model, it is difficult to apply this model on estimation of soil moisture and surface roughness directly. In this study, we show a simplified model derived from the Integral Equation Model for estimation of soil moisture and surface roughness. We show a test of this model using JPL L-band AIRSAR data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL, Summaries of the Fifth Annual JPL Airborne Earth Science Workshop. Volume 3: AIRSAR Workshop; p 51-54
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