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At least 667 records · Page 37

All sources NASA NTRS DOE OSTI

NASA NTRS1976

Experimental aerodynamic characteristics for slender bodies with thin wings at angles of attack from 0 deg to 58 deg and Mach numbers from 0.6 to 2.0

An experimental investigation was conducted in the Ames 6-by-6-Foot Wind Tunnel to measure the static aerodynamic characteristics for bodies of circular and elliptic cross section with various thin flat-plate wings. Eighteen configuration combinations were tested at Mach numbers of 0.6, 0.9, 1.2, 1.5, and 2.0 at angles of attack from 0 deg to 58 deg. The data demonstrate that taper ratio and aspect ratio had only small effect on the aerodynamic characteristics, especially at the higher angles of attack. Undesirable side forces and yawing moments, which developed at angles of attack greater than about 25 deg, were generally no greater than those for the bodies tested alone. As for the bodies alone, the side forces and yawing moments increased as the nose fineness ratio increased and/or as the subsonic Mach number decreased.

Jorgensen, L. H.↗

NASA NTRS1975

Remote sensing of Mississippi River characteristics

A data collection program initiated by the Vicksburg District, to develop a workable knowledge of the principles relating to the transport of water and sediment to gain a better understanding of the Mississippi River characteristics is introduced. Aerial photographs and thermal infrared imagery were collected over two test reaches at low and high water stages. Qualitative interpretation of the data relates to the river characteristics such as flow patterns, relative velocities, sediment concentration distribution, water-depth effects, and effects of man made structures. Ground truth information is correlated with the remotely sensed data.

Ruff, J. F.↗

NASA NTRS1976

Effect of wing bend on the experimental force and moment characteristics of an oblique wing

Static longitudinal and lateral/directional force and moment characteristics are presented for an elliptical oblique wing mounted on top of a Sears-Haack body of revolution. The wing had an aspect ratio of 6 (based on the unswept span) and was tested at various sweep angles relative to the body axis ranging from 0 to 60 deg. In an attempt to create more symmetrical spanwise wing stalling characteristics, both wing panels were bent upward to produce washout on the trailing wing panel and washing on the leading wing panel. Small fluorescent tufts were attached to the wing surface to indicate the stall progression on the wing. The tests were conducted throughout a Mach number range from 0.6 to 1.4 at a constant unit Reynolds number of 8.2 x 10 per meter. The test results indicate that upward bending of the wing panels had only a small effect on the linearity of the moment curves and would require an impractical wing-pivot location at low lift to eliminate the rolling moment resulting from this bending.

Hopkins, E. J.↗

NASA NTRS1976

Subsonic and transonic dynamic stability characteristics of the space shuttle launch vehicle

An investigation has been conducted to determine the subsonic and transonic dynamic stability characteristics of a 0.015 scale model of the space shuttle launch vehicle. These tests were conducted in the Langley 8-foot transonic pressure tunnel over a Mach number range from 0.3 to 1.2. Forced oscillation equipment was used to determine the damping characteristics of several configurations about all three axes. The test results show that the model exhibited positive damping in pitch except at the highest Mach number (1.2) where there was a region of negative damping at 2 deg angle of attack. The yawing oscillation tests show that the model exhibited nonlinearities and negative damping at Mach numbers of 0.3 and 0.6. The model exhibited positive roll damping throughout the test angle of attack and Mach range.

Freeman, D. C., Jr.↗

NASA NTRS1976

Vibration characteristics of composite fan blades and comparison with measured data

The vibration characteristics of a composite fan blade for high-tip-speed applications were determined theoretically and the results compared with measured data. The theoretical results were obtained using a computerized capability consisting of NASTRAN coupled with composite mechanics by way of pre- and postprocessors. The predicted vibration frequencies and mode shapes were in reasonable agreement with the measured data. Theoretical results showed that different laminate configurations from the same composite system had only small effects on the blade frequency. However, the use of adhesively bonded titanium/beryllium laminar composites may improve considerably the blade vibration characteristics.

Chamis, C. C.↗

NASA NTRS1976

Effect of Reynolds number on the aerodynamic stability and control characteristics of a 55 deg clipped-delta-wing orbiter configuration at supersonic Mach numbers

A wind-tunnel investigation has been conducted at Mach numbers from 1.60 to 4.63 for Reynolds numbers varying from approximately 0.8 million to 10.0 million (based on body length) to determine the Reynolds number effects on the static longitudinal and lateral aerodynamic stability and control characteristics of two scale models of the Grumman H-33 space shuttle orbiter. The results indicate that for the Reynolds number range investigated, there are no Reynolds number effects on the longitudinal or lateral aerodynamic characteristics of either model with zero control deflections and only negligible effects with control deflections. The roll control is constant for both models with the possible exception of a slight increase with increases in Reynolds number up to 2.0 million at the lower Mach numbers. This very small Reynolds number effect is much more apparent for the smaller model and disappears with increasing Mach and Reynolds numbers.

Blair, A. B., Jr.↗

NASA NTRS1976

Aerodynamic characteristics of a 1/6-scale model of the rotor systems research aircraft with the rotors removed

A wind-tunnel investigation was conducted to refine the aerodynamic characteristics of the rotor systems research aircraft. For the investigation, a 1/6-scale model without a main rotor or a tail rotor was used. The model provided the capability for testing different engine nacelle sizes, engine pylon fairings, and tail configurations. The engine thrust effects were modeled by small engine simulators (fans). Data were obtained primarily over an angle-of-attack range from -13 deg to 13 deg at several values of sideslip. Stability characteristics and control effectiveness were investigated. The model with the scaled engine nacelles and the combination T-tail and lower horizontal tail displayed longitudinal and lateral-directional stability. Results show that by reducing the horizontal or vertical-tail span the longitudinal stability is decreased. Reducing the engine nacelle size increases the static stability of the model. Effective dihedral is essentially zero at 0 deg angle of attack and 0 deg wing incidence.

Mineck, R. E.↗

NASA NTRS1976

The effect of winglets on the static aerodynamic stability characteristics of a representative second generation jet transport model

A baseline wing and a version of the same wing fitted with winglets were tested. The longitudinal aerodynamic characteristics were determined through an angle-of-attack range from -1 deg to 10 deg at an angle of sideslip of 0 deg for Mach numbers of 0.750, 0.800, and 0.825. The lateral aerodynamic characteristics were determined through the same angle-of-attack range at fixed sideslip angles of 2.5 deg and 5 deg. Both configurations were investigated at Reynolds numbers of 13,000,000, per meter (4,000,000 per foot) and approximately 20,000,000 per meter (6,000,000 per foot). The winglet configuration showed slight increases over the baseline wing in static longitudinal and lateral aerodynamic stability throughout the test Mach number range for a model design lift coefficient of 0.53. Reynolds number variation had very little effect on stability.

Jacobs, P. F.↗

NASA NTRS1976

Effect of external jet-flow deflector geometry on OTW aero-acoustic characteristics

The effect of geometry variations in the design of external deflectors for use with over-the-wing (OTW) configurations was studied at model scale and subsonic jet velocities. Included in the variations were deflector size and angle as well as wing size and flap setting. A conical nozzle (5.2-cm diameter) mounted at 0.1 chord above and downstream of the wing leading edges was used. The data indicate that external deflectors provide satisfactory takeoff and approach aerodynamic performance and acoustic characteristics for OTW configurations. These characteristics together with expected good cruise aerodynamics, since external deflectors are storable, may provide optimum OTW design configurations.

Vonglahn, U.↗

NASA NTRS1976

Hardwall acoustical characteristics and measurement capabilities of the NASA Lewis 9 x 15 foot low speed wind tunnel

Experimental evaluations of the acoustical characteristics and source sound power and directionality measurement capabilities of the NASA Lewis 9 x 15 foot low speed wind tunnel in the untreated or hardwall configuration were performed. The results indicate that source sound power estimates can be made using only settling chamber sound pressure measurements. The accuracy of these estimates, expressed as one standard deviation, can be improved from + or - 4 db to + or - 1 db if sound pressure measurements in the preparation room and diffuser are also used and source directivity information is utilized. A simple procedure is presented. Acceptably accurate measurements of source direct field acoustic radiation were found to be limited by the test section reverberant characteristics to 3.0 feet for omni-directional and highly directional sources. Wind-on noise measurements in the test section, settling chamber and preparation room were found to depend on the sixth power of tunnel velocity. The levels were compared with various analytic models. Results are presented and discussed.

Rentz, P. E.↗

NASA NTRS1976

Softwall acoustical characteristics and measurement capabilities of the NASA Lewis 9x15 foot low speed wind tunnel

Acoustical characteristics and source directionality measurement capabilities of the wind tunnel in the softwall configuration were evaluated, using aerodynamically clean microphone supports. The radius of measurement was limited by the size of the test section, instead of the 3.0 foot (1 m) limitation of the hardwall test section. The wind-on noise level in the test section was reduced 10 dB. Reflections from the microphone support boom, after absorptive covering, induced measurement errors in the lower frequency bands. Reflections from the diffuser back wall were shown to be significant. Tunnel noise coming up the diffuser was postulated as being responsible, at least partially, for the wind-on noise in the test section and settling chamber. The near field characteristics of finite-sized sources and the theoretical response of a porous strip sensor in the presence of wind are presented.

Rentz, P. E.↗

NASA NTRS1976

Acoustic radiation and surface pressure characteristics of an airfoil due to incident turbulence

A theoretical and experimental investigation of the noise and unsteady surface pressure characteristics of an isolated airfoil in a uniform mean velocity, homogeneous, nearly-isotropic turbulence field was conducted. Wind tunnel experiments were performed with a 23 cm chord, two dimensional NACA 0012 airfoil over a free stream Mach number range of 0.1 to 0.5. Far-field noise spectra and directivity were measured in an anechoic chamber that surrounded the tunnel open jet test section. Spanwise and chordwise distribution of unsteady airfoil surface pressure spectra and surface pressure cross-spectra were obtained. Incident turbulence intensities, length scales, spectra, and spanwise cross-spectra, required in the calculation of far-field noise and surface pressure characteristics were also measured.

Paterson, R. W.↗

NASA NTRS1976

Spectral reflectance characteristics of the meteorite classes

The results are presented of spectral reflectance measurements on more than 150 individual meteorite specimens representing essentially all types and subtypes of meteorites. A brief review is provided of the nature of the compositional information contained in a reflection spectrum of a natural material. Attention is given to the spectral reflectance characteristics of mineral assemblages, and to meteorite class spectral characteristics.

Gaffey, M. J.↗

NASA NTRS1975

Propagation characteristics of solar flare particles

A statistical study on the propagation characteristics of about 80 solar particle events is carried out using the data from Goddard cosmic-ray experiments. It is found that for particles near onset as well as maximum particle intensity at 1 AU, a linear relation exists between the velocity and the traveled distance. This holds for both relativistic electrons (0.5-1.1 MeV) and nonrelativistic protons (4-80 MeV). The relation indicates that particle propagation is independent of both rigidity and energy. It is shown that in general interplanetary diffusion plays a minor role in particle propagation during the initial phase of a flare effect. A study of the onset characteristics indicates that the speed of particle transport in the corona may be as high as 40 deg/hr. This behavior can not be accounted for by either magnetic-field or curvature drift.

Ma Sung, L. S.↗

NASA NTRS1976

Vibration characteristics of composite fan blades and comparison with measured data

Chamis, C. C.↗

NASA NTRS1976

Maximum likelihood estimates of lift and drag characteristics obtained from dynamic aircraft maneuvers

A maximum likelihood estimation method for obtaining lift and drag characteristics from dynamic flight maneuvers was investigated. This paper describes the method and compares the estimates of lift and drag obtained by using the method with estimates obtained from wind-tunnel tests and from established methods for obtaining estimates from flight data. In general, the lift and drag coefficients extracted from dynamic flight maneuvers by the maximum likelihood estimation technique are in good agreement with the estimates obtained from the wind-tunnel tests and the other methods. When maneuvers that met the requirements of both flight methods were analyzed, the results of each method were nearly the same. The maximum likelihood estimation technique showed promise in terms of estimating lift and drag characteristics from dynamic flight maneuvers. Further studies should be made to assess the best mathematical model and the most desirable type of dynamic maneuver to get the highest quality results from this technique.

Iliff, K. W.↗

NASA NTRS1976

Characteristics procedure for supersonic flows including consideration of viscous contributions to flow rotationality

A characteristics procedure has been developed which includes viscous and conductive transport terms normal to streamlines. By introducing the transport terms as corrections, the equations retain their hyperbolic character. The solutions have been developed using an inverse grid scheme in a streamline-normal network. Inclusion of the transport terms enables tracing of shock waves through the supersonic portion of the boundary layer so that shock reflections are well-located. Excellent agreement is obtained with the results of other characteristics procedures and with the experimental pressure distributions for the waisted body of Winter, Smith and Rotta.

Anderson, B. H.↗

NASA NTRS1975

Performance characteristics of the 12 GHz, 200 watt Transmitter Experiment Package for CTS

Measured performance characteristics from ground test of the Transmitter Experiment Package (TEP) for the Communications Technology Satellite are presented. The experiment package consists of a 200 W Output Stage Tube (OST) powered by a Power Processing System (PPS). Descriptions of both the PPS and OST are given. The PPS provides the necessary voltages with a measured dc/dc conversion efficiency of 89 per cent. The OST, a traveling wave tube with multiple collectors, has a saturated rf output power of 224 W and operates at an overall efficiency exceeding 40 per cent over an 85 MHz bandwidth at 12 GHz. OST performance given includes frequency response, saturation characteristics, group delay, AM to PM conversion, intermodulation distortion, and two channel gain suppression. Single and dual channel FM video performance is presented. It was determined that for 12 MHz peak to peak frequency deviation on each channel, dual channel FM television signals can be transmitted through the TEP at 60 W, each channel, with 40 MHz channel spacing (center to center).

Miller, E. F.↗