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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17

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NASA NTRS1991

Simplified computational methods for elastic and elastic-plastic fracture problems

This paper presents an overview of some of the recent (1984-1991) developments in computational/analytical methods in the mechanics of fracture: (i) analytical solutions for elliptical or circular cracks embedded in isotropic or transversely isotropic solids (the crack-plane being at an arbitrary angle to the axis of transverse isotropy), with crack-faces being subjected to arbitrary tractions; (ii) finite-element or boundary-element alternating methods for two- and three-dimensional crack problems; (iii) a "direct-stiffness" method for stiffened panels with flexible fasteners and with multiple cracks, using the alternating method; (iv) multiplesite-damage near a row of fastener holes; (v) analysis of cracks with bonded repair patches; (vi) methods for generation of weight-functions for 2- and 3-D crack problems, and (vii) domain-integral methods for elastic-plastic or inelastic crack mechanics.

Aging Aircraft↗

NASA NTRS1981

Numerical Simulation of Three-Dimensional Boattail Afterbody Flowfields

The thin shear-layer approximations of the three-dimensional, compressible Navier-Stokes equations are solved for subsonic, transonic, and supersonic now over axisymmetric boattail bodies at moderate angles of attack. The plume is simulated by a solid body configuration identical to those used In experimental tests. An implicit algorithm of second-order accuracy is used to solve the equations on the ILLIAC 4 computer. The turbulence is expressed by an algebraic model applicable to three-dimensional flowfields with moderate separation. The formulation used is attractive in its independence of boundary-layer parameters. Such a simple model, however, is incapable of supporting detailed quantitative descriptions of complex shear flows. Never-the-less, good qualitative comparisons are found with three different sets of experimental date. Quantitative improvement will depend on improved turbulence transport descriptions.

Deiwert, G. S.↗

NASA NTRS2011

Blade Displacement Measurements of the Full-Scale UH-60A Airloads Rotor

Blade displacement measurements were acquired during a wind tunnel test of the full-scale UH-60A Airloads rotor. The test was conducted in the 40- by 80-Foot Wind Tunnel of the National Full-Scale Aerodynamics Complex at NASA Ames Research Center. Multi-camera photogrammetry was used to measure the blade displacements of the four-bladed rotor. These measurements encompass a range of test conditions that include advance ratios from 0.15 to unique slowed-rotor simulations as high as 1.0, thrust coefficient to rotor solidity ratios from 0.01 to 0.13, and rotor shaft angles from -10.0 to 8.0 degrees. The objective of these measurements is to provide a benchmark blade displacement database to be utilized in the development and validation of rotorcraft computational tools. The methodology, system development, measurement techniques, and preliminary sample blade displacement measurements are presented.

Barrows, Danny A.↗

NASA NTRS2012

Blade Displacement Measurement Technique Applied to a Full-Scale Rotor Test

Blade displacement measurements using multi-camera photogrammetry were acquired during the full-scale wind tunnel test of the UH-60A Airloads rotor, conducted in the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel. The objectives were to measure the blade displacement and deformation of the four rotor blades as they rotated through the entire rotor azimuth. These measurements are expected to provide a unique dataset to aid in the development and validation of rotorcraft prediction techniques. They are used to resolve the blade shape and position, including pitch, flap, lag and elastic deformation. Photogrammetric data encompass advance ratios from 0.15 to slowed rotor simulations of 1.0, thrust coefficient to rotor solidity ratios from 0.01 to 0.13, and rotor shaft angles from -10.0 to 8.0 degrees. An overview of the blade displacement measurement methodology and system development, descriptions of image processing, uncertainty considerations, preliminary results covering static and moderate advance ratio test conditions and future considerations are presented. Comparisons of experimental and computational results for a moderate advance ratio forward flight condition show good trend agreements, but also indicate significant mean discrepancies in lag and elastic twist. Blade displacement pitch measurements agree well with both the wind tunnel commanded and measured values.

Abrego, Anita I.↗

NASA NTRS2009

John F. Kennedy Space Center's Wireless Hang Angle Instrumentation System

The technology is a high-precision, wireless inclinometer. The system was designed for monitoring the suspension angle of the Orbiter vehicle during loading onto the Solid Rocket Boosters of the Space Shuttle. Originally, operators manually measured the alignment of the Orbiter with a hand-held inclinometer on a nonrigid surface. The measurement was open to interpretation by the loader. If the Orbiter is misaligned, it can crush ball joints and delay the loading while repairs are made. With this system, the Orbiter can be loaded without damage and without manual measurement.

Kohler, Jeff↗

NASA NTRS2016

Summary of Full-Scale Blade Displacement Measurements of the UH- 60A Airloads Rotor

Blade displacement measurements using multi-camera photogrammetry techniques were acquired for a full-scale UH-60A rotor, tested in the National Full-Scale Aerodynamic Complex 40-Foot by 80-Foot Wind Tunnel. The measurements, acquired over the full rotor azimuth, encompass a range of test conditions that include advance ratios from 0.15 to 1.0, thrust coefficient to rotor solidity ratios from 0.01 to 0.13, and rotor shaft angles from -10.0 to 8.0 degrees. The objective was to measure the blade displacements and deformations of the four rotor blades and provide a benchmark blade displacement database to be utilized in the development and validation of rotorcraft prediction techniques. An overview of the blade displacement measurement methodology, system development, and data analysis techniques are presented. Sample results based on the final set of camera calibrations, data reduction procedures and estimated corrections that account for registration errors due to blade elasticity are shown. Differences in blade root pitch, flap and lag between the previously reported results and the current results are small. However, even small changes in estimated root flap and pitch can lead to significant differences in the blade elasticity values.

Displacement↗

NASA NTRSDate not supplied

Asymmetric Flow State Switching in the Space Launch System Block 2 Liftoff Environment

An in-depth investigation was conducted at the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel to evaluate flow state switching in the liftoff flow environment of the Space Launch System Block 2 Crew launch vehicle using force measurements, two-component particle image velocimetry, and tuft flow visualization. Multimodal flow states were observed in the gap flow between the centerbody and solid rocket boosters at a range of incoming flow angles and were characterized for the relative strength of state switches. When flow switches occur, the flow is predominantly bimodal, but trimodal flow states are observed with the launch tower downstream of the vehicle. Tuft visualization indicates three-dimensionality during flow state switching, which initiates at one part of the gap and quickly transitions throughout the length of the booster. Due to the long time scales between switches, statistics such as frequency of flow state switches and converged state probabilities cannot be established without significantly increased acquisition times.

Lee J. Mears↗

NASA NTRSDate not supplied

Asymmetric Flow State Switching on the Space Launch System (SLS) Block 2 Crew Vehicle

An in-depth investigation was conducted at the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel to evaluate flow state switching in the liftoff flow environment of the Space Launch System Block 2 Crew launch vehicle using side force measurements, two-component particle image velocimetry, and tufts flow visualization. Multimodal flow states were observed in the gap flow between the centerbody and solid rocket boosters at a range of incoming flow angles and were characterized for the relative strength of state switches. When flow switches occur, the flow is predominantly bimodal, but trimodal flow states are observed with the launch tower downstream of the vehicle. Tufts visualization indicates three-dimensionality during flow state switching, which initiates at one part of the gap and quickly transitions throughout the length of the booster. Due to the long time scales between switches, statistics such as frequency of flow state switches and converged state probabilities cannot be established without significantly increased acquisition times.

Lee J. Mears↗

NASA NTRS1940

A Full-scale Investigation of the Effect of Several Factors on the Shimmy of Cantering Wheels

A full-scale investigation has been conducted to determine the effect of various factors on the shimmy of castering wheels. The factors considered were the geometric arrangement, the tire types, the variations of load, the spindle moment of inertia, and the tire inflation. A comparison of the results of the present investigation with those calculated from existing theory was made. The constants needed in the calculations to determine the damping required for a castering wheel were measured. The results indicate that solid friction appears to be impracticable as the sole damping agent for castering nose wheels on large airplanes. Also it was concluded that the existing theory is adequate for calculating the damping required to prevent shimmy. The caster angle and the spindle moment of inertia were found to influence the solid friction required to prevent shimmy. The effect of variations in the type and the pressure of the tire was insignificant.

Howard, Walter B , Jr↗

NASA NTRS1979

A rocket-borne energy spectrometer using multiple solid-state detectors for particle identification

A rocket-borne experiment using energy spectrometers that allows particle identification by the use of multiple solid-state detectors is described. The instrumentation provides information regarding the energy spectrum, pitch-angle distribution, and the type of energetic particles present in the ionosphere. Particle identification was accomplished by considering detector loss mechanisms and their effects on various types of particles. Solid state detectors with gold and aluminum surfaces of several thicknesses were used. The ratios of measured energies for the various detectors were compared against known relationships during ground-based analysis. Pitch-angle information was obtained by using detectors with small geometrical factors mounted with several look angles. Particle flux was recorded as a function of rocket azimuth angle. By considering the rocket azimuth, the rocket precession, and the location of the detectors on the rocket, the pitched angle of the incident particles was derived.

Fries, K. L.↗

NASA NTRS1994

Multiple View Zenith Angle Observations of Reflectance From Ponderosa Pine Stands

Reflectance factors (RF(lambda)) from dense and sparse ponderosa pine (Pinus ponderosa) stands, derived from radiance data collected in the solar principal plane by the Advanced Solid-State Array Spectro-radiometer (ASAS), were examined as a function of view zenith angle (theta(sub v)). RF(lambda) was maximized with theta(sub v) nearest the solar retrodirection, and minimized near the specular direction throughout the ASAS spectral region. The dense stand had much higher RF anisotropy (ma)dmurn RF is minimum RF) in the red region than did the sparse stand (relative differences of 5.3 vs. 2.75, respectively), as a function of theta(sub v), due to the shadow component in the canopy. Anisotropy in the near-infrared (NIR) was more similar between the two stands (2.5 in the dense stand and 2.25 in the sparse stand); the dense stand exhibited a greater hotspot effect than 20 the sparse stand in this spectral region. Two common vegetation transforms, the NIR/red ratio and the normalized difference vegetation index (NDVI), both showed a theta(sub v) dependence for the dense stand. Minimum values occurred near the retrodirection and maximum values occurred near the specular direction. Greater relative differences were noted for the NIR/red ratio (2.1) than for the NDVI (1.3). The sparse stand showed no obvious dependence on theta(sub v) for either transform, except for slightly elevated values toward the specular direction.

Johnson, Lee F.↗

NASA NTRS1976

Supersonic dynamic-stability derivatives of the space shuttle launch vehicle

An investigation was made to determine the dynamic stability characteristics of a 0.015-scale model of the space shuttle launch vehicle at supersonic speeds. These tests were made at angles of attack from -10 deg to 10 deg at Mach numbers of 2.00, 2.86, 3.96, and 4.63. The complete launch vehicle, consisting of the orbiter, external tank, and solid rocket boosters, has positive damping in pitch, roll, and yaw over the angle-of-attack and Mach number range. The orbiter external tank configuration has a region of negative angles pitch damping for small negative of attack at a Mach number of 2.00. At all other test conditions, the orbiter external tank configuration has positive damping about all three axes.

Boyden, R. P.↗

NASA NTRS1973

Two-dimensional cascade test of a highly loaded, low-solidity, tandem airfoil turbine rotor blade

A tip region section of a low-solidity tandem airfoil blade for a turbine rotor was tested in a two-dimensional cascade tunnel at solidities of 0.736 and 0.912. Blade surface static pressures and blade exit total and static pressure and flow angle were surveyed. Blade surface velocities, wake shapes, and kinetic energy losses were analyzed and compared with values for 1.852 solidity tandem airfoil blading.

Kline, J. F.↗

NASA NTRS1975

Fiber reinforced solids possessing great fracture toughness: The role of interfacial strength

The results of angle-ply investigations for strength and toughness of brittle fiber/brittle filament composites are presented. General results are discussed for both unidirectional and angle-ply intermittently bonded boron/epoxy composites as affected by soaking and freezing water environments. A description of and the operating instructions are included for the modified 230 mm (9 inch) wide intermittent coating tape making apparatus.

Atkins, A. G.↗

NASA NTRS1975

An investigation in MSFC 14-inch TWT to determine the static stability characteristics of 0.004-scale model (74-OTS) space shuttle vehicle 5 configuration (IA33), volume 1

Wind tunnel tests were conducted to: (1) determine the static stability characteristics of the Shuttle Vehicle 5 configuration; (2) determine the effect on the Vehicle 5 aerodynamic characteristics of External Tank (ET) and Solid Rocket Booster (SRB) nose shape, SRB nozzle shroud flare angle, orbiter to tank fairing, and sting location; (3) provide flow visualization using thin film oil paint; and (4) determine rudder, body flap, and inboard and outboard elevon hinge moments. The mated vehicle model was mounted in three different ways: (1) the orbiter mounted on the balance with the SRB's attached to the tank and the tank in turn attached to the orbiter; (2) the tank mounted on the balance (with the sting protruding through the tank base) with the SRB's and orbiter attached to the tank, and (3) with the tank mounted on the balance and the balance in turn supported by a forked sting entering the nozzle of each SRB, extending forward into the SRB's then crossing over to the tank to provide a balance socket. Data were obtained for Mach numbers from 0.6 through 4.96 at angles-of-attack and -sideslip from -10 to 10 degrees.

Allen, E. C.↗

NASA NTRS1976

An investigation in the MSFC TWT to determine spoiler effects on wing loads and elevon hinge moments utilizing 0.004-scale models (77-0 and 74-OTS) of the shuttle vehicle 5 configuration (IA125)

Information is presented for wind tunnel tests (IA125) of a 0.004-scale orbiter, external tank, and solid rocket motor integrated vehicle model (77-0 and 74-OTS) in the MSFC Trisonic Wind Tunnel. These tests were conducted in support of MCR's 1344 and 1346. Data from these tests provide spoiler effects on wing bending/torsion and elevon hinge moments, elevon effectiveness data and the influence of solid plumes from Mach numbers of 0.6 through 2.74 at angles of attack and sideslip from -10 through 10 degrees.

Allen, E. C.↗

NASA NTRS1992

Dynamic performance of an aero-assist spacecraft - AFE

Dynamic performance of the Aero-assist Flight Experiment (AFE) spacecraft was investigated using a high-fidelity 6-DOF simulation model. Baseline guidance logic, control logic, and a strapdown navigation system to be used on the AFE spacecraft are also modeled in the 6-DOF simulation. During the AFE mission, uncertainties in the environment and the spacecraft are described by an error space which includes both correlated and uncorrelated error sources. The principal error sources modeled in this study include navigation errors, initial state vector errors, atmospheric variations, aerodynamic uncertainties, center-of-gravity off-sets, and weight uncertainties. The impact of the perturbations on the spacecraft performance is investigated using Monte Carlo repetitive statistical techniques. During the Solid Rocket Motor (SRM) deorbit phase, a target flight path angle of -4.76 deg at entry interface (EI) offers very high probability of avoiding SRM casing skip-out from the atmosphere. Generally speaking, the baseline designs of the guidance, navigation, and control systems satisfy most of the science and mission requirements.

Chang, Ho-Pen↗

NASA NTRS2015

Detached Eddy Simulation Results for a Space Launch System Configuration at Liftoff Conditions and Comparison with Experiment

Computational simulations for a Space Launch System configuration at liftoff conditions for incidence angles from 0 to 90 degrees were conducted in order to generate integrated force and moment data and longitudinal lineloads. While the integrated force and moment coefficients can be obtained from wind tunnel testing, computational analyses are indispensable in obtaining the extensive amount of surface information required to generate proper lineloads. However, beyond an incidence angle of about 15 degrees, the effects of massive flow separation on the leeward pressure field is not well captured with state of the art Reynolds Averaged Navier-Stokes methods, necessitating the employment of a Detached Eddy Simulation method. Results from these simulations are compared to the liftoff force and moment database and surface pressure data derived from a test in the NASA Langley 14- by 22-Foot Subsonic Wind Tunnel.

Computational fluid dynamics↗