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Results for “PERFORMANCE PREDICTION”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

An interaction solution algorithm for viscous aerodynamic performance prediction

A weak-interaction solution algorithm is established for aerodynamic flow field prediction about an isolated airfoil. It requires numerical solution of differential equations governing potential flow, viscous and turbulent boundary layer flow, and the turbulent wake flow downstream of a trailing edge. The algorithm accounts for computed viscous displacement effects on the potential flow. These in turn alter the viscous flow through imposed pressure gradients. Closure for turbulence is accomplished using a second order model. Numerical evaluations assess factors affecting solution accuracy, convergence and stability for the combined potential, boundary layer, and parabolic Navier-Stokes equation systems as solved using a finite element algorithm.

Baker, A. J.↗
NASA NTRS1978

Entry dynamics performance predictions for Pioneer Venus probes

The scientific experiments planned for the Pioneer Venus entry probes require that the probes provide a stable platform at a controlled roll rate throughout the atmospheric phase of the mission. The 45-degree half-cone forebody common to both the small and large probe configurations provides a design which meets all stability and attitude requirements. The uncertainty in the dynamic stability parameter coupled with the possible variability of roll rate due to ablation induced roll torques could, however, result in slight angle of attack divergence in the transonic flight regime. Minimum roll rate requirements on the small probe are passively achieved by a vane mounted on the pressure-temperature sensing arm. The vane was sized to provide minimum dynamic disturbance.

Mccloy, R. D.↗
NASA NTRS1980

A Portable Oxygen Subsystem - Description and preliminary thermal performance prediction

This paper describes the use, operation, and preliminary thermal modeling of a Portable Oxygen Subsystem (POS). The POS is a partial rebreather which is being developed for Shuttle Orbiter support. Normally used as a pre-breather for denitrogenization prior to EVA, this semi-closed, breath powered breathing system can also be used for emergencies in the event of a contaminated or oxygen-deficient cabin atmosphere, to support an emergency transfer between vehicles, or as a clean oxygen supply in the event of a contaminated ambient atmosphere in the vicinity of the Orbiter after landing.

Sribnik, F.↗
NASA NTRS1981

Analytical performance prediction for large antennas

A linear mathematical modeling of the static and dynamic characteristics of a deployable offset wrap rib antenna was attempted using small motions in an effort to simulate the surface distortion resulting from thermal loading and transient oscillations from control. Both cyclic symmetry and model synthesis were used for parametric analysis. Although the ribs can be modeled as slender beams varying cross sections and equivalent linear material properties, the mesh poses a problem since its equivalent stress strain relations are highly nonlinear and sensitive to the biaxial prestressed state. Consequently, the macroscopic material properties were measured experimentally in the neighborhood of the design prestress. An equivalent tangent modulus technique was then adopted about this equilibrium state and assumed to be valid within a small range of incremental stresses.

El-Raheb, M.↗
NASA NTRS1981

Layered synthetic microstructures as Bragg diffractors for X rays and extreme ultraviolet - Theory and predicted performance

The theory of X-ray diffraction by periodic structures is applied to the layered synthetic microstructures (LSMs) made possible by recent developments in thin film technology, and approximate formulas for estimating their performance are presented. A more complete computation scheme based on optical multilayer theory is also described, and it is shown that the diffracting properties may be tailored to specific applications by adjusting the refractive indices and thicknesses of the component layers. The theory may be modified to take account of imperfections in the LMS structure, and the properties of nonperiodic structures thereby computed. Structures with high integrated reflectivity constructed according to the methods defined have potential application in many areas of X-ray or EUV research and instrumentation.

Underwood, J. H.↗
NASA NTRS1982

Analytical performance prediction for large antennas

The coupled free-free modes of the 55M LMSS antenna configuration are shown. They were determined using modal synthesis. Reflector modes clamped at the hub were calculated adopting the efficient cyclic symmetry technique. Similarly, clamped hub modes of the offset boom structure were calculated. The modes of the two substructures were then combined through the process of modal synthesis on the assumption that the interface at the hub structure is rigid thus satisfying statically determinate matching conditions. For attitude control purposes, only modes associated with symmetric components zero and one involve net motions of the center of gravity of the reflector. This condition restricts the set of admissible eigenfunctions for modal synthesis. Modes with symmetric components higher than one are excited only by forces acting on the ribs. These modes are totally uncoupled from the boom dynamics.

El-Raheb, M.↗
NASA NTRS1982

Distorted reflector antenna performance prediction technique

The application of a 3-D curve-fit technique to the electromagnetic analysis of reflector antennas is presented. the reflector antennas are described by the coordinates of an irregular distribution of measured points on the reflector surface. The reflector antenna analysis method used to calculate radiation patterns is geometric-optics with aperture-integration since an efficient and accurate computer code was readily available for modification.

Bailey, M. C.↗
NASA NTRS1986

Bearing Thermal Performance Prediction

Parameter called lubricant percent volume or cavity factor (XCAV) used primarily in calculation of ball or roller drag and, therefore, significantly affects calculated bearing-heat generation and temperature distribution. New equation accounts for sensitivity of XCAV to shaft speed, lubricant flow rate, and bearing size, and provides significant improvement over previous estimation methods.

Parker, R. J.↗
NASA NTRS1986

A new, improved method for separating turbulent boundary layer for aerodynamic performance prediction of trailing edge stall airfoils

A method based on integral techniques is presented to determine the turbulent separation location and separation pressure for trailing edge stall airfoils exhibiting extensive separated flow regions during prestall and poststall conditions. The method and experimental laser velocimetry data in the turbulence amplification region are used to establish a relationship between fluctuating velocity components and mean velocity in the boundary layer. The method is demonstrated for symmetrical, cambered, conventional and supercritical airfoils in the 5-to-21-percent thickness ratio range, and over a Reynolds number range of 2 to 22 million. Good agreement with experimental data is found, and the method is used in conjunction with the NASA Multi-Component Airfoil Computer Program to predict maximum L/D ratios and maximum section/lift coefficients.

Goradia, S.↗
NASA NTRS1986

Measured ground performance and predicted orbital performance of the superfluid helium dewar for the Cosmic Background Explorer

A critical component of the Cosmic Background Explorer observatory, which is to be lifted to orbit in 1988, is the 650-l superfluid He dewar housing a far-IR absolute spectrophotometer and a diffuse IR background experiment. Attention is presently given to the results of a four-month-long test program encompassing dewar filling verification, vibration characteristics, thermal performance over orbital lifetime, and aperture cover ejection behavior. No significant flaws have been noted; the orbital cryogen lifetime is projected to be 14 months.

Hopkins, Richard A.↗
NASA NTRS1986

Analysis and performance prediction of scramjet inlets utilizing a three-dimensional Navier-Stokes code

A series of inlet analysis codes (2-D, axisymmetric, 3-D) were developed which can analyze complicated flow through complex inlet geometries in a reasonably efficient manner. The codes were verified and are being used extensively to analyze practical inlet geometries both at Langley as well as industries. Newly installed VPS 32 computer will allow more complex configurations to be analyzed. Scalar FORTRAN versions are available to increase transportability of the codes for use on other Scalar computers and on the Cray vector processing computer.

Kumar, Ajay↗
NASA NTRS1989

Predicted performance of InP solar cells in Cassegrainian and slats space concentrator arrays at 20 to 100 AM0, 80 to 100 C

Researchers have calculated the expected performance dependence of near-optimally designed shallow homojunction n+pp+InP solar cells on incident intensities up 200 AM0 and temperatures up to 100 C (373K). Both circular and rectangular cells have been considered, the former for use in a Cassegrainian concentrator array at 100 AM0, 80 to 100 C and the latter for use in a Slats type concentrator array at 20 AM0 80 to 100 C. Calculation of the temperature dependence of the performance parameters I sub sc, V sub oc, FF and eta was done by first verifying that the use of the measured temperature variation of I sub sc, of the best published value of the temperature dependence of the bandgap of InP, and of the temperature dependences of the lifetimes and mobilities of electrons and holes the same as in equivalently doped GaAs, gave calculated results that closely matched measured data on the temperature variation of I sub sc, V sub oc, and FF of four existing InP cells at 1 AM0. It was then assumed that the same temperature dependences of I sub sc, the bandgap and lifetimes and mobilities would hold in the near-optimally designed cells at the higher concentrations.

Goradia, Chandra↗
NASA NTRS1989

Feasibility of predicting performance degradation of airfoils in heavy rain

The heavy rain aerodynamic performance penalty program is detailed. This effort supported the design of a fullscale test program as well as examined the feasibility of estimating the degradation of performance of airfoils from first principles. The analytic efforts were supplemented by a droplet splashback test program in an attempt to observe the physics of impact and generation of ejecta. These tests demonstrated that the interaction of rain with an airfoil is a highly complex phenomenon and this interaction is not likely to be analyzed analytically with existing tools.

Bilanin, A. J.↗
NASA NTRS1988

An entropy and viscosity corrected potential method for rotor performance prediction

An unsteady Full-Potential Rotor code (FPR) has been enhanced with modifications directed at improving its drag prediction capability. The shock generated entropy has been included to provide solutions comparable to the Euler equations. A weakly interacted integral boundary layer has also been coupled to FPR in order to estimate skin-friction drag. Pressure distributions, shock positions, and drag comparisons are made with various data sets derived from two-dimensional airfoil, hovering, and advancing high speed rotor tests. In all these comparisons, the effect of the nonisentropic modification improves (i.e., weakens) the shock strength and wave drag. In addition, the boundary layer method yields reasonable estimates of skin-friction drag. Airfoil drag and hover torque data comparisons are excellent, as are predicted shock strength and positions for a high speed advancing rotor.

Bridgeman, John O.↗
NASA NTRS1988

Design and predicted performance of the GPS demonstration receiver for the NASA Topex satellite

NASA's Ocean Topography Experiment (Topex) satellite will perform topographic ocean mapping. Topex will carry an experimental tracking system based on the use of GPS (Global Positioning System). An onboard GPS Demonstration Receiver (GPSDR) will be used with a network of up to ten receivers at precisely known ground sites. Following a brief overview of the Topex mission and its derived accuracy requirements, the authors describe the design of the GPSDR. The major hardware and software components are reviewed and discussed. Projected receiver tracking and navigation performance measures are presented and discussed.

Carson, Lance↗
NASA NTRS1988

Predicted performance of near-optimally designed indium phosphide space solar cells at high intensities and temperatures

The authors calculated the expected performance dependence of near-optimally designed shallow homojunction n+pp+ InP solar cells on incident intensities up to 200 AM0 and temperatures up to 100 deg C (373 K). Both circular and rectangular cells were considered, the former for use in a Cassegrainian concentrator array at 100 AM0, 80-100 deg C and the latter for use in a Slats concentrator array at 20 AM0, 80-100 deg C. With efficiencies near 22 percent at 80 deg C, both the circular and rectangular InP shallow homojunction solar cells compare very favorably to GaAs cells of the same design and may be preferable to the GaAs cells for space applications because of the superior radiation tolerance of the InP cells.

Goradia, Chandra↗