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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

IOS and ECS line coupling calculation for the CO-He system - Influence on the vibration-rotation band shapes

Line coupling coefficients resulting from rotational excitation of CO perturbed by He are computed within the infinite order sudden approximation (IOSA) and within the energy corrected sudden approximation (ECSA). The influence of this line coupling on the 1-0 CO-He vibration-rotation band shape is then computed for the case of weakly overlapping lines in the 292-78 K temperature range. The IOS and ECS results differ only at 78 K by a weak amount at high frequencies. Comparison with an additive superposition of Lorentzian lines shows strong modifications in the troughs between the lines. These calculated modifications are in excellent quantitative agreement with recent experimental data for all the temperatures considered. The applicability of previous approaches to CO-He system, based on either the strong collision model or exponential energy gap law, is also discussed.

Boissoles, J.↗
NASA NTRS1970

Apparatus for simultaneous ion counting and current recording in mass spectrometry

Ion counting system is coupled to the last dynode of an Allen-type electron multiplier on the mass analyzer of a double focusing mass spectrometer. This leaves the anode available for an electrometer, making possible simultaneous measurements. Coupling is achieved by a ferrite core transformer and associated circuitry.

Kohl, F. J.↗
NASA NTRS1971

A method for determining the response of space shuttle to atmospheric turbulence. Volume 1: Space shuttle turbulence response

A computer program has been developed and demonstrated that can analyze the response of space shuttle to atmospheric turbulence. The method developed accounts for propellant slosh, gimballed engine, and stability augmentation system (SAS) coupling with the elastic vehicle. Statistical outputs are generated that relate vehicle loads and accelerations to level of random turbulence. For discrete turbulence descriptions, response time-histories are computed. Preliminary turbulence response analyses of space shuttle were conducted for one ascent and one booster flyback subsonic flight condition. The ascent case considered both symmetric and antisymmetric boundary conditions, while only the symmetric analysis was conducted for booster flyback. The three conditions were analyzed with SAS active and inactive, but apparent instabilities with SAS active (arising from improper gains) invalidated the results. Load and acceleration responses in all cases, however, were well within vehicle design limits.

Source record↗
NASA NTRS1974

Identification of aircraft stability and control parameters using multilevel, hierarchical estimation

Previous attempts to identify aircraft stability and control derivatives from flight test data, using three-degrees-of-freedom (3-DOF) longitudinal or lateral-directional perturbation-equations-of-motion models, suffer from the disadvantage that the coupling between the longitudinal and lateral-directional dynamics has been ignored. In this paper the identification of aircraft stability parameters is accomplished using a more accurate 6-DOF model which includes this coupling. Hierarchical system identification theory is used to reduce the computational effort involved. The 6-DOF system of equations is decomposed into two 3-DOF subsystems, one for the longitudinal dynamics and the other for the lateral-directional dynamics. The two subsystem parameter identification processes are then coordinated in such a way that the overall system parameter identification problem is solved.

Fry, C. M.↗
NASA NTRS1976

STOLAND

The STOLAND system includes air data, navigation, guidance, flight director (including a throttle flight director on the Augmentor Wing), 3-axis autopilot and autothrottle functions. The 3-axis autopilot and autothrottle control through parallel electric servos on both aircraft and on the augmentor wing, the system also interfaces with three electrohydraulic series actuators which drive the roll control surfaces, elevator and rudder. The system incorporates automatic configuration control of the flaps and nozzles on the augmentor wing and of the flaps on the Twin Otter. Interfaces are also provided to control the wing flap chokes on the Augmentor Wing and the spoilers on the Twin Otter. The STOLAND system has all the capabilities of a conventional integrated avionics system. Aircraft stabilization is provided in pitch, roll and yaw including control wheel steering in pitch and roll. The basic modes include altitude hold and select, indicated airspeed hold and select, flight path angle hold and select, and heading hold and select. The system can couple to TACAN and VOR/DME navaids for conventional radial flying.

Grgurich, J.↗
NASA NTRS1978

A three-dimensional model of corotating streams in the solar wind. 1: Theoretical foundations

The theoretical and mathematical background pertinent to the study of steady, corotating solar wind structure in all three spatial dimensions (3-D) is discussed. The dynamical evolution of the plasma in interplanetary space (defined as the region beyond roughly 35 solar radii where the flow is supersonic) is approximately described by the nonlinear, single fluid, polytropic (magneto-) hydrodynamic equations. Efficient numerical techniques for solving this complex system of coupled, hyperbolic partial differential equations are outlined. The formulation is inviscid and nonmagnetic, but methods allow for the potential inclusion of both features with only modest modifications. One simple, highly idealized, hydrodynamic model stream is examined to illustrate the fundamental processes involved in the 3-D dynamics of stream evolution. Spatial variations in the rotational stream interaction mechanism were found to produce small nonradial flows on a global scale that lead to the transport of mass, energy, and momentum away from regions of relative compression and into regions of relative rarefaction.

Pizzo, V. J.↗
NASA NTRS1977

An electrostatically driven surface for flexible wall drag reduction studies

This paper describes the theoretical analysis, experimental development and surface motion data from an electrostatically driven flexible wall capable of producing high frequency, large amplitude, short wavelength standing wave motions. The driven wall was developed for use in studying flexible wall-turbulent boundary layer interactions. The theoretical analysis considers the coupled electrochemical system using a continuum model. For the system under consideration the electrical field is uncoupled from the mechanical system leading to a simplified analysis. The structural problem is a non-linear (moderately) large amplitude problem and details of the analysis are presented. Surface motion measurements, made using a modified schlieren type optical system, are discussed and details of the surface motion under different excitations are presented. Fair agreement is obtained between experimental measurements and theoretical calculations.

Weinstein, L. M.↗
NASA NTRS1978

High speed cylindrical roller bearing analysis, SKF computer program CYBEAN. Volume 2: User's manual

The CYBEAN (Cylindrical Bearing Analysis) was created to detail radially loaded, aligned and misaligned cylindrical roller bearing performance under a variety of operating conditions. Emphasis was placed on detailing the effects of high speed, preload and system thermal coupling. Roller tilt, skew, radial, circumferential and axial displacement as well as flange contact were considered. Variable housing and flexible out-of-round outer ring geometries, and both steady state and time transient temperature calculations were enabled. The complete range of elastohydrodynamic contact considerations, employing full and partial film conditions were treated in the computation of raceway and flange contacts. Input and output architectures containing guidelines for use and a sample execution are detailed.

Kleckner, R. J.↗
NASA NTRS1979

An impedance technique for determining low-frequency payload environments

The technique presented is based on frequency domain analysis and eliminates the necessity of final eigen solution for coupled payload/booster systems. A demonstration of the technique using Titan flight data and a low frequency environment prediction for a Shuttle payload are included. Criteria and philosophy for the technique for future payloads is discussed.

Payne, K. R.↗
NASA NTRS1978

'Smart' from a NEEDS perspective

A description is presented of the characteristics which are considered essential for the NASA information system if it is to satisfy the sensor/user needs of the 1980's. The present data/information (DI) system is a complex arrangement of functions which has evolved to meet the increased demands placed upon it by the changing nature of the space program. Even though today's ground system is handling today's DI flow, it has certain limitations, and in some cases lacks consistency in organization and structure that would allow it to cope with the new requirements. A systematic analysis and overview of the total system is necessary for the planning of an efficient and effective information system for the 1980's. The NASA End-to-End Data System (NEEDS) program is an attempt to significantly increase the effectiveness and efficiency of the system that couples the user of the space data with the sensors.

Blanchard, D. L.↗
NASA NTRS1978

A three-dimensional model of corotating streams in the solar wind. I - Theoretical foundations

The paper is concerned with the development of the theoretical and mathematical background pertinent to the study of steady, corotating solar wind structure in all three spatial dimensions. The dynamical evolution of the plasma in interplanetary space (defined as the region beyond roughly 35 Rs where the flow is supersonic) is approximately described by the nonlinear, single-fluid, polytropic magnetohydrodynamic or hydrodynamic equations. Efficient numerical techniques are outlined for solving this complex system of coupled, hyperbolic partial differential equations. The present formulation is inviscid and nonmagnetic, but the methods used allow for the potential inclusion of both features with only modest modifications. A simple, highly idealized hydrodynamic model stream is examined to illustrate the fundamental processes involved in the three-dimensional dynamics of stream evolution. It is found that spatial variations in the rotational stream interaction mechanism produce small nonradial flows on a global scale that lead to the transport of mass, energy, and momentum away from regions of relative compression and into regions of relative rarefaction. Comparison with simpler models demonstrates the essential nonlinear, multidimensional nature of the interplanetary dynamics.

Pizzo, V.↗
NASA NTRS1979

Adaptable structural synthesis using advanced analysis and optimization coupled by a computer operating system

A finite element program is linked with a general purpose optimization program in a 'programing system' which includes user supplied codes that contain problem dependent formulations of the design variables, objective function and constraints. The result is a system adaptable to a wide spectrum of structural optimization problems. In a sample of numerical examples, the design variables are the cross-sectional dimensions and the parameters of overall shape geometry, constraints are applied to stresses, displacements, buckling and vibration characteristics, and structural mass is the objective function. Thin-walled, built-up structures and frameworks are included in the sample. Details of the system organization and characteristics of the component programs are given.

Sobieszczanski-Sobieski, J.↗