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Bushnell, D.

Publications and source records attributed to Bushnell, D..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Submicron-Particle Generator

Particle generator supplies submicron-size particles to high-pressure airstream. Particles serve as light scatterers in laser velocimeter for ultra-high-speed gas. Advantage of generator: produces cloud of uniform, submicron particles at high ambient pressures and high flow rates.

Morrisette, E.↗
NASA NTRS1984

Mobile spectrometer measures radar backscatter

The present article is concerned with a helicopter-borne spectrometer (Heloscat), which has been developed to permit high-quality scattering measurements from a mobile platform at remote sites. The term 'spectrometer' referes to a class of scatterometers. The term 'scatterometer' is employed to denote a specialized radar for measuring scattering coefficients as a function of angle. A spectrometer, on the other hand, is a scatterometer which can measure backscatter at several frequencies. The Heloscat system is discussed, taking into account two antennas, RF hardware, and an externally mounted pendulum for angle encoding. A dual-antenna configuration is used for cross-polarized measurements, while a single-antenna system is used for like-polarized measurements. Attention is also given to oscillator characteristics, efficient data handling, and aspects of calibration.

Gogineni, S.↗
NASA NTRS1983

Optimum design of dewar supports

A number of struts or straps support a rigid, delicate mass (dewar) which must be successfully launched and maintained in orbit for a long time at very low temperature. The support system must be designed so that the heat flow into the mass is minimized subject to constraints on minimum allowable natural frequency of the mass during launch, minimum natural frequency of the mass in orbit, maximum allowable stress in any support member during launch, and no buckling or slackening of any support member during launch. Optimum designs are obtained via the CONMIN program for a support system consisting of simple tension straps and support systems with passive thermal disconnect features by means of which the thermal conductance is greatly reduced during the transition from the launch condition to the orbital condition. The theory indicates that either of the optimized thermal disconnect support systems will allow the mass to stay cold far longer than will the optimized tension strap support system.

Bushnell, D.↗
NASA NTRS1981

Longitudinal grooves for bluff body drag reduction

Wind tunnel test results are presented for four axisymmetric bluff body configurations in order to determine their effect on form and pressure drag. It was found that drag reductions on the order of 40% are obtainable with an afterbody incorporating four longitudinal 'V' grooves. Although this effect may be due to the functioning of the grooves as longitudinal, continuous vortex generators, it is concluded that further research is needed to elucidate the physical basis of the test results. Optimization of the effect will be useful in base drag reduction for such vehicles as automobiles and cargo aircraft with sharply upswept afterbodies.

Quass, B.↗
NASA NTRS1974

Stress, stability and vibration of complex, branched shells of revolution

A comprehensive computer program, designated BOSOR4, for analysis of the stress, stability, and vibration of segmented, ring-stiffened, branched shells of revolution and prismatic shells and panels is described. The program performs large-deflection axisymmetric stress analysis, small-deflection nonsymmetric stress analysis, modal vibration analysis with axisymmetric nonlinear prestress included, and buckling analysis with axisymmetric or nonsymmetric prestress. One of the main advantages of the code is the provision for realistic engineering details such as eccentric load paths, internal supports, arbitrary branching conditions, and a 'library' of wall constructions. The program is based on the finite-difference energy method, which is very rapidly convergent with increasing numbers of mesh points. The organization of the program is briefly described with the flow of calculations charted for each of the types of analysis. Overlay charts and core storage requirements are given for the CDC 6600, IBM 370/165, and UNIVAC 1108 versions of BOSOR4.

Bushnell, D.↗
NASA NTRS1973

Stress, stability, and vibration of complex, branched shells of revolution.

A comprehensive computer program, designated BOSOR4, for analysis of the stress, stability, and vibration of segmented, ring-stiffened, branched shells of revolution and prismatic shells and panels is described. The program performs large-deflection axisymmetric stress analysis, small-deflection nonsymmetric stress analysis, modal vibration analysis with axisymmetric nonlinear prestress included, and buckling analysis with axisymmetric or nonsymmetric prestress. One of the main advantages of the code is the provision for realistic engineering details such as eccentric load paths, internal supports, arbitrary branching conditions, and a library of wall constructions. The program is based on the finite-difference energy method, which is very rapidly convergent with increasing numbers of mesh points.

Bushnell, D.↗