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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Rigid/Compliant Helicopter Rotor

Rotor structure ensures both effective aerodynamic support and efficient pitch changes. Four blades are shells with rigid inner I-beam arms integrated with rotor hub. Through each blade, control arm extends from pitch-control actuator in hub. Elastomeric bearings allow control arms to twist blades and thus change blade pitch without turning I-beam arms. Centrifugal force carried by tension strap. Leading and lagging movements of blades restrained by dampers. Ducts inside leading and trailing edges of blade shells carry air for partial cyclic aerodynamic control of lift and pitch. Structure permits more efficient pitch control with less weight. At same time, improves reliability through redundancy in supports and control mechanisms.

Jeffery, P.↗
NASA NTRS1985

Superconducting magnet

Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

Source record↗
NASA NTRS1983

An aerodynamic analysis computer program and design notes for low speed wing flap systems

The expanded capabilities for analysis and design of low speed flap systems afforded by recent modifications of an existing computer program is described. The program provides for the simultaneous analysis of up to 25 pairs of leading-edge and trailing-edge flap deflection schedules. Among other new features of the program are a revised attainable thrust estimation method to provide more accurate predictions for low Mach numbers, and a choice of three options for estimation of leading-edge separation vortex flow effects. Comparison of program results with low speed experimental data for an arrow wing supersonic cruise configuration with leading-edge and trailing-edge flaps showed good agreement over most of the range of flap deflections. Other force data comparisons and an independent study of airfoil and wing pressure distributions indicated that wind-tunnel measurements of the aerodynamic performance of twisted and cambered wings and wings with leading-edge flaps can be very sensitive to Reynolds number effects.

Carlson, H. W.↗
NASA NTRS1986

A computational transonic flutter boundary tracking procedure

An automated flutter boundary tracking procedure for the efficient calculation of transonic flutter boundaries is presented. The procedure uses aeroelastic responses to march along the boundary by taking steps in speed and Mach number, thereby reducing the number of response calculations previously required to determine a transonic flutter boundary. Flutter boundary results are presented for a typical airfoil section oscillating with pitch and plunge degrees of freedom. These transonic flutter boundaries are in good agreement with exact boundaries calculated using the conventional time-marching method. The tracking procedure is extended to include static aeroelastic twist as a simulation of the static deformation of a wing and contains all of the essential features that are required to apply it to practical three-dimensional cases. The procedure is also applied to flutter boundaries as a function of structural parameters.

Gallman, J. W.↗
NASA NTRS1985

The use of a panel code on high lift configurations of a swept forward wing

A study was done on high lift configurations of a generic swept forward wing using a panel code prediction method. A survey was done of existing codes available at Ames, frow which the program VSAERO was chosen. The results of VSAERO were compared with data obtained from the Ames 7- by 10-foot wind tunnel. The results of the comparison in lift were good (within 3.5%). The comparison of the pressure coefficients was also good. The pitching moment coefficients obtained by VSAERO were not in good agreement with experiment. VSAERO's ability to predict drag is questionable and cannot be counted on for accurate trends. Further studies were done on the effects of a leading edge glove, canards, leading edge sweeps and various wing twists on spanwise loading and trim lift with encouraging results. An unsuccessful attempt was made to model spanwise blowing and boundary layer control on the trailing edge flap. The potential results of VSAERO were compared with experimental data of flap deflections with boundary layer control to check the first order effects.

Scheib, J. S.↗
NASA NTRS1985

Alfvenic pulses in the solar atmosphere

Some nonlinear aspects of Alfvenic pulses propagating in coronal loops and the underlying chromosphere are numerically investigated. Heat conduction and radiation are included. The Alfvenic pulses are modeled as axisymmetric twists on a vertical cylindrical flux tube. They nonlinearly couple into acoustic-gravity waves propagating along the flux tube. A single Alfvenic pulse is found to leave two acoustic-gravity pulses in its wake. These pulses can result in significant motions of the transition region and underlying chromosphere. These motions do not resemble spicules, but they may correspond to a variety of observations indicating that the solar atmosphere is in a continual dynamic state. It is suggested that a dynamic chromosphere and transition region may be the inevitable consequence of the coronal heating process itself.

Mariska, J. T.↗
NASA NTRS1986

Summary of a high subsonic force/pressure experiment for 58 deg cambered/twisted thick delta wings

This paper summarizes the results of a force, moment, and pressure experiment involving six thick, cambered and twisted, delta wings with 58 deg leading-edge sweep. This experiment was conducted in the NASA Langley 7- by 10-foot High-Speed Tunnel at Mach numbers of 0.75, 0.80, and 0.83. The design goal was a configuration which was self-trimming at a lift coefficient of 0.25 and Mach number of 0.80. Although the design goal was not met, the configuration which came closest and which had the best overall performance was selected for further study. Wing surface pressure data and limited surface oil flow data for this configuration are presented to show the extent of attached flow at the design point. For selected cases, inviscid solutions from vortex lattice method/suction analogy, PAN AIR, FLO-28, and FLO-57 are compared with the experimental force, moment, and pressure data.

Chu, J.↗
NASA NTRS1986

Design of a natural laminar flow wing for a transonic corporate transport

Two- and three-dimensional computational methods were used to design a wing for a transonic corporate transport that had significant runs of laminar flow on both upper and lower wing surfaces at the cruise condition. The airfoil was derived from a low-speed laminar-flow section. The contour was systematically modified based on results from a two-dimensional transonic code to give favorable pressure gradients to 50-percent chord on the upper surface and 65-percent chord on the lower surface. Three-dimensional transonic codes were used to determine the wing twist and to evaluate the aerodynamic characteristics of the complete configuration at various flight conditions. A leading-edge modification for improved stall characteristics was also designed. The theoretical pressure distributions for the final airfoil correlated well with results from wind-tunnel tests.

Campbell, R. L.↗
NASA NTRS1986

Investigation of chord ratio, stagger, decalage angle, and flap angle for dual wing configurations

Aerodynamical closely coupled dual wing configurations of unequal chords are investigated for medium speed general aviation applications. Vortex panel and momentum boundary layer analysis are utilized for the two-dimensional predictions. A multi-surface vortex lattice method is used for the three-dimensional predictions. In the process of searching for the highest lift to drag ratio upper airfoil to lower airfoil chord ratios, both greater than and less than one, are investigated in terms of stagger, decalage angle, and gap. With the optimum chord ratio, at the optimum stagger and gap, proper spanwise decalage distribution is shown to yield the lowest two dimensional drag results. Various wing taper ratios and wing twists are investigated to increase wing efficiency. Comparisons are made between optimized dual and optimized single wing configurations both with the same fuselage, stabilator surfaces, engines, payload, and fuel. The dual wing configuration is shown to have significantly less drag and hence longer range than the conventional single wing configuration.

Selberg, B. P.↗
NASA NTRS1986

A numerical method for the design and analysis of counter-rotating propellers

A numerical method has been developed using the techniques of Lock and Theodorsen as described by Davidson to design and analyze counter-rotating propellers. The design method develops the optimum propeller geometry by calculating the planform and twist distribution for each propeller disk through the use of specific inputs of engine shaft horsepower, diameter, and disk spacing. The analysis method calculates the performance of a given counter-rotating propeller system at any flight condition. Using the NACA four-digit airfoil family, the performance of a counter-rotating propeller design for a given flight condition was investigated in the design and analysis mode.

Playle, S. C.↗
NASA NTRS1985

On the dynamo generation of flux ropes in the Venus ionosphere

Small scale magnetic field structures or 'flux ropes' observed in the ionosphere of Venus can be interpreted as the result of a kinematic dynamo process acting on weak seed fields. The seed fields result from the prevailing downward convection of magnetic flux from the vicinity of the ionopause, while small scale fluctuations in the velocity of the ionospheric plasma, which can be caused by collisional coupling to gravity waves in the neutral atmosphere, provide the mechanism by which the field is twisted and redistributed into features of similar scale. This mechanism naturally explains some of the average properties of flux ropes such as the variation of their characteristics with altitude and solar zenith angle. It also elucidates the relationship between the large scale and small scale ionospheric magnetic fields.

Luhmann, J. G.↗
NASA NTRS1986

Aerodynamic performance of two fifteen-percent-scale wind-tunnel drive fan designs

An experimental and analytical investigation of two fan blade designs was conducted. The fan blades tested were 15 percent scale models of the blades used in the National Full Scale Aerodynamic Complex fan drive at NASA Ames Research Center. The fan blades were composed of NACA-65 and modified NACA-65-series airfoil design sections. The blades with modified 65-series sections incorporated increased thickness on the upper surface, between the leading edge and the one-half chord position. Twist and taper were the same for both blade designs. The fan blades with modified 65-series sections were found to have an increase in stall margin when they were compared with the unmodified blades. The experimental performance data agreed favorably with theoretical calculations.

Signor, D. B.↗
NASA NTRS1985

Pilot usage of decoupled flight path and pitch controls

Data from decoupled flight maneuvers have been collected and analyzed for four AFTI-F-16 pilots operating this aircraft's highly augmented fly-by-wire control system, in order to obtain spectral density, cross spectra, and Bode amplitude data, as well as coherences and phase angles for the two longitudinal axis control functions of each of 50 20-sec epochs. The analysis of each epoch yielded five distinct plotted parameters for the left hand twist grip and right hand sidestick controller output time series. These two control devices allow the left hand to generate vertical translation, direct lift, or pitch-pointing commands that are decoupled from those of the right hand. Attention is given to the control patterns obtained for decoupled normal flight, air-to-air gun engagement decoupled maneuvering, and decoupled air-to-surface bombing run maneuvering.

Berkhout, J.↗
NASA NTRS1986

Dynamic characteristics of an assembly of prop-fan blades

In contrast to conventional propellers, propfan blades are thin and highly swept-back, thereby giving rise to large bending and twisting deformations and complex vibratory characteristics. Aerodynamic performance depends on the extent of steady state deformation, and the aeroelastic response depends on the vibratory frequency and mode shape. Attention is presently given to the principal results of structural analyses for a five-bladed propfan assembly; these results are compared with test data. The results encompass both steady deformations and vibratory frequencies and mode shapes in a vacuum centrifugal environment.

Srinivasan, A. V.↗
NASA NTRS1985

Design aspects of the XV-15 advanced technology blade program

The paper discusses the design of a tiltrotor blade for application to the XV-15 research demonstration aircraft. The design features 43 deg nonlinear twist and nonuniform tapered planform. The structure is composite with extensive use of graphite in the primary structure. Instrumentation and wiring is encapsulated in the composite structure during the cure cycle. The tip shell is removable, providing access to the tracking and balance weights. This feature provides research facility of alternate tip configurations. The cuff is similarly removable. The graphite epoxy system used is high strain American Cyanamid's Celion 6000ST/Cycom 950. This is the first application of this material in rotor blades.

Smith, K. E.↗
NASA NTRS1986

A computational transonic flutter boundary tracking procedure

An automated flutter boundary tracking procedure is presented for the efficient calculation of transonic flutter boundaries. The new procedure uses aeroelastic responses to march along the boundary by taking steps in speed and Mach number, thereby reducing the number of response calculations previously required to determine a transonic flutter boundary. The tracking procedure reduces computational costs since only two response calculations are required per Mach number and provides a complete boundary in a single job submission. Flutter boundary results are presented for a typical airfoil section oscillating with pitch and plunge degrees of freedom. These transonic flutter boundaries are in good agreement with 'exact' boundaries calculated using the conventional time-marching method. The tracking procedure was also extended to include static aeroelastic twist as a simulation of the static deformation of a wing and thus contains all of the essential features that are required to apply it to practical three-dimensional cases. Application of the procedure is also made to flutter boundaries as a function of structural parameters, the capability of which is useful as a design tool.

Gallman, J. W.↗
NASA NTRS1986

Thermal stresses in composite tubes

This paper summarizes work to determine the thermally-induced stresses and deformations in specially-constructed angle-ply composite tubes subjected to a uniform temperature change relative to their stress-free cure state. The tubes are designed for application to space structures and have high axial stiffness. Four angle-ply designs are examined in an effort to determine which design might have the most favorable thermally-induced response. A planar elasticity solution is used, the solution being valid away from the ends of the tube. Of the four designs considered, none has any particular advantage as far as stress levels are concerned. However, despite the fact that the tube wall is a balanced laminate, one design exhibits a significant amount of thermally-induced twist.

Hyer, M. W.↗
NASA NTRS1987

Quick-Change Anode for Plating

Proposed fastener for attaching electroplating anode improves quality of plating and increases productivity. Notches in twist-lock fastener mates with projections on end of anode bar. Fastener made of titanium for compatibility with copper-plating solution. Also constructed in snap-on, snap-off configuration.

Beasley, J. L.↗