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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

SYMBOD - A computer program for the automatic generation of symbolic equations of motion for systems of hinge-connected rigid bodies

A computer program is described that can automatically generate symbolic equations of motion for systems of hinge-connected rigid bodies with tree topologies. The dynamical formulation underlying the program is outlined, and examples are given to show how a symbolic language is used to code the formulation. The program is applied to generate the equations of motion for a four-body model of the Galileo spacecraft. The resulting equations are shown to be a factor of three faster in execution time than conventional numerical subroutines.

Macala, G. A.↗
NASA NTRS1984

Hinge specification for a square-faceted tetrahedral truss

A square-faceted tetrahedral truss is geometrically analyzed. Expressions are developed for single degree of freedom hinges which allow packaging of the structure into a configuration in which all members are parallel and closely packed in a square pattern. Deployment is sequential, thus providing control over the structure during deployment.

Adams, L. R.↗
NASA NTRS1987

Hinge spectrometer - A grating Fabry-Perot instrument for far-infrared/submillimeter spectroscopy in space

A compact submillimeter spectrometer can be constructed through the use of a combination of grating and Fabry-Perot techniques. The instrument has only one moving part, a grating that pivots about an accurately placed hinge. The entire optical train is cooled to liquid helium temperature for low-background low-noise operation and is designed for use in astronomical observations from aircraft, balloons, or space vehicles. Resolving power R about 20,000 at about 150 microns is demonstrated.

Harwit, Martin↗
NASA NTRS1989

Hinged, Magnetic Holder For Radiographic Film

Hinged holder equipped with magnets enables positive, accurate, and repeatable placement and orientation of radiographic film at hidden and otherwise inaccessible location. Made from simple, readily available parts. Film and holder inserted in end of duct and pulled along by magnets on outside. Holder removed by reversing sequence of motions.

Pierce, Darryl E.↗
NASA NTRS1988

Validation of a pair of computer codes for estimation and optimization of subsonic aerodynamic performance of simple hinged-flap systems for thin swept wings

Extensive correlations of computer code results with experimental data are employed to illustrate the use of linearized theory attached flow methods for the estimation and optimization of the aerodynamic performance of simple hinged flap systems. Use of attached flow methods is based on the premise that high levels of aerodynamic efficiency require a flow that is as nearly attached as circumstances permit. A variety of swept wing configurations are considered ranging from fighters to supersonic transports, all with leading- and trailing-edge flaps for enhancement of subsonic aerodynamic efficiency. The results indicate that linearized theory attached flow computer code methods provide a rational basis for the estimation and optimization of flap system aerodynamic performance at subsonic speeds. The analysis also indicates that vortex flap design is not an opposing approach but is closely related to attached flow design concepts. The successful vortex flap design actually suppresses the formation of detached vortices to produce a small vortex which is restricted almost entirely to the leading edge flap itself.

Carlson, Harry W.↗
NASA NTRS1990

Precise Hinge Has Low Friction

Precise hinge rotates with minimal friction and without "slop". Axis of rotation at central axis of concentric, self-retaining assembly. Blades in same plane, and both edges of blades and apexes of grooves lie along same line, allowing free rotation without either binding or slop. Blades on rotor engage grooves on stator. Blades pivot about edges through arc defined by slotted openings in stator housing.

Collins, Earl R., Jr.↗
NASA NTRS1991

Design of a Shape Memory Alloy deployment hinge for reflector facets

A design concept for a Shape Memory Alloy (SMA) actuated hinge mechanism for deploying segmented facet-type reflector surfaces on antenna truss structures is presented. The mechanism uses nitinol, a nickel-titanium shape memory alloy, as a displacement-force micro-actuator. An electrical current is used to resistively heat a 'plastically' elongated SMA actuator wire, causing it to contract in response to a thermally-induced phase transformation. The resulting tension creates a moment, imparting rotary motion between two adjacent panels. Mechanical stops are designed into the device to limit its range of motion and to establish positioning accuracy at the termination of deployment. The concept and its operation are discussed in detail, and an analytical dynamic simulation model is presented. The model has been used to perform nondimensionalized parametric design studies.

Anders, W. S.↗
NASA NTRS1933

Rolling, yawing, and hinge moments produced by rectangular ailerons

Ailerons described in references 1, 2, and 3, are summarized in the form of empirical equations which relate the aileron dimensions and displacements to the rolling, yawing, and hinge moments for pitch angles of 0 and 12 degrees, corresponding to angles of attack of the wings of 4 and 16 degrees, respectively.

Heald, R H↗
NASA NTRS1950

The Longitudinal Stability, Control Effectiveness, and Control Hinge Moment Characteristics Obtained from a Flight Investigation of a Canard Missile Configuration at Transonic and Supersonic Speeds

A 60 degree delta wing canard missile configuration was flight-tested at the Langley pilotless aircraft research station at Wallops Island, Va. The results include the longitudinal stability derivatives, control effectiveness, drag characteristics, and control-surface hinge-moment characteristics for a Mach number range of 0.7 to 1.45.

Niewald, Roy J↗
NASA NTRS1932

Effect of variation of chord and span of ailerons on hinge moments at several angles of pitch

This report presents the results of an investigation of the hinge moments of ailerons of various chords and spans on two airfoils having the Clark Y and USA-27 wing sections, supplementing the investigations described in NACA-TR-298 and NACA-TR-343, of the rolling and yawing moments due to similar ailerons on these two airfoil sections. The measurements were made at various angles of pitch, but at zero angle of roll and yaw, the wing chord being set at an angle of +4 degrees to the fuselage axis. In the case of the Clark Y airfoil the measurements have been extended to a pitch angle of 40 degrees, using ailerons of span equal to 67 per cent of the wing semispan and chord equal to 20 and 30 per cent of the wing chord. The investigation was conducted on models of 60-inch span and 10-inch chord, having square tips, no taper in plan form or thickness, zero dihedral, and zero sweepback.

Monish, B H↗
NASA NTRS1944

Effect of hinge-moment parameters on elevator stick forces in rapid maneuvers

The importance of the stick force per unit normal acceleration as a criterion of longitudinal stability and the critical dependence of this gradient on elevator hinge-moment parameters have been shown in previous reports. The present report continues the investigation with special reference to transient effects for maneuvers of short duration.

Jones, Robert T↗
NASA NTRS1951

Equations and charts for the rapid estimation of hinge-moment and effectiveness parameters for trailing-edge controls having leading and trailing edges swept ahead of the Mach lines

Existing conical-flow solutions have been used to calculate the hinge-moments and effectiveness parameters of trailing-edge controls having leading and trailing edges swept ahead of the Mach lines and having streamwise root and tip chords. Equations and detailed charts are presented for the rapid estimation of these parameters. Also included is an approximate method by which these parameters may be corrected for airfoil-section thickness.

Goin, Kennith L↗
NASA NTRS1958

Theory of self-excited mechanical oscillations of helicopter rotors with hinged blades

Vibrations of rotary-wing aircraft may derive their energy from the rotation of the rotor rather than from the air forces. A theoretical analysis of these vibrations is described and methods for its application are explained in Chapter one. Chapter two reports the results of an investigation of the mechanical stability of a rotor having two vertically hinged blades mounted upon symmetrical supports, that is, of equal stiffness and mass in all horizontal directions. Chapter three presents the theory of ground vibrations of a two-blade helicopter rotor on anisotropic flexible supports.

Coleman, Robert P↗
NASA NTRS1955

An Experimental Investigation of the Hinge-moment Characteristics of a Constant-chord Control Surface Oscillating at High Frequency

The results of an experimental investigation of the hinge-moment characteristics of a constant-chord control surface oscillating at high frequency is presented. The control surface was mounted on an aspect-ratio-2 triangular wing. The aerodynamic restoring-moment coefficient and damping-moment coefficient were determined at a frequency of 260 cycles per second for a Mach number range of 0.6 to 0.8 and 1.3 to 1.9 at angles of attack of 5 degrees and 10 degrees. The test results showed linear theory to be a reliable guide to the prediction of the trend of the restoring-moment coefficient with Mach number for the supersonic speed range of the investigation but overestimated the magnitude of the coefficient. The experimental values of the damping-moment coefficient were, for the most part, more positive than those indicated by the theory and, for some conditions, could lead to instability of the control surface. Comparison of the results of this investigation with those of previous investigations at 0 and 50 cycles per second showed that frequency had little effect on the restoring-moment coefficient. The damping-moment coefficient was similarly insensitive to frequency at an oscillation amplitude of plus-or-minus 1.0 degrees but at an amplitude ofplus-or-minus 2.5 degrees the results showed a destabilizing shift with increasing frequency.

Reese, David E JR↗
NASA NTRS1934

Impact buckling of thin bars in the elastic range hinged at both ends

Following the development of the well-known differential equations of the problem and their resolution for failure in tension, the bending (transverse) oscillations of an originally not quite straight bar hinged at both ends and subjected to a constant longitudinal force (shock load) are analyzed. To this end the course of the bar form is expanded in a sinusoidal series, after which the investigation is carried through separately for the fundamental oscillation and the (n-1)the higher oscillations. The analysis of the fundamental oscillation distinguishes three cases: shock load lower, equal to, or higher than the Eulerian load. The investigation leads to functions which are proportional to the maximum stresses in time and space due to the shock stresses in buckling.

Koning, Carel↗
NASA NTRS1993

Fuel-optimal slewing of an experimental hinged-free beam

With the recent development of numerical methods for exactly solving larger order fuel-optlmal control problems, the implementation of exact real-time fuel-optimal control becomes possible. This paper describes a physical experiment in which a hinged-free beam is slewed in a fuel-optimal manner. A comparison between experimental results and the analytical predictions highlights the sources of errors typical of this class of problems.

Silverberg, Larry↗