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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A damper for ground wind-induced launch vehicle oscillations

Prelaunch oscillatory bending deflections of the Atlas/Centaur launch vehicle are restrained by a damper mechanism mounted on the end of a horizontal boom supported from the umbilical tower. A single vertical pin on the vehicle engages the mechanism, and the damper is connected to the vehicle until liftoff. As the attach pin rises with the vehicle, a retractable arm mechanism provides initial clearance. An explosive release mechanism allows the boom to swing clear of the vehicle like a pendulum, while a snubber mechanism decelerates the free swinging boom and damper mechanism to a safe stop.

Bodle, J. G.↗
NASA NTRS1976

Impact dynamics research facility for full-scale aircraft crash testing

An impact dynamics research facility (IDRF) was developed to crash test full-scale general aviation aircraft under free-flight test conditions. The aircraft are crashed into the impact surface as free bodies; a pendulum swing method is used to obtain desired flight paths and velocities. Flight paths up to -60 deg and aircraft velocities along the flight paths up to about 27.0 m/s can be obtained with a combination of swing-cable lengths and release heights made available by a large gantry. Seven twin engine, 2721-kg aircraft were successfully crash tested at the facility, and all systems functioned properly. Acquisition of data from signals generated by accelerometers on board the aircraft and from external and onboard camera coverage was successful in spite of the amount of damage which occurred during each crash. Test parameters at the IDRF are controllable with flight path angles accurate within 8 percent, aircraft velocity accurate within 6 percent, pitch angles accurate to 4.25 deg, and roll and yaw angles acceptable under wind velocities up to 4.5 m/s.

Vaughan, V. L. J.↗
NASA NTRS1974

Manual control

Man's nonlinear characteristics and his use of control with compatible and incompatible multiple inputs, both visual and vestibular were studied. Experiments were also made with pulse and bang-bang controllers and the effects of sudden changes in control stick mechanical impedance. Closing the loop through the dynamics of the controlled vehicle allowed experiments on the limits of control of unstable vehicles with and without motion cues. The inverted pendulum controlled element, programmed as a self pacing element, was used extensively as a scalar performance index. In addition, the motorbike equations of motion were studied with regard to required human equalization. Abstracts are included for a series of published data on manual control.

Source record↗
NASA NTRS1976

Multi-Fiber Composites

Resin matrix composites having improved resistance to foreign object damage in gas turbine engine fan blade applications were developed. Materials evaluated include epoxy matrix graphite/glass and boron/glass hybrids, thermoplastic matrix boron/glass hybrids, and superhybrids consisting of graphite/epoxy, boron/aluminum, and titanium alloy sheets. Static, pendulum impact, and ballistic impact test results are reported for all materials. Superhybrid blade like specimens are shown to be capable of withstanding relatively severe ballistic impacts from gelatin spheres without fracture. The effects of ply configuration and projectile angle of incidence on impact behavior are described. Predictions of surface strains during ballistic impact are presented and shown to be in reasonable agreement with experimental measurements.

Novak, R. C.↗
NASA NTRS1976

Effect of angleplying and matrix enhancement on impact-resistant boron/aluminum composites

Efforts to improve the impact resistance of B/Al are reviewed and analyzed. Tensile and dynamic modulus tests, thin sheet Charpy and Izod impact tests, and standard full size Charpy impact tests were conducted on 0.20 mm (8 mil) diameter-B/1100 Al matrix composites. Angleplies ranged from unidirectional to + or - 30 deg. The best compromise between reduced longitudinal properties and increased transverse properties was obtained with + or - 15 deg angleply. The pendulum impact strengths of improved B/Al were higher than that of notched titanium and appear to be enough to warrant consideration of B/Cl for application to fan blades in aircraft gas turbine engines.

Mcdanels, D. L.↗
NASA NTRS1975

Visual reaction times during prolonged angular acceleration parallel the subjective perception of rotation

The effect of prolonged angular acceleration on choice reaction time to an accelerating visual stimulus was investigated, with 10 commercial airline pilots serving as subjects. The pattern of reaction times during and following acceleration was compared with the pattern of velocity estimates reported during identical trials. Both reaction times and velocity estimates increased at the onset of acceleration, declined prior to the termination of acceleration, and showed an aftereffect. These results are inconsistent with the torsion-pendulum theory of semicircular canal function and suggest that the vestibular adaptation is of central origin.

Mattson, D. L.↗
NASA NTRS1975

Drogue parachute deployment dynamics of the space shuttle solid rocket booster

Theoretical analysis and experimental investigations are presented for two deployment concepts of the drogue parachute deployment for the space shuttle solid rocket booster. The analysis represents the motion of three coupled rigid bodies, with one of the bodies having variable mass and moment of inertia. The unfurling process of the parachute from the bag is idealized as the flow of a continuum out of a control surface. The pilot parachute or tethered nose cap is modeled as a flexible pendulum with a nonlinear spring and a moving support. Measured wind tunnel test data compare reasonably well with the theory.

Banerjee, A. K.↗
NASA NTRS1976

The method of Ritz applied to the equation of Hamilton

Without any reference to the theory of differential equations, the initial value problem of the nonlinear, nonconservative double pendulum system is solved by the application of the method of Ritz to the equation of Hamilton. Also shown is an example of the reduction of the traditional eigenvalue problem of linear, homogeneous, differential equations of motion to the solution of a set of nonhomogeneous algebraic equations. No theory of differential equations is used. Solution of the time-space path of the linear oscillator is demonstrated and compared to the exact solution.

Bailey, C. D.↗
NASA NTRS1976

Improved impact-resistant boron/aluminum composites for use as turbine engine fan blades

Thin-sheet Charpy and Izod impact tests and standard full-size Charpy impact tests were conducted on unidirectional and angleply composites containing 4, 5.6 and 8 mil boron in 1100, 2024, 5052 and 6061 Al matrices. Impact failure modes of B/Al are proposed to describe the mechanisms involved and to provide insight for maximizing impact resistance. The impact strength of B/Al was significantly increased by proper selection of materials and processing. The use of more ductile matrices and larger diameter boron fibers gave the highest impact strengths by allowing matrix shear deformation and multiple fiber breakage. Pendulum impact test results of improved B/Al were higher than notched titanium and indicate sufficient foreign object damage protection to warrant consideration of B/Al for application to fan blades in aircraft gas turbine engines.

Mcdanels, D. L.↗
NASA NTRS1976

Apparatus for measuring internal friction Q factors in brittle materials

A flexural analog of the torsion pendulum for measuring the Young's modulus and the internal friction Q factor of brittle materials has been developed for Q greater than 10 to the 3rd measurements at a zero static stress and at 10 to the -7th strains of brittle materials in the Hz frequency range. The present design was motivated by the desire to measure Q in fragile lunar return samples at zero static stress to shed light on the anomalously low attenuation of seismic waves on the moon. The use of the apparatus is demonstrated with data on fused silica and on a terrestrial analog of lunar basalt.

Tittmann, B. R.↗
NASA NTRS1977

Gravimetric geoid in the Northwest Pacific Ocean

A total of 3708 1 x 1 deg free-air gravity anomaly averages have been used to construct a new 1 x 1 deg gravimetric geoid of the Northwest Pacific Ocean. The 1 x 1 deg averages are based on a compilation of 147,000 surface ship and pendulum gravity measurements. Difference geoid undulations range from a maximum of +19 m over the Hawaiian ridge to a minimum of -31 m over the junction of the Kuril and Aleutian trenches. The Hawaiian swell is associated with a geoidal high of up to +15 m with wavelengths of about 2200 km and the topographic rises seaward of deep-sea trenches are associated with geoidal highs of up to 4 m with wavelengths of about 220-900 km. The agreement between the gravimetric geoid and Skylab-4 and Geos-3 altimeter data is close for wavelengths greater than about 300 km but poor for shorter wavelengths.

Watts, A. B.↗
NASA NTRS1978

Experimental determination of the rattle of simple models

The effect of the excitation frequency on the rattle boundaries of simple models was investigated. The frequency range investigated was from 40 to 4,000 Hz. A 1-inch steel ball was studied to determine the rattle boundary for both vertical motion and for the ball suspended as a pendulum. Effects of surface contact and weight were also studied. Results indicate that the shape of the rattle boundary depends on the particular configuration being investigated as well as the range of frequency being investigated. Although there was condiderable scatter in the data, the general trend indicates that the level of acceleration required for the onset of rattle was independent of excitation frequency.

Clevenson, S. A.↗
NASA NTRS1978

Angle detector

An angle detector for determining a transducer's angular disposition to a capacitive pickup element is described. The transducer comprises a pendulum mounted inductive element moving past the capacitive pickup element. The capacitive pickup element divides the inductive element into two parts L sub 1 and L sub 2 which form the arms of one side of an a-c bridge. Two networks R sub 1 and R sub 2 having a plurality of binary weighted resistors and an equal number of digitally controlled switches for removing resistors from the networks form the arms of the other side of the a-c bridge. A binary counter, controlled by a phase detector, balances the bridge by adjusting the resistance of R sub 1 and R sub 2. The binary output of the counter is representative of the angle.

Parra, G. T.↗
NASA NTRS1977

Quantitative analysis of the Dermott-Gold theory for Uranus's rings

A summary is presented of an investigation which supplements the largely qualitative analysis conducted by Dermott and Gold (1977). Dermott and Gold have attempted to explain the locations of Uranus's rings in terms of resonances between ring particles and pairs of satellites. An equation of motion, analogous to that of a pendulum, is derived, taking into account a study by Wilkens (1933) of possible three-body resonances involving one minor and two major planets. Dermott and Gold had concluded that the observed pattern is probably due primarily to the effect of Ariel-Titania and Ariel-Oberon pairs. However, on the basis of the values derived in the reported investigation it is seen that Miranda plays the key role rather than Ariel, in spite of the small mass of the former. It is concluded that a decisive test of the Dermott-Gold theory has to await further observational details concerning the Uranus's rings.

Aksnes, K.↗
NASA NTRS1978

Low blow Charpy impact of silicon carbides

The room-temperature impact resistance of several commercial silicon carbides was examined using an instrumented pendulum-type machine and Charpy-type specimens. Energy balance compliance methods and fracture toughness approaches, both applicable to other ceramics, were used for analysis. The results illustrate the importance of separating the machine and the specimen energy contributions and confirm the equivalence of KIc and KId. The material's impact energy was simply the specimen's stored elastic strain energy at fracture.

Abe, H.↗
NASA NTRS1978

A user oriented microcomputer facility for designing linear quadratic Gaussian feedback compensators

A laboratory design facility for digital microprocessor implementation of linear-quadratic-Gaussian feedback compensators is described. Outputs from user interactive programs for solving infinite time horizon LQ regulator and Kalman filter problems were conditioned for implementation on the laboratory microcomputer system. The software consisted of two parts: an offline high-level program for solving the LQ Ricatti equations and generating associated feedback and filter gains and a cross compiler/macro assembler which generates object code for the target microprocessor system. A PDP 11/70 with a UNIX operating system was used for all high level program and data management, and the target microprocessor system is an Intel MDS (8080-based processor). Application to the control of a two dimensional inverted pendulum is presented and issues in expanding the design/prototyping system to other target machine architectures are discussed.

Houpt, P. K.↗
NASA NTRS1978

Sun tracking solar energy collector

A parabolic reflector is supported so that it can track the sun. The support for this reflector comprises an azimuth frame supported on two wheels and a central pivotal point which are positioned in a substantially triangular configuration. On top of the azimuth frame, there is provided an elevation frame. The reflector rides on wheels captured within curved rails. The wheels of the azimuth frame are driven by an azimuth actuator. The reflector structure is counterbalanced about its elevation axis by a pendulum cable system which is driven by a motor. At the focal point of the parabolic reflector, a heat engine or receiver is mounted independently on the reflector. Suitable means are provided for moving the reflector about its two axes.

Perkins, G. S.↗
NASA NTRS1978

World gravity standards

In order to use gravity anomalies in geodetic computations and geophysical interpretations, the observed gravity values from which anomalies are derived should be referred to one consistent world wide system. The International Gravity Standardization Net 1971 was adapted by the International Union of Geodesy and Geophysics at Moscow in 1971, the network was result of extensive cooperation by many organizations and individuals around the world. The network contains more than 1800 stations around the world. The data used in the adjustment included more than 25,000 gravimetry, pendulum and absolute measurements.

Uotila, U. A.↗