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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Interactions between SAS-C spacecraft nutations and spin control system

The SAS-C spacecraft is stabilized by a momentum biased reaction wheel and passive nutation damper. A closed-loop low-speed spacecraft spin rate control system is included which uses a single-axis gyro and a variable speed range on the reaction wheel. Dynamic instability can result from interactions among the gyro, damper, and spacecraft dynamic unbalance. This instability may be aggravated by gyro angular misalignment, gyro error signals, and spacecraft nutations. Analytic eigenvector, and digital computer analyses of the coupled systems are presented. Mechanisms for instability are described as well as the effects that gyro error signal, tilt, and spacecraft dynamic unbalance produce on control system performance.

Tossman, B. E.↗
NASA NTRS1975

Free-flight model investigation of a vertical-attitude VTOL fighter

Tests were made in the Langley full-scale tunnel and included a study of the stability and control characteristics of delta- and swept-wing configurations from hovering through the transition to normal forward flight. Static force tests were also conducted to aid in the analysis of the flight tests. With conventional artificial rate stabilization, very smooth transitions could be made consistently with relatively little difficulty. Because of the lower apparent damping and a tendency to diverge in yaw, however, the swept-wing configuration was considered to be much more difficult to fly than the delta-wing configuration. With rate dampers off, both configurations were very difficult to control and the control power needed for satisfactory flights was substantially higher than with the rate dampers operating.

Newsom, W. A., Jr.↗
NASA NTRS1975

Transonic flight flutter tests of a control surface utilizing an impedance response technique

Transonic flight flutter tests of the XF3H-1 Demon Airplane were conducted utilizing a frequency response technique in which the oscillating rudder provides the means of system excitation. These tests were conducted as a result of a rudder flutter incident in the transonic speed range. The technique employed is presented including a brief theoretical development of basic concepts. Test data obtained during the flight are included and the method of interpretation of these data is indicated. This method is based on an impedance matching technique. It is shown that an artificial stabilizing device, such as a damper, may be incorporated in the system for test purposes without complicating the interpretation of the test results of the normal configuration. Data are presented which define the margin of stability introduced to the originally unstable rudder by design changes which involve higher control system stiffness and external damper. It is concluded that this technique of flight flutter testing is a feasible means of obtaining flutter stability information in flight.

Mirowitz, L. I.↗
NASA NTRS1976

Simulator study of the effectiveness of an automatic control system designed to improve the high-angle-of-attack characteristics of a fighter airplane

A piloted, fixed-base simulation was conducted to study the effectiveness of some automatic control system features designed to improve the stability and control characteristics of fighter airplanes at high angles of attack. These features include an angle-of-attack limiter, a normal-acceleration limiter, an aileron-rudder interconnect, and a stability-axis yaw damper. The study was based on a current lightweight fighter prototype. The aerodynamic data used in the simulation were measured on a 0.15-scale model at low Reynolds number and low subsonic Mach number. The simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative combat maneuvering. Results of the investigation show the fully augmented airplane to be quite stable and maneuverable throughout the operational angle-of-attack range. The angle-of-attack/normal-acceleration limiting feature of the pitch control system is found to be a necessity to avoid angle-of-attack excursions at high angles of attack. The aileron-rudder interconnect system is shown to be very effective in making the airplane departure resistant while the stability-axis yaw damper provided improved high-angle-of-attack roll performance with a minimum of sideslip excursions.

Gilbert, W. P.↗
NASA NTRS1975

Drive-train dynamics technology - State-of-the-art and design of a test facility for advanced development

A program for the development and verification of drive-train dynamic technology is described along with its basis and the results expected from it. A central feature of this program is a drive-train test facility designed for the testing and development of advanced drive-train components, including shaft systems, dampers, and couplings. Previous efforts in designing flexible dynamic drive-train systems are reviewed, and the present state of the art is briefly summarized. The design of the test facility is discussed with major attention given to the formulation of the test-rig concept, dynamic scaling of model shafts, and the specification of design parameters. Specific efforts envisioned for the test facility are briefly noted, including evaluations of supercritical test shafts, stability thresholds for various sources and types of instabilities that can exist in shaft systems, effects of structural flexibility on the dynamic performance of dampers, and methods for vibration control in two-level and three-level flexible shaft systems.

Badgley, R. H.↗
NASA NTRS1976

Air-bearing spin facility for measuring energy dissipation

The air-bearing spin facility was developed to determine experimentally the effect of energy dissipation upon the motion of spinning spacecraft. The facility consists of an air-bearing spin table, a telemetry system, a command system, and a ground control station. The air-bearing spin table was designed to operate in a vacuum chamber. Tests were run on spacecraft components such as fuel tanks, nutation dampers, reaction wheels, and active nutation damper systems. Each of these items affected the attitude of a spinning spacecraft. An experimental approach to determine these effects was required because the dissipation of these components could not be adequately analyzed. The results of these experiments have been used, with excellent results, to predict spacecraft motion.

Peterson, R. L.↗
NASA NTRS1978

Low-frequency vibration isolation

Viscoelastic shear dampers help eliminate microinch deflections resulting from low frequency vibrations. Dampers are applicable to control of tones and resonances in record players and turntables and other audio engineering equipment where vibration isolation is critical.

Miller, D. C.↗
NASA NTRS1978

Vibration effects of the space shuttle main engine high pressure oxidizer turbopump bellows

A welded metal bellows was subjected to a series of vibration tests in a 400 psi oxygen environment to evaluate the effects of the bellows convolutes rubbing on the damper ring in the high pressure oxidizer turbopump of the space shuttle main engine. The bellows was subjected to approximately 2 million cycles at 0.007 in. double amplitude displacement during this series of tests, at a frequency of 400 Hz. Intrumentation of the test specimen revealed no significant heat buildup caused by the rubbing of the bellows convolutes on the damper ring. A final destruct test was made to determine if a fire would result if the bellows ruptured in the 400 psi oxygen environment, thus exposing a fresh metal surface. The vibration input was changed to 0.8 in. double amplitude displacement at 20 Hz to intentionally rupture the bellows. Failure occurred after 2.5 sec; no fire or heat buildup was encountered.

Harp, J. A.↗
NASA NTRS1980

Solar heating system at Quitman County Bank, Marks, Mississippi

Information on the Solar Energy Heating System installed in a single story wood frame, cedar exterior, sloped roof building is presented. The system has on-site temperature and power measurements readouts. The 468 square feet of Solaron air flat plate collectors provide for 2,000 square feet of space heating, an estimated 60 percent of the heating load. Solar heated air is distributed to the 235 cubic foot rock storage box or to the load (space heating) by a 960 cubic feet per minute air handler unit. A 7.5 ton Carrier air-to-air heat pump with 15 kilowatts of electric booster strips serve as a back-up (auxiliary) to the solar system. Motorized dampers control the direction of airflow and back draft dampers prevent thermal siphoning of conditioned air.

Source record↗
NASA NTRS1980

Solar heating system at Security State Bank, Starkville, Mississippi

The 312 square feet of Solaron flat plate air collectors provide for 788 square feet of space heating, an estimated 55 percent of the heating load. Solar heated air is distributed to the 96 cubic foot steel cylinder, which contains two inch diameter rocks. An air handler unit moves the air over the collector and into the steel cylinder. Four motorized dampers and two gravity dampers are also part of the system. A Solaron controller which has sensors located at the collectors, rock storage, and at the return air, automatically controls the system. Auxiliary heating energy is provided by electric resistance duct heaters.

Source record↗
NASA NTRS1981

Solar Heating System installed at Belz Investment Company, Memphis, Tennessee

A hot air solar system which utilizes flat plate air collectors is discussed. Collector areas for each of four buildings cover 780 sq ft, with storage capacity of 390 cu ft per building. The air system has a special air handling unit to move air through the collectors and into and out of the rock storage, with connection to the air duct distribution system. The heat of the motor is added to the heat delivered to the system. The solar system also includes four motorized special low leakage dampers and two gravity fabric dampers. The system is automatically controlled by a solid state controller with three thermistors: one located in the collectors, one in the rock box to plenum, one in the return air duct from the heated space. A three stage heating thermostat, located in the conditioned space, controls the operation.

Source record↗
NASA NTRS1983

Transducer Joint for Kidney-Stone Ultrasonics

Ultrasonic therapy for kidney stones improved by new way of connecting wire-probe ultrasonic waveguide to transducer. Improved mounting allows joint to last long enough for effective treatment. Sheath and rubber dampers constrain lateral vibration of wire waveguide. Combination of V-shaped mounting groove, sheath, and rubber dampers increases life expectancy of wire 15 times or more.

Angulo, E. D.↗
NASA NTRS1983

Periodic motions (close to stationary) of an axisymmetric satellite with magnetic damping

Close to stationary periodic motions of an axisymmetric satellite in a circular orbit are considered. The satellite was equipped with a spherical magnetic damper. The investigation was conducted on the assumption that a strong magnet was installed on the damper float. Stationary rotations of the satellite around the axis of symmetry are selected as the generating solutions. The solutions are constructed in the form of power series of the smaller parameter, and they are extended numerically to the region of random values of the damping coefficient. The stability of the resulting solutions was investigated.

Ovchinnikov, M. Y.↗
NASA NTRS1983

Friction damping of flutter in gas turbine engine airfoils

This paper investigates the feasibility of using blade-to-ground friction dampers to stabilize flutter in blades. The response of an equivalent one mode model in which the aerodynamic force is represented as negative viscous damping is examined to investigate the following issues: the range of amplitudes over which friction damping can stabilize the response, the maximum negative aerodynamic damping that can be stabilized in such a manner, the effect of simultaneous resonant excitation on these stability limits, and the determination of those damper parameters which will be the best for flutter control.

Sinha, A.↗
NASA NTRS1982

Damping of thermoacoustic oscillations

A commonly encountered and troublesome problem in cryogenic systems is related to the occurrence of thermoacoustic oscillations (TAO). The oscillations are accompanied by large heat fluxes which can cause large increases in the boiloff from dewars. Such a boiloff can lead to a serious degradation in performance. It appears, therefore, highly advisable to incorporate mechanisms for damping TAO in those parts of the system where there oscillations might occur. The present investigation is concerned with the criteria for the design of such damping mechanisms. Attention is given to the theory regrading the suppression of TAO, a damper consisting of a capillary with a surge tank, and porous solid dampers.

Tward, E.↗
NASA NTRS1983

Simulation of the Galileo spacecraft axial - Delta-V algorithm

Preliminary results are presented from the analysis of the Galileo spacecraft axial delta-V algorithm. The Galileo spacecraft is a dual spin interplanetary spacecraft which will study the four Galilean moons of Jupiter as well as the Jovian environment and atmosphere. In order to achieve orbit about Jupiter and accurately deliver the probe to the planet's upper atmosphere, the Galileo spacecraft must be capable of performing many trajectory corrections or delta-V maneuvers. Twelve 10 Newton thrusters and one 400 Newton engine are utilized for this purpose. There are many maneuver modes and control algorithms available to the spacecraft. In this paper only the analysis of the axial delta-V algorithm will be discussed. The analysis consists of two parts: an analytic study and a simulation study. The analytic results are based on rigid body dynamics, while the simulation includes the first order effect of the flexible magnetometer boom and nutation damper. The simulation utilizes a program developed at JPL which allows flexible body effects to be simulated by modeling a collection of rigid bodies attached together by hinges, springs and dampers. In this preliminary study of the Galileo only two rigid bodies were used in the simulation, but many more can and will be used in the final tests. In this analysis, the algorithm appears to be working correctly and the analytic and simulation results agree very well.

Longuski, J. M.↗
NASA NTRS1987

Component response to random vibratory motion of the carrier vehicle

Two physical models of component plus supporting substructure are considered. Each model consists of a rigid body attached to a moving base by means of linear springs and viscous dampers. The second model differs from the first in that its dampers are elastically supported. The first model receives the more extensive treatment. Base motion, assumed a random translational motion parallel to a fixed axis, is prescribed only to the extent that the power spectral density (PSD) of its acceleration is given; and, as given, its plot on log-log graph paper is a series of straight line segments, each segment having an extremity in common with the adjacent segment. Closed expressions are given for the mean squares of base acceleration, base velocity, and base displacement. The component is restricted to planar motion and allowed two degrees of freedom, one translational and one rotational. Integral expressions are given for the mean squares of component response variables, the transfer functions essential to mean square computation being available via the equations of motion. Closed expressions are given for mean squares of certain of the response variables for the case wherein the base acceleration PSD is constant.

Tuell, L. P.↗
NASA NTRS1987

Analytical investigation of the dynamics of tethered constellations in Earth orbit (phase 2)

Simulation of two short distance crawling maneuvers of the elevator both with and without environmental perturbations acting upon the system is discussed. These simulation runs were performed in order to provide results useful for the interpretation of the data from the tests, on the ground, of a scaled down engineering model of the elevator. In these simulation runs the elevator crawls along the tether in accordance to the developed mirror image motion control law (MIMCL). Results from the simulation of the 4 km long maneuver run were compared to those obtained by adopting the modified hyperbolic tangent control law (MHTCL). A preprocessor was developed for setting up the initial conditions of a tethered system with L platforms, M longitudinal dampers, and N lumped masses (platforms plus tether beads). A short test run of the 4-platform system with 3 longitudinal dampers and 10 lumper mass without any perturbation acting upon the system is illustrated. In support of the Tether Applications Working Group, SAO is preparing a catalog of tether simulations, has prepared a set of simulator test cases, obtained results from SKYHOOK, and solicited results from simulators at other institutions, and prepared a paper on a specific analytic solution.

Lorenzini, Enrico C.↗