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Results for “dynamic solar control”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Space Station Freedom solar dynamic modules structural modelling and analysis

In support of the Space Station Freedom (SSF) Solar Dynamic Power Module effort, structural design studies were performed to investigate issues related to the design of the power module, its pointing capabilities, and the integration of the module into the SSF infrastructure. Of particular concern from a structural viewpoint are the dynamics of the power module, the impact of the power module on the Space Station dynamics and controls, and the required control effort for obtaining the specified Solar Dynamic Power Module pointing accuracy. Structural analyses were performed to determine the structural dynamics attributes of both the existing and the proposed structural dynamics module designs. The objectives of these analyses were to generate validated Solar Dynamic Power Module NASTRAN finite element models, combine Space Station and power module models into integrated system models, perform finite element modal analyses to assess the effect of the relocations of the power module center of mass, and provide modal data to controls designers for control systems design.

Lawrence, Charles↗
NASA NTRS2012

Data Distribution System (DDS) and Solar Dynamic Observatory Ground Station (SDOGS) Integration Manager

The DDS SDOGS Integration Manager (DSIM) provides translation between native control and status formats for systems within DDS and SDOGS, and the ASIST (Advanced Spacecraft Integration and System Test) control environment in the SDO MOC (Solar Dynamics Observatory Mission Operations Center). This system was created in response for a need to centralize remote monitor and control of SDO Ground Station equipments using ASIST control environment in SDO MOC, and to have configurable table definition for equipment. It provides translation of status and monitoring information from the native systems into ASIST-readable format to display on pages in the MOC. The manager is lightweight, user friendly, and efficient. It allows data trending, correlation, and storing. It allows using ASIST as common interface for remote monitor and control of heterogeneous equipments. It also provides failover capability to back up machines.

Pham, Kim↗
NASA NTRS2014

Recent Progress in Heliogyro Solar Sail Structural Dynamics

Results from recent National Aeronautics and Space Administration (NASA) research on the structural dynamics and control characteristics of heliogyro solar sails are summarized. Specific areas under investigation include coupled nonlinear finite element analysis of heliogyro membrane blade with solar radiation pressure effects, system identification of spinning membrane structures, solarelastic stability analysis of heliogyro solar sails, including stability during blade deployment, and results from small-scale in vacuo dynamics experiments with spinning high-aspect ratio membranes. A low-cost, rideshare payload heliogyro technology demonstration mission concept, used as a mission context for these heliogyro structural dynamics and solarelasticity investigations, is also described.

Wilkie, William K.↗
NASA NTRS1992

Solar dynamic modules for Space Station Freedom: The relationship between fine-pointing control and thermal loading of the aperture plate

Dynamic simulations of Space Station Freedom (SSF) configured with solar dynamic (SD) power modules were performed. The structure was subjected to Space Shuttle docking disturbances, while being controlled with a 'natural' vibration and tracking control approach. Three control cases were investigated for the purpose of investigating the relationship between actuator effort, SD pointing, and thermal loading on the receiver aperture plate. Transient, one-dimensional heat transfer analyses were performed to conservatively predict temperatures of the multi-layered receiver aperture plate assembly and thermal stresses in its shield layer. Results indicate that the proposed aperture plate is tolerant of concentrated flux impingement during short-lived structural disturbances. Pointing requirements may be loosened and the requirement control torques lessened from that previously specified. Downsizing and simplifying the joint drive system should result in a considerable savings mass.

Quinn, Roger D.↗
NASA NTRS1980

SPS structural dynamics and control workshop: Findings and recommendations

The structural dynamics and control of the Solar Power Satellite (SPS), a concept which holds promise for meeting a portion of the energy needs of the United States beyond the year 2000 are examined. The assumptions, methodologies and conclusions of existing SPS studies in the areas of structural dynamics and control (with structural design and materials also being considered) are assessed.

Ried, R. C.↗
NASA NTRS1985

Dependence of Venus ionopause altitude and ionospheric magnetic field on solar wind dynamic pressure

The shape of the dayside Venus ionopause, and its dependence on solar wind parameters, is examined using Pioneer Venus Orbiter field and particle data. The ionopause is defined here as the altitude of pressure equality between magnetosheath pressure and ionospheric thermal pressure; its typical altitudes range from about 300 km near the subsolar point to about 900 km near the terminator. A strong correlation between ionopause altitude and magnetosheath magnetic pressure is demonstrated; correlation between magnetic pressure and the normally incident component of solar wind dynamic pressure is also evident. The data support the hypothesis of control of the ionopause altitude by solar wind dynamic pressure, manifested in the sheath as magnetic pressure. The presence of large scale magnetic fields in the ionosphere is observed primarily when dynamic pressure is high and the ionopause is low.

Phillips, J. L.↗
NASA NTRS1984

High precision active nutation control for a flexible momentum biased spacecraft

The controller design for the Solar Dynamics Observatory (SDO) is presented. SDO is a momentum biased spacecraft with three flexible appendages. Its primary scientific instrument, the solar oscillations imager (SOI), is rigidly attached to the spacecraft bus and has arc-second pointing requirements. Meeting these requirements necessitates the use of an active nutation controller (ANC) which is here mechanized with a small reaction wheel oriented along a bus transverse axis. The ANC does its job by orchestrating the transfer of angular momentum out of the bus transverse axes and into the momentum wheel. A simulation study verifies that the controller provides quick, stable, and accurate response.

Laskin, R. A.↗
NASA NTRS1991

Latitudinal dynamics of steady solar wind flows

In many previous studies, it has been assumed that the streamlines of the solar wind are in a purely radial direction beyond a few solar radii. Therefore, the nonradial modulations by the magnetic force and gas pressure is neglected at large heliocentric distances. The work reported in this paper includes a two-dimensional magnetohydrodynamic (MHD) study of the latitudinal structure of solar wind flows. The dynamical effects of the interplanetary magnetic field (IMF) are investigated by MHD solutions and by comparing them with both one-dimensional and two-dimensional hydrodynamic (HD) solutions. The corotational effect of the sun and the influence of transient events in the solar atmosphere are neglected. With such a simplification, the latitudinal structure of the steady solar wind is controlled by the dynamic balance of the magnetic force and the gas pressure. Several different patterns of the evolution of the solar wind latitudinal structure are exhibited in the calculation. The results indicate the existence of a proton number density maximum at the magnetic neutral line, whether or not there is a density maximum or minimum at the inner boundary. The drift motion of magnetic field lines toward the magnetic neutral line enhances the magnetic field strength around the neutral sheet, which may provide a possible explanation of the discrepancy between the measured IMF at 1 AU and that extrapolated from the photospheric magnetic field by the current source-surface modeling.

Yang, W.-H.↗
NASA NTRS1984

Orientation and shape-control of an orbiting flexible beam under the influence of solar radiation pressure

In this paper, the uncontrolled and controlled dynamics of a thin flexible beam in orbit and in the presence of solar radiation disturbance are analyzed. A beam nominally oriented along (i) the local horizontal and carrying a gimballed rigid dumbbell for gravity stabilization, and (ii) a beam nominally oriented along the local vertical are considered. The uncontrolled dynamics of the beam in the presence of the solar radiation pressure disturbance shows the excitation of the rigid pitch mode. The control laws previously designed for the case where the environmental effects were neglected, are found to be inadequate to control the shape and orientation of very flexible beams that are exposed to solar radiation disturbances. The control laws and the gain parameters are reevaluated for both cases of nominal beam orientations; this results, in general, in increased robustness of the closed-loop system. Methods of obtaining a robust control system in the presence of environmental perturbations are discussed.

Krishna, R.↗
NASA NTRS2017

Inflight Performance of the SDO Fine Pointing Science Mode

The Solar Dynamics Observatory (SDO) was successfully launched and deployed from its Atlas V launch vehicle on February 11, 2010. Three months later, on May 14, 2010, the fully commissioned heliophysics laboratory was handed over to Space Systems Mission Operations to begin its science mission. SDO is an Explorer-class mission now operating in a geosynchronous orbit, sending data 24 hours per day to a dedicated ground station in White Sands, New Mexico. It carries a suite of instruments designed to observe the Sun in multiple wavelengths at unprecedented resolution. The Atmospheric Imaging Assembly (AIA) includes four telescopes with 4096x4096 focal plane CCDs that can image the full solar disk in seven extreme ultraviolet and three ultraviolet-visible wavelengths. The Extreme Ultraviolet Variability Experiment (EVE) collects time-correlated data on the activity of the Sun's corona. The Helioseismic and Magnetic Imager (HMI) enables study of pressure waves moving through the body of the Sun.

Control↗
NASA NTRS1998

Global Ultraviolet Imaging of the Aurora from Space

Global observation of the aurora by the Ultraviolet Imager (UVI) on the Polar spacecraft has provided both the benefit of placing ground and space-based observations in the context of auroral activity as well as the ability to make quantitative measurements of important parameters that characterize energy transfer to the ionosphere. The UVI images have provided simultaneously the timing of substorm onsets, the location of auroral boundaries, the polar cap area, and changes in the intensity of auroral activity at all local times. Increased accuracy in the measurement of energy flux and characteristic energy of the precipitating electrons in conjunction with auroral precipitation models are now available at high time resolution over many hours through the use of narrow-band far ultraviolet filters on the UVI. We will discuss how ultraviolet imaging of the aurora from space has provided fresh insight into processes such as substorm energy loading and deposition, substorm triggering, and solar wind control of substorm dynamics.

Brittnacher, M. J.↗
NASA NTRS1998

Global Ultraviolet Imaging of the Aurora from Space

Global observation of the aurora by the Ultraviolet Imager (UVI) on the Polar spacecraft has provided both the benefit of placing-ground and space-based observations in the context of auroral activity as well as the ability to make quantitative measurements of important parameters that characterize energy transfer to the ionosphere. The UVI images have provided simultaneously the the timing of substorm onsets, the location of auroral boundaries, the polar cap area, and changes in the intensity of aurora] activity at all local times. Increased accuracy in the measurement of energy flux and characteristic energy of the precipitating electrons in conjunction with auroral precipitation models are now available at high time resolution over many hours through the use of narrow-band far ultraviolet filters on the UVI. We will discuss how ultraviolet imaging of the aurora from space has provided fresh insight into processes such as substorm energy loading and deposition, substorm triggering, and solar wind control of substorm dynamics.

Brittnacher, M. J.↗
NASA NTRS1996

Passive Optical Sample Assembly (POSA-2) Space Flight Experiment

NASA Lewis Research Center's Electro-Physics Branch is participating in the POSA-2 Space Flight Experiment to assess the effects of low Earth orbit and spacecraft environment contamination on power system materials and surfaces. This experiment package will be flown for 1 year in low Earth orbit and will be returned to Earth for subsequent evaluation of optical and thermal properties. Representative samples of solar array blanket materials, solar dynamic reflector materials, thermal control coatings, and sapphire are included in the experiment package.

Source record↗
NASA NTRS2004

A practical six-degree of freedom solar sail dynamics model for optimizing solar sail trajectories with torque constraints

Controlled flight of a solar sail-propelled spacecraft ('sailcraft') is a six-degree-of-freedom dynamics problem. Current state-of-the-art tools that simulate and optimize the trajectories flown by sailcraft do not treat the full kinetic (i.e. force and torque-constrained) motion, instead treating a discrete history of commanded sail attitudes, and either neglecting the sail attitude motion over an integration timestep, or treating the attitude evolution kinematically with a spline or similar treatment. The present paper discusses an aspect of developing a next generation sailcraf trajectory designing optimization tool JPL, for NASA's Solar Sail Spaceflight Simulation Software (SS). The aspect discussed in an experimental approach to modeling full six-degree-of-freedom kinetic motion of a solar sail in a trajectory propagator. Early results from implementing this approach in a new trajectory propagation tool are given.

six-degree-of-freedom↗
NASA NTRS1980

A modern control approach to the design of the SPS control system

The structural dynamics of the solar power satellite were considered. The requirements on the vibration of the microwave antenna and the possibility of thermal induced vibration and severe structural-thermal interactions were considered. The possibility of using an active control system and modern control methods to mitigate structural problems is discussed.

Gran, R.↗
NASA NTRS1991

Control and dynamics of a flexible spacecraft during stationkeeping maneuvers

A case study of a spacecraft having flexible solar arrays is presented. A stationkeeping attitude control mode using both earth and rate gyro reference signals and a flexible vehicle dynamics modeling and implementation is discussed. The control system is designed to achieve both pointing accuracy and structural mode stability during stationkeeping maneuvers. Reduction of structural mode interactions over the entire mode duration is presented. The control mode using a discrete time observer structure is described to show the convergence of the spacecraft attitude transients during Delta-V thrusting maneuvers without preloading thrusting bias to the onboard control processor. The simulation performance using the three axis, body stabilized nonlinear dynamics is provided. The details of a five body dynamics model are discussed. The spacecraft is modeled as a central rigid body having cantilevered flexible antennas, a pair of flexible articulated solar arrays, and to gimballed momentum wheels. The vehicle is free to undergo unrestricted rotations and translations relative to inertial space. A direct implementation of the equations of motion is compared to an indirect implementation that uses a symbolic manipulation software to generate rigid body equations.

Liu, D.↗
NASA NTRS1990

Control/structure interactions of Freedom's solar dynamic modules

The purpose of this paper is to address potential control/structures interaction (CSI) problems of large flexible multibody structures in the presence of pointing and tracking requirements. A control approach is introduced for the simultaneous tracking and vibration control of multibody space structures. The application that is discussed is Space Station Freedom configured with solar dynamic (SD) modules. The SD fine-pointing and tracking requirements may necessitate controller frequencies above the structural natural frequencies of Freedom and the SD modules. It is well known that this can give rise to CSI problems if the controller is designed without due consideration given to the structural dynamics of the system. In this paper, possible CSI problems of Freedom's solar dynamic power systems are demonstrated using a simple lumped mass model. A NASTRAN model of Freedom developed at NASA Lewis is used to demonstrate potential CSI problems and the proposed tracking and vibration control approach.

Quinn, R. D.↗
NASA NTRS1984

Dynamics and control of orbiting flexible beams and platforms under the influence of solar radiation and thermal effects

Expressions for thermal deflections of uniform thin beams and plates exposed to solar heating are obtained as a function of the properties of the material and the solar incidence angle. The major effect of the solar radiation pressure interacting with the thermally deformed structure is found to give rise to disturbance moments on the structure. The thermal deformations of the structures are assumed to be within 0.1 percent of the characteristic length of the structure. With the assumed thermal deformations, the resulting uncontrolled transient responses of these geosynchronous orbiting structures to the solar radiation pressure induced disturbances are simulated. The resulting rigid modal oscillations are found to be an order of magnitude larger than for those cases previously considered in which only the solar radiation pressure effect on vibrating structures was treated. Modifications of control laws and/or the feedback gain values are considered in order to improve the transient response characteristics under the thermally induced disturbances.

Krishna, R.↗