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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 379 records · Page 21

On the shape and orientation control of an orbiting shallow spherical shell structure

The dynamics of orbiting shallow flexible spherical shell structures under the influence of control actuators was studied. Control laws are developed to provide both attitude and shape control of the structure. The elastic modal frequencies for the fundamental and lower modes are closely grouped due to the effect of the shell curvature. The shell is gravity stabilized by a spring loaded dumbbell type damper attached at its apex. Control laws are developed based on the pole clustering techniques. Savings in fuel consumption can be realized by using the hybrid shell dumbbell system together with point actuators. It is indicated that instability may result by not including the orbital and first order gravity gradient effects in the plant prior to control law design.

Bainum, P. M.↗

On the shape and orientation control of orbiting shallow spherical shell structure

The dynamics of orbiting shallow flexible spherical shell structures under the influence of control actuators was studied. Control laws are developed to provide both attitude and shape control of the structure. The elastic modal frequencies for the fundamental and lower modes are closely grouped due to the effect of the shell curvature. The shell is gravity stabilized by a spring loaded dumbell type damper attached at its apex. Control laws are developed based on the pole clustering techniques. Savings in fuel consumption can be realized by using the hybrid shell dumbbell system together with point actuators. It is indicated that instability may result by not including the orbital and first order gravity gradient effects in the plant prior to control law design. Previously announced in STAR as N82-17243

Bainum, P. M.↗

Novel Phases and Dynamics of Multi-orbital Mott Insulators

The goal of this project is to gain theoretical insight into magnetism in the presence of spin-orbit coupling (SOC) for multi-orbital Mott insulators. Inspired by the exact solution of the Kitaev model that harbors a quantum spin liquid with novel excitations and struck by its relevance for materials with anisotropic orbital interactions, the PI will explore various new classes of 4d and 5d transition metal oxides. Starting with all electron Hamiltonians, the PI will derive minimal magnetic models. The aim will be to understand the role played by orbital frustration, even in the absence of any geometric frustration, in creating orbitally ordered as well as spin-orbital liquid phases. Orbital frustration arises primarily from the directional or anisotropic nature of d-orbitals in contrast to the isotropic nature of the spin degree of freedom. These models will be investigated by a variety of theoretical and numerical methods, including exact diagonalization, mean field theories, density matrix renormalization group and quantum Monte Carlo methods. Testable predictions for three experiments: nuclear magnetic resonance (NMR) and resonant x-ray scattering (RXS) to probe orbital ordering and pump-probe experiments to probe quantum dynamics will test the validity of these models for materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Spacelab 2 Upper Atmospheric Modification experiment over Arecibo. I - Neutral gas dynamics

The Orbital Maneuvering Subsystem engines of the Space Shuttle were used to inject H2, CO2, H2O and other combustion products into the upper atmosphere over the Arecibo Observatory. Images of the airglow enhancements that resulted from chemical reactions between the exhaust gases and the F-layer plasma showed that the exhaust vapor trail came to rest 80 km downstream from the center of the burn. A computer simulation of the gas dynamics shows that the region of the burn was dominated by a 'snow plow' effect sweeping out a corridor in the atmosphere and collisionally heating the injected vapors.

Bernhardt, P. A.↗

Reduced-Dynamic Technique For Determination Of Orbits

Orbits determined more accurately than in dynamic or geometric method. Report discusses reduced-dynamic technique for use of signals from satellites in Global Positioning System (GPS) to determine orbit of satellite in low orbit around Earth. Formed from combination of dynamic and geometric (nondynamic) tracking techniques, and combines advantages of both to increase accuracy of estimated orbit under conditions in which neither clearly superior.

Wu, Sien-Chong↗

Analytical and experimental investigation of a 1/8-scale dynamic model of the shuttle orbiter. Volume 1: Summary report

A 1/8-scale structural dynamics model of the space shuttle orbiter was analyzed using the NASA Structural Analysis System (NASTRAN). Comparison of the calculated eigenvalues with preliminary test data for the unrestrained condition indicate that the analytical model was consistently stiffer, being about 20% higher in the first mode. The eigenvectors show reasonably good agreement with test data. A series of analytical and experimental investigations undertaken to resolve the discrepancy are described. Modifications in the NASTRAN model based upon these investigations resulted in close agreement for both eigenvalues and eigenvectors.

Mason, P. W.↗

The Solar Dynamics Observatory: Your On-Orbit Eye on the Sun

The Solar Dynamics Observatory (SDO) was launched on February 11, 2010 into the partly cloudy skies above Cape Canaveral, Florida. Over the next month SDO moved into a 28 degree inclined geosynchronous orbit at the longitude of the ground station in New Mexico. SDO is the first Space Weather Mission in NASA's Living With a Star Program. SDO's main goal is to understand and predict those solar variations that influence life on Earth and our technological systems. The SDO science investigations will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere as the solar wind, energetic particles, and variations in the solar irradiance. The SDO mission consists of three scientific investigations (AIA, EVE, and HMI), a spacecraft bus, and a dedicated Ka-band ground station to handle the 150 Mbps data flow. SDO continues a long tradition of NASA missions providing calibrated solar spectral irradiance data, in this case using multiple measurements of the irradiance and rocket underflights of the spacecraft. The other instruments on SDO will be used to explain and develop predictive models of the solar spectral irradiance in the extreme ultraviolet. Science teams at LMSAL, LASP, and Stanford are responsible for processing, analyzing, distributing, and archiving the science data. We will talk about the launch of SDO and describe the data and science it is providing to NASA.

Pesnell, W. Dean↗

Flight Dynamics Operations: Methods and Lessons Learned from Space Shuttle Orbit Operations

The Flight Dynamics Officer is responsible for trajectory maintenance of the Space Shuttle. This paper will cover high level operational considerations, methodology, procedures, and lessons learned involved in performing the functions of orbit and rendezvous Flight Dynamics Officer and leading the team of flight dynamics specialists during different phases of flight. The primary functions that will be address are: onboard state vector maintenance, ground ephemeris maintenance, calculation of ground and spacecraft acquisitions, collision avoidance, burn targeting for the primary mission, rendezvous, deorbit and contingencies, separation sequences, emergency deorbit preparation, mass properties coordination, payload deployment planning, coordination with the International Space Station, and coordination with worldwide trajectory customers. Each of these tasks require the Flight Dynamics Officer to have cognizance of the current trajectory state as well as the impact of future events on the trajectory plan in order to properly analyze and react to real-time changes. Additionally, considerations are made to prepare flexible alternative trajectory plans in the case timeline changes or a systems failure impact the primary plan. The evolution of the methodology, procedures, and techniques used by the Flight Dynamics Officer to perform these tasks will be discussed. Particular attention will be given to how specific Space Shuttle mission and training simulation experiences, particularly off-nominal or unexpected events such as shortened mission durations, tank failures, contingency deorbit, navigation errors, conjunctions, and unexpected payload deployments, have influenced the operational procedures and training for performing Space Shuttle flight dynamics operations over the history of the program. These lessons learned can then be extended to future vehicle trajectory operations.

Cutri-Kohart, Rebecca M.↗

Substorm phenomena and the uniqueness of the geostationary orbit for observation of dynamic processes in the magnetosphere

During the Spring equinox, both ATS-6 and ATS-5 were in geosynchronous orbit with a separation of about 11 deg longitude. A ground-based campaign was undertaken by Eather, Mende, and Judge to observe aurora at the foot of the ATS field line with a variety of instruments. Initial results support the injection boundary hypothesis of Mauk and McIlwain. Also during this period, the Cs-ion thrusters on both spacecraft were exercized in a deliberate attempt to control the spacecraft potential. Some success was achieved, and the presence of a sheath with a potential minimum about ATS-5 has been demonstrated (the sheath about ATS-6 is observed directly).

Deforest, S. E.↗

On protection of Freedom's solar dynamic radiator from the orbital debris environment. II - Further testing and analyses

Presented here are results of a test program undertaken to further define the response of the solar dynamic radiator to hypervelocity impact (HVI). Tests were conducted on representative radiator panels (under ambient, nonoperating conditions) over a range of velocity. Target parameters are also varied. Data indicate that analytical penetration predictions are conservative (i.e., pessimistic) for the specific configuration of the solar dynamic radiator. Test results are used to define the solar dynamic radiator reliability with respect to HVI more rigorously than previous studies. Test data, reliability, and survivability results are presented.

Rhatigan, Jennifer L.↗

On protection of Freedom's solar dynamic radiator from the orbital debris environment. Part 2: Further testing and analyses

Presented here are results of a test program undertaken to further define the response of the solar dynamic radiator to hypervelocity impact (HVI). Tests were conducted on representative radiator panels (under ambient, nonoperating conditions) over a range of velocity. Target parameters are also varied. Data indicate that analytical penetration predictions are conservative (i.e., pessimistic) for the specific configuration of the solar dynamic radiator. Test results are used to define the solar dynamic radiator reliability with respect to HVI more rigorously than previous studies. Test data, reliability, and survivability results are presented.

Rhatigan, Jennifer L.↗

Control and stability problems of remote orbital capture

The dynamics and control aspects of orbital capture of space objects were studied. Differential angular rates and orientation between the object and the grappler were used to investigate the effects of misalignment as well as stability and control. The control responses after capture are discussed. The feasibility of nulling combined spin and nutation of a typical satellite is demonstrated by a Lagrangian formulation to establish a baseline situation. A free-flying teleoperator (FFTO) with a dynamically unbalanced grappler is shown to be desirable because extremely adverse cyclic torques may be generated. A combined teleoperator-satellite system assuming misalignments during capture was dynamically analyzed. Related responses and stability evaluations are included.

Kaplan, M. H.↗