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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Ultrasonic Resonance Spectroscopy of Composite Rings for Flywheel Rotors

Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for utilization in the International Space Station. These composite material systems were investigated with a recently developed ultrasonic resonance spectroscopy technique. The system employs a swept frequency approach and performs a fast Fourier transform on the frequency spectrum of the response signal. In addition. the system allows for equalization of the frequency spectrum, providing all frequencies with equal amounts of energy to excite higher order resonant harmonics. Interpretation of the second fast Fourier transform, along with equalization of the frequency spectrum, offers greater assurance in acquiring and analyzing the fundamental frequency, or spectrum resonance spacing. The range of frequencies swept in a pitch-catch mode was varied up to 8 MHz, depending on the material and geometry of the component. Single and multilayered material samples, with and without known defects, were evaluated to determine how the constituents of a composite material system affect the resonant frequency. Amplitude and frequency changes in the spectrum and spectrum resonance spacing domains were examined from ultrasonic responses of a flat composite coupon, thin composite rings, and thick composite rings. Also, the ultrasonic spectroscopy responses from areas with an intentional delamination and a foreign material insert, similar to defects that may occur during manufacturing malfunctions, were compared with those from defect-free areas in thin composite rings. A thick composite ring with varying thickness was tested to investigate the full-thickness resonant frequency and any possible bulk interfacial bond issues. Finally, the effect on the frequency response of naturally occurring single and clustered voids in a composite ring was established.

Harmon, Laura M.↗
NASA NTRS2002

Erratum: Voyager Color Photometry of Saturn's Main Rings

We correct a calibration error in our earlier analysis of Voyager color observations of Saturn's main rings at 14 deg phase angle and present thoroughly revised and reanalyzed radial profiles of the brightness of the main rings in Voyager G, V, and UV filters, and ratios of these brightnesses. These results are consistent with more recent HST results at 6 deg phase angle, once allowance is made for plausible phase reddening of the rings. Unfortunately, the Voyager camera calibration factors are simply not sufficiently well known for a combination of the Voyager and HST data to be used to constrain the phase reddening quantitatively. However, some interesting radial variations in reddening between 6-14 deg phase angles are hinted at. We update a ring-and-satellite color vs. albedo plot from Cuzzi and Estrada in several ways. The A and B rings are still found to be in a significantly redder part of color-albedo space than Saturn's icy satellites.

Estrada, Paul R.↗
NASA NTRS1998

Detection of centimeter-sized meteoroid impact events in Saturn's F ring

Voyager images reveal that three prominent clumps in Saturn's F ring were short-lived, appearing rapidly and then spreading and decaying in brightness over periods of approximately 2 weeks. These features arise from hypervelocity impacts by approximately 10-centimeter meteoroids into F ring bodies. Future ring observations of these impact events could constrain the centimeter-sized component of the meteoroid population, which is otherwise unmeasurable but plays an important role in the evolution of rings and surfaces in the outer solar system. The F ring's numerous other clumps are much longer lived and appear to be unrelated to impacts.

Flight Experiment↗
NASA NTRS2005

Cassini CIRS Observations of Saturn's Rings

In the spring of 2004, during Cassini s approach to Saturn, the Cassini Composite Infrared Spectrometer (CIRS) began acquiring thermal spectra of Saturn s rings. CIRS is a Fourier-transform spectrometer that measures radiation in the thermal infrared from 7 microns to 1 millimeter (1400 to 10/cm). CIRS has a set of 21 detectors, consisting of two 1 x 10 linear arrays with a pixel size of 0.3 mrad, and one 4 mrad circular detector. Just after the completion of the Saturn orbit insertion (SOI) burn, CIRS performed an especially high spatial resolution scan of portions of Saturn s A, B and C rings. In the months following SOI, additional ring measurements have been obtained, including radial scans on the lit and unlit sides of the rings, and azimuthal scans across the shadowed regions of the A, B and C rings.

Spilker, Linda J.↗
NASA NTRS2005

The Second Ring-Moon System of Uranus: Discovery and Dynamics

Deep exposures of Uranus taken with the Hubble Space Telescope reveal two small moons and two faint rings. All orbit outside of Uranus's previously known (main) ring system, but interior to the large, classical moons. The outer new moon, U XXVI Mab, orbits at roughly twice the radius of the main rings and shares its orbit with a dust ring. The second moon, U XXVII Cupid, orbits just interior to the satellite Belinda. A second ring falls between the orbits of Portia and Rosalind, in a region with no known source bodies. Collectively, these constitute a densely-packed, rapidly varying and possibly unstable dynamica1 system.

Showalter, M. R.↗
NASA NTRS1991

Monlithic nonplanar ring oscillator and method

A monolithic nonplanar ring oscillator having an optically isotropic solid-state laser body for propagating laser radiation about a nonplanar ring path internal to the laser body is disclosed. The monolithic laser body is configured to produce a 2N reflection nonplanar ring light path, where N is an integer greater than or equal to 2, comprising 2N-1 total internal reflections and one reflection at a coupler in a single round trip. Undirectional traveling wave oscillation of the laser is induced by the geometry of the nonplanar ring path together with the effect of an applied magnetic field and partial polarizer characteristics of the oblique reflection from the coupler. The 6-reflection nonplanar ring oscillator makes possible otpimal unidirectional oscillation (low loss for the oscillating direction of propagation and, simultaneously high loss for the nonoscillating direction of propagation) in monolithic NPROs using materials with index of refraction smaller than the square root of 3, for example, laser glass.

Nilsson, Alan C.↗
NASA NTRS2008

Vacuum Packaging of MEMS With Multiple Internal Seal Rings

A proposed method of design and fabrication of vacuum-packaged microelectromechanical systems (MEMS) and of individual microelectromechanical devices involves the use of multiple internal seal rings (MISRs) in conjunction with vias (through holes plated with metal for electrical contacts). The proposed method is compatible with mass production in a wafer-level fabrication process, in which the dozens of MEMS or individual microelectromechanical devices on a typical wafer are simultaneously vacuum packaged by bonding a capping wafer before the devices are singulated (cut apart by use of a dicing saw). In addition to being compatible with mass production, the proposed method would eliminate the need for some complex and expensive production steps and would yield more reliable vacuum seals. Conventionally, each MEMS or individual microelectromechanical device is fabricated as one of many identical units on a device wafer. Vacuum packaging is accomplished by bonding the device wafer to a capping wafer with metal seal rings (one ring surrounding each unit) that have been formed on the capping wafer. The electrical leads of each unit are laid out on what would otherwise be a flat surface of the device wafer, against which the seal ring is to be pressed for sealing. The resulting pattern of metal lines and their insulating oxide coverings presents a very rough and uneven surface, upon which it is difficult to pattern the sealing metal. Consequently, the seal is prone to leakage unless additional costly and complex planarization steps are performed before patterning the seal ring and bonding the wafers.

Hayworth, Ken↗
NASA NTRS2010

Stacked Corrugated Horn Rings

This Brief describes a method of machining and assembly when the depth of corrugations far exceeds the width and conventional machining is not practical. The horn is divided into easily machined, individual rings with shoulders to control the depth. In this specific instance, each of the corrugations is identical in profile, and only differs in diameter and outer profile. The horn is segmented into rings that are cut with an interference fit (zero clearance with all machining errors biased toward contact). The interference faces can be cut with a reverse taper to increase the holding strength of the joint. The taper is a compromise between the interference fit and the clearance of the two faces during assembly. Each internal ring is dipped in liquid nitrogen, then nested in the previous, larger ring. The ring is rotated in the nest until the temperature of the two parts equalizes and the pieces lock together. The resulting assay is stable, strong, and has an internal finish that cannot be achieved through other methods.

Sosnowski, John B.↗
NASA NTRS2010

On the Role of Global Magnetic Field Configuration in Affecting Ring Current Dynamics

Plasma and field interaction is one important aspect of inner magnetospheric physics. The magnetic field controls particle motion through gradient, curvature drifts and E cross B drift. In this presentation, we show how the global magnetic field affects dynamics of the ring current through simulations of two moderate geomagnetic storms (20 November 2007 and 8-9 March 2008). Preliminary results of coupling the Comprehensive Ring Current Model (CRCM) with a three-dimensional plasma force balance code (to achieve self-consistency in both E and B fields) indicate that inclusion of self-consistency in B tends to mitigate the intensification of the ring current as other similar coupling efforts have shown. In our approach, self-consistency in the electric field is already an existing capability of the CRCM. The magnetic self-consistency is achieved by computing the three-dimensional magnetic field in force balance with anisotropic ring current ion distributions. We discuss the coupling methodology and its further improvement. In addition, comparative studies by using various magnetic field models will be shown. Simulation results will be put into a global context by analyzing the morphology of the ring current, its anisotropy and characteristics ofthe interconnected region 2 field-aligned currents.

Zheng, Y.↗
NASA NTRS2003

Grease-Resistant O Rings for Joints in Solid Rocket Motors

There is a continuing effort to develop improved O rings for sealing joints in solid-fuel rocket motors. Following an approach based on the lessons learned in the explosion of the space shuttle Challenger, investigators have been seeking O-ring materials that exhibit adequate resilience for effective sealing over a broad temperature range: What are desired are O rings that expand far and fast enough to maintain seals, even when metal sealing surfaces at a joint move slightly away from each other shortly after ignition and the motor was exposed to cold weather before ignition. Other qualities desired of the improved O rings include adequate resistance to ablation by hot rocket gases and resistance to swelling when exposed to hydrocarbon-based greases used to protect some motor components against corrosion. Five rubber formulations two based on a fluorosilicone polymer and three based on copolymers of epichlorohydrin with ethylene oxide were tested as candidate O-ring materials. Of these, one of the epichlorohydrin/ethylene oxide formulations was found to offer the closest to the desired combination of properties and was selected for further evaluation.

Harvey, Albert R.↗
NASA NTRS2012

Micro Ring Grating Spectrometer with Adjustable Aperture

A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

Park, Yeonjoon↗
NASA NTRS2012

An Eccentric Debris Ring Around the Nearby G Star HD 202628

A new debris disk has been imaged in visible light around the G2V star HD 202628 using the STIS coronagraph on the Hubble Space Telescope. The broad ring is inclined 61 deg from face-on and extends as far as 260 AU from the star. The star is noticeably displaced from the apparent ring center by 20 AU. The ring inner edge is sharp and well-described by an inclined ellipse with a= 158 AU, e= 0.18, and the star at one focus. These properties are similar to the Fomalhaut debris ring and likewise suggest ring sculpting by a planetary-mass companion with semi-major axis approx.> 100 AU. The presence of a planet so widely separated from a solar-type star poses a new challenge for planet formation theories.

Stapelfeldt, Karl R.↗
NASA NTRS2014

The Vibration Ring

The vibration ring was conceived as a driveline damping device to prevent structure-borne noise in machines. It has the appearance of a metal ring, and can be installed between any two driveline components like an ordinary mechanical spacer. Damping is achieved using a ring-shaped piezoelectric stack that is poled in the axial direction and connected to an electrical shunt circuit. Surrounding the stack is a metal structure, called the compression cage, which squeezes the stack along its poled axis when excited by radial driveline forces. The stack in turn generates electrical energy, which is either dissipated or harvested using the shunt circuit. Removing energy from the system creates a net damping effect. The vibration ring is much stiffer than traditional damping devices, which allows it to be used in a driveline without disrupting normal operation. In phase 1 of this NASA Seedling Fund project, a combination of design and analysis was used to examine the feasibility of this concept. Several designs were evaluated using solid modeling, finite element analysis, and by creating prototype hardware. Then an analytical model representing the coupled electromechanical response was formulated in closed form. The model was exercised parametrically to examine the stiffness and loss factor spectra of the vibration ring, as well as simulate its damping effect in the context of a simplified driveline model. The results of this work showed that this is a viable mechanism for driveline damping, and provided several lessons for continued development.

Asnani, Vivake M.↗
NASA NTRS2016

Exocometary Gas in the HD 181327 Debris Ring

An increasing number of observations have shown that gaseous debris discs are not an exception. However, until now, we only knew of cases around A stars. Here we present the first detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with radiative transfer calculations, we study the dust and CO mass distribution. We find the dust is distributed in a ring with a radius of 86.0 +/- 0.4 au and a radial width of 23.2 +/- 1.0 au. At this frequency, the ring radius is smaller than in the optical, revealing grain size segregation expected due to radiation pressure. We also report on the detection of low-level continuum emission beyond the main ring out to approximately 200 au. We model the CO emission in the non-local thermodynamic equilibrium regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging between 1.2 x 10(exp -6) solar mass and 2.9 x 10(exp -6) solar mass, depending on the gas kinetic temperature and collisional partners densities. The CO densities and location suggest a secondary origin, i.e. released from icy planetesimals in the ring. We derive a CO+CO2 cometary composition that is consistent with Solar system comets. Due to the low gas densities, it is unlikely that the gas is shaping the dust distribution.

exocometary gas↗
NASA NTRS2019

A Persistent, Large-Scale, and Ordered Electrodynamic Connection Between Saturn and Its Main Rings

Auroral hiss emissions are ubiquitous in planetary magnetospheres, particularly in regions where electric current systems are present. They are generally diagnostic of electrodynamic coupling between conductive bodies, thus making auroral and moon-connected magnetic field lines prime locations for their detection. However, the role of Saturn's rings as a dynamic conductive body has been elusive and of great interest to the community. Cassini's Grand Finale orbits afforded a unique opportunity to directly sample magnetic field lines connected to the main rings. Here we provide strong evidence for the persistent and organized presence of auroral hiss demonstrably associated with the main rings. This is in contrast to recent observations suggesting that Saturn's rings may be barriers to field-aligned currents. Our results provide a new view of Saturn's rings as a dynamic system that is in continuous and ordered electrodynamic coupling with the planet.

Sulaiman, A. H.↗
NASA NTRS2019

A Titan gravity-assist technique for ballistic tours skimming over the rings of Saturn

A novel type of Titan-flyby orbits featuring passes of the Saturn rings at close range has been recently discovered. The purpose of this study is to explore the trajectory design space and assess the applicability of such orbits to the design of a Saturn Ring Tour mission concept. A set of initial conditions required to start a tour of the rings is first determined and a flyby sequence to maximize the science observation time over desired ring regions in terms of range distance, relative velocity and duration is then selected. To demonstrate the potential of this technique, a sample high-fidelity ballistic ring tour is detailed.

Tiscareno, Matthew↗
NASA NTRS2024

SOFIA/HAWC+ Far-Infrared Polarimetric Large Area CMZ Exploration Survey II: Detection of a Magnetized Dust Ring in the Galactic Center

We present the detection of a magnetized dust ring (M0.8–0.2)in the central molecular zone (CMZ) of the Galactic center. The results presented in this paper utilize the first data release of the Far-Infrared Polarimetric Large Area CMZE mission (FIREPLACE) survey (i.e., Paper I of this series). The FIREPLACE survey is a 214μm polarimetric survey of the Galactic center using the SOFIA/HAWC+ telescope. The M0.8–0.2 ring is a region of gas and dust that has a circular morphology with a central depression. The dust polarization in the M0.8–0.2 ring implies a curved magnetic field that traces the ring-like structure of the cloud. We posit an interpretation in which an expanding shell compresses and concentrates the ambient gas and magnetic field. We argue that this compression results in strengthening of the magnetic field, as we infer from the observations toward the interior of the ring.

Dust continuum emmision↗
DOE OSTI2020

Dual magnetic phase material rings for AC electric machines

An AC electric machine that includes a dual magnetic phase material ring is disclosed. The AC electric machine includes a stator assembly and a rotor assembly positioned within the stator assembly and configured to rotate relative thereto, the rotor assembly comprising a rotor core including a stack of rotor laminations that collectively form the rotor core, the rotor core including a plurality of rotor poles separated by gaps therebetween. The AC electric machine also includes a dual magnetic phase material ring positioned about the stack of rotor laminations, the dual magnetic phase material ring comprising a first ring portion comprising a magnetic portion and a second ring portion comprising a non-magnetic portion.

42 ENGINEERING↗