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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Bending waves and the structure of Saturn's rings

The surface mass density profiles at four locations within Saturn's rings are calculated using Voyager spacecraft images of spiral bending waves. The identification of a feature in Saturn's outer B ring as Mimas's 4:2 bending waves is confirmed, and these 4:2 waves are analyzed to determine the surface density in Saturn's B ring. A fourth set of bending waves, the Mimas 7:4, located in the inner A ring, is identified and analyzed. Mimas's 5:3 and 8:5 bending waves, observed in the middle and outer A ring respectively, are reanalyzed.

Lissauer, J. J.↗
NASA NTRS1986

Structure of the Uranian rings. II - Ring orbits and widths

A square-well model was used to calculate the midtimes, widths and optical depths at visible and IR wavelengths of the nine Uranian rings based on 13 occultation measurements from 1977-1983. Many of the measurement campaigns contained data from repeated crossings. An improved kinematical model is developed for the ring system, noting that the gamma and delta rings were confirmed to depart from Keplerian ellipses. Upper limits are calculated for the sizes of shepherd satellites of various potential densities. The ring width determinations demonstrate the existence of significant width perturbations in the rings, which all displayed particle shadowing.

French, R. G.↗
NASA NTRS1991

Resonance structures in Saturn's rings probed by radio occultation. I - Methods and examples

Individual and comparative analyses are conducted for 29 of the wavelike features revealed by optical depth profiles of Saturn's rings; of these, 18 are in Ring A, one is in Ring B, and 10 are in Ring C. Only 20 of these were identifiable with known resonances, and all eight of the unexplained wave features are in Ring C. For 14 weak density waves in Ring A, a linear density wave theory modeling of the waveform near resonance yields independent estimates of the surface mass density together with reliable estimates of resonance location.

Rosen, Paul A.↗
NASA NTRS1986

Nonlinear density waves in planetary rings

The steady-state structure of planetary rings in the presence of density waves at the Lindblad resonances of a satellite is indicated. The study is based on the dispersion relation and damping rate for nonlinear density waves, derived by Shu et al. (1985) and by Borderies, Goldreich, and Tremaine (1985). It is shown that strong density waves lead to an enhancement of the background surface density in the wave zone.

Borderies, Nicole↗
DOE OSTI2021

Lithium calix[4]arenes: structural studies and use in the ring opening polymerization of cyclic esters

We have structurally characterized a number of lithiated calix[4]arenes, where the bridge in the calix[4]arene is thia (–S–, L S H 4 ), sulfinyl (–SO–, L SO H 4 ), sulfonyl (–SO 2 –, L SO2 H 4 ), dimethyleneoxa (–CH 2 OCH 2 –, L COC H 4 ) or methylene (–CH 2 –, LH 4 ). In the case of L 4S H 4 , interaction with LiO t Bu led to the isolation of the complex [Li 8 (L 4S ) 2 (THF) 4 ]·5THF ( 1 ·5THF), whilst similar interaction of L 4SO H 4 led to the isolation of [Li 6 (L 4SO H) 2 (THF) 2 ]·5(THF) ( 2 ·5THF). Interestingly, the mixed sulfinyl/sulfonyl complexes [Li 8 (calix[4]arene(SO)(SO 2 )(SO 1.68 ) 2 ) 2 (THF) 6 ]·8(THF) ( 3 ·8THF) and [Li 5 Na(L SO/3SO2 H) 2 (THF) 5 ]·7.5(THF) ( 4 ·7.5(THF) have also been characterized. Interaction of LiO t Bu with L SO2 H 4 and L COC H 4 afforded [Li 5 L 4SO2 (OH)(THF) 4 ]·2THF ( 5 ·2THF) and [Li 6 (L COC ) 2 (HO t Bu) 2 ]·0.78THF·1.22hexane ( 6 ·0.78THF·1.22hexane), respectively. In the case of LH 4 , reaction with LiO t Bu in THF afforded a monoclinic polymorph [LH 2 Li 2 (thf)(OH 2 ) 2 ]·3THF ( 7 ·3THF) of a known triclinic form of the complex, whilst reaction of the de-butylated analogue of LH 4 , namely de-BuLH 4 , afforded a polymeric chain structure {[Li 5 (de-BuL)(OH)(NCMe) 3 ]·2MeCN} n ( 8 ·2MeCN). For comparative catalytic studies, the complex [Li 6 (L Pr ) 2 (H 2 O) 2 ]·hexane ( 9 hexane), where L Pr2 H 2 = 1,3-di- n -propyloxycalix[4]areneH 2 , was also prepared. The molecular crystal structures of 1–9 are reported, and their ability to act as catalysts for the ring opening (co-)/polymerization (ROP) of the cyclic esters ε-caprolactone, δ-valerolactone, and rac -lactide has been investigated. In most of the cases, complex 6 outperformed the other systems, allowing for higher conversions and/or greated polymer M n .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Optical and Mechanical Properties of Glass Blown In Vacuo

Theoretically, the strength of glass processed in vacuum should be higher due to outgassing of contaminants normally present in the glass, such as bulk water in the form of OH bonds that tends to weaken the glass structure. In this research, small discs of a few types of glass have been subjected to various temperatures for extended periods of time in vacuum. Their strength was then tested using a standard flexure technique, facilitated by a custom-designed test fixture, and the results were compared to glass tested in air using the same fixture. The purpose of the glass blowing investigation was to prove the basic feasibility of a high-level concept for in-space manufacture of optical elements. The central requirement was that the glass bubble had to be blown into a support structure such that the bubble could be handled by manipulation of the structure. The blown bubble attached itself to a mullite ring geometrically and mechanically, as a demonstration in the initial experiments described here, by expanding through and around it. The vacuum system used was custom made, as were most of the components of the system, such as the heating element, the glass and ring support structure, and the gas inlet system that provided the pressure needed to blow the glass.

Manning, andrew↗
NASA NTRS1981

Moonlets in Saturn's rings

The brightness structure within Cassini's division in Saturn's rings is explained in terms of perturbations produced by moonlets embedded within an optically thin disk of smaller ring particles. The moonlets exert gravitational torques on neighboring ring particles and create gaps; diffusion acts to fill the gaps. A new explanation is offered for the inner edge of the Cassini division being located at the 2:1 resonance with Mimas.

Lissauer, J. J.↗
NASA NTRS1986

Structure and evolution of Saturn's rings

It is noted that many Voyager observations on the structure and evolution of Saturn's rings remain largely unexplained. The variation of ring thickness and particle size with composition may be partly explained by the input of density waves in the 'heating' of such rings as the outer A ring; in addition, the particles appear to resemble Weidenschilling et al.'s (1984) 'ephemeral bodies' rather than chunks of ice. It is suggested that many current difficulties may be resolved by positing that at least ring A is young, having been created by the destruction of one of the ring moons.

Esposito, L. W.↗
DOE OSTI2022

A kinematic excess in the annular gap and gas-depleted cavity in the disc around HD 169142

ABSTRACT We present ALMA band 6 images of the 12CO, 13CO, and C18O J = 2-1 line emissions for the circumstellar disc around HD 169142, at ∼8 au spatial resolution. We resolve a central gas-depleted cavity, along with two independent near-symmetric ring-like structures in line emission: a well-defined inner gas ring [∼25 au] and a second relatively fainter and diffuse outer gas ring [∼65 au]. We identify a localized super-Keplerian feature or vertical flow with a magnitude of ∼75 ms−1 in the 12CO map. This feature has the shape of an arc that spans azimuthally across a position angle range of −60° to 45° and radially in between the B1[26au] and B2[59au] dust rings. Through reconstruction of the gas surface density profile, we find that the magnitude of the background perturbations by the pressure support and self-gravity terms are not significant enough to account for the kinematic excess. If of planetary origin, the relative depletion in the gas-density profile would suggest a 1 MJ planet. In contrast, the central cavity displays relatively smooth kinematics, suggesting either a low-mass companion and/or a binary orbit with a minimal vertical velocity component.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

Photoionization and ion cyclotron resonance studies of the ion chemistry of ethylene oxide

The formation of the ethylene oxide molecular ion and its subsequent ion-molecule reactions leading to the products C2H5O(+) and C3H5O(+) have been studied using time-resolved photoionization mass spectroscopy, ion cyclotron resonance spectroscopy, and photoelectron spectroscopy. An examination of the effects of internal energy on reactivity shows that the ratio of C3H5O(+) to C2H5O(+) increases by an order of magnitude with a single quantum of vibrational energy. The formation of (C2H4O/+/)-asterisk in a collision-induced isomerization is found which yields a ring-opened structure by C-C bond cleavage. The relaxed ring-opened C2H4O(+) ion reacts with neutral ethylene oxide by CH2(+) transfer to yield an intermediate product ion C3H6O(+) which gives C3H5O(+) by loss of H.

Corderman, R. R.↗
DOE OSTI2024

Thermochemical Data for Furan-based Monomer Candidates for Frontal Ring-Opening Metathesis Polymerization (FROMP)

This dataset includes 471 furan-based monomer candidates for frontal ring-opening metathesis polymerization (FROMP) and relevant thermochemistry as calculated with density functional theory (DFT). The monomer candidates were combinatorically enumerated using Diels-Alder reactions of furan derivatives as dienes and four types of dienophiles (alkenes, alkynes, allenes, and benzynes). Common substituents were enumerated for the dienophile classes, and methyl substitution on the diene was explored. We used the SMILES arbitrary target specification (SMARTS) language to produce monomers and ring-opened structures from diene and dienophile precursor SMILES, and we studied the ring-opening reaction using a homodesmotic equation with ethene. RDKit conformers were initially generated from SMILES, then optimized with GFN2-xTB. The two conformers lowest in energy were then optimized with DFT using the wb97x-D3 functional, def2-TZVP basis set, and def2/J auxiliary basis set. Gibbs free energy corrections were obtained through frequency calculations. Structures with imaginary frequencies below -50 cm^{-1} were excluded from this work, and smaller imaginary modes were flipped to be positive for free energy calculations. Modes below 50 cm^{-1} were treated with the modified rigid rotor approximation, and all thermochemical values were calculated at T=200C. The CSV file contains the monomer SMILES, the free energy of reaction for Diels-Alder addition (G_DA_200), and the enthalpy of the ring-opening reaction (H_RO_200). All energies are given in kcal/mol. An interactive HTML is also included to visualize the monomers in this dataset.

Chua, Lauren↗
DOE OSTI2021

Aggregation of solutes in bosonic versus fermionic quantum fluids

Quantum fluid droplets made of helium-3 ( 3 He) or helium-4 ( 4 He) isotopes have long been considered as ideal cryogenic nanolabs, enabling unique ultracold chemistry and spectroscopy applications. The droplets were believed to provide a homogeneous environment in which dopant atoms and molecules could move and react almost as in free space but at temperatures close to absolute zero. Here, we report ultrafast x-ray diffraction experiments on xenon-doped 3 He and 4 He nanodroplets, demonstrating that the unavoidable rotational excitation of isolated droplets leads to highly anisotropic and inhomogeneous interactions between the host matrix and enclosed dopants. Superfluid 4 He droplets are laced with quantum vortices that trap the embedded particles, leading to the formation of filament-shaped clusters. In comparison, dopants in 3 He droplets gather in diffuse, ring-shaped structures along the equator. The shapes of droplets carrying filaments or rings are direct evidence that rotational excitation is the root cause for the inhomogeneous dopant distributions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Application of the Collision-Imparted Velocity Method for Analyzing the Responses of Containment and Deflector Structures to Engine Rotor Fragment Impact

An approximate analysis, termed the Collision Imparted Velocity Method (CIVM), was employed for predicting the transient structural responses of containment rings or deflector rings which are subjected to impact from turbojet-engine rotor burst fragments. These 2-d structural rings may be initially circular or arbitrarily curved and may have either uniform or variable thickness; elastic, strain hardening, and strain rate material properties are accommodated. This approximate analysis utilizes kinetic energy and momentum conservation relations in order to predict the after-impact velocities of the fragment and the impacted ring segment. This information is then used in conjunction with a finite element structural response computation code to predict the transient, large deflection responses of the ring. Similarly, the equations of motion for each fragment are solved in small steps in time. Also, some comparisons of predictions with experimental data for fragment-impacted free containment rings are presented.

Collins, T. P.↗
NASA NTRS2015

Combined Structural and Compositional Evolution of Planetary Rings Due to Micrometeoroid Impacts and Ballistic Transport

We introduce improved numerical techniques for simulating the structural and compositional evolution of planetary rings due to micrometeoroid bombardment and subsequent ballistic transport of impact ejecta. Our current, robust code is capable of modeling structural changes and pollution transport simultaneously over long times on both local and global scales. In this paper, we describe the methodology based on the original structural code of Durisen et al. (1989, Icarus 80, 136-166) and on the pollution transport code of Cuzzi and Estrada (1998, Icarus 132, 1-35). We provide demonstrative simulations to compare with, and extend upon previous work, as well as examples of how ballistic transport can maintain the observed structure in Saturn's rings using available Cassini occultation optical depth data. In particular, we explicitly verify the claim that the inner B (and presumably A) ring edge can be maintained over long periods of time due to an ejecta distribution that is heavily biased in the prograde direction through a balance between the sharpening effects of ballistic transport and the broadening effects of viscosity. We also see that a "ramp"-like feature forms over time just inside that edge. However, it does not remain linear for the duration of the runs presented here unless a less steep ejecta velocity distribution is adopted. We also model the C ring plateaus and find that their outer edges can be maintained at their observed sharpness for long periods due to ballistic transport. We hypothesize that the addition of a significant component of a retrograde-biased ejecta distribution may help explain the linearity of the ramp and is probably essential for maintaining the sharpness of C ring plateau inner edges. This component would arise for the subset of micrometeoroid impacts which are destructive rather than merely cratering. Such a distribution will be introduced in future work.

Cassini↗
NASA NTRS1987

The production of braids in Saturn's F ring

The braided structure noted in Voyager images of the Saturn F ring is presently addressed by two models. In the first, the pattern is generated by a narrow and initially uniform ring's passing of a nearby satellite, followed by an embedded moonlet gravitational acceleration-induced doubling back so that trajectories of the ring particles traverse one end of the classic horseshoe orbit. In the second model, the F ring is composed of two separated strands before the Moon's passage, so that a long braided pattern can be generated by the subsequent drift in relative phase; the embedded moonlet is thereby obviated.

Lissauer, Jack J.↗