Baseline Mechanical Testing Characterization
This poster shows the performance of 5KN and 50KN proving rings based on their historical verification data collected following ASTM E4 standards.
2022 Intern Poster Session↗
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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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Silver-base ternary alloy proves superior for slip ring lead wires
Slip ring lead wires composed of ternary alloys of silver, have high electrical conductivity, a tensile strength of at least 30,000 psi, high ductility, and are solderable and weldable. An unexpected advantage of these alloys is their resistance to discoloration on heating in air.
Ernst, R. H.↗
Experimental assessment of advanced Stirling component concepts
The results of an experimental assessment of some advanced Stirling engine component concepts are presented. High performance piston rings, reciprocating oil scrapers and heat pipes with getters and with mechanical couplings were tested. The tests yielded the following results: (1) Bonded, split, pumping piston rings, in preliminary testing, proved a promising concept, exhibiting low leakage and friction losses. Solid piston rings proved impractical in view of their sensitivity to the operating temperature; (2) A babbit oil scraper in a compliant housing performed well in atmospheric endurance testing. In pressurized tests the scraper did not perform well as a containment seal. The latter tests suggest modifications which may adapt Ti successfully to that application; and (3) Heat pipe endurance tests indicated the adequacy of simple, inexpensive fabrication and filling procedures. Getters were provided to increase the tolerance of the heat pipes to the presence of air and commercially available couplings were demonstrated to be suitable for heat pipe application. In addition to the above tests, the program also included a design effort for a split shaft applicable to a swashplate driven engine with a pressurized crank-case. The design is aimed, and does accomplish, an increase in component life to more than 10,000 hours.
Ziph, B.↗
The Structure of the Uranian Rings and the Search for Rings Around Neptune
The nine narrow rings of Uranus, presently the only confirmed features of this system, have been observed with the diffraction-limited resolution (3.5 km) of ground-based occultations since their discovery in 1977. These data have been used to establish an orbit model, from which the five Keplerian orbit parameters for each ring, the pole of the mean ring plane, and the gravitational harmonic coefficients J sub 2 and J sub 4 have been determined. The rings are typically a few kilometers wide with eccentricities of about 0.001 and inclinations of a few hundredths of a degree, although a few have no measurable eccentricity or inclination. Interesting Voyager investigations would include probing the structure of the rings at higher spatial resolution, searching for new rings in the system (including inter-ring material), locating the postulated shepherd satellites, and searching for satellites inside the orbit of Miranda that might have dynamical influence on the rings. The high precision (approx 2 km) of the ring orbits might prove useful for spacecraft navigation. For Neptune, occultation searches have revealed no rings to a limit of a few hundreths optical depth, within a few hundred kilometers from the top of the planet's atmosphere (for equatorial rings).
Elliot, J. L.↗
Echo mapping of active galactic nuclei broad-line regions: Fundamental algorithms
We formulate and test a series of algorithms for echo mapping the emission-line regions near active galactic nuclei from measurements of correlated variability in their line and continuum light curves. The linear regularization method (LRM) employs a direct inversion of evenly spaced light-curve data, with a regularization parameter that can be used to control the trade-off between noise and resolution. Matrix formulas express the formal solution as well as its variance and covariance in terms of uncertainties in the measurements. Unlike the maximum-entropy method (MEM), LRM applies to kernels with both positive and negative values, but the results are somewhat limited by ringing effects. A positivity constraint proves effective in controlling the ringing. MEM combines regularization and positivity in a natural way, but similar results are also found using positivity constraints with nonentropic regularization functions. Direct inversions of unevenly sampled light curves require interpolating the noisy data. In this case better results are found by solving for both the continuum light curve and kernel function in a simultaneous fit to the data. Our conclusion is that while echo mapping currently gives ambiguous results, the algorithms are not the limiting factor. Progress depends on efforts to increase the accuracy and completeness of sampling of the observed light curves.
Vio, Roberto↗
Aperture synthesis CO observations of the inner disk of NGC 1068
NGC 1068 is probably the nearest galaxy with both a high rate of star formation and a high luminosity active nucleus. About one-half of the total IR luminosity originates in a disk approximately 30 seconds in size, which has been taken as evidence for a high rate of massive star formation (Telesco et al. 1984). Previous CO line observations have shown the existence of a ring at the outer boundary of the inner disk (Myers and Scoville 1987). Although these observations have proved that this ring is extremely rich in molecular gas (as suggested by Scoville et al. 1983), the angular resolution (approx. 6 seconds) was not high enough to resolve its structure. New aperture synthesis observations of the CO (J=1 to 0) emission in the inner disk of NGC 1068 have been carried out with the Owens Valley Radio Observatory (OVRO) mm Interferometer. The new receivers installed for the 88/89 season have allowed researchers to obtain a high sensitivity map of the CO emission. The molecular cloud ring has been resolved and continuum as well as line emission from the nucleus of the galaxy have been detected.
Planesas, P.↗
The ring arcs of Neptune
After the corotation resonance with an exterior satellite proved inapplicable to the Neptune ring arc confinement, a search for other mechanisms settled on the possible influence of Neptune's magnetic field. The areas of greater optical depth around the ring are much dustier than the low optical depth regions. These particles reside in a plasma; therefore, they must carry some charge. The components of Neptune's magnetic field on the equator at the radius of the ring arcs as a function of Neptunian longitude are shown. The components are those of an offset tilted dipole model. Although the dipole model is probably not a good approximation so close to the planet, the magnitude of the field that is given is probably close to the actual value. The possible importance of the magnetic field on the smallest particles in the ring is indicated by the ratio of the magnetic field on the smallest particles in the ring is indicated by the ratio of the magnetic force to the central gravitation attraction with the field strength of B = 0.01 gauss at the ring distance. A preferred position in the orbit for magnetically perturbed particles seems to require a commensurability between the rotation of the planet and the motion of the particle in the orbit. The period of rotation is assumed to be that of the radio bursts at 16.11 hours. However, without a model for the radio emission, one cannot be absolutely sure. Jupiter's decametric radiation depends on Io's orbital position as well as the rotation, so a synodic periodicity might be appropriate. But the latter radiation is highly directed, whereas Neptune's was seen all along the spacecraft trajectory on the 16.11 hour schedule, i.e., with no shifts in phase relative to a fixed longitude on the planet. The ring orbital period is 10.536 hours which is not commensurate with the rotation period. If the 16.11 hours is interpreted as a synodic period between the rotation and a satellite motion, the closest rotation periods to 16 hours are 15.9 hours if the satellite is 1989N4 and 18.2 hours if the satellite is Triton. The former is near a 3:2 resonance with the ring particle motion. The problem deserves some more thought before a possible herding of small particles by the magnetic field is abandoned.
Peale, S. J.↗
Wireless Inductive Power Device Suppresses Blade Vibrations
Vibration in turbomachinery can cause blade failures and leads to the use of heavier, thicker blades that result in lower aerodynamic efficiency and increased noise. Metal and/or composite fatigue in the blades of jet engines has resulted in blade destruction and loss of lives. Techniques for suppressing low-frequency blade vibration, such as gtuned circuit resistive dissipation of vibratory energy, h or simply "passive damping," can require electronics incorporating coils of unwieldy dimensions and adding unwanted weight to the rotor. Other approaches, using vibration-dampening devices or damping material, could add undesirable weight to the blades or hub, making them less efficient. A wireless inductive power device (WIPD) was designed, fabricated, and developed for use in the NASA Glenn's "Dynamic Spin Rig" (DSR) facility. The DSR is used to simulate the functionality of turbomachinery. The relatively small and lightweight device [10 lb (approx.=4.5 kg)] replaces the existing venerable and bulky slip-ring. The goal is the eventual integration of this technology into actual turbomachinery such as jet engines or electric power generators, wherein the device will facilitate the suppression of potentially destructive vibrations in fan blades. This technology obviates slip rings, which require cooling and can prove unreliable or be problematic over time. The WIPD consists of two parts: a remote element, which is positioned on the rotor and provides up to 100 W of electrical power to thin, lightweight piezoelectric patches strategically placed on/in fan blades; and a stationary base unit that wirelessly communicates with the remote unit. The base unit supplies inductive power, and also acts as an input and output corridor for wireless measurement, and active control command to the remote unit. Efficient engine operation necessitates minimal disturbance to the gas flow across the turbine blades in any effort to moderate blade vibration. This innovation makes it possible to moderate vibration on or in turbomachinery blades by providing 100 W of wireless electrical power and actuation control to thin, lightweight vibration-suppressing piezoelectric patches (eight actuation and eight sensor patches in this prototype, for a total of 16 channels) positioned strategically on the surface of, or within, titanium fan blades, or embedded in composite fan blades. This approach moves significantly closer to the ultimate integration of "active" vibration suppression technology into jet engines and other turbomachinery devices such as turbine electrical generators used in the power industry. The novel feature of this device is in its utilization of wireless technology to simultaneously sense and actively control vibration in rotating or stationary turbomachinery blades using piezoelectric patches. In the past, wireless technology was used solely for sensing and diagnostics. This technology, however, will accomplish much more, in terms of simultaneously sensing, suppressing blade vibration, and making it possible for detailed study of vibration impact in turbomachinery blades.
Morrison, Carlos R.↗
Some implications of large impact craters and basins on Venus for terrestrial ringed craters and planetary evolution
Approximately 950 impact craters have been identified on the surface of Venus, mainly in Magellan radar images. From a combination of Earth-based Arecibo, Venera 15/1, and Magellan radar images, we have interpreted 72 as unequivocal peak-ring craters and four as multiringed basins. The morphological and structural preservation of these craters is high owing to the low level of geologic activity on the venusian surface (which is in some ways similar to the terrestrial benthic environment). Thus these craters should prove crucial to understanding the mechanics of ringed crater formation. They are also the most direct analogs for craters formed on the Earth in Phanerozoic time, such as Chicxulub. We summarize our findings to date concerning these structures.
Mckinnon, W. B.↗
Cassini's Grand Finale: A Mission Planning Retrospective
On September 15, 2017, Cassini plunged deep into Saturn, down to where the atmosphere was sufficiently dense to destroy the spacecraft, making it part of Saturn forever. In the five months leading up to its destruction, Cassini flew between Saturn and its rings 22 times, collecting data from the never before-explored region of the Kronian system. These orbits, the Grand Finale of Cassini, were the culmination of years of planning by the Cassini flight team. This paper looks back upon the mission planning effort in particular, comparing the baseline operational scenarios and contingency plans to the as flown Grand Finale. The bulk of the Grand Finale mission planning effort was focused on the environmental hazards present in the region between Saturn and its rings: the dust and the atmosphere. Dust hazard and atmospheric transit contingency plans were in place to help ensure spacecraft health and maximize science data return. The dust hazard plan gave the operations team the option to turn the spacecraft to a safe attitude during ring-plane crossings had the dust environment proved more threatening than anticipated. The atmospheric transit plan would have made use of an orbital trim maneuver in order to raise or lower periapsis depending on the density of the atmosphere. The proximal environment did have its surprises, though they were good surprises. The dust was significantly less hazardous than predicted. So much so that elements of the contingency plan were leveraged in order to remove a dust hazard protection from the baseline plan, rather than add one to it. While the atmosphere was substantially denser than predicted, it was not dense enough to warrant a periapsis-raise maneuver and actually meant that better in-situ data was gathered. Ultimately, from a mission planning perspective, the Grand Finale went better than expected.
Sturm II, Erick J.↗
High-pressure cryogenic seals for pressure vessels
Problems associated with maintaining high pressures at cryogenic temperatures in pressure vessels are investigated. The goals were to identify the appropriate materials and design for a seal intended for cryogenic applications at pressures up to 4,080 bars (60,000 psi), and to examine the factors affecting the seal performance. The method employed and the apparatus used in a series of experimental seal system tests, and the test results are described in detail. It is concluded that the common seal designs and extrusion seal-ring materials such as Teflon, tin, and lead are not suitable. However, new seal systems developed using indium seal rings, brass or 304 stainless steel anvil rings, and two 0-rings of silicone rubber or Kel-F did prove suitable.
Buggle, A. E.↗
Fairness of channel access for non-time-critical traffic using the FDDI token ring protocol
The Fiber Distributed Data Interface (FDDI) is an ANSI draft proposed standard for a 100 megabit per second fiber optic token ring. FDDI supports two types of traffic, synchronous and asynchronous. Synchronous traffic is time critical traffic; stations are assigned guaranteed bandwidth to support their synchronous needs. Asynchronous traffic is lower priority and is sent only if time permits. It is proved analytically that the FDDI access protocol provides all stations on the ring with equal access to the channel to transmit asynchronous frames, regardless of the relative sizes of synchronous bandwidth allocations for individual stations. Analytic results are supported with data from simulation runs.
Johnson, M. J.↗
Discovery of a new Jupiter satellite
During detailed analysis of Voyager 2 pictures of the Jupiter ring, a starlike object was identified in the plane of the ring. The same object was subsequently found on a higher-resolution frame and proved to be a satellite of Jupiter. This satellite has a circular orbit whose radius is 1.8 Jupiter radii, a period of 7 hours and 8 minutes, and a diameter of less than 40 kilometers. It is located at the outer edge of the Jupiter ring.
Jewitt, D. C.↗
Development of a class of antennas for space-based Navstar GPS applications
This paper describes the performance of several unique antenna/ground plane configurations currently being developed for the TOPEX satellite and which may also be used for improved ground station operation. These antennas are designed with the objective of achieving nearly hemispherical coverage with sharp pattern cutoff above the horizon together with uniform phase response over the entire coverage area. The most promising of these designs is a uniform choke ring approximately 2 lambda in diameter. The ground planes, when used with the Dorne-Margolin C246 antenna element, produce smooth pattern cutoff of the order of 0.25 dB per deg over 135 deg, excellent LCP rejection, and rms phase deviation of 5-5.7 deg. Other ground plane designs, including larger choke ring structures, slotted ground planes, and the use of absorber material, proved much less effective.
Tranquilla, J. M.↗
Quantifying the Role of EMIC Wave Scattering During the 27 February 2014 Storm by RAM–SCB Simulations
Electromagnetic Ion Cyclotron (EMIC) wave scattering has been proved to be responsible for the fast loss of both radiation belt (RB) electrons and ring current (RC) protons. However, its role in the concurrent dropout of these two co–located populations remains to be quantified. In this work, we study the effect of EMIC wave scattering on both populations during the 27 February 2014 storm by employing the global physics–based RAM–SCB model. Throughout this storm event, MeV RB electrons and 100s keV RC protons experienced simultaneous dropout following the occurrence of intense EMIC waves. By implementing data–driven initial and boundary conditions, we perform simulations for both populations through the interplay with EMIC waves and compare them against Van Allen Probes observations. Notably, the results indicate that by including EMIC wave scattering loss, especially by the He–band EMIC waves, the model aligns closely with data for both populations. Additionally, we investigate the simulated pitch angle distributions (PADs) for both populations. Including EMIC wave scattering in our model predicts a 90° peaked PAD for electrons with stronger losses at lower pitch angles, while protons exhibit an isotropic PAD with enhanced losses at pitch angles above 40°. Furthermore, our model predicts considerable precipitation of both particle populations, predominantly confined to the afternoon to midnight sector (12 hr < MLT < 24 hr) during the storm's main phase, corresponding closely with the presence of EMIC waves.
79 ASTRONOMY AND ASTROPHYSICS↗
Capture of novel sp 3 hybridized Z-BN by compressing boron nitride nanotubes with small diameter
Experimental synthesis of new sp 3 hybridized carbon/boron nitride structures remains challenging despite that numerous sp 3 structures have been proposed in theory. Here, we showed that compressed multi-walled boron nitride nanotubes (MWBNNTs) and boron nitride peapods (C 60 @BNNTs) with small diameters could transform into a new sp 3 hybridized boron nitride allotrope (Z-BN). This strategy is considered from the topological transition point of view in boron nitride nanotubes upon compression. Due to the increased curvature in compressed small-diameter MWBNNTs, the uncommon 4- and 8-membered rings in Z-BN could be more favorably formed. And the irreversible tube collapse is proved to be a critical factor for the capture of the formed Z-BN, because of the competition between the resilience of tube before collapse and the stress limitation for the lattice stabilization of Z-BN upon decompression. In this case, Z-BN starts to form above 19.0 GPa, which is fully reversible below 45 GPa and finally becomes quenchable at 93.5 GPa. Consequently, this collapse-induced capture of the high-pressure phase could also be extended to other tubular materials for quenching novel sp 3 structures.
36 MATERIALS SCIENCE↗
Analytical Dynamic Aperture Calculation Compared to Tracking Results
In studying dynamic aperture in the storage rings, it is becoming increasing beneficial to understand the growth of the fractal boundary of the dynamic aperture without tracking for millions of turns in a hadron ring. This note describes the J. Gao theory applied to the Electron Ion Collider (EIC) Hadron Storage Ring (HSR) and compares simulation results to theoretical predictions to show that the analytical method may prove useful in quick determinations of improved dynamic aperture based on sextupole and octupole configurations.
43 PARTICLE ACCELERATORS↗
Proof that timing requirements of the FDDI token ring protocol are satisfied
The fiber distributed data interface (FDDI) is an ANSI draft proposed standard for a 100 Mbit/s fiber-optic token ring. The FDDI timed token access protocol provides dynamic adjustment of the load offered to the ring, with the goal of maintaining a specified token rotation time and of providing a guaranteed upper bound on time between successive arrivals of the token at a station. FDDI also provides automatic recovery when errors occur. The bound on time between successive token arrivals is guaranteed only if the token rotates quickly enough to satisfy timer requirements in each station when all ring resources are functioning properly. Otherwise, recovery would be initiated unnecessarily. The purpose of this paper is to prove that FDDI timing requirements are satisfied, i.e., the token rotates quickly enough to prevent initiation of recovery unless there is failure of a physical resource or unless the network management entity within a station initiates the recovery process.
Johnson, Marjory J.↗