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Results for “misalignment”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

A generalized theory for eccentric and misalignment effects in high-pressure annular seals

High-pressure annular seal leakage and dynamic coefficients vary with eccentricity and misalignment. Recent seal leakage data with both concentric and fully eccentric alignments support the seal leakage model with surface roughness and eccentricity effects included. In this paper, the seal dynamic coefficient calculation has been generalized and allows direct calculation of the seal dynamic coefficients at any circumferential location. The generalized solution agrees with the results obtained by using the calculated values of an earlier paper and performing a coordinate transformation. The analysis results coincide with the measured data in showing that the stiffness and damping matrices of seal coefficients are not skew symmetric, and the main diagonal seal coefficients are not equal. The measured direct stiffnesses were found higher than predicted by the concentric seal theory, but this may be explained by the presence of eccentricity in the test operating mode.

Chen, W. C.↗
NASA NTRS1986

Lidar telescope overlap function and effects of misalignment for unstable resonator transmitter and coherent receiver

Effects of lidar telescope overlap function modeling on the accuracy of aerosol backscatter measurements are discussed. The treatment pertains primarily to a lidar arrangement which combines high sensitivity and a large degree of geometrical signal compression but places stringent requirements on the accuracy of the overlap function modeling - coherent IR lidar with noncoaxial (side-by-side) transmit and receive telescopes. A model is presented which includes an unstable resonator transmitter and accommodates both coaxial and noncoaxial arrangements, and comparison is made to experimental results including effects of misalignment.

Ancellet, G. M.↗
NASA NTRS1991

Optoelectronic Shaft-Angle Encoder Tolerates Misalignments

Optoelectronic shaft-angle encoder measures angle of rotation of shaft with high precision while minimizing effects of eccentricity and other misalignments. Grooves on disk serve as reference marks to locate reading heads and measure increments of rotation of disk. Shaft-angle encoder, resembling optical compact-disk drive, includes two tracking heads illuminating grooves on disk and measures reflections from them.

Osborne, Eric P.↗
NASA NTRS1991

Docking System Would Accommodate Misalignments

Conceptual docking system absorbs kinetic energy along each of three orthogonal directions. Accommodates large misalignments between docking objects. Lightweight system consists of probe on one of two docking objects and drogue on other object. Probe contains latching mechanism; pitch, roll, and yaw dampers; and centering and rigidizing mechanisms. Three eddy-current dampers absorb energy of motion along orthogonal directions, bringing docking objects to smooth stop. Conceived for docking Space Shuttle in Space Station, system useful in other applications in which large moving object must be aligned with and joined to another - such as, cranes, robots, and fuel or material-loading lines.

Ajemian, Rasmik↗
NASA NTRS1994

Kinematic misalignments in remnants of multiple mergers

Observations indicate that the rotation and minor axes in elliptical galaxies are usually well aligned. However, computer models of dissipationless mergers of pairs of disk galaxies have failed to establish such a correlation, implying that most ellipticals probably did not originate in this manner. Here we consider remnants produced from repeated merging in small groups of a half-dozen or so disk galaxies and find that the internal kinematics of such objects are more representative of actual elliptical galaxies. Although our coverage of parameter space is not complete, the remnants produced in our simulations invariably possess small kinematic misalignments. These results suggest that the majority of elliptical galaxies have had evolutionary histories more complex than those envisaged by simple merger hypotheses.

Weil, Melinda L.↗
NASA NTRS1998

Misalignment Accommodating Connector Assembly

Misalignment accommodating connector assembly for removably connecting first and second objects which may comprise: a first connector subassembly having an arm member extending therefrom transversely through which is provided a tubular member; a second connector subassembly having a pair of spaced apart arm members each of which is provided with a transversely disposed coaxially aligned semi-cylindrical recess for receiving opposite ends of the first connector tubular member upon lateral insertion of the first connector arm member into the space between the second connector pair of arm members. An axially extendable and contractible fastener subassembly carried by the first connector tubular member is extendable to allow insertion or removal of the first connector arm member into or from the space between the second connector pair of arm members and contractible when the opposite ends of the tubular member are substantially received by the semi-cylindrical recesses of the pair of spaced apart arm members to lock the first and second connector subassemblies together.

Stemper, Jack S.↗
NASA NTRS2008

Gas Foil Bearing Misalignment and Unbalance Effects

The effects of misalignment and unbalance on gas foil bearings are presented. The future of U.S. space exploration includes plans to conduct science missions aboard space vehicles, return humans to the Moon, and place humans on Mars. All of these endeavors are of long duration, and require high amounts of electrical power for propulsion, life support, mission operations, etc. One potential source of electrical power of sufficient magnitude and duration is a nuclear-fission-based system. The system architecture would consist of a nuclear reactor heat source with the resulting thermal energy converted to electrical energy through a dynamic power conversion and heat rejection system. Various types of power conversion systems can be utilized, but the Closed Brayton Cycle (CBC) turboalternator is one of the leading candidates. In the CBC, an inert gas heated by the reactor drives a turboalternator, rejects excess heat to space through a heat exchanger, and returns to the reactor in a closed loop configuration. The use of the CBC for space power and propulsion is described in more detail in the literature (Mason, 2003). In the CBC system just described, the process fluid is a high pressure inert gas such as argon, krypton, or a helium-xenon mixture. Due to the closed loop nature of the system and the associated potential for damage to components in the system, contamination of the working fluid is intolerable. Since a potential source of contamination is the lubricant used in conventional turbomachinery bearings, Gas Foil Bearings (GFB) have high potential for the rotor support system. GFBs are compliant, hydrodynamic journal and thrust bearings that use a gas, such as the CBC working fluid, as their lubricant. Thus, GFBs eliminate the possibility of contamination due to lubricant leaks into the closed loop system. Gas foil bearings are currently used in many commercial applications, both terrestrial and aerospace. Aircraft Air Cycle Machines (ACMs) and ground-based microturbines have demonstrated histories of successful long-term operation using GFBs (Heshmat et al., 2000). Small aircraft propulsion engines, helicopter gas turbines, and high-speed electric motors are potential future applications.

Howard, Samuel A.↗
NASA NTRS2009

On the Spin-Orbit Misalignment of the XO-3 Exoplanetary System

We presented photometric and spectroscopic observations of the 2009 February 2 transit of the exoplanet XO-3b. The new data showed that the planetary orbital axis and stellar rotation axis are misaligned, as reported earlier by Hebrard and coworkers. XO-3b was the first exoplanet known to have a highly inclined orbit relative to the equatorial plane of its parent star, and as such it may fulfill the predictions of some scenarios for the migration of massive planets into close-in orbits.

Winn, Joshua N.↗
NASA NTRS2011

A 5 Micron of beta Pictoris B at a Sub-Jupiter Projected Separation: Evidence for a Misalignment Between the Planet and the Inner, Warped Disk

We present and analyze a new M' detection of the young exoplanet Beta Pictoris b from 2008 VLT/NaCo data at a separation of approx. = 4 AU and a high signal-to-noise rereduction of L' data taken in December 2Q09. Based on our orbital analysis, the planet's orbit is viewed almost perfectly edge-on (i approx. 89 degrees) and has a Saturn-like semimajor axis of 9.50AU(+3.93 AU)/-(1.7AU) . Intriguingly, the planet's orbit is aligned with the major axis of the outer disk (Omega approx.31 degrees) but probably misaligned with the warp/inclined disk at 80 AU often cited as a signpost for the planet's existence. Our results motivate new studies to clarify how Beta Pic b sculpts debris disk structures and whether a second planet is required to explain the warp/inclined disk

Currie, Thayne↗
NASA NTRS2021

TOI-1518b: A Misaligned Ultra-hot Jupiter with Iron in Its Atmosphere

We present the discovery of TOI-1518b—an ultra-hot Jupiter orbiting a bright star (V = 8.95). The transiting planet is confirmed using high-resolution optical transmission spectra from EXPRES. It is inflated, with Rp = 1.875 ± 0.053 RJ, and exhibits several interesting properties, including a misaligned orbit (240.34 (+0.93, -0.98) degrees) and nearly grazing transit (b=0.9036 (+0.0061, -0.0053)). The planet orbits a fast-rotating F0 host star (Teff ≃ 7300 K) in 1.9 days and experiences intense irradiation. Notably, the TESS data show a clear secondary eclipse with a depth of 364 ± 28 ppm and a significant phase-curve signal, from which we obtain a relative day–night planetary flux difference of roughly 320 ppm and a 5.2σ detection of ellipsoidal distortion on the host star. Prompted by recent detections of atomic and ionized species in ultra-hot Jupiter atmospheres, we conduct an atmospheric cross-correlation analysis. We detect neutral iron (5.2σ), at K(p) = 157 (+68, -44) km/s and V(sys) = -16 (+2, -4), adding another object to the small sample of highly irradiated gas-giant planets with Fe detections in transmission. Detections so far favor particularly inflated gas giants with radii ≳1.78 R(J), which may be due to observational bias. With an equilibrium temperature of T(eq) = 2492 ± 38 K and a measured dayside brightness temperature of 3237 ± 59 K (assuming zero geometric albedo), TOI-1518b is a promising candidate for future emission spectroscopy to probe for a thermal inversion.

Samuel H. C. Cabot↗
DOE OSTI2026

Dark Photons from Perturbative Decay of a Misaligned Higgs Field

We reconsider the production of dark photons $A'$ as dark matter, from the perturbative decay of a dark Higgs field $h$, that is stochastically misaligned from the minimum of its potential during inflation. This is a simple and predictive framework for generating the $A'$ relic abundance. It is constrained by structure formation, since the $A'$ are initially boosted, and inflationary isocurvature fluctuations, which require small quartic couplings $λh^4$. We identify $A'$ masses between 100 eV and 1 GeV and gauge couplings $g\sim 10^{-15}-10^{-10}$ that are consistent in this scenario, and which become more tightly constrained if a generic level of kinetic mixing is present. The favored parameter region could be tested through future CMB or Lyman-$α$ observations, and, in the presence of kinetic mixing, by direct detection experiments or diffuse soft gamma-ray searches.

Cline, James M. [McGill U., Montreal (main)]↗
DOE OSTI2024

Interactions in misaligned layered materials

The deliberate introduction of stacking faults has been found to induce properties markedly distinct from those of perfectly stacked particles or sheets, with even minute deviations leading to significant alterations in material characteristics. In this review article, we discuss the effects of stacking faults – both linear and rotational – on surface structures influencing ion adsorption, particle–particle affinity governing crystal growth, friction, and electronic properties. In conclusion, our comprehensive overview sheds light on the multifaceted impact of stacking faults on these phenomena, offering insights that bridge multiple disciplines, and provides numerous interdisciplinary research questions, paving the way for future innovations.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Two-dimensional Thomson scattering measurements of misaligned electron density and temperature gradients and associated Biermann battery produced fields

We present optical Thomson scattering measurements of electron density and temperature in high Mach number laser-driven blast waves in homogeneous gases. Taylor–Sedov blast waves are launched in nitrogen (N2) or helium (He) at pressures between 0.4 mTorr and 10 Torr by ablating a solid plastic target with a high energy laser pulse (10 J, 1012 W/cm2). Experiments are performed at high repetition rate (1 Hz), which allows one-dimensional and two-dimensional Thomson scattering measurements over an area of several cm2 by automatically translating the scattering volume between shots. Electron temperature and density in the blast wave fronts were seen to increase with increasing background gas pressure. Measured electron density and temperature gradients were used to calculate ∂B/∂t∝∇Te×∇ne. The experimentally measured ∂B/∂t showed agreement with the magnetic field probe (B-dot) measurements, revealing that magnetic fields are generated in the observed blast waves via the Biermann battery effect. The results are compared to numerical three-dimensional collisional magnetohydrodynamic simulations performed with FLASH, and are discussed in the context of spontaneous magnetic field generation via the Biermann battery effect.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗