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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

Studying Open Quantum Systems Relevant to Chemistry on a Trapped-Ion Quantum Simulator (Final Technical Report)

This project advances the trapped-ion quantum simulator as a versatile platform for studying open quantum system phenomena. We aim to contribute to the emerging quantum simulation toolkits and enable simulation of nanoscale energy processes. Trapped-ion platforms offer unique capabilities: their vibrational motion can be precisely manipulated, measured, and coherently coupled to auxiliary qubits. The vibrational mode can function both as a highly sensitive quantum sensor and a programmable environment bath. Using this platform, we achieved three major outcomes. First, we demonstrated using the vibrational mode as an ultrasensitive probe for testing fundamental physics, including possible nonlinear quantum mechanics effects. Second, we established that these modes can act as controllable baths in which tunable noise and loss can enhance or modify energy-transfer dynamics, providing the experimental preparation toward studying mechanisms relevant to chemical reactions and light-harvesting systems. Third, by introducing controllable nonlinear gain and loss, we showed theoretically how simulations using trapped ions can model vibrationally-assisted energy transport in a non‐Hermitian quantum system comprising a chromophore dimer weakly coupled to a vibrational mode. Exploring the non‐Hermitian dynamics of the whole system including vibrations, we found that energy transfer accompanied by absorption of phonons from a vibrational mode can be significantly enhanced near an exceptional point. This theoretical work on simulation of energy transfer processes in driven non‐Hermitian quantum systems revealed an interesting novel path to study open quantum systems dynamics under conditions of gain and loss. We then further explored the benefits of controllable gain and loss with an experimental realization of quantum analogs of nonlinear oscillators, namely, the van der Pol oscillator. Here we observed mutual synchronization mediated by collective dissipation between two oscillators. In parallel, we explored related quantum networking protocols using the same trapped-ion platform, developing fast, high-fidelity schemes for distributing entanglement. Together, these achievements show that trapped-ion vibrational modes provide a highly programmable and high-fidelity platform for investigating complex dissipative quantum behavior, while enabling new approaches to remote quantum sensing, energy science, and nonlinear quantum dynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Feedback control of vibrations in a moving flexible robot arm with rotary and prismatic joints

A robot with a long extendible flexible arm which can also undergo both vertical translation and rotary motion is considered. First, A distributed-parameter model for the robot arm dynamics is developed. It is found that the extending motion could enhance the arm vibrations. Then, a Galerkin-type approximation based on an appropriate time-dependent basis for the solution space is used to obtain an approximate finite-dimensional model for simulation studies. A feedback control for damping the motion-induced vibrations is derived by considering the time rate-of-change of the total vibrational energy of the flexible arm. The authors conclude with some simulation results for a special case with the proposed control law.

Wang, P. K. C.↗

Active Vibration Isolation of Microgravity Experiments with Spring Umbilicals Using an Electrodynamic Actuator

Microgravity experiments will require active vibration isolation in the low to mid frequency range of 0.1 Hz to 10 Hz. Approximately two orders of acceleration reduction (40 dB) will be required. Previous works have reported results for accelerations transmitted through the umbilical. This paper describes experimental and theoretical results for vibration isolation in one dimension (horizontal) where the simulated experiment is connected to the spacecraft by a spring umbilical. The experiment consisted of a spacecraft (shaker), experiment (mass), umbilical, accelerometer, control electronics, and Lorentz actuator. The experiment mass was supported in magnetic bearings to avoid any stiction problems. Acceleration feedback control was employed to obtain the vibration isolation. Three different spring umbilicals were employed. Acceleration reductions on the order of 40 dB were obtained over the frequency range of 0.1 Hz to 10 Hz. Good agreement was obtained between theory and experiment.

Banerjee, B. B.↗

Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization

This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.

Mendoza, J.↗

Airplane wing vibrations due to atmospheric turbulence

The magnitude of error introduced due to wing vibration when measuring atmospheric turbulence with a wind probe mounted at the wing tip was studied. It was also determined whether accelerometers mounted on the wing tip are needed to correct this error. A spectrum analysis approach is used to determine the error. Estimates of the B-57 wing characteristics are used to simulate the airplane wing, and von Karman's cross spectrum function is used to simulate atmospheric turbulence. It was found that wing vibration introduces large error in measured spectra of turbulence in the frequency's range close to the natural frequencies of the wing.

Pastel, R. L.↗

Density measurements in an expanding flow using holographic interferometry

A nonequilibrium expansion of nitrogen through a 2-dimensional nozzle of a reflected shock tunnel is investigated with laser holography, time resolved pressure measurements and emission spectroscopy to characterize the flow field for vibrational relaxation measurements. A 2D computation is used to simulate the nozzle flow field. Synthetic holograms are generated using the computed density profiles and are compared with the experimental holograms. Also, using a quasi 1-D approximation, populations for each vibrational level are computed by (1) solving the master equations and (2) using the Landau-Teller formulation. Computational accuracy of both models is assessed against the experimental data.

Sharma, Surendra P.↗

Prospects for detecting UF6 hydrolysis intermediates by mass spectrometry, resonance Raman, and NQR spectroscopy

Simulations are performed to consider several spectrometric and spectroscopic candidates for elucidating the mechanism of the hydrolysis of uranium hexafluoride (UF6). This study is among the first to benchmark the def-mTZVP basis sets for actinide-containing molecules, and it is shown to be a suitable basis set for surveying geometrical structures and vibrational spectra when used in conjunction with density functional theory. An experiment is proposed coupling mass spectrometric ion selection with vibrational spectroscopy, and supporting infrared and Raman spectral simulations demonstrate that ionization blue-shifts bands and can change their qualitative features. Ultraviolet resonance Raman is shown to have good prospects for discriminating U–O–U bridged intermediates, evidence for which was observed recently [L. E. McNamara et al., J. Phys. Chem. A 130, 775–786 (2026)]. As a more speculative approach, we also consider the prospect of addressing 233U or 235U nuclei by quadrupole resonance (NQR) spectroscopy for assigning early stage intermediate complexes. In doing so, we provide a first order-of-magnitude estimate for the collision-induced NQR signal for the UF6 dimer, which is of interest for the interpretation of a fast decoherence time observed in liquid-phase nuclear magnetic resonance. Having provided critical insights into the formation and stability of UF6 hydrolysis intermediates in previous studies, this computational spectroscopy survey is expected to help guide and expedite future laboratory campaigns.

Lutz, Jesse J. [Center for Computing Research, San↗

Dynamic mode decomposition of nonequilibrium electron-phonon dynamics: accelerating the first-principles real-time Boltzmann equation

Abstract Nonequilibrium dynamics governed by electron–phonon ( e -ph) interactions plays a key role in electronic devices and spectroscopies and is central to understanding electronic excitations in materials. The real-time Boltzmann transport equation (rt-BTE) with collision processes computed from first principles can describe the coupled dynamics of electrons and atomic vibrations (phonons). Yet, a bottleneck of these simulations is the calculation of e –ph scattering integrals on dense momentum grids at each time step. Here we show a data-driven approach based on dynamic mode decomposition (DMD) that can accelerate the time propagation of the rt-BTE and identify dominant electronic processes. We apply this approach to two case studies, high-field charge transport and ultrafast excited electron relaxation. In both cases, simulating only a short time window of ~10% of the dynamics suffices to predict the dynamics from initial excitation to steady state using DMD extrapolation. Analysis of the momentum-space modes extracted from DMD sheds light on the microscopic mechanisms governing electron relaxation to a steady state or equilibrium. The combination of accuracy and efficiency makes our DMD-based method a valuable tool for investigating ultrafast dynamics in a wide range of materials.

36 MATERIALS SCIENCE↗

Stabilization of Hydroxide Ions at the Interface of a Hydrophobic Monolayer on Water via Reduced Proton Transfer

We report a joint study using surface-specific sum-frequency vibrational spectroscopy and ab initio molecular dynamics simulations, respectively, on a pristine hydrophobic (sub)monolayer hexane-water interface, namely, the hexane/water interface with varied vapor pressures of hexane and different pHs in water. We show clear evidence that hexane on water revises the interfacial water structure in a way that stabilizes the hypercoordinated solvation structure and slows down the migration of hydroxide ion (OH – ) relative to that in bulk water. Furthermore, this mechanism effectively attracts the OH – to the water-hydrophobic interface with respect to its counterion. The result illustrates the striking difference of proton transfer of hydrated OH – at the interface and in the bulk, which is responsible for the intrinsic charging effect at the hydrophobic interface.

74 ATOMIC AND MOLECULAR PHYSICS↗

Protective coatings for columbium applied in the field.

The various aspects of field repair of columbium alloy panels with protective coatings designed as part of the Space Shuttle thermal protection system are examined. The field repair of the coatings is accomplished by employing ceramic cement repairs, and reapplying the fused slurry silicide coating. Techniques are described which improve the practicality of these repairs by employing torch heating. The repair coating quality is demonstrated by testing which simulates flight temperature, pressure, stress and acoustic vibration conditions as a function of time. Conclusions on the present status of field repair coatings are presented and recommendations are given for appropriate future activities relative to the use on an operational Space Shuttle system.

Carter, J.↗

Space Shuttle Program Progress Report

A status report is presented on progress in the design, manufacturing and testing of components of the space transportation system (STS), and primarily the Space Shuttle vehicles. Project landmarks from 1969 to 1981 are indicated, fabrication of the Shuttle Orbiter and rollout of the first prototype are described, fabrication and assembly of some Orbiter parts are sketched, and some of the subsystems (thermal protection, avionics, maneuvering aids, reaction control, remote manipulator) are described. Also discussed are: Orbiter carrier aircraft, Shuttle main engine and tests, external fuel tank, solid rocket booster, launch and landing facilities. A separate section is devoted to ground tests (vibration, propulsion, electronics, avionics integration), trainers and simulators, and flight tests (captive flight, free flight, landing and approach, orbital flight).

Thompson, R. F.↗

NTS-2 retroreflector array

The NTS-II Laser Retroreflector consists of a honeycomb tray onto which are mounted 44 fused silica cube corners with a 50-millimeter hexagonal entrance pupil and single infrared cube. A thermal shield with a highly reflective outer surface and a black inner surface was incorporated to shroud the assembly protecting it from extreme high temperature exposure thus reducing cube corner thermal distortions to a minimum. A dummy retroreflector, utilizing simulated aluminum cube corners was fabricated and vibration tested to qualification levels to substantiate the integrity of the tray and cube mounting clips. This dummy was further used in the spacecraft spin balance test. The flight Laser Retroreflector was tested to the flight level vibration spectrum to verify that the unit will survive its expected vibration environment. During this test several GFE cube corners exhibited slight crazing at the clip support mounting holes. These cubes were reworked and retested and proved to be satisfactory.

Source record↗

Analytical investigation of the dynamics of tethered constellations in Earth orbit (phase 2)

The deployment maneuver of three axis vertical constellations with elastic tethers is analyzed. The deployment strategy devised previously was improved. Dampers were added to the system. Effective algorithms for damping out the fundamental vibrational modes of the system were implemented. Simulations of a complete deployment and a subsequent station keeping phase of a three mass constellation is shown.

Lorenzini, E.↗

An assessment of OH airglow interference on the remote sensing of stratospheric HCl via limb sounding in the near-I.R.

Chemiluminescent emission from the formation of vibrationally excited OH at an altitude of approximately 85 km presents a barrier to earth-limb measurements of NIR emissions originating in the stratosphere. High-resolution measured spectra of OH airglow have not been reported, and thus it is difficult to assess its impact on moderately-high-resolution earth-limb spectroscopy capable of looking between strong OH lines. Low-resolution rocketborne spectrometer earth-limb measurements of OH airglow are mathematically inverted to recover vibrational-state populations that are used to simulate a higher resolution spectrum in the neighbourhood of 2843/cm. Implications for remote sensing HCl are presented.

Mergenthaler, J. L.↗

Adaptive suppression of biodynamic interference in helmet mounted and head down displays

This paper addresses errors caused by vibrations or turbulence in airborne helmet teleoperation, helmet mounted, and head down displays. A preliminary study is presented which indicates that these errors can be significantly suppressed by adaptive filtering. A modified version of the LMS adaptive noise suppression algorithm facilitates the separation of the voluntary large head movements from the vibration-induced small nonvoluntary head movements. Computer simulations demonstrate the potential of the approach in suppressing both aiming errors and apparent display blurring.

Merhav, Shmuel J.↗

Learning control for slewing of a flexible panel

This paper studies the applicability of a discrete-time learning control method to the slewing control of a large flexible panel. Among the issues discussed are feasibility of the desired trajectories and their specification schemes, learning control by linear feedback, limitation of the actuator device output, and robustness to parameter changes or modeling errors associated with the chosen learning control design. To demonstrate the effectiveness of learning control, the system is designed with a proportional controller of the base angle only. Then application of the learning control is shown to make the system learn quickly to achieve the desired slewing without residual vibration at the end of the maneuver. Simulation results are reported and discussed.

Phan, M.↗

Modeling and stability of segmented reflector telescopes - A decentralized approach

The decentralization of a segmented reflector telescope based on a finite-element model of its structure is considered. The decentralization of the system at the panel level is considered. Each panel is originally treated as an isolated subsystem so that the controller design is performed independently at the local level, and then applied to the composite system for stability analysis. The panel-level control laws were designed by means of pole placement using local output feedback. Simulation results show a better 1000:1 vibration attenuation in panel position when compared to the open-loop system. It is shown that the overall closed-loop system is exponentially stable provided that certain conditions are met. The advantage to the decentralized approach is that the design is performed in terms of the low-dimensionality subsystems, thus drastically reducing the design computational complexities.

Ryaciotaki-Boussalis, Helen A.↗

Dynamic response of a hammerhead launch vehicle wind-tunnel model

NASA-Langley has wind tunnel-tested an aeroelastically-scaled (1/10th-scale) Atlas-Centaur I Large Payload Fairing launch-vehicle model capable of simulating either of the first two bending vibration modes of the full-scale vehicle, on the basis of a partial-mode technique. While the primary emphasis was on the vehicle's buffet response, angle-of-attack studies were conducted for several payload fairing configurations with a view to both the buffet response and the dynamic stability of off-design conditions. No dynamic instabilities were discovered among the range of configurations, and payload fairing L/D variations were found to have only small buffet effects except for the smallest such value, in the second bending mode configuration.

Cole, Stanley R.↗