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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Embedded Data Acquisition Tools for Rotorcraft Diagnostic Sensors

Rotorcraft drive trains must withstand enormous pressure while operating continuously in extreme temperature and vibration environments. Captive components, such as planetary and spiral bevel gears, see enormous strain but are not accessible to fixed instrumentation, such as a piezoelectric transducer. Thus, it is difficult to directly monitor components that are most susceptible to damage. This innovation is a self-contained data processing unit within a specialized fixture that installs directly inside the rotating pinion gear in the gearbox. From this location, it detects and transmits high-resolution prognostic data to a fixed transceiver. The sensor is based on microelectromechanical systems (MEMS) technology and uses innovative circuit designs to capture high-bandwidth data and transmit it wirelessly from inside an operational helicopter transmission. With Ridgetop's advanced MEMS-based sensor, researchers have, for the first time, been able to extract high-resolution acoustic signatures wirelessly from sensors within the transmission that would otherwise be muffled by background gear noises. Ridgetop's innovative instrument will help researchers perform dynamic analysis of gear interaction and develop improved designs for gear components. In addition, data from this instrument can be used to validate new algorithms that detect and predict faults based on external acoustic signatures, for prognostic purposes. The result of this work will be an improvement in safety, performance, and cost for future generations of rotating components.

Wagoner, Robert↗
DOE OSTI2026

Complex and Unusual Excited-State Relaxation Dynamics of 9,9′-Bifluorenylidene Revealed by Comprehensive Time-Resolved Spectroscopy and MRSF-TDDFT Calculations

Design of novel photochemical molecular motors often requires molecular building blocks that exhibit rather unusual photoactivity, for which conventional analyses of spectroscopic data can lead to conflicting interpretations. We here systematically investigated the excited-state relaxation dynamics of one such molecule, 9,9′-bifluorenylidene (BF), through comprehensive and complementary integration of ultrafast transient absorption (TA) and femtosecond stimulated Raman (FSRS) spectroscopies and first-principles mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT). TA and FSRS identified two sequentially formed transients following photoexcitation. The decay kinetics of the two intermediates differ in response to excitation wavelengths and the viscosity/polarity of solvents. MRSF-TDDFT calculations reveal a direct, barrierless internal-conversion pathway from the bright Franck−Condon state to a dark S1 minimum, where the excited-state population is transiently trapped, accounting for the first transient species observed in spectroscopic experiments. Further tracking down along the PES with MRSF-TDDFT mapped out two nonradiative relaxation pathways via conical intersections that connect the dark S 1 state to three configurations in the ground-state manifolds, within which a ring structure with a C8−C8′ bond and the vibrationally excited ground-state BF were identified from spectroscopic and kinetic data. The complexity of relaxation kinetics was attributed to the flexible torsional and twisting motions about the C9−C9′ bridge bond enabled by the diradical character of the S 1 state. These findings clarify unusual photoactive relaxation dynamics stemming from a novel correlation between structural flexibility and shifting electronic characteristics, and they demonstrate the importance of integrating spectroscopic and advanced electronic structure calculation studies for judicious clarification of complex, competing relaxation pathways of excited states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Quantum computation solves a half-century-old enigma: Elusive vibrational states of magnesium dimer found

The high-lying vibrational states of the magnesium dimer (Mg 2 ), which has been recognized as an important system in studies of ultracold and collisional phenomena, have eluded experimental characterization for half a century. Until now, only the first 14 vibrational states of Mg 2 have been experimentally resolved, although it has been suggested that the ground-state potential may support five additional levels. Here, we present highly accurate ab initio potential energy curves based on state-of-the-art coupled-cluster and full configuration interaction computations for the ground and excited electronic states involved in the experimental investigations of Mg 2 . Our ground-state potential unambiguously confirms the existence of 19 vibrational levels, with ~1 cm -1 root mean square deviation between the calculated rovibrational term values and the available experimental and experimentally derived data. Our computations reproduce the latest laser-induced fluorescence spectrum and provide guidance for the experimental detection of the previously unresolved vibrational levels.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1996

Analytic Methods for Predicting Significant Multi-Quanta Effects in Collisional Molecular Energy Transfer

Collision-induced transitions can significantly affect molecular vibrational-rotational populations and energy transfer in atmospheres and gaseous systems. This, in turn. can strongly influence convective heat transfer through dissociation and recombination of diatomics. and radiative heat transfer due to strong vibrational coupling. It is necessary to know state-to-state rates to predict engine performance and aerothermodynamic behavior of hypersonic flows, to analyze diagnostic radiative data obtained from experimental test facilities, and to design heat shields and other thermal protective systems. Furthermore, transfer rates between vibrational and translational modes can strongly influence energy flow in various 'disturbed' environments, particularly where the vibrational and translational temperatures are not equilibrated.

Bieniek, Ronald J.↗
NASA NTRS1990

Nonequilibrium and equilibrium shock front radiation measurements

The intensities of the radiation emitted behind a normal shock wave in N were measured in an electric-arc driven shock tube at a shock velocity of 6.2 km/sec. Both a time-resolved broad-band radiation intensity measurement and a time-frozen spectral measurement were conducted. The rotational and vibrational temperatures are determined in both the equilibrium and the nonequilibrium regions. The results are compared with the similar data obtained by Allen et al. (1961). The measured rotational temperature seems to be in nonequilibrium, contradicting the two-temperature assumption of Park (1988), but the measured vibrational temperature agrees with Park's model.

Sharma, Surendra P.↗
DOE OSTI2022

Bearing Fault Detection on Wind Turbine Gearbox Vibrations Using Generalized Likelihood Ratio-Based Indicators: Preprint

Studies in condition monitoring literature often aim to detect rolling element bearing faults because they have one of the biggest shares among defects in turbo machinery. Accordingly, several prognosis and diagnosis methods have been devised to identify fault signatures from vibration signals. The underlying idea behind traditional indicators often revolves around tracking both cyclostationarity and abnormal impulses in the vibration signals without distinguishing the two. A recently proposed method to capture the rolling element bearing degradation lays out the groundwork for new indicator families utilizing generalized likelihood ratio test. This novel approach exploits the cyclostationarity and the impulsiveness of vibration signals independently in order to estimate the most suitable indicators for a given fault. However, the method has yet to be tested on complex experimental vibration signals such as those of a wind turbine gearbox. In this study, the approach is applied to the NREL Wind Turbine Gearbox Condition Monitoring Round Robin Study data set for bearing fault detection purposes. The data set is measured on an experimental test rig of a wind turbine gearbox, hence the complexity of the vibration signals is similar to a real case. Furthermore, the new indicators are also tested with signals that carry multiple fault signatures. The outcome demonstrates that the proposed method is capable of distinguishing between healthy and damaged vibration signals measured on a complex wind turbine gearbox.

condition monitoring↗
NASA NTRS1980

Summary of Aerodynamic Vibration Effects on ALL Turret

The effects of the airborne environment on a pointing and tracking system using a turret external to an aircraft are summarized. The data covered a series of flight tests and a span of seven years. The two major airborne effects were shown to be direct pressure loading of optical elements and vibrations of the entire turret. The direct optical loading problem was minimized by fence designs for the turret.

Merritt, P.↗
NASA NTRS1978

Space qualification of optical instruments using the NASA Long-Duration Exposure Facility

The NASA Long-Duration Exposure Facility (LDEF), designed for the in situ testing of optical instrumentation in the space environment is described. The LDEF is basically a reusable structure which is three-axis gravity-gradient stabilized when flying free in space. The structure weighs about 8,000 lbs. and accommodates experiment trays weighing about 10,000 lbs. A vacuum exposure control canister is being designed for controlled exposure experiments. The LDEF will have an experiment power and data system and a shuttle bay environmental measurements system is being designed for measuring parameters such as acoustics, vibration, acceleration. The induced environment contamination monitor will evaluate the contamination levels of shuttle payloads. Experiments currently under development include the evaluation of active optical components and the study of fiber optic data transmission.

Clark, L. G.↗
NASA NTRSDate not supplied

Heat Transfer Measurements of NASA Liquid Kerosene/Oxygen Rotating Detonation Rocket Engine

The RDRE has been identified as a viable high performance propulsion system with numerous advantages over the state-of-the-art (SOA) liquid rocket engine. NASA has been investigating this combustion device for applications ranging from lander, upper stage, thruster, and hypersonics. All of the activities funded to date have been focused on closing major technology gaps preventing the RDRE from being used more broadly by industry. One of those gaps include the prediction and management of heat transfer to the walls from the extreme combustion environment. This work overviews the heat transfer measurements made using new and existing hardware. A liquid oxygen / liquid RP-1 RDRE was tested utilizing a calorimeter outer body and outer body nozzle extension. An actively cooled inner body with axial running cooling channels was also used. A bimetallic GRCop-42 / Monel K500 injector was developed and demonstrated to be a viable technology for RDRE environments. Trends in bulk heat loads are discussed along with a direct comparison to constant pressure theory predictions of wall heat transfer. The experimental data obtained in this investigation showed similar heat fluxes to constant pressure theory indicating deflagration may have dominated the flow field. Only a single detonation wave was observed in all tests which imparted a significant dynamic load (vibration) on the test article making measurement of combustor performances extremely challenging. Both accelerometer and load cell data corroborate the extreme G-forces measured. The single wave mode yielded relatively low performances compared with other hot fire test data sets available. This leads to the conclusion that a single detonation wave in this geometry is not sufficient for high performance. Wave multiplicity, or rather, a specific number of waves may yield higher performances.

Thomas Teasley↗
NASA NTRS2010

Incorporating Vibration Test Results for the Advanced Stirling Convertor into the System Dynamic Model

The U.S. Department of Energy (DOE), Lockheed Martin Corporation (LM), and NASA Glenn Research Center (GRC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. As part of the extended operation testing of this power system, the Advanced Stirling Convertors (ASC) at NASA GRC undergo a vibration test sequence intended to simulate the vibration history that an ASC would experience when used in an ASRG for a space mission. During these tests, a data system collects several performance-related parameters from the convertor under test for health monitoring and analysis. Recently, an additional sensor recorded the slip table position during vibration testing to qualification level. The System Dynamic Model (SDM) integrates Stirling cycle thermodynamics, heat flow, mechanical mass, spring, damper systems, and electrical characteristics of the linear alternator and controller. This Paper presents a comparison of the performance of the ASC when exposed to vibration to that predicted by the SDM when exposed to the same vibration.

Meer, David W.↗
DOE OSTI2023

Acoustic signal based analysis of batteries

Systems and methods for acoustic signal based analysis, include obtaining acoustic response signal data of at least a portion of a battery cell, the acoustic response signal data comprising waveforms generated by transmitting one or more acoustic excitation signals into at least the portion of the battery cell and recording response vibration signals to the one or more acoustic excitation signals. One or more metrics are determined from at least the acoustic response signal data, the one or more metrics being determined based on correlation of the one or more metrics to one or more characteristics of battery cells and a reference model is generated from the one or more metrics. A test battery can be evaluated using the reference model. Actionable insights or recommendations can be generated based on the evaluation. The reference model can also be updated based on the evaluation.

Van Tassell, Barry J.↗
NASA NTRS1997

XV-15 Structural-Acoustic Data

Tiltrotor aircraft are a potentially viable means of intercity travel. The tiltrotor is able to transport passengers relatively quickly from the center of a city to destinations within a 300-mile radius. For such vehicles to be commercially viable, the interior noise and vibration levels must be acceptable to the passengers. A review of the literature revealed very little structural-acoustic data related to the tiltrotor. For this reason, structural-acoustic measurements were taken aboard an XV-15 tiltrotor. The six flight conditions included five in level flight, nominally 140-220 knots, for airplane mode (nacelle at 0 degrees) and one out-of-ground-effect (OGE) hover (nacelle at 90 degrees). The flight test measurements included nine exterior surface pressures, five structural accelerations, and two interior pressures. These sensors were located near the tip path plane on the port side of the aircraft. One minute of data was acquired at each condition. The data is presented as time histories, autospectra, coherence functions, and cross-spectra. In general, for level flight, the measured data showed very little effect of forward flight speed except to change the amplitude of the response; however, the character of the response was found to be dependent on spatial location. In contrast, in the hover mode the spatial location had very little effect on the character of the response. Additionally, the report highlights: the coherence between the transducer data and the rotor tach signal; and transfer function calculations between the exterior pressures.

Lyle, Karen H.↗
DOE OSTI2022

Bearing Fault Detection on Wind Turbine Gearbox Vibrations Using Generalized Likelihood Ratio-Based Indicators

Studies in condition monitoring literature often aim to detect rolling element bearing faults because they have one of the biggest shares among defects in turbo machinery. Accordingly, several prognosis and diagnosis methods have been devised to identify fault signatures from vibration signals. A recently proposed method to capture the rolling element bearing degradation provides the groundwork for new indicator families utilizing the generalized likelihood ratio test. This novel approach exploits the cyclostationarity and the impulsiveness of vibration signals independently in order to estimate the most suitable indicators for a given fault. However, the method has yet to be tested on complex experimental vibration signals such as those of a wind turbine gearbox. In this study, the approach is applied to the National Renewable Energy Laboratory Wind Turbine Gearbox Condition Monitoring Round Robin Study data set for bearing fault detection purposes. The data set is measured on an experimental test rig of a wind turbine gearbox; hence the complexity of the vibration signals is similar to a real case. The outcome demonstrates that the proposed method is capable of distinguishing between healthy and damaged vibration signals measured on a complex wind turbine gearbox.

condition monitoring↗
NASA NTRS2003

Unsteady Flowfield in a High-Pressure Turbine Modeled by TURBO

Forced response, or resonant vibrations, in turbomachinery components can cause blades to crack or fail because of the large vibratory blade stresses and subsequent high-cycle fatigue. Forced-response vibrations occur when turbomachinery blades are subjected to periodic excitation at a frequency close to their natural frequency. Rotor blades in a turbine are constantly subjected to periodic excitations when they pass through the spatially nonuniform flowfield created by upstream vanes. Accurate numerical prediction of the unsteady aerodynamics phenomena that cause forced-response vibrations can lead to an improved understanding of the problem and offer potential approaches to reduce or eliminate specific forced-response problems. The objective of the current work was to validate an unsteady aerodynamics code (named TURBO) for the modeling of the unsteady blade row interactions that can cause forced response vibrations. The three-dimensional, unsteady, multi-blade-row, Reynolds-averaged Navier-Stokes turbomachinery code named TURBO was used to model a high-pressure turbine stage for which benchmark data were recently acquired under a NASA contract by researchers at the Ohio State University. The test article was an initial design for a high-pressure turbine stage that experienced forced-response vibrations which were eliminated by increasing the axial gap. The data, acquired in a short duration or shock tunnel test facility, included unsteady blade surface pressures and vibratory strains.

Bakhle, Milind A.↗
DOE OSTI2026

Gearbox bearing crack growth prognostics and uncertainty quantification with physics-informed machine learning

This paper introduces the extreme theory of functional connections (X-TFC), a physics-informed machine learning algorithm, and tailors it to estimate the remaining useful life (RUL) of wind turbine gearbox bearings experiencing fatigue crack growth. Unlike purely data-driven methods, X-TFC embeds a physics model, based on Head's theory in this work, into its training objective. The core of X-TFC is a random-projection single-layer neural network trained via an extreme learning machine, which requires only limited damage progression data and solves for output weights with a least-squares optimization algorithm. A composite loss function balances the network's fit to observed degradation data against the residuals of the governing crack growth differential equation, ensuring the learned damage trajectory remains physically plausible. When applied to a vibration-based health-index (HI) dataset measured during the growth of a crack on the inner ring of a high-speed bearing in a wind turbine gearbox (Bechhoefer and Dubé, 2020), X-TFC achieves near-zero prediction bias. Even when trained on only the first 10 %–20 % of the damage progression data, with sufficient physics weighting its predictions remain monotonic and smooth, delivering high prognosability and trendability. To quantify the epistemic uncertainty, we employ a Monte Carlo ensemble of independently initialized X-TFC models trained on noise-perturbed data, which yields confidence intervals around each RUL estimate and captures both model-parameter and epistemic uncertainty. In addition to a vibration-based HI, we demonstrate that the proposed framework can be directly applied to a supervisory control and data acquisition (SCADA) data-based HI (Eftekhari Milani et al., 2026) measured during similar wind turbine gearbox bearing crack faults, preserving its accuracy and interpretability. This extension shows the versatility of our approach, which is applicable to bearings of multiple gearbox manufacturers, models, and ratings using only SCADA data. By integrating domain knowledge with machine learning, X-TFC offers a rapid, reliable tool for crack prognostics. Its adaptability to other bearing failure modes, such as pitch bearing ring cracks, positions X-TFC as a powerful enabler of data-driven, physics-informed asset management in the wind energy sector and beyond.

17 WIND ENERGY↗
NASA NTRS1991

Theoretical studies of important processes in planetary and comet atmospheres

The dissociative recombination (DR) of the AB(+) molecular ion with an electron has been shown to be an important component in the detailed interpretation of planetary ionosphere data. A first principles theoretical approach is developed for calculating the DR cross sections and rates for AB(+) molecular ions. The calculations focus on O2(+) and N2(+) DR, and are the first to include the indirect DR mechanism (Ryberg vibrational levels below v = 0 level of ion) for a molecule larger than H2(+). The importance of electron capture width in calculating the cross sections and rates is also examined. Electron capture widths are given for all states of O2 that are of importance to DR (lowest 10 vibrational levels of ion). Knowledge of the details of dissociative recombination will be needed for interpretation of data from future interplanetary and comet atmospheric studies.

Guberman, Steven L.↗
NASA NTRS2008

Post-Flight Estimation of Motion of Space Structures: Part 1

A computer program estimates the relative positions and orientations of two space structures from data on the angular positions and distances of fiducial objects on one structure as measured by a target tracking electronic camera and laser range finders on another structure. The program is written specifically for determining the relative alignments of two antennas, connected by a long truss, deployed in outer space from a space shuttle. The program is based partly on transformations among the various coordinate systems involved in the measurements and on a nonlinear mathematical model of vibrations of the truss. The program implements a Kalman filter that blends the measurement data with data from the model. Using time series of measurement data from the tracking camera and range finders, the program generates time series of data on the relative position and orientation of the antennas. A similar program described in a prior NASA Tech Briefs article was used onboard for monitoring the structures during flight. The present program is more precise and designed for use on Earth in post-flight processing of the measurement data to enable correction, for antenna motions, of scientific data acquired by use of the antennas.

Brugarolas, Paul↗