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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Use of Convolutional Neural Network Image Classification and High-Speed Ion Probe Data Toward Real-Time Detonation Characterization in a Water-Cooled Rotating Detonation Engine

As rotating detonation engines (RDEs) progress in maturity, the importance of monitoring advancements toward development of active control becomes more critical. Experimental RDE data processing at time scales which satisfy real-time diagnostics will likely require the use of machine learning. This study aims to develop and deploy a novel real-time monitoring technique capable of determining detonation wave number, direction, frequency, and individual wave speeds throughout experimental RDE operational windows. To do so, the diagnostic integrates image classification by a convolutional neural network (CNN) and ionization current signal analysis. Wave mode identification through single-image CNN classification bypasses the need to evaluate sequential images and offers instantaneous identification of the wave mode present in the RDE annulus. Here, real-time processing speeds are achieved due to low data volumes required by the methodology, namely one short-exposure image and a short window of sensor data to generate each diagnostic output. The diagnostic acquires live data using a modified experimental setup alongside Pylon and PyDAQmx libraries within a python data acquisition environment. Lab-deployed diagnostic results are presented across varying wave modes, operating conditions, and data quality, currently executed at 3–4 Hz with a variety of iteration speed optimization options to be considered as future work. These speeds exceed that of conventional techniques and offer a proven structure for real-time RDE monitoring. The demonstrated ability to analyze detonation wave presence and behavior during RDE operation will certainly play a vital role in the development of RDE active control, necessary for RDE technology maturation toward industrial integration.

42 ENGINEERING↗
NASA NTRS1988

Rocketdyne automated dynamics data analysis and management system

An automated dynamics data analysis and management systems implemented on a DEC VAX minicomputer cluster is described. Multichannel acquisition, Fast Fourier Transformation analysis, and an online database have significantly improved the analysis of wideband transducer responses from Space Shuttle Main Engine testing. Leakage error correction to recover sinusoid amplitudes and correct for frequency slewing is described. The phase errors caused by FM recorder/playback head misalignment are automatically measured and used to correct the data. Data compression methods are described and compared. The system hardware is described. Applications using the data base are introduced, including software for power spectral density, instantaneous time history, amplitude histogram, fatigue analysis, and rotordynamics expert system analysis.

Tarn, Robert B.↗
NASA NTRS1968

Data Acquisition and Prompt Analysis System for High Altitude Balloon Experiments

An inexpensive and simple data acquisition system has been developed for balloon borne experiments and has been tested with a gamma ray detector in a balloon flight launched from Palestine, Texas. The detector used for the test consisted of an NaI(T1) scintillation crystal encased in a 1/8 in. plastic scintillator-charged particle shield. The combination was viewed by a single photomultiplier and charged particle gating was accomplished by a conventional phoswich discriminator. The pulse height analysis of the NaI events, not associated with prompt charged particle interactions, is accomplished by converting to a time spectrum using an airborne height to time converter. A range of pulse widths from 5 microseconds to 250 microseconds corresponds to energy losses in NaI from 100 to 1000 keV. The time spectrum information, along with charged particle events and barometric pressure, is fed to a mixer which modulates a 252.4 Mc FM transmitter. The original scintillator spectrum is recovered on the ground utilizing conversion circuitry at the receiver video output and a 128 channel commercial pulse height analyzer. The charged particle events of standard time width are stored with the spectrum at a fixed channel position and are therefore represented by a sharp line riding on the lower part of the NaI energy loss spectrum. An energy loss greater than 1000 keV is presented by the maximum pulse width of the converter and stored in the last analyzer channel. Barometric pressure data is transmitted by low frequency modulation of the sme FM carrier. In flight operation, the receiver video output can be recorded on a wide band tape recorder and simultaneously analyzed by the 128 channel analyzer, or the telemetered data can be analyzed later. The flight system features high pulse resolution, essentially instantaneous time response, high data rate, and flexibility; and is of modest cost. A detailed description of the system and operating performance is discussed.

Sarkady, A. A.↗
DOE OSTI2022

Application of wideband pulsed high-frequency EPR to molecular quantum spin science

This presentation provides an overview of a range of new applications in the area of molecular quantum spin science that are now possible at the US National High Magnetic Field Laboratory as a result of the development of a wideband, high-power 94 GHz pulsed EPR spectrometer. Here, this instrument allows true Fourier-transform detected experiments spanning a 1 GHz instantaneous bandwidth, akin to what has been possible in NMR for several decades. The presentation will begin by describing experiments on a nitroxide radical using chirped pulses, enabling acquisition of the full spectrum in a single sequence, thus providing a very efficient and convenient means to measure the field orientation dependence of the spin-lattice relaxation time, T 1 . This will be followed by a discussion of a coherent population transfer protocol involving the 2S + 1 = 8 Zeeman levels associated with the spin S = 7/2 Gd 3+ ion, potentially paving the way towards implementation of well-known quantum search algorithms. It will also be shown how the use of chirped pulses provides a route to achieving highly non-thermal spin populations, suggesting novel initialization schemes.

47 OTHER INSTRUMENTATION↗
NASA NTRS1974

A motion-constraint logic for moving-base simulators based on variable filter parameters

A motion-constraint logic for moving-base simulators has been developed that is a modification to the linear second-order filters generally employed in conventional constraints. In the modified constraint logic, the filter parameters are not constant but vary with the instantaneous motion-base position to increase the constraint as the system approaches the positional limits. With the modified constraint logic, accelerations larger than originally expected are limited while conventional linear filters would result in automatic shutdown of the motion base. In addition, the modified washout logic has frequency-response characteristics that are an improvement over conventional linear filters with braking for low-frequency pilot inputs. During simulated landing approaches of an externally blown flap short take-off and landing (STOL) transport using decoupled longitudinal controls, the pilots were unable to detect much difference between the modified constraint logic and the logic based on linear filters with braking.

Miller, G. K., Jr.↗
NASA NTRS1995

Fundamental phenomena on fuel decomposition and boundary-layer combustion processes with applications to hybrid rocket motors

The experimental study on the fundamental processes involved in fuel decomposition and boundary-layer combustion in hybrid rocket motors is continuously being conducted at the High Pressure Combustion Laboratory of The Pennsylvania State University. This research will provide a useful engineering technology base in the development of hybrid rocket motors as well as a fundamental understanding of the complex processes involved in hybrid propulsion. A high-pressure, 2-D slab motor has been designed, manufactured, and utilized for conducting seven test firings using HTPB fuel processed at PSU. A total of 20 fuel slabs have been received from the Mcdonnell Douglas Aerospace Corporation. Ten of these fuel slabs contain an array of fine-wire thermocouples for measuring solid fuel surface and subsurface temperatures. Diagnostic instrumentation used in the test include high-frequency pressure transducers for measuring static and dynamic motor pressures and fine-wire thermocouples for measuring solid fuel surface and subsurface temperatures. The ultrasonic pulse-echo technique as well as a real-time x-ray radiography system have been used to obtain independent measurements of instantaneous solid fuel regression rates.

Kuo, Kenneth K.↗
NASA NTRSDate not supplied

Wind Tunnel to Full Scale Mapping of Winds and Loads for Launch-Vehicle Ground Wind Loads

A launch vehicle ground-wind-loads program was conducted at the NASA Langley Transonic Dynamics Tunnel. The objectives were to quantify key aerodynamic and structural characteristics that impact the occurrence of large wind-induced oscillations of a launch vehicle when exposed to ground winds prior to launch. Of particular interest is the dynamic response of a launch vehicle when a von Kármán vortex street forms in the wake of the vehicle resulting in quasiperiodic lift and drag forces.Vehicle response to these quasiperiodic forces can become quite large when the frequency of vortex shedding nears that of a lowly-damped structural mode thereby exciting a resonant response. The study of ground-wind-loads presents unique challenges to quantify significant characteristics of the approaching wind and to relate the wind-tunnel acquired static, dynamic, and gravitational loads to full-scale vehicles. This paper will explain the correlation process between model-scale and full-scale wind characteristics and resulting structural loads. Characterization of the wind at a launch site requires knowledge of the vehicle dynamics and the anemometer performance. Vehicle dynamics dictate the frequency range of interest in characterization of the atmospheric turbulence, and in defining the required data window-length to model dynamic oscillation build-up during wind-gust analysis. Knowledge of the anemometer performance is required to infer peak wind magnitudes since most anemometers cannot directly measure instantaneous peak values. Following proper wind-speed correlation, static and dynamic wind-tunnel loads must be converted to full-scale equivalent values to derive design and operational guidance. In addition to the direct computation of full-scale equivalent loads using relevant scaling parameters, the corrections applied to dynamic loads accounting for differences in structural damping will also be discussed. Furthermore, a phenomenon that manifests in many slender and flexible launch vehicles is a load magnification due to gravity resulting from mass offset under deflection. A method for scaling this contribution from model-scale to full-scale is presented. Finally, a comparison of wind-tunnel derived loads using the described methodologies to launch vehicle measured loads is presented.

ground wind loads↗
NASA NTRSDate not supplied

Wind-Tunnel to Full-Scale Mapping of Winds and Loads for Launch-Vehicle Ground Wind Loads

A launch vehicle ground-wind-loads program was conducted at the NASA Langley Transonic Dynamics Tunnel. The objectives were to quantify key aerodynamic and structural characteristics that impact the occurrence of large wind-induced oscillations of a launch vehicle when exposed to ground winds prior to launch. Of particular interest is the dynamic response of a launch vehicle when a von Kármán vortex street forms in the wake of the vehicle resulting in quasiperiodic lift and drag forces. Vehicle response to these quasiperiodic forces can become quite large when the frequency of vortex shedding nears that of a lowly-damped structural mode thereby exciting a resonant response. The study of ground-wind-loads presents unique challenges to quantify significant characteristics of the approaching wind and to relate the wind-tunnel acquired static, dynamic, and gravitational loads to full-scale vehicles. This paper will explain the correlation process between model-scale and full-scale wind characteristics and resulting structural loads. Characterization of the wind at a launch site requires knowledge of the vehicle dynamics and the anemometer performance. Vehicle dynamics dictate the frequency range of interest in characterization of the atmospheric turbulence, and in defining the required data window-length to model dynamic oscillation build-up during wind-gust analysis. Knowledge of the anemometer performance is required to infer peak wind magnitudes since most anemometers cannot directly measure instantaneous peak values. Following proper wind-speed correlation, static and dynamic wind-tunnel loads must be converted to full-scale equivalent values to derive design and operational guidance. In addition to the direct computation of full-scale equivalent loads using relevant scaling parameters, the corrections applied to dynamic loads accounting for differences in structural damping will also be discussed. Furthermore, a phenomenon that manifests in many slender and flexible launch vehicles is a load magnification due to gravity resulting from mass offset under deflection. A method for scaling this contribution from model-scale to full-scale is presented. Finally, a comparison of wind-tunnel derived loads using the described methodologies to launch vehicle measured loads is presented.

Ground wind loads↗
DOE OSTI2022

An Electron-scattering Time Delay in Black Hole Accretion Disks

Abstract Universal to black hole X-ray binaries, the high-frequency soft lag gets longer during the hard-to-intermediate state transition, evolving from ≲1 to ∼10 ms. The soft lag production mechanism is thermal disk reprocessing of nonthermal coronal irradiation. X-ray reverberation models account for the light-travel time delay external to the disk, but assume instantaneous reprocessing of the irradiation inside the electron-scattering-dominated disk atmosphere. We model this neglected scattering time delay as a random walk within an α -disk atmosphere, with approximate opacities. To explain soft lag trends, we consider a limiting case of the scattering time delay that we dub the thermalization time delay, t th ; this is the time for irradiation to scatter its way down to the effective photosphere, where it gets thermalized, and then scatter its way back out. We demonstrate that t th plausibly evolves from being inconsequential for low mass accretion rates m ̇ characteristic of the hard state, to rivaling or exceeding the light-travel time delay for m ̇ characteristic of the intermediate state. However, our crude model confines t th to a narrow annulus near peak accretion power dissipation, so cannot yet explain in detail the anomalously long-duration soft lags associated with larger disk radii. We call for time-dependent models with accurate opacities to assess the potential relevance of a scattering delay.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1973

Applications of radio interferometry to navigation

Radio astronomy experiments have demonstrated the feasibility of making precise position measurements using interferometry techniques. The application of this method to navigation and marine geodesy is discussed, and comparisons are made with existing navigation systems. The very long baseline technique, with a master station, can use either an artificial satellite or natural sources as position references; a high-speed data link is required. A completely ship-borne system is shown to be feasible, at the cost of poorer sensitivity for natural sources. A comparison of Doppler, delay and phase-track modes of operating a very long baseline configuration is made, as that between instantaneous measurements and those where a source can be tracked from horizon to transit. Geometric limitations in latitude and longitude coverage are discussed. The characteristics of natural radio sources, their flux, distribution on the sky, and apparent size are shown to provide a limit on position measurements precision. The atmosphere and frequency standard used both contribute to position measurement uncertainty by affecting interferometric phase.

Knowles, S. H.↗
DOE OSTI2023

Energy transfer in random-matrix ensembles of Floquet Hamiltonians

Here, we explore the statistical properties of energy transfer in ensembles of doubly driven random-matrix Floquet Hamiltonians based on universal symmetry arguments. The energy-pumping efficiency distribution P⁡($\overline{E}$) is associated with the Hamiltonian parameter ensemble and the eigenvalue statistics of the Floquet operator. For specific Hamiltonian ensembles, P⁡($\overline{E}$) undergoes a transition which cannot be associated with a symmetry breaking of the instantaneous Hamiltonian. The Floquet eigenvalue spacing distribution indicates the considered ensembles constitute generic nonintegrable Hamiltonian families. As a step towards Hamiltonian engineering, we develop a machine-learning classifier to understand the relative parameter importance in resulting high-conversion efficiency. We propose random Floquet Hamiltonians as a general framework to investigate frequency conversion effects in a class of generic dynamical processes beyond adiabatic pumps.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1978

Origin and evolution of the radio emission from immediate postoutburst supernovae

Several models for the radio emission from immediate postoutburst supernovae are examined under the assumption that the expanding remnant consists of a homogeneously mixed distribution of relativistic particles, magnetic field, and thermal plasma. The evolutionary models are: (1) an adiabatic expansion model; (2) a model incorporating the existence of a central pulsar; and (3) variations on the first two models in which relativistic electrons are accelerated either instantaneously or over an extended period of time and in which ionization, bremsstrahlung, synchrotron, Compton, and expansion losses are explicitly included. The character of the radio emission expected from these models is quite dissimilar. Whereas in adiabatic expansion models the emission is expected to increase slowly and become most intense at high frequencies, in models involving a central pulsar the emission should increase rapidly with a maximum flux density that is the same at all frequencies. The theoretical evolution of the radio emission for each model is compared with observations of SN 1970g.

Marscher, A. P.↗
NASA NTRS2004

More About the Phase-Synchronized Enhancement Method

A report presents further details regarding the subject matter of "Phase-Synchronized Enhancement Method for Engine Diagnostics" (MFS-26435), NASA Tech Briefs, Vol. 22, No. 1 (January 1998), page 54. To recapitulate: The phase-synchronized enhancement method (PSEM) involves the digital resampling of a quasi-periodic signal in synchronism with the instantaneous phase of one of its spectral components. This resampling transforms the quasi-periodic signal into a periodic one more amenable to analysis. It is particularly useful for diagnosis of a rotating machine through analysis of vibration spectra that include components at the fundamental and harmonics of a slightly fluctuating rotation frequency. The report discusses the machinery-signal-analysis problem, outlines the PSEM algorithms, presents the mathematical basis of the PSEM, and presents examples of application of the PSEM in some computational simulations.

Jong, Jen-Yi↗
NASA NTRS1983

The effect of a leading-edge slat on the dynamic stall of an oscillating airfoil

The dynamic stall characteristics of a slatted airfoil were investigated experimentally on a 2-ft-chord airfoil oscillating in pitch at M = 0.2 for a range of reduced frequency and mean angle of oscillation. The slat produced a flow that remained attached to the airfoil for angles well above those normally attained by the retreating blade of a helicopter during high speed flight. The dynamic stall vortex usually associated with these flight conditions was completely eliminated for all angles under 30 deg. Instantaneous surface pressure, lift, and pitching moment data are presented as a function of incidence throughout the oscillation cycle; a detailed analysis of instantaneous boundary-layer flow behavior for the various test conditions is included.

Carr, L. W.↗
NASA NTRS2002

Unsteady Pressures in a Transonic Fan Cascade Due to a Single Oscillating Airfoil

An extensive set of unsteady pressure data was acquired along the midspan of a modern transonic fan blade for simulated flutter conditions. The data set was acquired in a nine-blade linear cascade with an oscillating middle blade to provide a database for the influence coefficient method to calculate instantaneous blade loadings. The cascade was set for an incidence of 10 dg. The data were acquired on three stationary blades on each side of the middle blade that was oscillated at an amplitude of 0.6 dg. The matrix of test conditions covered inlet Mach numbers of 0.5, 0.8, and 1.1 and the oscillation frequencies of 200, 300, 400, and 500 Hz. A simple quasiunsteady two-dimensional computer simulation was developed to aid in the running of the experimental program. For high Mach number subsonic inlet flows the blade pressures exhibit very strong, low-frequency, self-induced oscillations even without forced blade oscillations, while for low subsonic and supersonic inlet Mach numbers the blade pressure unsteadiness is quite low. The amplitude of forced pressure fluctuations on neighboring stationary blades strongly depends on the inlet Mach number and forcing frequency. The flowfield behavior is believed to be governed by strong nonlinear effects due to a combination of viscosity, compressibility, and unsteadiness. Therefore, the validity of the quasi-unsteady simplified computer simulation is limited to conditions when the flowfield is behaving in a linear, steady manner. Finally, an extensive set of unsteady pressure data was acquired to help development and verification of computer codes for blade flutter effects.

Lepicovsky, J.↗
NASA NTRS1987

The calibration and operation of a constant-temperature crossed-wire probe in supersonic flow

The calibration and operation of a constant-temperature crossed-wire probe in supersonic flow is considered. Crossed-wire probes offer considerable advantages over single, inclined wires: the kinematic shear stress can be derived from a single point measurement; the rms quantities can be derived from the same measurement, and the instantaneous quantities can be obtained as a continuous function of time. However, using a crossed-wire probe in supersonic flow is subject to the following practical difficulties: the problem of flow interference, where the shock waves from one wire and its supports interfere with the flow over the other wire; the necessity for high frequency response to resolve the spectral content, and the sensitivity of the results to small changes in the calibration constants. In the present contribution, each of these problems is addressed. Practical solutions are suggested, and some encouraging results are presented.

Fernando, E. M.↗
DOE OSTI2022

Thoughts and Hypotheses on the Metrics and Needs for the Stability of Highly Inverter-Based Island Systems

As levels of wind, photovoltaics (PVs), and battery energy storage on power systems rise, it is useful to be able to quickly compare how much generation (instantaneous power and annual energy) comes from these inverter-based resources (IBRs). A commonly used metric is the percentage of inverter-based generation (% IBR) in a dispatch scenario (as a percentage of the total generation or total load), which can be useful for estimating when certain operational challenges arise (high rates of change of frequency, underdamped control interactions, low system strength, low fault current availability, and so on). Another similar and commonly used metric pioneered on the relatively large island of Ireland, system nonsynchronous penetration (SNSP), is similar to the % IBR and is subject to similar limitations. SNSP has the advantage of handling high-voltage dc in a defined way.

fault currents↗
NASA NTRS1988

Source localization of Jupiter's Io dependent radio emissions

The peak frequencies of the Io-dependent part of the Jovian emissions are compared with the surface gyrofrequency determined from Jovian magnetic models in order to localize the source of Jovian radio emissions. The bulk of the Io-controlled emissions was found to be delayed by up to 70 deg of equatorial longitude from the predicted instantaneous position of the Io flux tube, with the L and S emissions both displaying this same unexpected behavior. It is suggested that the source of these emissions is delayed substantially with respect to Io either as an Alfven-wave delay or because of errors in the magnetic field models.

Aubier, Monique G.↗