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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 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Online Bayesian State Estimation for Real-Time Monitoring of Growth Kinetics in Thin Film Synthesis

Rapid validation of newly predicted materials through autonomous synthesis requires real-time adaptive control methods that exploit physics knowledge, a capability that is lacking in most systems. Here, in this study, we demonstrate an approach to enable real-time control of thin film synthesis by combining in situ optical diagnostics with a Bayesian state estimation method. We developed a physical model for film growth and applied the direct filter (DF) method for real-time estimation of nucleation and growth rates during pulsed laser deposition (PLD). We validated the approach using simulated and experimental reflectivity data for WSe 2 growth and ultimately deployed the algorithm on an autonomous PLD system during the growth of 1T'-MoTe 2 . The DF robustly estimates growth parameters in real time at early stages of growth, down to 15% monolayer area coverage. This fusion of in situ diagnostics, data assimilation, and physical modeling opens new opportunities in adaptive control of synthesis trajectories toward desired material states.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Anomalous Growth Rate of Ag Nanocrystals Revealed by in situ STEM

In situ microscopy of colloidal nanocrystal growth offers a unique opportunity to acquire direct and straightforward data for assessing classical growth models. For this study, we observe the growth trajectories of individual Ag nanoparticles in solution using in situ scanning transmission electron microscopy. For the first time, we provide experimental evidence of growth rates of Ag nanoparticles in the presence of Pt in solution that are significantly faster than predicted by Lifshitz-Slyozov-Wagner theory. We attribute these observed anomalous growth rates to the synergistic effects of the catalytic properties of Pt and the electron beam itself. Transiently reduced Pt atoms serve as active sites for Ag ions to grow, thereby playing a key role in controlling the growth kinetics. Electron beam illumination greatly increases the local concentration of free radicals, thereby strongly influencing particle growth rate and the resulting particle morphology. Through a systematic investigation, we demonstrate the feasibility of utilizing these synergistic effects for controlling the growth rates and particle morphologies at the nanoscale. Our findings not only expand the current scope of crystal growth theory, but may also lead to a broader scientific application of nanocrystal synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2014

The collisional depolarization of OH(A {sup 2}Σ{sup +}) and NO(A {sup 2}Σ{sup +}) with Kr

Quantum beat spectroscopy has been used to measure rate coefficients at 300 K for collisional depolarization for NO(A {sup 2}Σ{sup +}) and OH(A {sup 2}Σ{sup +}) with krypton. Elastic depolarization rate coefficients have also been determined for OH(A) + Kr, and shown to make a much more significant contribution to the total depolarization rate than for NO(A) + Kr. While the experimental data for NO(A) + Kr are in excellent agreement with single surface quasiclassical trajectory (QCT) calculations carried out on the upper 2A{sup ′} potential energy surface, the equivalent QCT and quantum mechanical calculations cannot account for the experimental results for OH(A) + Kr collisions, particularly at low N. This disagreement is due to the presence of competing electronic quenching at low N, which requires a multi-surface, non-adiabatic treatment. Somewhat improved agreement with experiment is obtained by means of trajectory surface hopping calculations that include non-adiabatic coupling between the ground 1A{sup ′} and excited 2A{sup ′} states of OH(X/A) + Kr, although the theoretical depolarization cross sections still significantly overestimate those obtained experimentally.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1974

Flight tests of Viking parachute system in three Mach number regimes. 1: Vehicle description, test operations, and performance

Flight qualifications for parachutes were tested on full-scale simulated Viking spacecraft at entry conditions for the Viking 1975 mission to Mars. The vehicle was carried to an altitude of 36.6 km for the supersonic and transonic tests by a 980.000 cu m balloon. The vehicles were released and propelled to test conditions with rocket engines. A 117,940 cu m balloon carried the test vehicle to an altitude of 27.5 km and the conditions for the subsonic tests were achieved in free fall. Aeroshell separation occurred on all test vehicles from 8 to 14 seconds after parachute deployment. This report describes: (1) the test vehicle; (2) methods used to insure that the test conditions were achieved; and (3) the balloon system design and operations. The report also presents the performance data from onboard and ground based instruments and the results from a statistical trajectory program which gives a continuous history of test-vehicle motions.

Lundstrom, R. R.↗
NASA NTRS1983

Space Shuttle base heating

First-stage and second-stage heating environments of the base region of the Space Shuttle are characterized in detail in terms of Orbiter-main-engine-plume and booster-plume radiation, freestream-air convective cooling, and reversed-plume-flow convective heating as they affect each base-region design point. Design predictions are compared with selected heating-rate data from flights STS-1 through STS-5; the flight data are found to show excellent interflight repeatability independent of small changes in trajectory, and to verify the validity of the prediction methodology. The impact of individual flight events on base heating is indicated.

Greenwood, T. F.↗
NASA NTRS1985

Navigation study for low-altitude Earth satellites

This document describes several navigation studies for low-altitude Earth satellites. The use of Global Positioning System Navigation Package data for LANDSAT-5 orbit determination is evaluated. In addition, a navigation analysis for the proposed Tracking and Data Aquisition System is presented. This analysis, based on simulations employing one-way Doppler data, is used to determine the agreement between the Research and Development Goddard Trajectory Determination System and the Sequential Error Analysis Program results. Properties of several geopotential error models are studied and an exploratory study of orbit smoother process noise is presented.

Pastor, P. R.↗
NASA NTRS1994

Groundspeed filtering for CTAS

Ground speed is one of the radar observables which is obtained along with position and heading from NASA Ames Center radar. Within the Center TRACON Automation System (CTAS), groundspeed is converted into airspeed using the wind speeds which CTAS obtains from the NOAA weather grid. This airspeed is then used in the trajectory synthesis logic which computes the trajectory for each individual aircraft. The time history of the typical radar groundspeed data is generally quite noisy, with high frequency variations on the order of five knots, and occasional 'outliers' which can be significantly different from the probable true speed. To try to smooth out these speeds and make the ETA estimate less erratic, filtering of the ground speed is done within CTAS. In its base form, the CTAS filter is a 'moving average' filter which averages the last ten radar values. In addition, there is separate logic to detect and correct for 'outliers', and acceleration logic which limits the groundspeed change in adjacent time samples. As will be shown, these additional modifications do cause significant changes in the actual groundspeed filter output. The conclusion is that the current ground speed filter logic is unable to track accurately the speed variations observed on many aircraft. The Kalman filter logic however, appears to be an improvement to the current algorithm used to smooth ground speed variations, while being simpler and more efficient to implement. Additional logic which can test for true 'outliers' can easily be added by looking at the difference in the a priori and post priori Kalman estimates, and not updating if the difference in these quantities is too large.

Slater, Gary L.↗
NASA NTRS1994

Analysis of tropospheric aerosol number density for aerosols of 0.2- to 3-micrometers diameter: Central and northeastern Canada

NASA's Atmospheric Boundary Layer Experiment conducted during the summer of 1990 focused on the distribution of trace species in central and northeastern Canada (altitudes less than 6 km) and the importance of surface sources/sinks, local emissions, distant transport, tropospheric/stratospheric exchange. Aircraft flights were based from North Bay, Ontario, and Goose Bay, Labrador, Canada. As part of the aircraft measurements, aerosol number density (0.2- to 3-micrometers diameter) was measured using an optical laser technique. Results show that summertime aerosol budgets of central and northeastern Canada can be significantly impacted by the transport of pollutants from distant source regions. Biomass burning in Alaska and western and central Canada exerts major influences on regional aerosol budgets. Urban emissions transported from the U.S./Canadian border regions are also important. Aerosol enhancements (mixed layer and free troposphere) were most prevalent in air with carbon monoxide mixing ratios greater than 110 parts per billion by volume (ppbv). When data were grouped as to the source of the air (5-day back trajectories) either north or south of the polar jet, aerosol number density in the mixed layer showed a tendency to be enhanced for air south of the jet relative to north of the jet. However, this difference was not observed for measurements at the higher altitudes (4 to 6 km). For some flights, mixed layer aerosol number densities were greater than 100 higher than free-tropospheric values (3- to 6-km altitude). The majority of the observed mixed layer enhancement was associated with transport of effluent-rich air into the Canadian regions. Aerosol emissions from natural Canadian ecosystems were relatively small when compared to transport.

Gregory, Gerald L.↗
NASA NTRS1996

Numerical Investigation of Two-Phase Flows With Charged Droplets in Electrostatic Field

A numerical method to solve two-phase turbulent flows with charged droplets in an electrostatic field is presented. The ensemble-averaged Navier-Stokes equations and the electrostatic potential equation are solved using a finite volume method. The transitional turbulence field is described using multiple-time-scale turbulence equations. The equations of motion of droplets are solved using a Lagrangian particle tracking scheme, and the inter-phase momentum exchange is described by the Particle-In-Cell scheme. The electrostatic force caused by an applied electrical potential is calculated using the electrostatic field obtained by solving a Laplacian equation and the force exerted by charged droplets is calculated using the Coulombic force equation. The method is applied to solve electro-hydrodynamic sprays. The calculated droplet velocity distributions for droplet dispersions occurring in a stagnant surrounding are in good agreement with the measured data. For droplet dispersions occurring in a two-phase flow, the droplet trajectories are influenced by aerodynamic forces, the Coulombic force, and the applied electrostatic potential field.

Kim, Sang-Wook↗
NASA NTRS1998

Engineering Aerothermal Analysis for X-34 Thermal Protection System Design

Design of the thermal protection system for any hypersonic flight vehicle requires determination of both the peak temperatures over the surface and the heating-rate history along the flight profile. In this paper, the process used to generate the aerothermal environments required for the X-34 Testbed Technology Demonstrator thermal protection system design is described as it has evolved from a relatively simplistic approach based on engineering methods applied to critical areas to one of detailed analyses over the entire vehicle. A brief description of the trajectory development leading to the selection of the thermal protection system design trajectory is included. Comparisons of engineering heating predictions with wind-tunnel test data and with results obtained using a Navier- Stokes flowfield code and an inviscid/boundary layer method are shown. Good agreement is demonstrated among all these methods for both the ground-test condition and the peak heating flight condition. Finally, the detailed analysis using engineering methods to interpolate the surface-heating-rate results from the inviscid/boundary layer method to predict the required thermal environments is described and results presented.

Wurster, Kathryn E.↗
NASA NTRS1998

Engineering Aerothermal Analysis for X-34 Thermal Protection System Design

Design of the thermal protection system for any hypersonic flight vehicle requires determination of both the peak temperatures over the surface and the heating-rate history along the flight profile. In this paper, the process used to generate the aerothermal environments required for the X-34 Testbed Technology Demonstrator thermal protection system design is described as it has evolved from a relatively simplistic approach based on engineering methods applied to critical areas to one of detailed analyses over the entire vehicle. A brief description of the trajectory development leading to the selection of the thermal protection system design trajectory is included. Comparisons of engineering heating predictions with wind-tunnel test data and with results obtained using a Navier-Stokes flowfield code and an inviscid/boundary layer method are shown. Good agreement is demonstrated among all these methods for both the ground-test condition and the peak heating flight condition. Finally, the detailed analysis using engineering methods to interpolate the surface-heating-rate results from the inviscid/boundary layer method to predict the required thermal environments is described and results presented.

Wurster, Kathryn E.↗
NASA NTRS1999

Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. I. Normal responses

The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in five squirrel monkeys with intact vestibular function. The VOR evoked by steps of acceleration in darkness (3,000 degrees /s(2) reaching a velocity of 150 degrees /s) began after a latency of 7.3 +/- 1.5 ms (mean +/- SD). Gain of the reflex during the acceleration was 14.2 +/- 5.2% greater than that measured once the plateau head velocity had been reached. A polynomial regression was used to analyze the trajectory of the responses to steps of acceleration. A better representation of the data was obtained from a polynomial that included a cubic term in contrast to an exclusively linear fit. For sinusoidal rotations of 0.5-15 Hz with a peak velocity of 20 degrees /s, the VOR gain measured 0.83 +/- 0.06 and did not vary across frequencies or animals. The phase of these responses was close to compensatory except at 15 Hz where a lag of 5.0 +/- 0.9 degrees was noted. The VOR gain did not vary with head velocity at 0.5 Hz but increased with velocity for rotations at frequencies of >/=4 Hz (0. 85 +/- 0.04 at 4 Hz, 20 degrees /s; 1.01 +/- 0.05 at 100 degrees /s, P < 0.0001). No responses to these rotations were noted in two animals that had undergone bilateral labyrinthectomy indicating that inertia of the eye had a negligible effect for these stimuli. We developed a mathematical model of VOR dynamics to account for these findings. The inputs to the reflex come from linear and nonlinear pathways. The linear pathway is responsible for the constant gain across frequencies at peak head velocity of 20 degrees /s and also for the phase lag at higher frequencies being less than that expected based on the reflex delay. The frequency- and velocity-dependent nonlinearity in VOR gain is accounted for by the dynamics of the nonlinear pathway. A transfer function that increases the gain of this pathway with frequency and a term related to the third power of head velocity are used to represent the dynamics of this pathway. This model accounts for the experimental findings and provides a method for interpreting responses to these stimuli after vestibular lesions.

NASA Program Biomedical Research and Countermeasur↗
NASA NTRS2005

Plasma Heating Simulation in the VASIMR System

The paper describes the recent development in the simulation of the ion-cyclotron acceleration of the plasma in the VASIMR experiment. The modeling is done using an improved EMIR code for RF field calculation together with particle trajectory code for plasma transport calculat ion. The simulation results correlate with experimental data on the p lasma loading and predict higher ICRH performance for a higher density plasma target. These simulations assist in optimizing the ICRF anten na so as to achieve higher VASIMR efficiency.

Ilin, Andrew V.↗
NASA NTRS2007

Mach 10 Stage Separation Analysis for the X43-A

This paper describes the pre-flight stage separation analysis that was conducted in support of the final flight of the X-43A. In that flight, which occurred less than eight months after the successful Mach 7 flight, the X-43A Research Vehicle attained a peak speed of Mach 9.6. Details are provided on how the lessons learned from the Mach 7 flight affected separation modeling and how adjustments were made to account for the increased flight Mach number. Also, the procedure for defining the feedback loop closure and feed-forward parameters employed in the separation control logic are described, and their effect on separation performance is explained. In addition, the range and nominal values of these parameters, which were included in the Mission Data Load, are presented. Once updates were made, the nominal pre-flight trajectory and Monte Carlo statistical results were determined and stress tests were performed to ensure system robustness. During flight the vehicle performed within the uncertainty bounds predicted in the pre-flight analysis and ultimately set the world record for airbreathing powered flight.

Tartabini, Paul V.↗
NASA NTRS2008

Overview of NASA's Integrated Design and Engineering Analysis (IDEA)Environment

Historically, the design of subsonic and supersonic aircraft has been divided into separate technical disciplines (such as propulsion, aerodynamics and structures) each of which performs their design and analysis in relative isolation from others. This is possible in most cases either because the amount of interdisciplinary coupling is minimal or because the interactions can be treated as linear. The design of hypersonic airbreathing vehicles, like NASA s X-43, is quite the opposite. Such systems are dominated by strong non-linear interactions between disciplines. The design of these systems demands that a multi-disciplinary approach be taken. Furthermore, increased analytical fidelity at the conceptual design phase is highly desirable as many of the non-linearities are not captured by lower fidelity tools. Only when these systems are designed from a true multi-disciplinary perspective can the real performance benefits be achieved and complete vehicle systems be fielded. Toward this end, the Vehicle Analysis Branch at NASA Langley Research Center has been developing the Integrated Design & Engineering Analysis (IDEA) Environment. IDEA is a collaborative environment for parametrically modeling conceptual and preliminary launch vehicle configurations using the Adaptive Modeling Language (AML) as the underlying framework. The environment integrates geometry, configuration, propulsion, aerodynamics, aerothermodynamics, trajectory, closure and structural analysis into a generative, parametric, unified computational model where data is shared seamlessly between the different disciplines. Plans are also in place to incorporate life cycle analysis tools into the environment which will estimate vehicle operability, reliability and cost. IDEA is currently being funded by NASA s Hypersonics Project, a part of the Fundamental Aeronautics Program within the Aeronautics Research Mission Directorate. The environment is currently focused around a two-stage-to-orbit configuration with a turbine based combined cycle (TBCC) first stage and reusable rocket second stage. This paper provides an overview of the development of the IDEA environment, a description of the current status and detail of future plans.

Robinson, Jeffrey S.↗
NASA NTRS2007

Overview of Key Saturn Probe Mission Trades

Ongoing studies, performed at NASA/JPL over the past two years in support of NASA's SSE Roadmap activities, proved the feasibility of a NF class Saturn probe mission. I. This proposed mission could also provide a good opportunity for international collaboration with the proposed Cosmic Vision KRONOS mission: a) With ESA contributed probes (descent modules) on a NASA lead mission; b) Early 2017 launch could be a good programmatic option for ESA-CV/NASA-NF. II. A number of mission architectures could be suitable for this mission: a) Probe Relay based architecture with short flight time (approx. 6.3-7 years); b) DTE probe telecom based architecture with long flight time (-11 years), and low probe data rate, but with the probes decoupled from the carrier, allowing for polar trajectories I orbiter. This option may need technology development for telecom; c) Orbiter would likely impact mission cost over flyby, but would provide significantly higher science return. The Saturn probes mission is expected to be identified in NASA's New Frontiers AO. Thus, further studies are recommended to refine the most suitable architecture. International collaboration is started through the KRONOS proposal work; further collaborated studies will follow once KRONOS is selected in October under ESA's Cosmic Vision Program.

probes↗