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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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NASA NTRS2004

Characterizing the Energy Scale of the XRS on Astro-E2

The XRS on Astro-E2 consists of a microcalorimeter array with 31 active pixels. The XRS energy scale, which converts the measured pulse heights to the energies of the photons incident on the array, is a non-linear function of the thermal properties of the pixels and the power and noise conditions on the array. Each of the pixels operates independently and requires an individual energy scale. Analytic models of the XRS pulses are currently being developed that will be used to model the energy scale. However, because of the inherent complexity, a full empirical calibration of the energy scale is being conducted. The XRS energy scale has been calibrated for a range of operating conditions including variations in the detector temperature, bath temperatures, and photon flux. This allows us to characterize the functional dependence of the energy scale on these variables and to then generate a semi-empirical model that can be used to account for variations in operating conditions in space. We will present the results of the empirical characterization and comparisons to the analytic models.

Cottam, J.↗
NASA NTRS2004

A History of Full-Scale Aircraft and Rotorcraft Crash Testing and Simulation at NASA Langley Research Center

This paper summarizes 2-1/2 decades of full-scale aircraft and rotorcraft crash testing performed at the Impact Dynamics Research Facility (IDRF) located at NASA Langley Research Center in Hampton, Virginia. The IDRF is a 240-ft.-high steel gantry that was built originally as a lunar landing simulator facility in the early 1960's. It was converted into a full-scale crash test facility for light aircraft and rotorcraft in the early 1970 s. Since the first full-scale crash test was preformed in February 1974, the IDRF has been used to conduct: 41 full-scale crash tests of General Aviation (GA) aircraft including landmark studies to establish baseline crash performance data for metallic and composite GA aircraft; 11 full-scale crash tests of helicopters including crash qualification tests of the Bell and Sikorsky Advanced Composite Airframe Program (ACAP) prototypes; 48 Wire Strike Protection System (WSPS) qualification tests of Army helicopters; 3 vertical drop tests of Boeing 707 transport aircraft fuselage sections; and, 60+ crash tests of the F-111 crew escape module. For some of these tests, nonlinear transient dynamic codes were utilized to simulate the impact response of the airframe. These simulations were performed to evaluate the capabilities of the analytical tools, as well as to validate the models through test-analysis correlation. In September 2003, NASA Langley closed the IDRF facility and plans are underway to demolish it in 2007. Consequently, it is important to document the contributions made to improve the crashworthiness of light aircraft and rotorcraft achieved through full-scale crash testing and simulation at the IDRF.

Jackson, Karen E.↗
NASA NTRS2005

Local Scale Radiobrightness Modeling During the Intensive Observing Period-4 of the Cold Land Processes Experiment-1

The NASA Cold Land Processes Field Experiment (CLPX-1) was designed to provide microwave remote sensing observations and ground truth for studies of snow and frozen ground remote sensing, particularly issues related to scaling. CLPX-1 was conducted in 2002 and 2003 in Colorado, USA. One of the goals of the experiment was to test the capabilities of microwave emission models at different scales. Initial forward model validation work has concentrated on the Local-Scale Observation Site (LSOS), a 0.8 ha study site consisting of open meadows separated by trees where the most detailed measurements were made of snow depth and temperature, density, and grain size profiles. Results obtained in the case of the 3& Intensive Observing Period (IOP3) period (Feb., 2003, dry snow) suggest that a model based on Dense Medium Radiative Transfer (DMRT) theory is able to model the recorded brightness temperatures using snow parameters derived from field measurements. This paper focuses on the ability of forward DMRT modelling, combined with snowpack measurements, to reproduce the radiobrightness signatures observed by the University of Michigan s Truck-Mounted Radiometer System (TMRS) at 19 and 37 GHz during the 4th IOP (IOP4) in March, 2003. Unlike IOP3, conditions during IOP4 include both wet and dry periods, providing a valuable test of DMRT model performance. In addition, a comparison will be made for the one day of coincident observations by the University of Tokyo's Ground-Based Microwave Radiometer-7 (GBMR-7) and the TMRS. The plot-scale study in this paper establishes a baseline of DMRT performance for later studies at successively larger scales. And these scaling studies will help guide the choice of future snow retrieval algorithms and the design of future Cold Lands observing systems.

Kim, Edward J.↗
NASA NTRS2005

Moisture-Induced Spallation and Interfacial Hydrogen Embrittlement of Alumina Scales

Thermal expansion mismatch stresses and interfacial sulfur activity are the major factors producing primary Al2O3 scale spallation on high temperature alloys. However, moisture-induced delayed spallation appears as a secondary, but often dramatic, illustration of an additional mechanistic detail. A historical review of delayed failure of alumina scales and TBC s on superalloys is presented herein. Similarities with metallic phenomena suggest that hydrogen embrittlement from ambient humidity, resulting from the reaction Al+3H2O=Al(OH)3+3H(+)+3e(-), is the operative mechanism. This proposal was tested by standard cathodic hydrogen charging in 1N H2SO4, applied to Rene N5 pre-oxidized at 1150 C for 1000 1-hr cycles, and monitored by weight change, induced current, and microstructure. Here cathodic polarization at -2.0 V abruptly stripped mature Al2O3 scales at the oxide-metal interface. Anodic polarization at +2.0 V, however, produced alloy dissolution. Finally, with no applied voltage, the electrolyte alone produced neither scale spallation nor alloy dissolution. These experiments thus highlight the detrimental effects of hydrogen charging on alumina scale adhesion. It is proposed that interfacial hydrogen embrittlement is produced by moist air and is the root cause of both moisture-induced, delayed scale spallation and desktop TBC failures.

Smialek, James L.↗
NASA NTRS2006

In-Flight Validation of a Pilot Rating Scale for Evaluating Failure Transients in Electronic Flight Control Systems

Engineering development and qualification of a Research Flight Control System (RFCS) for the Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) JUH-60A has motivated the development of a pilot rating scale for evaluating failure transients in fly-by-wire flight control systems. The RASCAL RFCS includes a highly-reliable, dual-channel Servo Control Unit (SCU) to command and monitor the performance of the fly-by-wire actuators and protect against the effects of erroneous commands from the flexible, but single-thread Flight Control Computer. During the design phase of the RFCS, two piloted simulations were conducted on the Ames Research Center Vertical Motion Simulator (VMS) to help define the required performance characteristics of the safety monitoring algorithms in the SCU. Simulated failures, including hard-over and slow-over commands, were injected into the command path, and the aircraft response and safety monitor performance were evaluated. A subjective Failure/Recovery Rating (F/RR) scale was developed as a means of quantifying the effects of the injected failures on the aircraft state and the degree of pilot effort required to safely recover the aircraft. A brief evaluation of the rating scale was also conducted on the Army/NASA CH-47B variable stability helicopter to confirm that the rating scale was likely to be equally applicable to in-flight evaluations. Following the initial research flight qualification of the RFCS in 2002, a flight test effort was begun to validate the performance of the safety monitors and to validate their design for the safe conduct of research flight testing. Simulated failures were injected into the SCU, and the F/RR scale was applied to assess the results. The results validate the performance of the monitors, and indicate that the Failure/Recovery Rating scale is a very useful tool for evaluating failure transients in fly-by-wire flight control systems.

Kalinowski, Kevin F.↗
NASA NTRS2007

ANOPP Landing Gear Noise Prediction Comparisons to Model-scale Data

The NASA Aircraft NOise Prediction Program (ANOPP) includes two methods for computing the noise from landing gear: the "Fink" method and the "Guo" method. Both methods have been predominately validated and used to predict full-scale landing gear noise. The two methods are compared, and their ability to predict the noise for model-scale landing gear is investigated. Predictions are made using both the Fink and Guo methods and compared to measured acoustic data obtained for a high-fidelity, 6.3%-scale, Boeing 777 main landing gear. A process is developed by which full-scale predictions can be scaled to compare with model-scale data. The measurements were obtained in the NASA Langley Quiet Flow Facility for a range of Mach numbers at a large number of observer polar (flyover) and azimuthal (sideline) observer angles. Spectra and contours of the measured sound pressure levels as a function of polar and azimuthal angle characterize the directivity of landing gear noise. Comparisons of predicted noise spectra and contours from each ANOPP method are made. Both methods predict comparable amplitudes and trends for the flyover locations, but deviate at the sideline locations. Neither method fully captures the measured noise directivity. The availability of these measured data provides the opportunity to further understand and advance noise prediction capabilities, particularly for noise directivity.

Burley, Casey L.↗
NASA NTRS2007

Design and Analysis of a Formation Flying System for the Cross-Scale Mission Concept

The ESA-funded "Cross-Scale Technology Reference Study has been carried out with the primary aim to identify and analyse a mission concept for the investigation of fundamental space plasma processes that involve dynamical non-linear coupling across multiple length scales. To fulfill this scientific mission goal, a constellation of spacecraft is required, flying in loose formations around the Earth and sampling three characteristic plasma scale distances simultaneously, with at least two satellites per scale: electron kinetic (~10 km), ion kinetic (~100-2000 km), magnetospheric fluid (~3000-15000 km). The key Cross-Scale mission drivers identified are the number of S/C, the space segment configuration, the reference orbit design, the transfer and deployment strategy, the inter-satellite localization and synchronization process and the mission operations. This paper presents a comprehensive overview of the mission design and analysis for the Cross-Scale concept and outlines a technically feasible mission architecture for a multi-dimensional investigation of space plasma phenomena. The main effort has been devoted to apply a thorough mission-level trade-off approach and to accomplish an exhaustive analysis, so as to allow the characterization of a wide range of mission requirements and design solutions.

Cornara, Stefania↗
NASA NTRS2008

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al: Scale Microstructures - Part 2

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

Raj, S. V.↗
NASA NTRS2008

Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al Part II: Scale Microstructures

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

Raj, Sai V.↗
NASA NTRS1954

Free-Flight Zero-Lift Drag Results from a 1/5-Scale Model and Several Small-Scale Equivalent Bodies of Revolution of the Convair F-102 Configuration at Mach Numbers up to 1.34

A 1/5-scale, rocket-propelled model of the Convair F-102 configuration was tested in free flight to determine zero-lift drag at Mach numbers up to 1.34 and at Reynolds numbers comparable to those of the full-scale airplane. This large-scale model corresponded to the prototype airplane and had air flow through the duct. Additional zero-lift drag tests involved a series of small equivalent bodies of revolution which were launched by means of a helium gun. The several small-scale models tested corresponded to: the basic configuration, the 1/5-scale rocket-propelled model configuration, a 2-foot (full-scale) fuselage-extension configuration, and a 7-foot (full-scale) fuselage-extension configuration. Models designed to correspond to the area distribution at a Mach number of 1.0 were flown for each of these 'shapes and, in addition, models designed to correspond to the area distribution at a Mach number of 1.2 were flown for the 1/5-scale rocket-propelled model and the 7-foot-fuselage-extension configuration. The value of external pressure drag coefficient (including base drag) obtained from the large-scale rocket model was 0.0190 at a Mach number of 1..05 and the corresponding values from the equivalent-body tests varied from 0.0183 for the rocket-propelled model shape to 0.0137 for the 7-foot-fuselage-extension configuration. From the results of tests of equivalent bodies designed to correspond to the area distribution at a Mach number of 1.0, it is evident that the small changes in shape incorporated in the basic and 2-foot-fuselage-extension configurations from that of the rocket-propelled model configuration will provide no significant change in pressure drag. On the other hand, the data from the 7-foot-fuselage-extension model indicate a substantial reduction in pressure drag at transonic speeds.

Wallskog, Harvey A.↗
NASA NTRS2010

Evaluation of the Water Film Weber Number in Glaze Icing Scaling

Icing scaling tests were performed in the NASA Glenn Icing Research Tunnel to evaluate a new scaling method, developed and proposed by Feo for glaze icing, in which the scale liquid water content and velocity were found by matching reference and scale values of the nondimensional water-film thickness expression and the film Weber number. For comparison purpose, tests were also conducted using the constant We(sub L) method for velocity scaling. The reference tests used a full-span, fiberglass, 91.4-cm-chord NACA 0012 model with velocities of 76 and 100 knot and MVD sizes of 150 and 195 microns. Scale-to-reference model size ratio was 1:2.6. All tests were made at 0deg AOA. Results will be presented for stagnation point freezing fractions of 0.3 and 0.5.

Tsao, Jen-Ching↗
NASA NTRS2010

Evaluation of Scaling Methods for Rotorcraft Icing

This paper reports result of an experimental study in the NASA Glenn Icing Research Tunnel (IRT) to evaluate how well the current recommended scaling methods developed for fixed-wing unprotected surface icing applications might apply to representative rotor blades at finite angle of attack. Unlike the fixed-wing case, there is no single scaling method that has been systematically developed and evaluated for rotorcraft icing applications. In the present study, scaling was based on the modified Ruff method with scale velocity determined by maintaining constant Weber number. Models were unswept NACA 0012 wing sections. The reference model had a chord of 91.4 cm and scale model had a chord of 35.6 cm. Reference tests were conducted with velocities of 76 and 100 kt (39 and 52 m/s), droplet MVDs of 150 and 195 fun, and with stagnation-point freezing fractions of 0.3 and 0.5 at angle of attack of 0deg and 5deg. It was shown that good ice shape scaling was achieved for NACA 0012 airfoils with angle of attack lip to 5deg.

Tsao, Jen-Ching↗
NASA NTRS2010

Phased Array Noise Source Localization Measurements of an F404 Nozzle Plume at Both Full and Model Scale

A 48-microphone planar phased array system was used to acquire jet noise source localization data on both a full-scale F404-GE-F400 engine and on a 1/4th scale model of a F400 series nozzle. The full-scale engine test data show the location of the dominant noise sources in the jet plume as a function of frequency for the engine in both baseline (no chevron) and chevron configurations. Data are presented for the engine operating both with and without afterburners. Based on lessons learned during this test, a set of recommendations are provided regarding how the phased array measurement system could be modified in order to obtain more useful acoustic source localization data on high-performance military engines in the future. The data obtained on the 1/4th scale F400 series nozzle provide useful insights regarding the full-scale engine jet noise source mechanisms, and document some of the differences associated with testing at model-scale versus fullscale.

Podboy, Gary G.↗
NASA NTRS2010

Similarity Rules for Scaling Solar Sail Systems

Future science missions will require solar sails on the order of 200 square meters (or larger). However, ground demonstrations and flight demonstrations must be conducted at significantly smaller sizes, due to limitations of ground-based facilities and cost and availability of flight opportunities. For this reason, the ability to understand the process of scalability, as it applies to solar sail system models and test data, is crucial to the advancement of this technology. This paper will approach the problem of scaling in solar sail models by developing a set of scaling laws or similarity criteria that will provide constraints in the sail design process. These scaling laws establish functional relationships between design parameters of a prototype and model sail that are created at different geometric sizes. This work is applied to a specific solar sail configuration and results in three (four) similarity criteria for static (dynamic) sail models. Further, it is demonstrated that even in the context of unique sail material requirements and gravitational load of earth-bound experiments, it is possible to develop appropriate scaled sail experiments. In the longer term, these scaling laws can be used in the design of scaled experimental tests for solar sails and in analyzing the results from such tests.

Canfield, Stephen L.↗
NASA NTRS2010

On the Scaling of Small, Heat Simulated Jet Noise Measurements to Moderate Size Exhaust Jets

Modern military aircraft jet engines are designed with variable geometry nozzles to provide optimum thrust in different operating conditions, depending on the flight envelope. However, the acoustic measurements for such nozzles are scarce, due to the cost involved in making full scale measurements and the lack of details about the exact geometry of these nozzles. Thus the present effort at The Pennsylvania State University and the NASA Glenn Research Center- in partnership with GE Aviation is aiming to study and characterize the acoustic field produced by supersonic jets issuing from converging-diverging military style nozzles. An equally important objective is to validate methodology for using data obtained from small and moderate scale experiments to reliably predict the most important components of full scale engine noise. The experimental results presented show reasonable agreement between small scale and moderate scale jet acoustic data, as well as between heated jets and heat-simulated ones. Unresolved issues however are identified that are currently receiving our attention, in particular the effect of the small bypass ratio airflow. Future activities will identify and test promising noise reduction techniques in an effort to predict how well such concepts will work with full scale engines in flight conditions.

McLaughlin, Dennis K.↗
NASA NTRS2012

Microphysics in Multi-scale Modeling System with Unified Physics

Recently, a multi-scale modeling system with unified physics was developed at NASA Goddard. It consists of (1) a cloud-resolving model (Goddard Cumulus Ensemble model, GCE model), (2) a regional scale model (a NASA unified weather research and forecast, WRF), (3) a coupled CRM and global model (Goddard Multi-scale Modeling Framework, MMF), and (4) a land modeling system. The same microphysical processes, long and short wave radiative transfer and land processes and the explicit cloud-radiation, and cloud-land surface interactive processes are applied in this multi-scale modeling system. This modeling system has been coupled with a multi-satellite simulator to use NASA high-resolution satellite data to identify the strengths and weaknesses of cloud and precipitation processes simulated by the model. In this talk, a review of developments and applications of the multi-scale modeling system will be presented. In particular, the microphysics development and its performance for the multi-scale modeling system will be presented.

Tao, Wei-Kuo↗
NASA NTRS2012

Multi-Scale Modeling of Magnetospheric Dynamics

Magnetic reconnection is a key element in many phenomena in space plasma, e.g. Coronal mass Ejections, Magnetosphere substorms. One of the major challenges in modeling the dynamics of large-scale systems involving magnetic reconnection is to quantifY the interaction between global evolution of the magnetosphere and microphysical kinetic processes in diffusion regions near reconnection sites. Recent advances in small-scale kinetic modeling of magnetic reconnection significantly improved our understanding of physical mechanisms controlling the dissipation in the vicinity of the reconnection site in collisionless plasma. However the progress in studies of small-scale geometries was not very helpful for large scale simulations. Global magnetosphere simulations usually include non-ideal processes in terms of numerical dissipation and/or ad hoc anomalous resistivity. Comparative studies of magnetic reconnection in small scale geometries demonstrated that MHD simulations that included non-ideal processes in terms of a resistive term 11 J did not produce fast reconnection rates observed in kinetic simulations. In collisionless magnetospheric plasma, the primary mechanism controlling the dissipation in the vicinity of the reconnection site is nongyrotropic pressure effects with spatial scales comparable with the particle Larmor radius. We utilize the global MHD code BATSRUS and replace ad hoc parameters such as "critical current density" and "anomalous resistivity" with a physically motivated model of dissipation. The primary mechanism controlling the dissipation in the vicinity of the reconnection site in incorporated into MHD description in terms of non-gyrotropic corrections to the induction equation. We will demonstrate that kinetic nongyrotropic effects can significantly alter the global magnetosphere evolution. Our approach allowed for the first time to model loading/unloading cycle in response to steady southward IMF driving. The role of solar wind parameters and ionospheric conductance on the dynamics of the loading/unloading cycle will be discussed.

Kuznetsova, M. M.↗
NASA NTRS2008

On the Scaling Laws and Similarity Spectra for Jet Noise in Subsonic and Supersonic Flow

The scaling laws for the simulation of noise from subsonic and ideally expanded supersonic jets are reviewed with regard to their applicability to deduce full-scale conditions from small-scale model testing. Important parameters of scale model testing for the simulation of jet noise are identified, and the methods of estimating full- scale noise levels from simulated scale model data are addressed. The limitations of cold-jet data in estimating high-temperature supersonic jet noise levels are discussed. New results are presented showing the dependence of overall sound power level on the jet temperature ratio at various jet Mach numbers. A generalized similarity spectrum is also proposed, which accounts for convective Mach number and angle to the jet axis.

Kandula, Max↗