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All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

A Feasibility Study for Perioperative Ventricular Tachycardia Prognosis and Detection and Noise Detection Using a Neural Network and Predictive Linear Operators

To locate the accessory pathway(s) in preexicitation syndromes, epicardial and endocardial ventricular mapping is performed during anterograde ventricular activation via accessory pathway(s) from data originally received in signal form. As the number of channels increases, it is pertinent that more automated detection of coherent/incoherent signals is achieved as well as the prediction and prognosis of ventricular tachywardia (VT). Today's computers and computer program algorithms are not good in simple perceptual tasks such as recognizing a pattern or identifying a sound. This discrepancy, among other things, has been a major motivating factor in developing brain-based, massively parallel computing architectures. Neural net paradigms have proven to be effective at pattern recognition tasks. In signal processing, the picking of coherent/incoherent signals represents a pattern recognition task for computer systems. The picking of signals representing the onset ot VT also represents such a computer task. We attacked this problem by defining four signal attributes for each potential first maximal arrival peak and one signal attribute over the entire signal as input to a back propagation neural network. One attribute was the predicted amplitude value after the maximum amplitude over a data window. Then, by using a set of known (user selected) coherent/incoherent signals, and signals representing the onset of VT, we trained the back propagation network to recognize coherent/incoherent signals, and signals indicating the onset of VT. Since our output scheme involves a true or false decision, and since the output unit computes values between 0 and 1, we used a Fuzzy Arithmetic approach to classify data as coherent/incoherent signals. Furthermore, a Mean-Square Error Analysis was used to determine system stability. The neural net based picking coherent/incoherent signal system achieved high accuracy on picking coherent/incoherent signals on different patients. The system also achieved a high accuracy of picking signals which represent the onset of VT, that is, VT immediately followed these signals. A special binary representation of the input and output data allowed the neural network to train very rapidly as compared to another standard decimal or normalized representations of the data.

Moebes, T. A.↗
NASA NTRS1984

Application of induction coil measurements to the study of superalloy hot corrosion and oxidation

The assessment of the degree of hot corrosion attack on nickel based alloys is a difficult task, especially when the definition specifies that it must be in terms of metal consumed and even more difficult if the measurement must be nondestructive. The inductance of a solenoid coil responds to changes in volume of fill and composition of metal cores, therefore, it may be used for nondestructive measurement of hot corrosion. The hot corrosion of U700 was studied at 900 C in a Mach 0.3 flame doped with 0.85 wppm of sodium. The change of inductance was found to define the known corrosion behavior and to suggest its use as a tool with predictive capabilities. Sufficient sensitivity exists to detect oxidation of this alloy at 900 C.

Deadmore, D. L.↗
NASA NTRS2008

Robustness Analysis and Reliable Flight Regime Estimation of an Integrated Resilent Control System for a Transport Aircraft

Formal robustness analysis of aircraft control upset prevention and recovery systems could play an important role in their validation and ultimate certification. As a part of the validation process, this paper describes an analysis method for determining a reliable flight regime in the flight envelope within which an integrated resilent control system can achieve the desired performance of tracking command signals and detecting additive faults in the presence of parameter uncertainty and unmodeled dynamics. To calculate a reliable flight regime, a structured singular value analysis method is applied to analyze the closed-loop system over the entire flight envelope. To use the structured singular value analysis method, a linear fractional transform (LFT) model of a transport aircraft longitudinal dynamics is developed over the flight envelope by using a preliminary LFT modeling software tool developed at the NASA Langley Research Center, which utilizes a matrix-based computational approach. The developed LFT model can capture original nonlinear dynamics over the flight envelope with the ! block which contains key varying parameters: angle of attack and velocity, and real parameter uncertainty: aerodynamic coefficient uncertainty and moment of inertia uncertainty. Using the developed LFT model and a formal robustness analysis method, a reliable flight regime is calculated for a transport aircraft closed-loop system.

Shin, Jong-Yeob↗
NASA NTRS2012

Boundary-Layer Instability Measurements in a Mach-6 Quiet Tunnel

Several experiments have been performed in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University. A 7 degree half angle cone at 6 degree angle of attack with temperature-sensitive paint (TSP) and PCB pressure transducers was tested under quiet flow. The stationary crossflow vortices appear to break down to turbulence near the lee ray for sufficiently high Reynolds numbers. Attempts to use roughness elements to control the spacing of hot streaks on a flared cone in quiet flow did not succeed. Roughness was observed to damp the second-mode waves in areas influenced by the roughness, and wide roughness spacing allowed hot streaks to form between the roughness elements. A forward-facing cavity was used for proof-of-concept studies for a laser perturber. The lowest density at which the freestream laser perturbations could be detected was 1.07 x 10(exp -2) kilograms per cubic meter. Experiments were conducted to determine the transition characteristics of a streamwise corner flow at hypersonic velocities. Quiet flow resulted in a delayed onset of hot streak spreading. Under low Reynolds number flow hot streak spreading did not occur along the model. A new shock tube has been built at Purdue. The shock tube is designed to create weak shocks suitable for calibrating sensors, particularly PCB-132 sensors. PCB-132 measurements in another shock tube show the shock response and a linear calibration over a moderate pressure range.

Berridge, Dennis C.↗
NASA NTRS1998

Mars Microprobe Entry Analysis

The Mars Microprobe mission will provide the first opportunity for subsurface measurements, including water detection, near the south pole of Mars. In this paper, performance of the Microprobe aeroshell design is evaluated through development of a six-degree-of-freedom (6-DOF) aerodynamic database and flight dynamics simulation. Numerous mission uncertainties are quantified and a Monte-Carlo analysis is performed to statistically assess mission performance. Results from this 6-DOF Monte-Carlo simulation demonstrate that, in a majority of the cases (approximately 2-sigma), the penetrator impact conditions are within current design tolerances. Several trajectories are identified in which the current set of impact requirements are not satisfied. From these cases, critical design parameters are highlighted and additional system requirements are suggested. In particular, a relatively large angle-of-attack range near peak heating is identified.

Braun, Robert D.↗
NASA NTRS2014

Visualization of Flow Separation Around an Atmospheric Entry Capsule at Low-Subsonic Mach Number Using Background-Oriented Schlieren (BOS)

This paper presents the results of visualization of separated flow around a generic entry capsule that resembles the Apollo Command Module (CM) and the Orion Multi-Purpose Crew Vehicle (MPCV). The model was tested at flow speeds up to Mach 0.4 at a single angle of attack of 28 degrees. For manned spacecraft using capsule-shaped vehicles, certain flight operations such as emergency abort maneuvers soon after launch and flight just prior to parachute deployment during the final stages of entry, the command module may fly at low Mach number. Under these flow conditions, the separated flow generated from the heat-shield surface on both windward and leeward sides of the capsule dominates the wake flow downstream of the capsule. In this paper, flow visualization of the separated flow was conducted using the background-oriented schlieren (BOS) method, which has the capability of visualizing significantly separated wake flows without the particle seeding required by other techniques. Experimental results herein show that BOS has detection capability of density changes on the order of 10(sup-5).

Mizukaki, Toshiharu↗
NASA NTRSDate not supplied

Automatic Boundary-Layer Adaptation of Structured Grids in VULCAN-CFD

In supersonic and hypersonic flow computations, well-resolved boundary layers are essential for accurate quantification of surface heating and transition prediction, particularly via linear stability analysis. Grid design for hypersonic flows with shocks, boundary-layer separation, and/or complex mean flow features incorporating spanwise/azimuthal inhomogeneities is a difficult issue. In comparison to a manual grid adaptation procedure, an autonomous grid adaptation technique offers significant improvements in computing time and solution quality. The VULCAN-CFD solver already includes a validated procedure for automatic adaption of structured grids to the bow shock. The present focus is on implementing an automatic boundary-layer adaptation capability in VULCAN-CFD that adapts structured, multiblock grids to both the bow shock and the boundary layer at the same time. The boundary-layer adaptation algorithm allows the user to specify the number of cells within the boundary layer, along with the input parameters used for detecting the edge of the boundary layer, namely, the variable used in the edge detection criterion,the edge detection method, the detection direction, and the relaxation factor used during the morphing of the grid. The algorithm automatically distributes grid points along the wall-normal direction to achieve a smooth variation in grid spacing from the edge of the boundary layer to a"junction" location within the outer part of the grid. Illustrative results are presented for three different high-speed configurations: the two-dimensional flow over a cylinder at Mach 17.6 and unit Reynolds number of Re=0.38x10^6 m^-1, the axisymmetric flow over a cone-cylinder-flare model at Mach 6.0 and Re = 10.5×10^6 m^-1, and the three-dimensional flow over a blunt, 7-degree half-angle cone at 5-degree angle of attack in a Mach 9.79 flow with Re = 17.1×10^6 m^-1. The automated boundary-layer adaptation is shown to provide an adequate grid topology that is aligned with the bow shock in the outer part of the grid and also resolves the viscous boundary-layer region close to the surface.

boundary layer transition↗
NASA NTRS2012

Rugged, Portable, Real-Time Optical Gaseous Analyzer for Hydrogen Fluoride

Hydrogen fluoride (HF) is a primary evolved combustion product of fluorinated and perfluorinated hydrocarbons. HF is produced during combustion by the presence of impurities and hydrogen- containing polymers including polyimides. This effect is especially dangerous in closed occupied volumes like spacecraft and submarines. In these systems, combinations of perfluorinated hydrocarbons and polyimides are used for insulating wiring. HF is both highly toxic and short-lived in closed environments due to its reactivity. The high reactivity also makes HF sampling problematic. An infrared optical sensor can detect promptly evolving HF with minimal sampling requirements, while providing both high sensitivity and high specificity. A rugged optical path length enhancement architecture enables both high HF sensitivity and rapid environmental sampling with minimal gaseous contact with the low-reactivity sensor surfaces. The inert optical sample cell, combined with infrared semiconductor lasers, is joined with an analog and digital electronic control architecture that allows for ruggedness and compactness. The combination provides both portability and battery operation on a simple camcorder battery for up to eight hours. Optical detection of gaseous HF is confounded by the need for rapid sampling with minimal contact between the sensor and the environmental sample. A sensor is required that must simultaneously provide the required sub-parts-permillion detection limits, but with the high specificity and selectivity expected of optical absorption techniques. It should also be rugged and compact for compatibility with operation onboard spacecraft and submarines. A new optical cell has been developed for which environmental sampling is accomplished by simply traversing the few mm-thick cell walls into an open volume where the measurement is made. A small, low-power fan or vacuum pump may be used to push or pull the gaseous sample into the sample volume for a response time of a few seconds. The optical cell simultaneously provides for an enhanced optical interaction path length between the environmental sample and the infrared laser. Further, the optical cell itself is comprised of inert materials that render it immune to attack by HF. In some cases, the sensor may be configured so that the optoelectronic devices themselves are protected and isolated from HF by the optical cell. The optical sample cell is combined with custom-developed analog and digital control electronics that provide rugged, compact operation on a platform that can run on a camcorder battery. The sensor is inert with respect to acidic gases like HF, while providing the required sensitivity, selectivity, and response time. Certain types of combustion events evolve copious amounts of HF, very little of other gases typically associated with combustion (e.g., carbon monoxide), and very low levels of aerosols and particulates (which confound traditional smoke detectors). The new sensor platform could warn occupants early enough to take the necessary countermeasures.

Pilgrim, Jeffrey↗
NASA NTRS1996

Discrete Deterministic and Stochastic Petri Nets

Petri nets augmented with timing specifications gained a wide acceptance in the area of performance and reliability evaluation of complex systems exhibiting concurrency, synchronization, and conflicts. The state space of time-extended Petri nets is mapped onto its basic underlying stochastic process, which can be shown to be Markovian under the assumption of exponentially distributed firing times. The integration of exponentially and non-exponentially distributed timing is still one of the major problems for the analysis and was first attacked for continuous time Petri nets at the cost of structural or analytical restrictions. We propose a discrete deterministic and stochastic Petri net (DDSPN) formalism with no imposed structural or analytical restrictions where transitions can fire either in zero time or according to arbitrary firing times that can be represented as the time to absorption in a finite absorbing discrete time Markov chain (DTMC). Exponentially distributed firing times are then approximated arbitrarily well by geometric distributions. Deterministic firing times are a special case of the geometric distribution. The underlying stochastic process of a DDSPN is then also a DTMC, from which the transient and stationary solution can be obtained by standard techniques. A comprehensive algorithm and some state space reduction techniques for the analysis of DDSPNs are presented comprising the automatic detection of conflicts and confusions, which removes a major obstacle for the analysis of discrete time models.

MATHEMATICAL MODELS↗
NASA NTRS2007

Noninvasive Test Detects Cardiovascular Disease

At NASA's Jet Propulsion Laboratory (JPL), NASA-developed Video Imaging Communication and Retrieval (VICAR) software laid the groundwork for analyzing images of all kinds. A project seeking to use imaging technology for health care diagnosis began when the imaging team considered using the VICAR software to analyze X-ray images of soft tissue. With marginal success using X-rays, the team applied the same methodology to ultrasound imagery, which was already digitally formatted. The new approach proved successful for assessing amounts of plaque build-up and arterial wall thickness, direct predictors of heart disease, and the result was a noninvasive diagnostic system with the ability to accurately predict heart health. Medical Technologies International Inc. (MTI) further developed and then submitted the technology to a vigorous review process at the FDA, which cleared the software for public use. The software, patented under the name Prowin, is being used in MTI's patented ArterioVision, a carotid intima-media thickness (CIMT) test that uses ultrasound image-capturing and analysis software to noninvasively identify the risk for the major cause of heart attack and strokes: atherosclerosis. ArterioVision provides a direct measurement of atherosclerosis by safely and painlessly measuring the thickness of the first two layers of the carotid artery wall using an ultrasound procedure and advanced image-analysis software. The technology is now in use in all 50 states and in many countries throughout the world.

Source record↗
NASA NTRS2022

High Speed Inlet Distortion Test for the X 59 Low Boom Flight Demonstrator in the NASA Glenn 8-by 6-Foot Supersonic Wind Tunnel

The Low Boom Flight Demonstrator (LBFD) High Speed Inlet Distortion Test (HSIDT) was completed in the NASA Glenn Research Center 8- by 6-Foot Supersonic Wind Tunnel (8x6 SWT) using a 9.5 percent-scale propulsion model of the X–59 to evaluate the compatibility and operability of the inlet and engine integration, focusing on the inlet dynamic effects at the engine face. The model was instrumented with steady-state and high-response total pressure probes in the conventional 40-point, equal-area array at the aerodynamic interface plane (AIP). The HSIDT successfully collected high response distortion data points for the X–59 from Mach = 0 to 1.55 for a wide range of angle-of-attack, angle-of-sideslip, and inlet flow. Analyses showed that inlet dynamic distortion and inlet planar wave (or inlet buzz) were within engine limits through most of the flight envelope. The test data showed that inlet planar wave was present at Mach 1.35 and above, at airflows between idle and maximum engine airflow. Engine throttle back will need to be limited when decelerating from supersonic flight Mach to avoid these regions of inlet planar wave. The HSIDT data was also used to compare the metric SUM40, computed from the 40 high-response AIP total pressure probes, with the metric SUM4, computed from four high-response inlet static pressure probes. The data showed that SUM4 can be used as a surrogate for SUM40 during the X–59 flight test to detect inlet planar wave.

X-59↗
NASA NTRS1999

Unified Model Deformation and Flow Transition Measurements

The number of optical techniques that may potentially be used during a given wind tunnel test is continually growing. These include parameter sensitive paints that are sensitive to temperature or pressure, several different types of off-body and on-body flow visualization techniques, optical angle-of-attack (AoA), optical measurement of model deformation, optical techniques for determining density or velocity, and spectroscopic techniques for determining various flow field parameters. Often in the past the various optical techniques were developed independently of each other, with little or no consideration for other techniques that might also be used during a given test. Recently two optical techniques have been increasingly requested for production measurements in NASA wind tunnels. These are the video photogrammetric (or videogrammetric) technique for measuring model deformation known as the video model deformation (VMD) technique, and the parameter sensitive paints for making global pressure and temperature measurements. Considerations for, and initial attempts at, simultaneous measurements with the pressure sensitive paint (PSP) and the videogrammetric techniques have been implemented. Temperature sensitive paint (TSP) has been found to be useful for boundary-layer transition detection since turbulent boundary layers convect heat at higher rates than laminar boundary layers of comparable thickness. Transition is marked by a characteristic surface temperature change wherever there is a difference between model and flow temperatures. Recently, additional capabilities have been implemented in the target-tracking videogrammetric measurement system. These capabilities have permitted practical simultaneous measurements using parameter sensitive paint and video model deformation measurements that led to the first successful unified test with TSP for transition detection in a large production wind tunnel.

Burner, Alpheus W.↗
NASA NTRS2013

Siberian Pine Decline and Mortality in Southern Siberian Mountains

The causes and resulting spatial patterns of Siberian pine mortality in eastern Kuznetzky Alatau Mountains, Siberia were analyzed based on satellite (Landsat, MODIS) and dendrochronology data. Climate variables studied included temperature, precipitation and Standardized Precipitation-Evapotranspiration Index (SPEI) drought index. Landsat data analysis showed that stand mortality was first detected in the year 2006 at an elevation of 650 m, and extended up to 900 m by the year 2012. Mortality was accompanied by a decrease in MODIS derived vegetation index (EVI).. The area of dead stands and the upper mortality line were correlated with increased drought. The uphill margin of mortality was limited by elevational precipitation gradients. Dead stands (i.e., >75% tree mortality) were located mainly on southern slopes. With respect to slope, mortality was observed within a 7 deg - 20 deg range with greatest mortality occurring on convex terrain. Tree radial incrementmeasurements correlate and were synchronous with SPEI (r sq = 0.37, r(sub s) = 80). Increasing synchrony between tree ring growth and SPEI indicates that drought has reduced the ecological niche of Siberian pine. The results also showed the primary role of drought stress on Siberian pine mortality. A secondary role may be played by bark beetles and root fungi attacks. The observed Siberian pine mortality is part of a broader phenomenon of "dark needle conifers" (DNC, i.e., Siberian pine, fir and spruce) decline and mortality in European Russia, Siberia, and the Russian Far East. All locations of DNC decline coincided with areas of observed drought increase. The results obtained are one of the first observations of drought-induced decline and mortality of DNC at the southern border of boreal forests. Meanwhile if model projections of increased aridity are correct DNC, within the southern part of its range may be replaced by drought-resistant Pinus silvestris and Larix sibirica.

tree die-off↗
NASA NTRS1995

An overview of the Evaluation of Oxygen Interactions with Materials 3 experiment: Space Shuttle Mission 46, July-August 1992

The Evaluation of Oxygen Interactions with Materials 3 (EOIM-3) flight experiment was developed to obtain benchmark atomic oxygen reactivity data and was conducted during Space Transportation System Mission 46 (STS-46), July 31 to August 7, 1992. In this paper, we present an overview of EOIM-3 and the results of the Lyndon B. Johnson Space Center (JSC) materials reactivity and mass spectrometer/carousel experiments. Mass spectrometer calibration methods are discussed briefly, as a prelude to a detailed discussion of the mass spectrometric results produced during STS-46. Mass spectrometric measurements of ambient O-atom flux and fluence are in good agreement with the values calculated using the MSIS-86 model of the thermosphere as well as estimates based on the extent of O-atom reaction with Kapton polyimide. Mass spectrometric measurements of gaseous products formed by O-atom reaction with C(13) labeled Kapton revealed CO, CO2, H2O, NO, and NO2. Finally, by operating the mass spectrometer so as to detect naturally occurring ionospheric species, we characterized the ambient ionosphere at various times during EOIM-3 and detected the gaseous reaction products formed when ambient ions interacted with the C(13) Kapton carousel sector. By direct comparison of the results of on-orbit O-atom exposures with those conducted in ground-based laboratory systems, which provide known O-atom fluences and translational energies, we have demonstrated the strong translational energy dependence of O-atom reactions with a variety of polymers. A 'line-of-centers' reactive scattering model was shown to provide a reasonably accurate description of the translational energy dependence of polymer reactions with O atoms at high atom kinetic energies while a Beckerle-Ceyer model provided an accurate description of O-atom reactivity over a three order-of-magnitude range in translational energy and a four order-of-magnitude range in reaction efficiency. Postflight studies of the polymer samples by x-ray photoelectron spectroscopy and infrared spectroscopy demonstrate that O-atom attack is confined to the near-surface region of the sample, i.e. within 50 to 100 A of the surface.

Koontz, Steven L.↗
NASA NTRS2013

Network Penetration Testing and Research

This paper will focus the on research and testing done on penetrating a network for security purposes. This research will provide the IT security office new methods of attacks across and against a company's network as well as introduce them to new platforms and software that can be used to better assist with protecting against such attacks. Throughout this paper testing and research has been done on two different Linux based operating systems, for attacking and compromising a Windows based host computer. Backtrack 5 and BlackBuntu (Linux based penetration testing operating systems) are two different "attacker'' computers that will attempt to plant viruses and or NASA USRP - Internship Final Report exploits on a host Windows 7 operating system, as well as try to retrieve information from the host. On each Linux OS (Backtrack 5 and BlackBuntu) there is penetration testing software which provides the necessary tools to create exploits that can compromise a windows system as well as other operating systems. This paper will focus on two main methods of deploying exploits 1 onto a host computer in order to retrieve information from a compromised system. One method of deployment for an exploit that was tested is known as a "social engineering" exploit. This type of method requires interaction from unsuspecting user. With this user interaction, a deployed exploit may allow a malicious user to gain access to the unsuspecting user's computer as well as the network that such computer is connected to. Due to more advance security setting and antivirus protection and detection, this method is easily identified and defended against. The second method of exploit deployment is the method mainly focused upon within this paper. This method required extensive research on the best way to compromise a security enabled protected network. Once a network has been compromised, then any and all devices connected to such network has the potential to be compromised as well. With a compromised network, computers and devices can be penetrated through deployed exploits. This paper will illustrate the research done to test ability to penetrate a network without user interaction, in order to retrieve personal information from a targeted host.

Murphy, Brandon F.↗
NASA NTRS2000

Active Control Technology at NASA Langley Research Center

NASA Langley has a long history of attacking important technical opportunities from a broad base of supporting disciplines. The research and development at Langley in this subject area range from the test tube to the test flight. The information covered here will range from the development of innovative new materials, sensors and actuators, to the incorporation of smart sensors and actuators in practical devices, to the optimization of the location of these devices, to, finally, a wide variety of applications of these devices utilizing Langley's facilities and expertise. Advanced materials are being developed for sensors and actuators, as well as polymers for integrating smart devices into composite structures. Contributions reside in three key areas: computational materials; advanced piezoelectric materials; and integrated composite structures. The computational materials effort is focused on developing predictive tools for the efficient design of new materials with the appropriate combination of properties for next generation smart airframe systems. Research in the area of advanced piezoelectrics includes optimizing the efficiency, force output, use temperature, and energy transfer between the structure and device for both ceramic and polymeric materials. For structural health monitoring, advanced non-destructive techniques including fiber optics are being developed for detection of delaminations, cracks and environmental deterioration in aircraft structures. The computational materials effort is focused on developing predictive tools for the efficient design of new materials with the appropriate combination of properties for next generation smart airframe system. Innovative fabrication techniques processing structural composites with sensor and actuator integration are being developed.

Antcliff, Richard R.↗
NASA NTRS2003

The Meteoritic Component in Impact Deposits

This proposal requested support for a broad-based research program designed to understand the chemical and mineralogical record of accretion of extraterrestrial matter to the Earth. The primary goal of this research is to study the accretion history of the Earth, to understand how this accretion history reflects the long-term flux of comets, asteroids, and dust in the inner solar system and how this flux is related to the geological and biological history of the Earth. This goal is approached by seeking out the most significant projects that can be attacked utilizing the expertise of the PI and potential collaborators. The greatest expertise of the PI is the analysis of meteoritic components in terrestrial sediments. This proposal identifies three primary areas of research, involving impact events in the early Archean (3.2 Ga), the late Eocene (35 Ma) and the late Pliocene (2 Ma). In the early Archean we investigate sediments that contain the oldest recorded impacts on Earth. These are thick spherule beds, three of which were deposited within 20 m.y. If these are impact deposits the flux of objects to Earth at this time was much greater than predicted by current models. Earlier work used Cr isotopes to prove that one of these contain extraterrestrial matter, from a projectile with Cr isotopes similar to CV chondrites. We planned to expand this work to other spherule beds and to search for additional evidence of other impact events. With samples from D. Lowe (Stanford Univ.) the PI proposed to screen samples for high Ir and Cr so that appropriate samples can be provided to A. Shukolyukov for Cr-isotopic analyses. This work was expected to provide evidence that at least one interval in the early Archean was a period of intense bombardment and to characterize the composition of objects accreted. The late Eocene is also a period of intense bombardment with multiple spherule deposits and two large craters. Farley et al. (1998) demonstrated an increased (3)He flux to marine sediments that was attributed to an increase in interplanetary dust due to a shower of comets invading the inner solar system. We planned to detect a change in the Cr-isotopic composition in the flux of fine-grained extraterrestrial matter to ocean sediments. This would provide evidence for the comet shower hypothesis. We planned attempt to locate late Eocene impact deposits in a new high resolution, hi-latitude site that had the potential for excellent preservation and new information of the sources and effects of these impacts. Although most impacts on Earth occur in deep-ocean basins, only one such event is known - the late Pliocene impact of the Eltanin asteroid. The ejecta from this impact includes Ir- rich impact melt, spherules, and actual meteorites from the km-sized mesosiderite asteroid. Through a study of the ejecta, we can learn about the formation, distribution, alteration and preservation of Ir-rich deposits. We can also learn about meteorite survival during hypervelocity impacts and we can study pieces of a km-sized object to learn more about the mesosiderite parent body. Analyses of sediment cores and geophysical exploration of the impact site can further our understanding of the processes involved in deep-ocean impacts and potential effects on the terrestrial climate and biosphere. We planned analyses of this ejecta, a search for ejecta 5000 km distant from the impact area, and a new oceanographic expedition to study and sample the impact site. In addition to these three specific areas of research, the PI planned to remain flexible and available to exploit new opportunities presented by new discoveries, and to engage in new collaborations if other researchers require his expertise to develop new projects that fit within the objectives of the overall research program.

Kyte, Frank T.↗
NASA NTRS1994

High-lift flow-physics flight experiments on a subsonic civil transport aircraft (B737-100)

As part of the subsonic transport high-lift program, flight experiments are being conducted using NASA Langley's B737-100 to measure the flow characteristics of the multi-element high-lift system at full-scale high-Reynolds-number conditions. The instrumentation consists of hot-film anemometers to measure boundary-layer states, an infra-red camera to detect transition from laminar to turbulent flow, Preston tubes to measure wall shear stress, boundary-layer rakes to measure off-surface velocity profiles, and pressure orifices to measure surface pressure distributions. The initial phase of this research project was recently concluded with two flights on July 14. This phase consisted of a total of twenty flights over a period of about ten weeks. In the coming months the data obtained in this initial set of flight experiments will be analyzed and the results will be used to finalize the instrumentation layout for the next set of flight experiments scheduled for Winter and Spring of 1995. The main goal of these upcoming flights will be: (1) to measure more detailed surface pressure distributions across the wing for a range of flight conditions and flap settings; (2) to visualize the surface flows across the multi-element wing at high-lift conditions using fluorescent mini tufts; and (3) to measure in more detail the changes in boundary-layer state on the various flap elements as a result of changes in flight condition and flap deflection. These flight measured results are being correlated with experimental data measured in ground-based facilities as well as with computational data calculated with methods based on the Navier-Stokes equations or a reduced set of these equations. Also these results provide insight into the extent of laminar flow that exists on actual multi-element lifting surfaces at full-scale high-life conditions. Preliminary results indicate that depending on the deflection angle, the slat and flap elements have significant regions of laminar flow over a wide range of angles of attack. Boundary-layer transition mechanisms that were observed include attachment-line contamination on the slat and inflectional instability on the slat and fore flap. Also, the results agree fairly well with the predictions reported in a paper presented at last year's AIAA Fluid Dynamics Conference. The fact that extended regions of laminar flow are shown to exist on the various elements of the high-lift system raises the question what the effect is of loss of laminar flow as a result of insect contamiantion, rain or ice accumulation on high-life performance.

Vandam, Cornelis P.↗