Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “feature impact”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

The Continuing Quest for "Regolithic" Howardites

The howardite, eucrite and diogenite (HED) meteorites likely originate from asteroid 4-Vesta, the first of two asteroids targeted by NASA's Dawn mission]. Howardites are polymict breccias dominantly composed of basaltic (eucrite) and orthopyroxenitic (diogenite) material. They are believed to originate from the surface of Vesta, and may represent the regolithic surface layer. Many howardites contain "regolith"-like features including fragmental breccias clasts, carbonaceous chondrite fragments and melt clasts (impact and volcanic). Though such features may relate to asteroid regolith formation processes, the exact regolithic nature of the howardite suite is not well defined.

Cartwright, J. A.↗
NASA NTRSDate not supplied

Results of the NASA Prediction Uncertainty Reduction Tech Challenge

In January 2021 the Advanced Air Vehicles Program approved a new Tech Challenge (TC) to be run out of the Commercial Supersonic Technology (CST) Project. The objective of the TC was to bring uncertainties in the empirical noise modeling for civilian supersonic aircraft into the same range as that of conventional aircraft. The TC goal statement was to “Produce data and demonstrate tools that reduce the uncertainty in predicting Landing & Takeoff Noise levels of supersonic-relevant designs by 5 EPNdB and are ready for use in studies to inform FAA rule-making.” To make the required improvements in noise prediction methods for supersonic aircraft, NASA decided to validate and use high-fidelity numerical simulations to acquire the needed noise data on supersonic propulsion configurations. High-fidelity component designs were developed, such as a two-stage propulsor behind a supersonic inlet designed by General Electric Aviation and variable area exhaust systems using input from recent contracts with GE and Rolls Royce. A noise database was generated as a function of geometric and flow parameters, providing corrections to the empirical noise models and added new input variables to describe the complexities created by the supersonic-specific design features. Statistically, the new models were able to predict the acoustic impact of supersonic-specific features, the reduction in uncertainty being reduced from the baseline 7.8 EPNdB at the beginning of the TC to 2.0 EPNdB at the end.

noise prediction↗
NASA NTRS1992

Compositional analysis and classification of projectile residues in LDEF impact craters

This catalog contains preliminary analyses of residues of hypervelocity projectiles that encountered gold substrates exposed by instrument A0187-1 on the Long Duration Exposure Facility (LDEF). This instrument was on LDEF's trailing edge where relative encounter speeds should be lowest for any non-spinning platform in low Earth orbit (LEO). Approximately 0.6 m(exp 2) of Au substrates yielded 198 impact craters greater than 20 micrometers in diameter. Some 30 percent of the craters were made by natural cosmic dust particles and some 15 percent by man-made objects. Some 50 percent of all features, however, have residues, if any, that are beyond the detection threshold of the SEM-EDXA method used. The purpose of this catalog is to provide detailed evidence and criteria that may be used to arrive at specific particle types on a case-by-case basis and to group such particles into compositional classes. Clearly this is a somewhat interpretative undertaking. For that reason, we encourage and solicit critique and comments from those interested in the systematic analysis of all impact features on LDEF.

Horz, Friedrich↗
NASA NTRS1992

Venusian impact basins and cratered terrains

The consensus regarding interpretation of Magellan radar imagery assigns Venus a young volcanic surface subjected in many areas to moderate crustal shortening. I infer that, on the contrary, ancient densely cratered terrain and large impact basins may be preserved over more than half the planet and that crustal shortening has been much overestimated. I see wind erosion and deposition as far more effective in modifying old structures. Integration with lunar chronology suggests that most of the surface of Venus may be older than 3.0 Ga and much may be older than 3.8 Ga. Broad volcanos, hug volcanic domes, plains preserving lobate flow patterns, and numerous lesser volcanic features, pocked sparsely by impact craters, are indeed obvious on Magellan imagery. Some of these postvolcanic impact craters have been slightly extended, but only a small portion has been flooded by still younger lavas. Relative ages of the young craters are indicated by the varying eolian removal of their forms and ejecta blankets and flow lobes, and the oldest are much subdued. If these young impact craters, maximum diameter 275 km, include all preserved impact structures, then their quantity and distribution indicate that Venus was largely resurfaced by volcanism approx. 0.5 Ga, subsequent eruptions having been at a much reduced rate. Away from the approx. 0.5 Ga volcanic features, much of Venus is, however, dominated by circular and subcircular features, 50-2000 km in diameter, many of them multiring, that may be mostly older impact and impact-melt structures substantially modified by wind action. Eolian erosion scoured to bedrock old ridges and uplands, including those that may be cratered terrains and the rims and outer-ring depressions of large impact basins, and removed all surficial deposits to the limits of resolution of the imagery. The complementary eolian deposits form not only dunes, wind streaks, and small plains, but also broad radar-dark plains, commonly assumed to be volcanic although lacking flow morphology, whose materials appear to be thick because they are smoothly compacted into buried craters.

Hamilton, Warren B.↗
NASA NTRS1998

Detection of centimeter-sized meteoroid impact events in Saturn's F ring

Voyager images reveal that three prominent clumps in Saturn's F ring were short-lived, appearing rapidly and then spreading and decaying in brightness over periods of approximately 2 weeks. These features arise from hypervelocity impacts by approximately 10-centimeter meteoroids into F ring bodies. Future ring observations of these impact events could constrain the centimeter-sized component of the meteoroid population, which is otherwise unmeasurable but plays an important role in the evolution of rings and surfaces in the outer solar system. The F ring's numerous other clumps are much longer lived and appear to be unrelated to impacts.

Flight Experiment↗
NASA NTRS1975

Seismically induced modification of lunar surface features

The formation of large impact craters and basins produced not only large volumes of ejecta but also catastrophic seismic waves. Theoretical models, extrapolation of terrestrial explosion data, and extrapolation of lunar impact data suggest surface displacements of 1-10 m at four crater radii from a Copernicus-size impact (4 x 10 to the 30th power ergs). Independent estimates of impact-generated stresses indicate that regions within 4 crater radii of an impact will receive shock waves with pressures exceeding 1 kbar. Greater areas also may receive shock effects as elastic waves following deep ray paths transform into shock waves near the surface. Additional seismic energy will be generated by impacts from secondary ejecta. The resulting large and long-lasting surface movement may contribute to the subdued appearance of the continuous ejecta blanket and secondary craters around large impact craters and to the degradation of small craters outside these zones.

Schultz, P. H.↗
NASA NTRS1977

Torque-while-turnaround scan mirror assembly

Mechanical aspects in the development of an oscillating scan mirror mechanism were reviewed, that featured a remarkably low level of structural vibration for the impact energies involved in mirror oscillation. Another feature was that energy lost during impact was returned to the mirror by applying torque only during the instant of impact. Because the duration of impact was only about 0.010 second, it was critical that energy losses be minimal because there was not much time to restore them.

Starkus, C. J.↗
DOE OSTI2020

Assessing DER Network Cybersecurity Defences in a Power-Communication Co-Simulation Environment

Increasing penetrations of interoperable distributed energy resources (DER) in the electric power system are expanding the power system attack surface. Maloperation or malicious control of DER equipment can now cause substantial disturbances to grid operations. Fortunately, many options exist to defend and limit adversary impact on these newly-created DER communication networks, which typically traverse the public internet. However, implementing these security features will increase communication latency, thereby adversely impacting real-time DER grid support service effectiveness. In this work, a collection of software tools called SCEPTRE were used to create a co-simulation environment where SunSpec-compliant PV inverters were deployed as virtual machines and interconnected to simulated communication network equipment. Network segmentation, encryption, and moving target defence security features were deployed on the control network to evaluate their influence on cybersecurity metrics and power system performance. The results indicated that adding these security features did not impact DER-based grid control systems but improved the cybersecurity posture of the network when implemented appropriately.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1993

Stratigraphy and sedimentology of the K/T boundary deposit in Haiti

The K/T boundary sequence is exposed in uplifted carbonate sediments of the southwest peninsula of Haiti. It is found at 15 localities within the Beloc formation, a sequence of limestone and marls interpreted as a monoclinal nappe structure thrust to the north. This tectonic deformation has affected the K/T boundary deposit to varying degrees. In some cases the less competent K/T deposit has acted as a slip plane leading to extensive shearing of the boundary layer, as well as duplication of the section. The presence of glassy tektites, shocked quartz, and an Ir anomaly directly link the deposit to a bolide impact. Stratigraphic and sedimentological features of the tripartite sequence indicate that it was formed by deposition from ballistic fallout of coarse tektites, emplacement of particle gravity flows and fine grained fallout of widely dispersed impact ejecta.

Carey, S.↗
DOE OSTI2024

Extensive Secondary Cratering From the InSight Sol 1034a Impact Event

Abstract Impact cratering is one of the fundamental processes throughout the history of the Solar System. The formation of new impact craters on planetary bodies has been observed with repeat images from orbiting satellites. However, the time gap between images is often large enough to preclude detailed analysis of smaller‐scale features such as secondary impact craters, which are often removed or buried over a short time period. Here we use a seismic event detected on Mars by the NASA InSight mission to investigate secondary cratering at a new impact crater. We strengthen the case that the seismic event that occurred on Sol 1034 (S1034a) is the result of a new impact cratering event. Using the exact timing of this event from InSight, we investigated the resulting new impact crater in orbital image data. The S1034a impact crater is approximately 9 m in diameter but is responsible for over 900 secondary impact events in the form of low albedo spots that are located at distances of up to almost 7 km from the primary crater. We suggest that the low albedo spots formed from relatively low energy ejecta, with individual ejecta block velocities less than 200 m s −1 . We estimate that the low albedo spots, the main evidence of secondary impact processes at this new impact event, fade within 200–300 days after formation.

Grindrod, P. M. [Natural History Museum London UK]↗
NASA NTRS1992

Hypervelocity impact facility for simulating materials exposure to impact by space debris

The Space Power Institute at Auburn University has constructed an electromagnetically driven particle accelerator for simulating the effects of space debris on the materials for use in advanced spacecraft. The facility consists of a capacitively driven accelerator section, a drift tube and a specimen impact chamber. The drift tube is sufficiently long that all electrical activity has ceased prior to impact in the specimen chamber. The impact chamber is large enough to allow a wide range of specimen geometries, ranging from small coupons to active portions of advanced spacecraft. The electric drive for the accelerator consists of a 67 kJ, 50 k capacitor bank arranged in a low inductance configuration. The bank is discharged through an aluminum armature/plastic ablator plate/projectile load in roughly 1.2 microsec. The evaporation of the ablaitor plate produces an expanding gas slug, mostly H2, traveling at a velocity of some 60 km/sec. Because of the pressure and local density, the expanding gas cloud accelerates projectiles due to plasma drag. To date, we have utilized projectiles consisting of 100 micron SiC, 100 and 400 micron Al2O3, 100 and 145 micron olivines. Since many particles are accelerated in a given experiment, there is a range of velocities for each shot as well as some particle breakup. Advanced diagnostics techniques allow determination of impact coordinates, velocity, and approximate size for as many as 50 individual impacts in a given experiment. We routinely measure velocities in the range 1-15 km/sec. We have used this facility to study a variety of impact generated phenomena on coated surfaces, both paint and plastic, thermal blanket material, solar cell arrays, and optical materials such as glass and quartz lenses. The operating characteristics of the gun, the advanced diagnostic scheme, and the results of studies of crater morphology are described in detail. Projectile residue analysis, as a function of impact velocity for the materials listed above, is also discussed. Wherever possible, these results are compared to those obtained by LDEF investigators and future experiments suggested which could help to explain unique features associated with LDEF impacts.

Rose, M. Frank↗
NASA NTRS1985

The geomorphology of Rhea - Implications for geologic history and surface processes

Morphological analyses of landforms on Rhea are used to define three physiographic provinces: cratered terrain 1 undifferentiated; cratered terrain 1 lineated; and cratered terrain 2. The important statigraphic relationships between the different provinces are examined with respect to major impact basins and tectonic features. It is shown that the formation of multiringed basins may have caused, or at least controlled the locations of major resurfacing and mantling events. The diameters of the central peaks relative to the impact crater diameters are found to be significantly larger than those within the craters of the moon or Mercury. Both cratered and noncrater lineaments have regional orientations which do not fit current global or regional stress models. On the basis of the morphological analysis, a chronological order is established for the origin of the three provinces: the cratered terrain 1 province was formed first; and cratered terrain 1 lineated and cratered terrain 2 were formed second, and last, respectively. It is shown that the chronological order is generally consistent with current theoretical models of the evolution of Rhea.

Moore, J. M.↗
NASA NTRS2019

Outstanding Natural Occurrence of TiO2-II at the Chicxulub Crater - Anatomy of A Shock-Produced High-Pressure Polymorph

Scientific drilling of the end-Cretaceous, approximately 180 kilometers-diameter Chicxulub crater (Yucatan Peninsula, Mexico) during IODP–ICDP (Integrated Ocean Drilling Program - International Continental Scientific Drilling Program) Expedition 364 has provided new insights into the formation, shock metamorphism, structural evolution, and thermal history of peak rings in large complex impact craters. An outstanding feature in uplifted granitoid rocks of the Chicxulub peak ring is the preservation of TiO2-II, an orthorhombic high-pressure polymorph of TiO2 with an alpha-PbO2 structure, produced during the impact from rutile and/or anatase at shock pressures of approximately 12.5-17.5 gigapascals. Unlike other mostly micro- and cryptocrystalline occurrences of TiO2-II at terrestrial impact sites, ejecta deposits, and in rare ultra-high pressure metamorphic rocks, TiO2-II at Chicxulub occurs as abundant euhedral crystals greater than or equal to 70 microns in size within aggregates of altered magmatic titanite. This mode of occurrence provides an excellent opportunity to investigate the crystallography and transformation kinetics of the shock-produced high-pressure polymorph using scanning electron microscopic, micro-Raman, electron backscatter diffraction (EBSD), focused ion beam (FIB), as well as transmission-EBSD and transmission electron microscopic (TEM) techniques. Here we present refined microstructural and new crystallographic results for TiO2-II at the Chicxulub crater.

Schmieder, Martin↗
NASA NTRS1999

Slate Islands, Lake Superior, Canada: A mid-size, Complex Impact Structure

The target rocks of the 30-32-km diameter Slate Islands impact structure in northern Lake Superior, Canada, are Archean supracrustal and igneous rocks and supracrustal Proterozoic rocks. Shatter cones, pseudotachylites, impact glasses, and microscopic shock metamorphic features were formed during the contact and compression phase of the impact process, followed, during excavation and central uplift, by polymict, clastic matrix breccias in the uplifted target, and by allogenic fall-back breccias (suevite and bunte breccia). Monomict, autoclastic breccias were mainly observed on Mortimer Island and the other outlying islands of the archipelago and were probably generated relatively late in the impact process (central uplift and/or crater modification). The frequency of low index planar shock metamorphic features in quartz was correlated with results from shock experiments to estimate shock pressures experienced by the target rocks. The resulting shock attenuation plan across the archipelago is irregular, probably because the shock wave did not expand from a point or spherical source, and because of the destruction of an originally more regular shock attenuation plan during the central uplift and crater modification stages of the impact process. No impact melt rock bodies have been positively identified on the islands. An impact melt may be present in the annular trough around the islands, though and-based on a weighted mixture of target rocks-may have an intermediate-mafic composition. No such impact melt was found on the archipelago. An Ar-40-Ar-39 release spectrum of a pseudotachylite provides an age of about 436 Ma for the impact structure, substantiating age constraints based on various stratigraphic considerations.

Dressler, B. O.↗
NASA NTRS1993

Ejecting basaltic achondrites from Vesta: Hydrodynamical impact models

Vesta is a large asteroid whose crust is mostly basaltic. Spectral heterogeneity suggests a sizable olivine feature which may be explained as impact excavation. The spectral data probably show a localized feature approximately 200 km in diameter or a diffuse feature approximately 400 km in diameter. Lightcurve irregularities suggest heterogeneity on a similar scale. This heterogeneity may represent the crater bowl, the extent of its ejecta deposit, or indeed something unrelated to cratering. In any case, drawing direct inferences about the state of Vesta's surface on the basis of these observations involves substantial speculation. We are still far from understanding the boundary between cratering and catastrophic disruption, particularly on targets for which strength and self-gravity both matter. But we are now able to model the underlying physical process -- dynamic fragmentation -- accurately with fragmentation hydrocodes such as SALE 2D and SPH3D. We present several impact scenarios for Vesta; our study is similar to a previous impact model for the formation of Stickney crater on Phobos. We illustrate the effects of impactors of different sizes and velocities, and the effect of gravity and structural inhomogeneity.

Asphaug, E.↗
NASA NTRSDate not supplied

Understanding the Impact of Unobservable Variables on the Performance of Predictive Models: The Need for Feature Space Partitioning and Fusion

When developing predictive models over a dataset, the model is globally optimized across the entire feature space to learn a decision boundary. However, when unobservable variables—which cannot be measured or estimated—interact with the observable variables, this can negatively impact the optimization applied to the decision boundary since the data samples introduced by unobservable variables may have little to no association with the applied global optimization. This, consequently, penalizes the entire decision boundary and model performance. This paper examines some of the detrimental effects of unobservable variables, particularly their role in creating new modes in the distribution of observable variables and reducing the separability of class distributions. Such challenges result in skewed or warped decision boundaries and decreased accuracy of model predictions, particularly for interpretable models like logistic regression and decision trees. Through two illustrative case examples, we highlight the need to address the challenges imposed by unobservable variables. We propose a strategy to mitigate these challenges by creating local regions within the feature space through partitioning. This enables the optimization of local models within the regions to overcome the impact of unobservability in different feature space localities. Research into a more sophisticated partitioning strategy and where the partition should be relative to the sample of interest is left as future work. Through the analysis of the impact of unobservability and the development of a partitioning method, we demonstrate the clear need for a partitioning strategy that integrates knowledge from multiple local models to estimate risk factors using information fusion. Thus, we establish the foundation and motivation for using partitioning and information fusion to overcome the effects of unobservability in predictive models. Formal fusion methods, such as Dempster-Shafer theory, can better leverage the information from local regions to improve the performance of interpretable predictive models in the presence of unobservable variables.

Time Series Data↗
DOE OSTI2022

Support Vector Machines for Classification of Direct Energy Deposition Standoff Distance for Improved Process Control

A critical factor in the implementation of direct energy deposition is the ability to maintain the standoff distance between the nozzle and the build surface, as this influences powder capture efficiency and overall part quality. Due to process-related variations, layer height may vary, causing unintended variation in standoff distance and poor build quality. While prior work has utilized contact probing to qualify standoff distance during processing, in situ methods for qualification of standoff distance are of major interest. The present work seeks to understand efficacy of image-based methods for classifying standoff distance variation in real-time using support vector machines (SVMs). It was hypothesized that the size of the melt pool and the amount of spatter will have significant correlations with deviations in the standoff distance; thus, SVMs were used on a dataset that is comprised of morphological features of melt pool size and image entropy. The SVM model was used to classify melt pool images into categories according to standoff distance variation from nominal. K-folds cross validation was used to find the optimal hyperparameters for the SVM model. To understand the impact of the selected features on the classification performance and inference speed, multiple models were trained with differing numbers of included features. Results for classification score, inference time, and image preprocessing/feature extraction from these data are reported. The present results show that the SVM model was able to predict the standoff distance classification with an accuracy of 97 percent and a speed of 0.122 s per image, making it a viable solution for real-time control of standoff distance.

Klesmith, Zoe↗