Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Data segmentation”

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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

A Real-Time Algorithm for Integrating Differential Satellite and Inertial Navigation Information During Helicopter Approach

A real-time, high-rate precision navigation Kalman filter algorithm is developed and analyzed. This navigation algorithm blends various navigation data collected during terminal area approach of an instrumented helicopter. Navigation data collected include helicopter position and velocity from a global position system in differential mode (DGPS) as well as helicopter velocity and attitude from an inertial navigation system (INS). The goal of the navigation algorithm is to increase the DGPS accuracy while producing navigational data at the 64 Hertz INS update rate. It is important to note that while the data was post flight processed, the navigation algorithm was designed for real-time analysis. The design of the navigation algorithm resulted in a nine-state Kalman filter. The Kalman filter's state matrix contains position, velocity, and velocity bias components. The filter updates positional readings with DGPS position, INS velocity, and velocity bias information. In addition, the filter incorporates a sporadic data rejection scheme. This relatively simple model met and exceeded the ten meter absolute positional requirement. The navigation algorithm results were compared with truth data derived from a laser tracker. The helicopter flight profile included terminal glideslope angles of 3, 6, and 9 degrees. Two flight segments extracted during each terminal approach were used to evaluate the navigation algorithm. The first segment recorded small dynamic maneuver in the lateral plane while motion in file vertical plane was recorded by the second segment. The longitudinal, lateral, and vertical averaged positional accuracies for all three glideslope approaches are as follows (mean +/- two standard deviations in meters): longitudinal (-0.03 +/- 1.41), lateral (-1.29 +/- 2.36), and vertical (-0.76 +/- 2.05).

Hoang, Ty↗
NASA NTRS2001

Selection of the Ground Segment for the Next Generation Space Telescope (NGST) Flight Demonstrator (Nexus)

Nexus was a technology demonstrator project that was designed to bridge from the Hubble Space Telescope (HST) to its successor, the Next Generation Space Telescope (NGST). This paper focuses on the process used in designing the ground segment for Nexus and the lessons learned in its development. Ground station cost drivers were: (1) Contact time, (2) Cost of transporting data between the ground stations and control center, and (3) Cost savings via ground automation. We found that reducing the communication requirement in just the first 100 days could have reduced the total ground station cost by 40%. Contact time cost dwarfed the cost trade between automation development and off-shift operations personnel. Real-time Telemetry and Control (T&C) system analysis was divided into: (1) Potential reuse of the Nexus real-time (T&C) system for NGST, (2) Feasibility of using a 'Finite State-Based Modeling' product, and (3) Selecting a Commercial Off the Shelf (COTS) versus Government Off The Shelf (GOTS) products. We found that each of the products evaluated in detail (ASIST, EPOCH 2000, and ITOS) could adequately support basic mission requirements. Lessons learned were: (1) Include operations at the beginning of the mission, and (2) Develop an operations concept as soon as possible.

Gal-Edd, Jonathan↗
NASA NTRS2003

The Development of the Ducted Fan Noise Propagation and Radiation Code CDUCT-LaRC

The development of the ducted fan noise propagation and radiation code CDUCT-LaRC at NASA Langley Research Center is described. This code calculates the propagation and radiation of given acoustic modes ahead of the fan face or aft of the exhaust guide vanes in the inlet or exhaust ducts, respectively. This paper gives a description of the modules comprising CDUCT-LaRC. The grid generation module provides automatic creation of numerical grids for complex (non-axisymmetric) geometries that include single or multiple pylons. Files for performing automatic inviscid mean flow calculations are also generated within this module. The duct propagation is based on the parabolic approximation theory of R. P. Dougherty. This theory allows the handling of complex internal geometries and the ability to study the effect of non-uniform (i.e. circumferentially and axially segmented) liners. Finally, the duct radiation module is based on the Ffowcs Williams-Hawkings (FW-H) equation with a penetrable data surface. Refraction of sound through the shear layer between the external flow and bypass duct flow is included. Results for benchmark annular ducts, as well as other geometries with pylons, are presented and compared with available analytical data.

Nark, Douglas M.↗
NASA NTRS2003

Numerical Models of Human Circulatory System under Altered Gravity: Brain Circulation

A computational fluid dynamics (CFD) approach is presented to model the blood flow through the human circulatory system under altered gravity conditions. Models required for CFD simulation relevant to major hemodynamic issues are introduced such as non-Newtonian flow models governed by red blood cells, a model for arterial wall motion due to fluid-wall interactions, a vascular bed model for outflow boundary conditions, and a model for auto-regulation mechanism. The three-dimensional unsteady incompressible Navier-Stokes equations coupled with these models are solved iteratively using the pseudocompressibility method and dual time stepping. Moving wall boundary conditions from the first-order fluid-wall interaction model are used to study the influence of arterial wall distensibility on flow patterns and wall shear stresses during the heart pulse. A vascular bed modeling utilizing the analogy with electric circuits is coupled with an auto-regulation algorithm for multiple outflow boundaries. For the treatment of complex geometry, a chimera overset grid technique is adopted to obtain connectivity between arterial branches. For code validation, computed results are compared with experimental data for steady and unsteady non-Newtonian flows. Good agreement is obtained for both cases. In sin-type Gravity Benchmark Problems, gravity source terms are added to the Navier-Stokes equations to study the effect of gravitational variation on the human circulatory system. This computational approach is then applied to localized blood flows through a realistic carotid bifurcation and two Circle of Willis models, one using an idealized geometry and the other model using an anatomical data set. A three- dimensional anatomical Circle of Willis configuration is reconstructed from human-specific magnetic resonance images using an image segmentation method. The blood flow through these Circle of Willis models is simulated to provide means for studying gravitational effects on the brain circulation under auto-regulation.

Kim, Chang Sung↗
NASA NTRS2010

Distribution of Chromosome Breakpoints in Human Epithelial Cells Exposed to Low- and High-LET Radiation

Low-and high-LET radiations produced distinct breakpoint distributions. The difference of the breakpoint distributions between low-and high-LET only appeared in break ends involved in interchromosome exchanges. The breakpoint distributions for break ends participating in intrachromosome exchanges were similar. Gene-rich regions do not necessarily have more chromosome breaks. High-LET appeared to produce long live (data not shown) or longer live breaks that can migrate a longer distance before rejoining with other breaks. Domains occupied by different segments of the chromosomes may be responsible for the breakpoint distribution. The dose responses for interchromosomal exchanges were linear in all four exposures. However, the dose response for intrachromosomal exchanges were none linear. Increasing dose of high dose rate exposure (Fe-ions or -rays) increase the fraction of cells with intrachromosome aberrations, whereas increasing dose of low dose rate exposure (neutrons or -rays) does not affect the fraction of cells with intrachromosome aberrations.

Hada, Megumi↗
NASA NTRS2007

Acoustic and Vibration Environment for Crew Launch Vehicle Mobile Launcher

A launch-induced acoustic environment represents a dynamic load on the exposed facilities and ground support equipment (GSE) in the form of random pressures fluctuating around the ambient atmospheric pressure. In response to these fluctuating pressures, structural vibrations are generated and transmitted throughout the structure and to the equipment items supported by the structure. Certain equipment items are also excited by the direct acoustic input as well as by the vibration transmitted through the supporting structure. This paper presents the predicted acoustic and vibration environments induced by the launch of the Crew Launch Vehicle (CLV) from Launch Complex (LC) 39. The predicted acoustic environment depicted in this paper was calculated by scaling the statistically processed measured data available from Saturn V launches to the anticipated environment of the CLV launch. The scaling was accomplished by using the 5-segment Solid Rocket Booster (SRB) engine parameters. Derivation of vibration environment for various Mobile Launcher (ML) structures throughout the base and tower was accomplished by scaling the Saturn V vibration environment.

Vu, Bruce T.↗
NASA NTRS2013

Data Mining for Anomaly Detection

The Vehicle Integrated Prognostics Reasoner (VIPR) program describes methods for enhanced diagnostics as well as a prognostic extension to current state of art Aircraft Diagnostic and Maintenance System (ADMS). VIPR introduced a new anomaly detection function for discovering previously undetected and undocumented situations, where there are clear deviations from nominal behavior. Once a baseline (nominal model of operations) is established, the detection and analysis is split between on-aircraft outlier generation and off-aircraft expert analysis to characterize and classify events that may not have been anticipated by individual system providers. Offline expert analysis is supported by data curation and data mining algorithms that can be applied in the contexts of supervised learning methods and unsupervised learning. In this report, we discuss efficient methods to implement the Kolmogorov complexity measure using compression algorithms, and run a systematic empirical analysis to determine the best compression measure. Our experiments established that the combination of the DZIP compression algorithm and CiDM distance measure provides the best results for capturing relevant properties of time series data encountered in aircraft operations. This combination was used as the basis for developing an unsupervised learning algorithm to define "nominal" flight segments using historical flight segments.

Biswas, Gautam↗
NASA NTRS2019

Impact of Facility Pressure on the Wear of the NASA HERMeS Hall Thruster

This work presents an overview and summary of the results acquired during the final segment of the TDU-3 Long Duration Wear Test, which was completed in October 2018. The overall goal of this segment was to quantify the impact of facility pressure on the wear of the Hall Effect Rocket with Magnetic Shielding Technology Demonstration Unit Three (TDU-3) Hall thruster. This was accomplished by operating TDU-3 for approximately 270 hours at the nominal 600 V/12.5 kW operating condition while a bleed or auxiliary flow of xenon propellant was injected into the vacuum facility in order to raise the operating pressure to match that of another test facility in which previous wear segments had been performed. The performance, plume, stability, and wear results acquired at this elevated pressure (11.7 µTorr) are compared with equivalent data taken at the nominal operating pressure (4.2 µTorr) in the same facility as well at the elevated operating pressure in the other facility. Implications of these results for acquiring facility-independent service life estimates are discussed.

Frieman, Jason D.↗
NASA NTRS1993

STS-56, RSRM-031, 360L031 KSC processing configuration and data report

KSC Processing Configuration and Data Report is being provided as a historical document and as an enhancement to future RSRM manufacturing and processing operations. The following sections provide information on segment receipt, aft booster build-up, booster assembly, and closeout for STS-56, RSRM flight set 36OL031. Section 2.0 contains a summary of RSRM-031 processing. Section 3.0 discusses any significant problems or special issues that require special attention. Sections 4.0 through 6.0 contain narrative descriptions of all key events, including any related processing problems. Appendix A provides engineering specifications and changes. A list and matrix of all problem reports (PR's) pertinent to this flight set is provided in Appendix B. The matrix was provided by the Thiokol LSS Quality Engineering office. Copies of the PR's generated during the processing of RSRM-031 will be provided upon request. Appendix C contains the motor set status matrix, which provides milestone dates for the RSRM-031 flow. Section 7.0 provides recommendations, if any, for the improvement of flight hardware processing. Section 8.0 contains data sheets that provide flight hardware parts and consumables information installed during the booster build-up and stacking operations by location, lot/serial number, expiration and cure dates/times, and installation dates.

Source record↗
NASA NTRS2014

Space Link Extension Protocol Emulation for High-Throughput, High-Latency Network Connections

New space missions require higher data rates and new protocols to meet these requirements. These high data rate space communication links push the limitations of not only the space communication links, but of the ground communication networks and protocols which forward user data to remote ground stations (GS) for transmission. The Consultative Committee for Space Data Systems, (CCSDS) Space Link Extension (SLE) standard protocol is one protocol that has been proposed for use by the NASA Space Network (SN) Ground Segment Sustainment (SGSS) program. New protocol implementations must be carefully tested to ensure that they provide the required functionality, especially because of the remote nature of spacecraft. The SLE protocol standard has been tested in the NASA Glenn Research Center's SCENIC Emulation Lab in order to observe its operation under realistic network delay conditions. More specifically, the delay between then NASA Integrated Services Network (NISN) and spacecraft has been emulated. The round trip time (RTT) delay for the continental NISN network has been shown to be up to 120ms; as such the SLE protocol was tested with network delays ranging from 0ms to 200ms. Both a base network condition and an SLE connection were tested with these RTT delays, and the reaction of both network tests to the delay conditions were recorded. Throughput for both of these links was set at 1.2Gbps. The results will show that, in the presence of realistic network delay, the SLE link throughput is significantly reduced while the base network throughput however remained at the 1.2Gbps specification. The decrease in SLE throughput has been attributed to the implementation's use of blocking calls. The decrease in throughput is not acceptable for high data rate links, as the link requires constant data a flow in order for spacecraft and ground radios to stay synchronized, unless significant data is queued a the ground station. In cases where queuing the data is not an option, such as during real time transmissions, the SLE implementation cannot support high data rate communication.

Computer Networking↗
NASA NTRS1999

Lidar Altimeter Measurements of Canopy Structure: Methods and Validation for Closed Canopy, Broadleaf Forests

Lidar altimeter observations of vegetated landscapes provide a time-resolved measure of laser pulse backscatter energy from canopy surfaces and the underlying ground. Airborne lidar altimeter data was acquired using the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) for a successional sequence of four, closed-canopy, deciduous forest stands in eastern Maryland. The four stands were selected so as to include a range of canopy structures of importance to forest ecosystem function, including variation in the height and roughness of the outer-most canopy surface and the vertical organization of canopy stories and gaps. The character of the SLICER backscatter signal is described and a method is developed that accounts for occlusion of the laser energy by canopy surfaces, transforming the backscatter signal to a canopy height profile (CHP) that quantitatively represents the relative vertical distribution of canopy surface area. The transformation applies an increased weighting to the backscatter amplitude as a function of closure through the canopy and assumes a horizontally random distribution of the canopy components. SLICER CHPs, averaged over areas of overlap where lidar ground tracks intersect, are shown to be highly reproducible. CHP transects across the four stands reveal spatial variations in vegetation, at the scale of the individual 10 m diameter laser footprints, within and between stands. Averaged SLICER CHPs are compared to analogous height profile results derived from ground-based sightings to plant intercepts measured on plots within the four stands. Tbe plots were located on the segments of the lidar ground tracks from which averaged SLICER CHPs were derived, and the ground observations were acquired within two weeks of the SLICER data acquisition to minimize temporal change. The differences in canopy structure between the four stands is similarly described by the SLICER and ground-based CHP results, however a Chi-square test of similarity documents differences that are statistically significant. The differences are discussed in terms of measurement properties that define the smoothness of the resulting CHPs and Lidar Altimeter Measurements of Canopy Structure - Harding et al. canopy properties that may vertically bias the CHP representations of canopy structure. The statistical differences are most likely due to the more noisy character of the ground-based CHPs, especially high in the canopy where ground-based sightings are rare resulting in an underestimate of canopy surface area and height, and to departures from the assumption of horizontal randomness which bias the CHPs toward the observer (upward for SLICER and downward for ground-based CHPs). The results demonstrate that the SLICER observations reliably provide a measure of canopy structure that reveals ecologically interesting structural variations such as those characterizing a successional sequence of closed-canopy, broadleaf forest stands.

Harding, D. J.↗
NASA NTRS1993

Mars 1994/1996: The French navigation tasks

In the fall of 1994, Russia will launch a spacecraft to Mars. France is involved in many scientific experiments which are onboard the spacecraft, as PI or CI. Some days before the Mars orbit insertion maneuver, two small stations and two penetrators will be injected into an entry trajectory. They will carry out for at least six months in situ analysis on the Martian surface. Two years later, a second spacecraft will be launched. It will carry the French balloon and a small rover. The scientific data of these landers will be relayed to earth via the spacecraft. However, during the first 20 days of their mission, Mars Observer will be used. To this end, a Mars balloon relay will be used, which will receive the data from the landers and store them into the memory of the Mars Observer camera. The spacecraft will also be used to localize the landers with the help of relative one-way Doppler measurements. An international cooperative is set up for this process, including JPS, Russian ballistic centers (Babakine, Institute of Applied Mathematics, Moscow Flight Control Center), and CNES Toulouse. Another task dedicated to the space mathematics division of CNES is to support the French scientists to prepare their telecommands and to analyze their telemetry. This second part is integrated into the French ground segment created for the Mars 94/96 mission. This paper describes the method used in CNES for the localization process, the support provided to the scientists, and the links for the data exchange.

Bonneau, Frederic↗
NASA NTRS1977

The effects of prolonged spaceflight on the regional distribution of fluid, muscle and fat: Biostereometric results from Skylab

Biostereometric analysis of body form was performed several times preflight and postflight on the astronauts of all three skylab flights. The analysis was made by deriving the three-dimensional coordinates of numerous points on the body surface from stereoscopic pairs of photographs of the subject, using a stereoplotter. The volume of segments of the body, and of the body as a whole, was calculated by integration of cross sectional areas derived from the coordinate data. All nine astronauts demonstrated regional changes in volume distribution which could be related to changes in total body water, muscle mass, and fat deposits. The change in water resulted from a redistribution of fluid in response to zero gravity. Changes in muscle mass resulted from an alternation in patterns of musclar activity in the absence of gravity, and changes in fat resulted from discrepancies between the individual's caloric needs and his food consumption.

Whittle, M. W.↗
NASA NTRS1984

Algorithm for Constructing Contour Plots

General computer algorithm developed for construction of contour plots. algorithm accepts as input data values at set of points irregularly distributed over plane. Algorithm based on interpolation scheme: points in plane connected by straight-line segments to form set of triangles. Program written in FORTRAN IV.

Johnson, W.↗
NASA NTRS1983

Customer premise service study for 30/20 GHz satellite system

Satellite systems in which the space segment operates in the 30/20 GHz frequency band are defined and compared as to their potential for providing various types of communications services to customer premises and the economic and technical feasibility of doing so. Technical tasks performed include: market postulation, definition of the ground segment, definition of the space segment, definition of the integrated satellite system, service costs for satellite systems, sensitivity analysis, and critical technology. Based on an analysis of market data, a sufficiently large market for services is projected so as to make the system economically viable. A large market, and hence a high capacity satellite system, is found to be necessary to minimize service costs, i.e., economy of scale is found to hold. The wide bandwidth expected to be available in the 30/20 GHz band, along with frequency reuse which further increases the effective system bandwidth, makes possible the high capacity system. Extensive ground networking is required in most systems to both connect users into the system and to interconnect Earth stations to provide spatial diversity. Earth station spatial diversity is found to be a cost effective means of compensating the large fading encountered in the 30/20 GHz operating band.

Milton, R. T.↗
NASA NTRS1983

Development of a Polysilicon Process Based on Chemical Vapor Deposition of Dichlorosilane in an Advanced Siemen's Reactor

Dichlorosilane (DCS) was used as the feedstock for an advanced decomposition reactor for silicon production. The advanced reactor had a cool bell jar wall temperature, 300 C, when compared to Siemen's reactors previously used for DCS decomposition. Previous reactors had bell jar wall temperatures of approximately 750 C. The cooler wall temperature allows higher DCS flow rates and concentrations. A silicon deposition rate of 2.28 gm/hr-cm was achieved with power consumption of 59 kWh/kg. Interpretation of data suggests that a 2.8 gm/hr-cm deposition rate is possible. Screening of lower cost materials of construction was done as a separate program segment. Stainless Steel (304 and 316), Hastalloy B, Monel 400 and 1010-Carbon Steel were placed individually in an experimental scale reactor. Silicon was deposited from trichlorosilane feedstock. The resultant silicon was analyzed for electrically active and metallic impurities as well as carbon. No material contributed significant amounts of electrically active or metallic impurities, but all contributed carbon.

Arevidson, A. N.↗
NASA NTRS1986

The rRNA evolution and procaryotic phylogeny

Studies of ribosomal RNA primary structure allow reconstruction of phylogenetic trees for prokaryotic organisms. Such studies reveal major dichotomy among the bacteria that separates them into eubacteria and archaebacteria. Both groupings are further segmented into several major divisions. The results obtained from 5S rRNA sequences are essentially the same as those obtained with the 16S rRNA data. In the case of Gram negative bacteria the ribosomal RNA sequencing results can also be directly compared with hybridization studies and cytochrome c sequencing studies. There is again excellent agreement among the several methods. It seems likely then that the overall picture of microbial phylogeny that is emerging from the RNA sequence studies is a good approximation of the true history of these organisms. The RNA data allow examination of the evolutionary process in a semi-quantitative way. The secondary structures of these RNAs are largely established. As a result it is possible to recognize examples of local structural evolution. Evolutionary pathways accounting for these events can be proposed and their probability can be assessed.

Fox, G. E.↗
NASA NTRS1990

Evaluation of EDR-3 vibration, shock, temperature, and humidity recording unit

The purpose of this evaluation was to determine if the self-contained, off-the-shelf, Environmental Data Recorder 3 (EDR-3) could be qualified to monitor shock, vibration, and temperature during rail transportation of space shuttle solid rocket components. The evaluation testing started in November 1989 and continued until June 1990. Two EDR-3 units were used to monitor both on- and off-plant shipments of shuttle components. In addition, extensive testing was performed at Thiokol's Vibration Test facility, T-53. Testing demonstrated that the EDR-3 is capable of successfully monitoring actual shipments of solid rocket hardware. Thiokol metrology has verified the accuracy of temperature monitoring. In addition, calibrated shock/vibration testing demonstrated that the EDR-3 does accurately record acceleration. It is recommended that the vendor modify the EDR-3 data recovery system to allow remote communication via a 30-foot cable. This would permit communication with the unit mounted on a case segment after a rail car cover is installed. The vendor will make this change and produce a new model, designated EDR-3-10. It is further recommended that Thiokol qualify the EDR-3-10 for transportation monitoring of redesigned solid rocket motor (RSRM) components.

Rees, Kevin G.↗