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At least 703 records · Page 39

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NASA NTRS2001

Locating Anomalies in Complex Data Sets Using Visualization and Simulation

The research goals are to create a simulation framework that can accept any combination of models written at the gate or behavioral level. The framework provides the ability to fault simulate and create scenarios of experiments using concurrent simulation. In order to meet these goals we have had to fulfill the following requirements. The ability to accept models written in VHDL, Verilog or the C languages. The ability to propagate faults through any model type. The ability to create experiment scenarios efficiently without generating every possible combination of variables. The ability to accept adversity of fault models beyond the single stuck-at model. Major development has been done to develop a parser that can accept models written in various languages. This work has generated considerable attention from other universities and industry for its flexibility and usefulness. The parser uses LEXX and YACC to parse Verilog and C. We have also utilized our industrial partnership with Alternative System's Inc. to import vhdl into our simulator. For multilevel simulation, we needed to modify the simulator architecture to accept models that contained multiple outputs. This enabled us to accept behavioral components. The next major accomplishment was the addition of "functional fault models". Functional fault models change the behavior of a gate or model. For example, a bridging fault can make an OR gate behave like an AND gate. This has applications beyond fault simulation. This modeling flexibility will make the simulator more useful for doing verification and model comparison. For instance, two or more versions of an ALU can be comparatively simulated in a single execution. The results will show where and how the models differed so that the performance and correctness of the models may be evaluated. A considerable amount of time has been dedicated to validating the simulator performance on larger models provided by industry and other universities.

Panetta, Karen↗

NASA NTRS2001

Solid Free-Form Fabrication of Continuous Fiber Reinforced Composites for Propulsion Application

For propulsion related applications, materials must be able to demonstrate excellent ablation and oxidation resistance at temperature approaching 3500 C, adequate load bearing capabilities, non-catastrophic failure modes, and ability to withstand transient thermal shock. A potential list of propulsion-material property requirements includes, low density, high elastic modulus, low thermal-expansion coefficient, high thermal conductivity, excellent erosion and oxidation/corrosion resistance, and flaw-insensitivity. In many cases, they will also need to be able to be joined, survive thermal cycling and multi-axial stress states, and for reusable applications, the materials must maintain the above attributes after prolonged exposure to extremely harsh chemical environments. The final and possibly most important attribute for these materials are the need to be lower cost and readily available in large quantities. Recently, Advanced Ceramics Research, Inc. (ACR) has developed low cost, flexible-manufacturing processes for Zr & Hf-based carbon fiber reinforced composites, materials with good oxidation and ablation resistance up to 3500 C. This process, called Continuous Composite Co-extrusion (C(sup 3)), incorporates carbon fibers to fabricate 'in-situ' carbide and boride-matrix/carbon fiber composites. M is a variation of ACR's manufacturing process for low-cost structural ceramic materials called Fibrous Monoliths with carbon fiber reinforcements. Fibrous Monolithic materials have a distinct fibrous texture, consist of intertwined cells of a primary phase, separated by cell boundaries of a tailored secondary phase and show very high fracture energies, damage tolerance, and graceful failure. Since they are monolithic powder based composites; they can be manufactured by conventional powder processing techniques using inexpensive raw materials. This combination of high performance and low cost is a breakthrough that could enable wider application of ceramics in high temperature applications. Typical volume fractions of the two phases are 80 to 95% for the cell phase and 5 to 20% for the interpenetrating cell boundary phase. ACR is currently developing an innovative solid freeform form fabrication (SFF) approach to produce Hf and Zr based ceramic composite components reinforced with continuous carbon fiber tows for critical structural components such as tubes and blisks. The process is simple, robust and will be widely applicable to a number of material systems. This technique was originally developed at the University of Delaware Center for Composite Materials (UD-CCM) for rapid fabrication of polymer matrix composites by a technique called automated tow placement or ATP. The current process is being developed in collaboration with UD-CCM. The paper will detail the freeform fabrication process to create low-cost ceramic fiber reinforced composites for high-temperature applications. The results of mechanical properties and microstructural characterization will be presented, together with examples of complex shapes and parts. It is believed that the process will be able to create complex shaped parts for propulsion applications at an order of magnitude lower cost than current CVI and PIP processes.

Vaidyanathan, R.↗

NASA NTRS2001

Development of Core Cladding Fabrication Techniques for Phase I Fission Propulsion Systems

Phase I fission propulsion systems focus on safety, timely development, and affordability. Prototype and flight units can be tested at full thrust, using resistance heaters to closely simulate heat from a fission reaction. In Phase I ground testing, one goal is to establish a reliable and affordable manufacturing technique for fabricating a flight-like core. A refractory metal (Mo) has been suggested for the core substrate, primarily due to the existence of a significant database for Mo/LJ02 fuel. The core can be fabricated by bundling Mo tubes with a bonding system that meets preliminary test goals. These criteria include materials compatibility, ability to maintain thermal and structural integrity during 10,000 hours of operation, and fabrication with existing facilities. This paper describes an effort to investigate several fabrication techniques in a cost-effective manner. First, inexpensive materials were tested at low temperatures to determine the relative effectiveness of such techniques as welding, brazing, plating, and vacuum plasma spraying (VPSing). Promising techniques were chosen for further evaluation, including thermal and structural studies, using ceramic tubing at intermediate temperatures. The most desirable technique will be tested on actual Mo tubing at anticipated operating temperatures. This work is being performed by the National Aeronautics & Space Administration (NASA) at George C. Marshall Space Flight Center (MSFC), Los Alamos National Laboratory (LANL), and Advanced Methods & Materials (AMM), Inc.

Salvail, Patrick G.↗

NASA NTRS2000

Theoretical Analysis of the Electron Spiral Toroid Concept

This report describes the analysis of the Electron Spiral Toroid (EST) concept being promoted by Electron Power Systems Inc. (EPS). The EST is described as a toroidal plasma structure composed Of ion and electron shells. It is claimed that the EST requires little or no external confinement, despite the extraordinarily large energy densities resulting from the self-generating magnetic fields. The present analysis is based upon documentation made available by EPS, a previous description of the model by the Massachusetts Institute of Technology (MIT), and direct discussions with EPS and MIT. It is found that claims of absolute stability and large energy storage capacities of the EST concept have not been substantiated. Notably, it can be demonstrated that the ion fluid is fundamentally unstable. Although various scenarios for ion confinement were subsequently suggested by EPS and MIT, none were found to be plausible. Although the experimental data does not prove the existence of EST configurations, there is undeniable experimental evidence that some type of plasma structures whose characteristics remain to be determined are observed. However, more realistic theoretical models must first be developed to explain their existence and properties before applications of interest to NASA can he assessed and developed.

Cambier, Jean-Luc↗

NASA NTRS2001

Metal Matrix Composite LOX Turbopump Housing Via Novel Tool-Less Net-Shape Pressure Infiltration Casting Technology

Metal matrix composites (MMC) offer relatively higher specific strength, specific stiffness, lower coefficient of thermal expansion (CTE) and lower density as compared with conventional alloys. These unique properties make them very attractive for aerospace turbomachinery applications where there is ever increasing emphasis to reduce weight and cost, and to increase engine performance. Through a joint effort between NASA and Metal Matrix Cast Composites, Inc., a complex liquid oxygen (LOX) compatible turbopump housing is being redesigned and manufactured from hybrid (particulate and fibers) Aluminum MMC. To this end, a revolutionary tool-less pressure infiltration casting technology is being perfected. Ceramic preforms for the composite are 3-dimensionally printed using a stereolithography file, acquired from a CAD model. The preforms are then invested into a refractory material and pressure infiltrated with liquid metal. After casting, the refractory material is washed away leaving behind a near net-shape composite part. Benefits of this process include increased composite uniformity, no mold machining, short time from design to part, properties matching traditional methods, ability to make previously impossible to manufacture parts and no size limitations with a newly developed joining technology. The results of materials, manufacturing and design optimizations, preform joining, and sub-element tests will be presented.

Shah, Sandeep↗

NASA NTRS2000

Chronology of KSC and KSC Related Events for 1999

This document is intended to serve as a record of Kennedy Space Center (KSC) events and is a reference source for historians and other researchers. Arrangement is by day and month and individual articles are attributed to published sources. Materials were researched and described by the KSC Library Archivist for KSC Library Services Contractor InDyne, Inc.

Liston, Elaine E.↗

NASA NTRS2001

Chronology of KSC and KSC Related Events for 2000

Liston, Elaine E.↗

NASA NTRS2001

Improved Humidity Sensing with the Chilled Mirror: Really?

Testing of the chilled mirror sensor was initiated at Wallops Island in 1997. The chilled mirror dew point system is integrated with the Sippican, Inc., MK2 radiosonde providing a relatively inexpensive instrument. Early tests suggested that better stratospheric humidity measurements might be available. But, recent tests with different configurations of the mirror's cooler indicated that the systems capability to cool to the very low dew point temperatures required in the stratosphere were not being met with the present system. Nonetheless, the present mirror technology, while still undergoing development gives better humidity information between 400 and 100 hPa than the current routine radiosonde sensor. Comparisons are given of the chilled mirror and the typical operational humidity sensors.

Schmidlin, Francis J.↗

NASA NTRS2001

Aeroelastic Stability of A Soft-Inplane Gimballed Tiltrotor Model In Hover

Soft-inplane rotor systems can significantly reduce the inplane rotor loads generated during the maneuvers of large tiltrotors, thereby reducing the strength requirements and the associated structural weight of the hub. Soft-inplane rotor systems. however, are subject to instabilities associated with ground resonance, and for tiltrotors this instability has increased complexity as compared to a conventional helicopter. Researchers at Langley Research Center and Bell Helicopter-Textron, Inc. have completed ail initial study of a soft-inplane gimballed tiltrotor model subject to ground resonance conditions in hover. Parametric variations of the rotor collective pitch and blade root damping, and their associated effects oil the model stability were examined. Also considered in the study was the effectiveness of ail active swash-plate and a generalized predictive control (GPC) algorithm for stability augmentation of the ground resonance conditions. Results of this study show that the ground resonance behavior of a gimballed soft-inplane tiltrotor can be significantly different from that of a classical soft-inplane helicopter rotor. The GPC-based active swash-plate was successfully implemented, and served to significantly augment damping of the critical modes to an acceptable value.

Nixon, Mark W.↗

NASA NTRS2000

High-Lift Flight Tunnel - Phase II Report

The High-Lift Flight Tunnel (HiLiFT) concept is a revolutionary approach to aerodynamic ground testing. This concept utilizes magnetic levitation and linear motors to propel an aerodynamic model through a tube containing a quiescent test medium. This medium (nitrogen) is cryogenic and pressurized to achieve full flight Reynolds numbers higher than any existing ground test facility world-wide for the range of 0.05 to 0.50 Mach. The results of the Phase II study provide excellent assurance that the HiLiFT concept will provide a valuable low-speed, high Reynolds number ground test facility. The design studies concluded that the HiLiFT facility is feasible to build and operate and the analytical studies revealed no insurmountable difficulties to realizing a practical high Reynolds number ground test facility. It was determined that a national HiLiFT facility, including development, would cost approximately $400M and could be operational by 2013 if fully funded. Study participants included National Aeronautics and Space Administration Langley Research Center as the Program Manager and MSE Technology Applications, Inc., (MSE) of Butte, Montana as the prime contractor and study integrator. MSE#s subcontractors included the University of Texas at Arlington for aerodynamic analyses and the Argonne National Laboratory for magnetic levitation and linear motor technology support.

Lofftus, David↗

NASA NTRS2001

Metal Matrix Composite LOX Turbopump Housing Via Novel Tool-Less Net-Shape Pressure Infiltration Casting Technology

Metal matrix composites (MMC) offer relatively higher specific strength, specific stiffness, lower coefficient of thermal expansion (CTE) and lower density as compared with conventional alloys. These unique properties make them very attractive for aerospace turbomachinery applications where there is ever increasing emphasis to reduce weight and cost, and to increase engine performance. Through a joint effort between NASA and Metal Matrix Cast Composites, Inc., a complex liquid oxygen (LOX) compatible turbopump housing is being redesigned and manufactured from hybrid (particulate and Fibers) Aluminum MMC. To this end, a revolutionary tool-less pressure infiltration casting technology is being perfected. Ceramic preforms for the composite are 3-dimensionally printed using a stereolithography file, acquired from a CAD model. The preforms are then invested into a refractory material and pressure infiltrated with liquid metal. After casting, the refractory material is washed away leaving behind a near net-shape composite part. Benefits of this process include increased composite uniformity, no mold machining, short time from design to part properties matching traditional methods, ability to make previously impossible to manufacture parts and no size limitations with a newly developed joining technology. The results of materials, manufacturing and design optimizations, preform joining, and sub element tests will be presented.

Shah, Sandeep↗

NASA NTRS2001

RADX34: A Future-X Demonstration of Autonomous Robust Abort Technologies on the X-34

The Charles Stark Draper Laboratory, Inc. has been conducting the RADX-34 Future-X Pathfinder Flight Demonstration experiment under the direction of the NASA Marshall Space Flight Center. The Future-X experiment will use the X-34 to demonstrate autonomous abort technologies needed for the next generation of reusable launch vehicles. This project will involve integration of real-time abort mission planning algorithms with the existing guidance and control to provide abort coverage for the low-Mach flights of the X-34. This paper describes the design and capability of the abort planner three months prior to the conclusion of its development. The mission planner described herein is able to respond to loss of thrust, determine which runways can be reached within the vehicle constraints, and designate an appropriate landing site. This project, when complete, will mark the first step in the development of the Next Generation of Guidance and Control (NGGC) autonomous algorithms. NGGC algorithms will help ensure the second generation of reusable launch vehicles will meet their cost, safety and reliability requirements.

Aron, Edward C.↗

NASA NTRS2001

Aeroelastic Stability of a Soft-Inplane Gimballed Tiltrotor Model in Hover

Soft-inplane rotor systems can significantly reduce the inplane rotor loads generated during the maneuvers of large tiltrotors, thereby reducing the strength requirements and the associated structural weight of the hub. Soft-inplane rotor systems, however, are subject to instabilities associated with ground resonance, and for tiltrotors this instability has increased complexity as compared to a conventional helicopter. Researchers at Langley Research Center and Bell Helicopter-Textron, Inc. have completed an initial study of a soft-inplane gimballed tiltrotor model subject to ground resonance conditions in hover. Parametric variations of the rotor collective pitch and blade root damping., and their associated effects on the model stability were examined. Also considered in the study was the effectiveness of an active swashplate and a generalized predictive control (GPC) algorithm for stability augmentation of the ground resonance conditions. Results of this study show that the ground resonance behavior of a gimballed soft-inplane tiltrotor can be significantly different from that of a classical soft-inplane helicopter rotor. The GPC-based active swashplate was successfully implemented, and served to significantly augment damping of the critical modes to an acceptable value.

Nixon, Mark W.↗

NASA NTRS1994

Performance of BLAS 3, FFTs and NAS Parallel Benchmarks on Cray T3D

Recently, a Cray T3D Emulator has been made available on the Cray Y-MP and C90 computers. The Pittsburgh Supercomputer Center has acquired a CRAY T3D system and many other centers like Jet Propulsion Laboratory (JPL) will have it by the end of 1994. The Cray T3D system is the firstphase system in Cray Research, Inc.'s (CRI) three-phase massively parallel processing (MPP) program. This system features a heterogeneous architecture that closely couples DEC's ALPHA microprocessors and CRI's parallel-vector technology, i.e. the Cray Y-MP and Cray C90. The Cray T3D Emulator will give prospective users a valuable experience in developing high performance applications on the MPP system. This emulator runs programs written in CRI's MPP Fortran programming model (data sharing and work sharing) or Parallel Virtual Machine (PVM) programming model. It will help the users to study data layout, data locality, and data reference patterns thereby providing feedback which will enable one to write more efficient parallel codes. An overview of the Cray T3D hardware, software, and three of its available programming models is presented.The Cray Fortran Programming Model comprising (a) Data Sharing, (b) Worksharing and (c) Message Passing, will be discussed with examples. We have also implemented distributed BLAS 3 (matrix-matrix multiplication) in data parallel model (using only CSHIFT); worksharing model using block distribution and collapsed distribution; and message passing model using PVM. We have also implemented 2D and 3D FFTs for radix-2 using PVM. The performance of NAS Parallel 'Benchmarks (NPB) on CRAY T3D will be compared with other highly parallel systems such as CM-5, Paragon, C90 etc.

Saini, Subhash↗

NASA NTRS2001

Meteorological Data for Geodynamics Use: IERS Special Bureau for the Atmosphere

During the life of this contract, the PI set up and operated a data center known as the "Special Bureau for the Atmosphere" of the International Earth Rotation Service (IERS) at Atmospheric and Environmental Research, Inc., and in conjunction with the U.S. National Oceanic and Atmospheric Administration. The role of the center is to calculate, archive, analyze, and distribute atmospheric data related to Earth rotation, polar motion and other motions of the Earth. We have produced data from 4 different operational meteorological centers. We have also produced data from atmospheric reanalyzes, spanning back about a half a century. The center is one of several centers under the Global Geophysical Fluids Center (GGFC) of the IERS; the GGFC is centered at NASA's Goddard Space Flight Center. Our data center has made data available to a large variety of scientists worldwide.

Salstein, David A.↗

NASA NTRS2001

Static and Wind Tunnel Aero-Performance Tests of NASA AST Separate Flow Nozzle Noise Reduction Configurations

This report presents the results of cold flow model tests to determine the static and wind tunnel performance of several NASA AST separate flow nozzle noise reduction configurations. The tests were conducted by Aero Systems Engineering, Inc., for NASA Glenn Research Center. The tests were performed in the Channels 14 and 6 static thrust stands and the Channel 10 transonic wind tunnel at the FluiDyne Aerodynamics Laboratory in Plymouth, Minnesota. Facility checkout tests were made using standard ASME long-radius metering nozzles. These tests demonstrated facility data accuracy at flow conditions similar to the model tests. Channel 14 static tests reported here consisted of 21 ASME nozzle facility checkout tests and 57 static model performance tests (including 22 at no charge). Fan nozzle pressure ratio varied from 1.4 to 2.0, and fan to core total pressure ratio varied from 1.0 to 1.19. Core to fan total temperature ratio was 1.0. Channel 10 wind tunnel tests consisted of 15 tests at Mach number 0.28 and 31 tests at Mach 0.8. The sting was checked out statically in Channel 6 before the wind tunnel tests. In the Channel 6 facility, 12 ASME nozzle data points were taken and 7 model data points were taken. In the wind tunnel, fan nozzle pressure ratio varied from 1.73 to 2.8, and fan to core total pressure ratio varied from 1.0 to 1.19. Core to fan total temperature ratio was 1.0. Test results include thrust coefficients, thrust vector angle, core and fan nozzle discharge coefficients, total pressure and temperature charging station profiles, and boat-tail static pressure distributions in the wind tunnel.

Mikkelsen, Kevin L.↗

NASA NTRS2001

New Horizons Regional Education Center 2001 FIRST Robotics Competition

The New Horizons Regional Education Center (NHREC) in Hampton, VA sought and received NASA funding to support its participation in the 2001 FIRST Robotics competition. FIRST, Inc. (For Inspiration and Recognition of Science and Technology) is an organization which encourages the application of creative science, math, and computer science principles to solve real-world engineering problems. The FIRST competition is an international engineering contest featuring high school, government, and business partnerships.

Source record↗

NASA NTRS2000

The Eclipse Project

The Eclipse Project by Tom Tucker provides a readable narrative and a number of documents that record an important flight research effort at NASA's Dryden Flight Research Center. Carried out by Kelly Space and Technology, Inc., in partnership with the Air Force and Dryden at Edwards Air Force Base in the Mojave Desert of California, this project tested and gathered data about a potential newer and less expensive way to launch satellites into space. Whether the new technology comes into actual use will depend on funding, market forces, and other factors at least partly beyond the control of the participants in the project. This is a familiar situation in the history of flight research.

Tucker, Tom↗