SEARCH · Search NASA

Results for “PROCESS CONTROL”

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.

SourceResearch connectionFrom yearThrough year

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

At least 1,477 records · Page 82

All sources NASA NTRS DOE OSTI

NASA NTRS1995

Powder-Coated Towpreg: Avenues to Near Net Shape Fabrication of High Performance Composites

Near net shape parts were fabricated from powder-coated preforms. Key issues including powder loss during weaving and tow/tow friction during braiding were addressed, respectively, by fusing the powder to the fiber prior to weaving and applying a water-based gel to the towpreg prior to braiding. A 4:1 debulking of a complex 3-D woven powder-coated preform was achieved in a single step utilizing expansion rubber molding. Also, a process was developed for using powder-coated towpreg to fabricate consolidated ribbon having good dimensional integrity and low voids. Such ribbon will be required for in situ fabrication of structural components via heated head advanced tow placement. To implement process control and ensure high quality ribbon, the ribbonizer heat transfer and pulling force were modeled from fundamental principles. Most of the new ribbons were fabricated from dry polyarylene ether and polymide powders.

Johnston, N. J.↗

NASA NTRS1996

Commercial Implementation of Ultrasonic Velocity Imaging Methods via Cooperative Agreement Between NASA Lewis Research Center and Sonix, Inc.

This article describes the commercial implementation of ultrasonic velocity imaging methods developed and refined at NASA Lewis Research Center on the Sonix c-scan inspection system. Two velocity imaging methods were implemented: thickness-based and non-thickness-based reflector plate methods. The article demonstrates capabilities of the commercial implementation and gives the detailed operating procedures required for Sonix customers to achieve optimum velocity imaging results. This commercial implementation of velocity imaging provides a 100x speed increase in scanning and processing over the lab-based methods developed at LeRC. The significance of this cooperative effort is that the aerospace and other materials development-intensive industries which use extensive ultrasonic inspection for process control and failure analysis will now have an alternative, highly accurate imaging method commercially available.

Roth, Don J.↗

NASA NTRS1995

Laser Material Processing for Microengineering Applications

The processing of materials via laser irradiation is presented in a brief survey. Various techniques currently used in laser processing are outlined and the significance to the development of space qualified microinstrumentation are identified. In general the laser processing technique permits the transferring of patterns (i.e. lithography), machining (i.e. with nanometer precision), material deposition (e.g., metals, dielectrics), the removal of contaminants/debris/passivation layers and the ability to provide process control through spectroscopy.

Helvajian, H.↗

NASA NTRS1997

Advanced Technology Composite Fuselage - Manufacturing

The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program is to develop the technology required for cost-and weight-efficient use of composite materials in transport fuselage structure. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements, and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of stringer-stiffened and sandwich skin panels. Circumferential and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant-section stiffening elements. Drape forming was chosen for stringers and other stiffening elements cocured to skin structures. Significant process development efforts included AFP, braiding, RTM, autoclave cure, and core blanket fabrication for both sandwich and stiffened-skin structure. Outer-mold-line and inner-mold-line tooling was developed for sandwich structures and stiffened-skin structure. The effect of design details, process control and tool design on repeatable, dimensionally stable, structure for low cost barrel assembly was assessed. Subcomponent panels representative of crown, keel, and side quadrant panels were fabricated to assess scale-up effects and manufacturing anomalies for full-scale structures. Manufacturing database including time studies, part quality, and manufacturing plans were generated to support the development of designs and analytical models to access cost, structural performance, and dimensional tolerance.

Wilden, K. S.↗

NASA NTRS1997

Management of a coordinated parts program

The organization of the management of a parts program is discussed. The organizational structure faced by the parts manager and the advantages and disadvantages of managing a coordinated parts program are analyzed. The reliable operation of an instrument is the key to the success of the mission, together with the management of the parts program. The analysis led to the conclusion that the setting up of the decision support model will aid the parts manager in the decision making and the process control.

Krishnan, G. S.↗

NASA NTRS1996

Chip-on-Board Technology 1996 Year-end Report (Design, Manufacturing, and Reliability Study)

The major impetus for flight qualifying Chip-On-Board (COB) packaging technology is the shift in emphasis for space missions to smaller, better, and cheaper spacecraft and satellites resulting from the NASA New Millenium initiative and similar requirements in DoD-sponsored programs. The most important benefit that can potentially be derived from miniaturizing spacecraft and satellites is the significant cost saving realizable if a smaller launch vehicle may be employed. Besides the program cost saving, there are several other advantages to building COB-based space hardware. First, once a well-controlled process is established, COB can be low cost compared to standard Multi-Chip Module (MCM) technology. This cost competitiveness is regarded as a result of the generally greater availability and lower cost of Known Good Die (KGD). Coupled with the elimination of the first level of packaging (chip package), compact, high-density circuit boards can be realized with Printed Wiring Boards (PWB) that can now be made with ever-decreasing feature size in line width and via hole. Since the COB packaging technique in this study is based mainly on populating bare dice on a suitable multi-layer laminate substrate which is not hermetically sealed, die coating for protection from the environment is required. In recent years, significant improvements have been made in die coating materials which further enhance the appeal of COB. Hysol epoxies, silicone, parylene and silicon nitride are desirable because of their compatible Thermal Coefficient of Expansion (TCE) and good moisture resistant capability. These die coating materials have all been used in the space and other industries with varying degrees of success. COB technology, specifically siliconnitride coated hardware, has been flown by Lockheed on the Polar satellite. In addition, DARPA has invested a substantial amount of resources on MCM and COB-related activities recently. With COB on the verge of becoming a dominant player in DoD programs, DARPA is increasing its support of the availability of KGDs which will help decrease their cost. Aside from the various major developments and trends in the space and defense industries that are favorable to the acceptance and widespread use of'COB packaging technology, implementing COB can be appealing in other aspects. Since the interconnection interface is usually the weak link in a system, the overall circuit or system reliability may actually be improved because of the elimination of a level of interconnect/packaging at the chip. With COB, mixing packaging technologies is possible. Because some devices are only available in commercial plastic packages, populating a multi-layer laminate substrate with both bare dice and plastic-package parts is inevitable. Another attractive feature of COB is that re-workability is possible if die coating is applied only on the die top. This method allows local replacement of individual dice that were found to be defective instead of replacing an entire board. In terms of thermal management, unpackaged devices offer a shorter thermal resistance path than their packaged counterparts thereby improving thermal sinking and heat removal from the parts.

Le, Binh Q.↗

NASA NTRS1998

An Investigation of Reliability Models for Ceramic Matrix Composites and their Implementation into Finite Element Codes

The development of modeling approaches for the failure analysis of ceramic-based material systems used in high temperature environments was the primary objective of this research effort. These materials have the potential to support many key engineering technologies related to the design of aeropropulsion systems. Monolithic ceramics exhibit a number of useful properties such as retention of strength at high temperatures, chemical inertness, and low density. However, the use of monolithic ceramics has been limited by their inherent brittleness and a large variation in strength. This behavior has motivated material scientists to reinforce the monolithic material with a ceramic fiber. The addition of a second ceramic phase with an optimized interface increases toughness and marginally increases strength. The primary purpose of the fiber is to arrest crack growth, not to increase strength. The material systems of interest in this research effort were laminated ceramic matrix composites, as well as two- and three- dimensional fabric reinforced ceramic composites. These emerging composite systems can compete with metals in many demanding applications. However, the ongoing metamorphosis of ceramic composite material systems, and the lack of standardized design data has in the past tended to minimize research efforts related to structural analysis. Many structural components fabricated from ceramic matrix composites (CMC) have been designed by "trial and error." The justification for this approach lies in the fact that during the initial developmental phases for a material system fabrication issues are paramount. Emphasis is placed on demonstrating feasibility rather than fully understanding the processes controlling mechanical behavior. This is understandable during periods of rapid improvements in material properties for any composite system. But to avoid the ad hoc approach, the analytical methods developed under this effort can be used to develop rational structural design protocols.

Duffy, Stephen F.↗

NASA NTRS1998

Orbital Processing of Eutectic Rod-Like Arrays

The eutectic is one of only three solidification classes that exist. The others are isostructural and peritectic-class reactions, respectively. Simplistically, in a binaryeutectic phase diagram, a single liquid phase isothermally decomposes to two solid phases in a cooperative manner. The melting point minimum at the eutectic composition, isothermal solidification temperature, near-isocompositional solidification and refined solidification microstructure lend themselves naturally to such applications as brazing and soldering; industries that eutectic alloys dominate. Interest in direct process control of microstructures has led, more recently, to in-situ eutectic directional solidification with applications in electro-magnetics and electro-optics. In these cases, controlled structural refinement and the high aspect ratio and regularity of the distributed eutectic phases is highly significant to the fabrication and application of these in-situ natural composites. The natural pattern formation and scaling of the dispersed phase on a sub-micron scale has enormous potential application, since fabricating bulk materials on this scale mechanically has proven to be particularly difficult. It is thus of obvious importance to understand the solidification of eutectic materials since they are of great commercial significance. The dominant theory that describes eutectic solidification was derived for diffusion-controlled growth of alloys where both solid eutectic phases solidify metallically, i.e. without faceting at the solidification interface. Both high volume fraction (lamellar) and low volume fraction (rod-like) regular metallic arrays are treated by this theory. Many of the useful solders and brazements, however, and most of the regular in-situ composites are characterized by solidification reactions that are faceted/non-faceted in nature, rather than doubly non-faceted (metallic). Further, diffusion-controlled growth conditions are atypical terrestrially since gravitationally-driven convection is pervasive. As a consequence, it is important to determine whether these faceted/non-faceted composites behave in the same manner as their doubly non-faceted counterparts, particularly in the presence of convection. Prior analytical convective sensitivity testing of this theory predicted insensitivity. Prior experimental testing of this theory offered broad-based agreement between theory and experiment, though most results were for high volume fraction lamellar eutectics that solidified without faceting at the solidification interface. Directional solidification experiments of low volume fraction rod eutectics under damped (microgravity or magnetic field) conditions, however, have demonstrated significant sensitivity, challenging this fundamental theory. More recent theories have been proposed which introduce kinetic undercooling, faceting, fluid shear of the solute redistribution zone and the possibility that the interface composition is not the same as the bulk liquid composition. This program tests the established and proposed analytical theories and addresses the origins of discrepancies between the experimental and analytical results.

Larson, David J., Jr.↗

NASA NTRS1999

Ignition, Transition, Flame Spread in Multidimensional Configurations in Microgravity

In the inhabited quarters of orbiting spacecraft, fire is a greatly feared hazard. Thus, the fire safety strategy in a spacecraft is (1) to keep any fire as small as possible, (2) to detect any fire as early as possible, and (3) to extinguish any fire as quickly as possible. This suggests that a material which undergoes a momentary ignition might be tolerable but a material which permits a transition from a localized ignition to flame spread would significantly increase the fire hazard in a spacecraft. If the transition does not take place, fire growth does not occur. Therefore, it is critical to understand what process controls the transition. Many previous works have studied ignition and flame spread separately or were limited to a two-dimensional configuration. In this study, time-dependent phenomena of the transition over a thermally thin sample is studied experimentally and theoretically in two- and three-dimensional (2D,3D) configurations. Furthermore, localized ignition can be initiated at the center portion of thermally thin paper sample instead of at one end of the sample. Thus, the transition to flame spread could occur either toward upstream or downstream or both directions simultaneously with an external flow. In this presentation, the difference in the transition between the 3D and 2D configurations is explained with the numerically calculated data. For sufficiently narrow samples edge effects exist. Some results on this issue are presented. New analysis of the surface smoldering experiments conducted in the space shuttle STS-75 flight is also described.

Kashiwagi, Takashi↗

NASA NTRS1999

Electrostatic Hazard Considerations for ODC Solvent Replacement Selection Testing

ODC solvents are used to clean many critical substrates during solid rocket motor production operations. Electrostatic charge generation incidental to these cleaning operations can pose a major safety issue. Therefore, while determining the acceptability of various ODC replacement cleaners, one aspect of the selection criteria included determining the extent of electric charge generation during a typical solvent cleaning operation. A total of six candidate replacement cleaners, sixteen critical substrates, and two types of cleaning swatch materials were studied in simulated cleaning operations. Charge generation and accumulation effects were investigated by measuring the peak voltage and brush discharging effects associated with each cleaning process combination. In some cases, charge generation was found to be very severe. Using the conductivity information for each cleaner, the peak voltage data could in some cases, be qualitatively predicted. Test results indicated that severe charging effects could result in brush discharges that could potentially result in flash fire hazards when occurring in close proximity to flammable vapor/air mixtures. Process controls to effectively mitigate these hazards are discussed.

Fairbourn, Brad↗

NASA NTRS1998

Friction Plug Welding of 2195 Al-Cu-Li for Manned Space Launch Vehicles

Friction Plug Welding (FPW) is currently being studied for use on the Space Transportation System's Super Light weight External Tank. This process has demonstrated the potential to solve on of Al-Li 2195's most challenging aspects repair welding. The current weld repair process is successful, but is labor intensive and inconsistent. Technology advances in FPW and tooling designs will be presented. The results of plug welding optimization, production implementation, considerations and cost benefit analysis are discussed. Among the tests to be discussed are tensile, surface crack tension, simulated service, liquid oxygen compatibility results and methods of repairing plug repairs. Tool design, computerized process control equipment and database record retention and analyses may also be addressed.

Takeshita, Riki P.↗

NASA NTRS1998

Friction-Stir Welding of Large Scale Cryogenic Fuel Tanks for Aerospace Applications

The Marshall Space Flight Center has established a facility for the joining of large-scale aluminum-lithium alloy 2195 cryogenic fuel tanks using the friction-stir welding process. Longitudinal welds, approximately five meters in length, were made possible by retrofitting an existing vertical fusion weld system, designed to fabricate tank barrel sections ranging from two to ten meters in diameter. The structural design requirements of the tooling, clamping and the spindle travel system will be described in this paper. Process controls and real-time data acquisition will also be described, and were critical elements contributing to successful weld operation.

Jones, Clyde S., III↗

NASA NTRS1995

Solar Particle Induced Upsets in the TDRS-1 Attitude Control System RAM During the October 1989 Solar Particle Events

The three large solar particle events, beginning on October 19, 1989 and lasting approximately six days, were characterized by high fluences of solar protons and heavy ions at 1 AU. During these events, an abnormally large number of upsets (243) were observed in the random access memory of the attitude control system (ACS) control processing electronics (CPE) on-board the geosynchronous TDRS-1 (Telemetry and Data Relay Satellite). The RAM unit affected was composed of eight Fairchild 93L422 memory chips. The Galileo spacecraft, launched on October 18, 1989 (one day prior to the solar particle events) observed the fluxes of heavy ions experienced by TDRS-1. Two solid-state detector telescopes on-board Galileo, designed to measure heavy ion species and energy, were turned on during time periods within each of the three separate events. The heavy ion data have been modeled and the time history of the events reconstructed to estimate heavy ion fluences. These fluences were converted to effective LET spectra after transport through the estimated shielding distribution around the TDRS-1 ACS system. The number of single event upsets (SEU) expected was calculated by integrating the measured cross section for the Fairchild 93L422 memory chip with average effective LET spectrum. The expected number of heavy ion induced SEU's calculated was 176. GOES-7 proton data, observed during the solar particle events, were used to estimate the number of proton-induced SEU's by integrating the proton fluence spectrum incident on the memory chips, with the two-parameter Bendel cross section for proton SEU'S. The proton fluence spectrum at the device level was gotten by transporting the protons through the estimated shielding distribution. The number of calculated proton-induced SEU's was 72, yielding a total of 248 predicted SEU'S, very dose to the 243 observed SEU'S. These calculations uniquely demonstrate the roles that solar heavy ions and protons played in the production of SEU's during the October 1989 solar particle events.

Croley, D. R.↗

NASA NTRS1999

Looking at NGST Through the Eyes of DCATT

The first phase of the Developmental Characterized Active Telescope Testbed (DCATT) hardware system was integrated at Goddard Space Flight Center in early March of 1999 and has been operational for almost a year. Experiments are currently being conducted on the testbed to quantify and refine various methods and techniques in the baseline wavefront sensing and control process. This paper addresses the actual optical design of the Phase 0 hardware configuration and discusses the open loop system level performance of the system. Lessons learned for NGST during the buildup and characterization of the system are presented.

Davila, Pam↗

NASA NTRS1996

Using Design Capability Indices to Satisfy Ranged Sets of Design Requirements

For robust design it is desirable to allow the design requirements to vary within a certain range rather than setting point targets. This is particularly important during the early stages of design when little is known about the system and its requirements. Toward this end, design capability indices are developed in this paper to assess the capability of a family of designs, represented by a range of top-level design specifications, to satisfy a ranged set of design requirements. Design capability indices are based on process capability indices from statistical process control and provide a single objective, alternate approach to the use of Taguchi's signal-to- noise ratio which is often used for robust design. Successful implementation of design capability indices ensures that a family of designs conforms to a given ranged set of design requirements. To demonstrate an application and the usefulness of design capability indices, the design of a solar powered irrigation system is presented. Our focus in this paper is on the development and implementation of design capability indices as an alternate approach to the use of the signal-to-noise ratio and not on the results of the example problem, per se.

Chen, Wei↗

NASA NTRS2000

Issues and Effects of Atomic Oxygen Interactions With Silicone Contamination on Spacecraft in Low Earth Orbit

The continued presence and use of silicones on spacecraft in low Earth orbit (LEO) has been found to cause the deposition of contaminant films on surfaces which are also exposed to atomic oxygen. The composition and optical properties of the resulting SiO(x)- based (where x is near 2) contaminant films may be dependent upon the relative rates of arrival of atomic oxygen, silicone contaminant and hydrocarbons. This paper presents results of in-space silicone contamination tests, ground laboratory simulation tests and analytical modeling to identify controlling processes that affect contaminant characteristics.

Banks, Bruce↗

NASA NTRS1999

Satellite Data Assimilation

Satellite altimetry provides the only routine observation of a dynamic variable of the global ocean. For instance, measurements from the TOPEX/POSEIDON altimeter have provided dramatic basin-wide images of the space-time evolution of sea level associated with the 1997-98 El Nino event. The nature of large-scale ocean circulation is being studied that underlies such sea level changes measured by satellite altimetry. To first approximation, properties of large-scale (order 1000 km and larger) sea level variability is latitudinally dependent. An analysis using a general circulation model shows that sea level changes are largely due to wind-driven baroclinic (depth dependent) circulation in the tropics (within 20 degrees of the equator), but are primarily due to the expansion and contraction of near surface water in temperate latitudes (between 20 deg. and 40 deg.) forced by seasonal heating and cooling. In contrast, wind-driven barotropic (depth independent) circulation dominates sea level variability in high latitudes (40 deg. and higher) characterized by periods that are as short as a few days. The presence of such inhomogeneity and the significance of high-frequency, large-scale sea level changes had not been fully recognized prior to this study, and are summarized in Fukumori et al. Numerical models provide theoretical relationships among properties that can be inverted using observations so as to estimate the entire state of the ocean, including properties that are otherwise difficult to measure remotely. The process is data assimilation. An approximate Kalman filter and smoother have been devised to assimilate three years of TOPEX/POSEIDON sea level data into a global ocean general circulation model. The figure below demonstrates the skill of the assimilation, and shows the altimeter assimilated estimate being in closer agreement than the simulation is with independent in situ measurements of subsur ace temperature and velocity, consistent with formal uncertainty estimates. Results from this study have been summarized and submitted for publication. The study demonstrates the feasibility of global ocean data assimilation and illustrates applications in monitoring and understanding of processes controlling the evolution of the ocean. Additional information is contained in the original.

Fukumori, Ichiro↗

NASA NTRS2000

A 3-D Model Analysis of The Impact of Asian Anthropogenic Emissions on the Sulfur Cycle Over the Pacific Ocean

The impact of anthropogenic activities on the SO2 and sulfate aerosol levels over the Pacific region is examined in the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. We focus on the analysis of the data from the NASA Pacific Exploratory Missions (PEM) over the western North Pacific and the tropical Pacific. These missions include PEM-West A in September-October 1991, when the Asian outflow was at the minimum but the upper atmosphere was heavily influenced by the Pinatubo volcanic eruption, and PEM-West B in March-April 1994 when the Asian outflow was at the maximum, and PEM-Tropics A in August-September at a region relatively free of direct anthropogenic influences. Specifically, we will examine the relative importance of anthropogenic, volcanic and biogenic sources to the SO2 and sulfate concentrations over the Pacific, and quantify the processes controlling the distributions of SO2 and sulfate in both the boundary layer and the free troposphere. We will also assess the global impact of SO2 emission in Asia on the sulfate aerosol loading.

Chin, Mian↗