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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Airborne full polarization radiometry using the MSFC Advanced Microwave Precipitation Radiometer (AMPR)

The applications of vertically and horizontally polarized brightness temperatures in both atmospheric and surface remote sensing have been long recognized by many investigators, particularly those studying SMMR and SSM/I data. Here, the large contrast between the first two Stokes' parameters (T(sub V) and T(sub H)) can be used for detection of sea ice, measurement of ocean surface wind speed, and measurement of cloud and water vapor opacity. High-resolution aircraft data from instruments such as the NASA/MSFC AMPR is crucial for verifying radiative transfer models and developing retrieval algorithms. Currently, the AMPR is outfitted with single-polarization channels at 10, 18, 37 and 85 GHz. To increase its utility, it is proposed that additional orthogonal linearly polarized channels be added to the AMPR. Since the AMPR's feedhorns are already configured for dual orthogonal linearly polarized modes, this would require only a duplication of the currently existing receivers. To circumvent the resulting polarization basis skew caused by the cross-track scanning mechanism, the technique of Electronic Polarization Basis Rotation is proposed to be implemented. Implementation of EPBR requires precise measurement of the third Stokes parameter and will eliminate polarization skew by allowing the feedhorn basis skew angle to be corrected in software. In addition to upgrading AMPR to dual polarization capability (without skew), the modifications will provide an opportunity to demonstrate EPBR on an airborne platform. This is a highly desirable intermediate step prior to satellite implementation.

Gasiewski, Al J.↗
NASA NTRS1993

Introduction of laser initiation for the 48-inch Advanced Solid Rocket Motor (ASRM) test motors at Marshall Space Flight Center (MSFC)

The Advanced Solid Rocket Motor is a new design for the Space Shuttle Solid Rocket Booster. The new design will provide more thrust and more payload capability, as well as incorporating many design improvements in all facets of the design and manufacturing process. A 48-inch (diameter) test motor program is part of the ASRM development program. This program has multiple purposes for testing of propellent, insulation, nozzle characteristics, etc. An overview of the evolution of the 48-inch ASRM test motor ignition system which culminated with the implementation of a laser ignition system is presented. The laser system requirements, development, and operation configuration are reviewed in detail.

Zimmerman, Chris J.↗
NASA NTRS1992

MSFC Three Point Docking Mechanism design review

In the next few decades, we will be launching expensive satellites and space platforms that will require recovery for economic reasons, because of initial malfunction, servicing, repairs, or out of a concern for post lifetime debris removal. The planned availability of a Three Point Docking Mechanism (TPDM) is a positive step towards an operational satellite retrieval infrastructure. This study effort supports NASA/MSFC engineering work in developing an automated docking capability. The work was performed by the Grumman Space & Electronics Group as a concept evaluation/test for the Tumbling Satellite Retrieval Kit. Simulation of a TPDM capture was performed in Grumman's Large Amplitude Space Simulator (LASS) using mockups of both parts (the mechanism and payload). Similar TPDM simulation activities and more extensive hardware testing was performed at NASA/MSFC in the Flight Robotics Laboratory and Space Station/Space Operations Mechanism Test Bed (6-DOF Facility).

Schaefer, Otto↗
NASA NTRS1991

The MSFC space station/space operations mechanism test bed

The Space Station/Space Operations Mechanism Test Bed consists of the following: a hydraulically driven, computer controlled Six Degree-of-Freedom Motion System (6DOF); a six degree-of-freedom force and moment sensor; remote driving stations with computer generated or live TV graphics; and a parallel digital processor that performs calculations to support the real time simulation. The function of the Mechanism Test Bed is to test docking and berthing mechanisms for Space Station Freedom and other orbiting space vehicles in a real time, hardware-in-the-loop simulation environment. Typically, the docking and berthing mechanisms are composed of two mating components, one for each vehicle. In the facility, one component is attached to the motion system, while the other component is mounted to the force/moment sensor fixed in the support structure above the 6DOF. The six components of the contact forces/moments acting on the test article and its mating component are measured by the force/moment sensor.

Sutton, William G.↗
NASA NTRS1993

MSFC nuclear thermal propulsion technology program

Viewgraphs on non-nuclear materials assessment, nuclear thermal propulsion (NTP) turbomachinery technologies, and high temperature superconducting magnetic bearing technology are presented. The objective of the materials task is to identify and evaluate candidate materials for use in NTP turbomachinery and propellant feed system applications. The objective of the turbomachinery technology task is to develop and validate advanced turbomachinery technologies at the component and turbopump assembly levels. The objective of the high temperature superconductors (HTS) task is to develop and validate advanced technology for HTS passive magnetic/hydrostatic bearing.

Swint, Shane↗
NASA NTRS1992

Microstrip proportional counter development at MSFC

Microstrip detectors are an exciting new development in proportional counter design fabricated using integrated circuit-type photolithography techniques; they therefore offer very high spatial accuracy and uniformity. A development program is underway at NASA-Marshall to produce large-area microstrips for use in an X-ray detector balloon flight program and to investigate the general performance limits of these new devices. Microstrips tested so far have been fabricated both in-house using standard photolithographic techniques and by an outside contractor using electron beam technology. Various substrate materials have been tested along with different electrode configurations. The distributions of pickup on subdivided cathodes on both top and bottom surfaces of the microstrips are also being investigated for use as two-dimensional imaging detectors. Data from these tests in the development of a large-area device will be presented.

Fulton, M. A.↗
NASA NTRS1994

CFD assessment of the carbon monoxide and nitric oxide formation from RD-170 hot-fire testing at MSFC

Computational Fluid Dynamics (CFD) technology has been used to assess the exhaust plume pollutant environment of the RD-170 engine hot-firing on the F1 Test Stand at Marshall Space Flight Center. Researchers know that rocket engine hot-firing has the potential for forming thermal nitric oxides (NOx), as well as producing carbon monoxide (CO) when hydrocarbon fuels are used. Because of the complicated physics involved, however, little attempt has been made to predict the pollutant emissions from ground-based engine testing, except for simplified methods which can grossly underpredict and/or overpredict the pollutant formations in a test environment. The objective of this work, therefore, has been to develop a technology using CFD to describe the underlying pollutant emission physics from ground-based rocket engine testing. This resultant technology is based on a three-dimensional, viscous flow, pressure-based CFD formulation, where wet CO and thermal NOx finite-rate chemistry mechanisms are solved with a Penalty function method.

Wang, Ten-See↗
NASA NTRS1994

MSFC institutional area network and ATM technology

The New Institutional Area Network (NEWIAN) at Marshall supports over 5000 end users with access to 26 file servers providing work presentation services. It is comprised of some 150 Ethernet LAN's interconnected by bridges/routers which are in turn connected to servers over two dual FDDI rings. The network supports various higher level protocols such as IP, IPX, AppleTalk (AT), and DECNet. At present IPX and AT protocols packets are routed, and IP protocol packets are bridged; however, work is in progress to route all IP packets. The impact of routing IP packets on network operation is examined. Broadband Integrated Services Data Network (BISDN), presently at various stages of development, is intended to provide voice, video, and data transfer services over a single network. BISDN will use asynchronous transfer mode (ATM) as a data transfer technique which provides for transmission, multiplexing, switching, and relaying of small size data units called cells. Limited ATM Wide Area Network (WAN) services are offered by Wiltel, AT&T, Sprint, and others. NASA is testing a pilot ATM WAN with a view to provide Program Support Communication Network services using ATM. ATM supports wide range of data rates and quality of service requirements. It is expected that ATM switches will penetrate campus networks as well. However, presently products in these areas are at various stages of development and standards are not yet complete. We examine development of ATM to help assess its role in the evolution of NEWIAN.

Amin, Ashok T.↗
NASA NTRS1996

Development of software for the MSFC solar vector magnetograph

The Marshall Space Flight Center Solar Vector Magnetograph is a special purpose telescope used to measure the vector magnetic field in active areas on the surface of the sun. This instrument measures the linear and circular polarization intensities (the Stokes vectors Q, U and V) produced by the Zeeman effect on a specific spectral line due to the solar magnetic field from which the longitudinal and transverse components of the magnetic field may be determined. Beginning in 1990 as a Summer Faculty Fellow in project JOVE and continuing under NASA Grant NAG8-1042, the author has been developing computer software to perform these computations, first using a DEC MicroVAX system equipped with a high speed array processor, and more recently using a DEC AXP/OSF system. This summer's work is a continuation of this development.

Kineke, Jack↗
NASA NTRS1996

Overview of CFD Analyses Supporting the Reusable Solid Rocket Motor (RSRM) Program at MSFC

During the past year, various computational fluid dynamic (CFD) analyses were performed at Marshall Space Flight Center to support the Reusable Solid Rocket Motor program. The successful completion of these analyses involved application of the CFD codes FDNS and CELMINT. The topics addressed by the analyses were: (1) the design and prediction of slag pool accumulation within the five inch test motor, (2) prediction of slag pool behavior and its response to lateral accelerations, (3) the clogging of potential insulation debonds within the nozzle by slag accumulation, (4) the behavior of jets within small voids inside nozzle joint gaps, (5) The effect of increased inhibitor stiffness on motor acoustics, and (6) the effect of a nozzle defect on particle impingement enhanced erosion. The emphasis of this presentation will be to further discuss the work in topics 3, 4, and 5.

Stewart, Eric↗
NASA NTRS1998

Investigation of Springback Associated with Composite Material Component Fabrication (MSFC Center Director's Discretionary Fund Final Report, Project 94-09)

The objective of this research project was to examine processing and design parameters in the fabrication of composite components to obtain a better understanding and attempt to minimize springback associated with composite materials. To accomplish this, both processing and design parameters were included in a Taguchi-designed experiment. Composite angled panels were fabricated, by hand layup techniques, and the fabricated panels were inspected for springback effects. This experiment yielded several significant results. The confirmation experiment validated the reproducibility of the factorial effects, error recognized, and experiment as reliable. The material used in the design of tooling needs to be a major consideration when fabricating composite components, as expected. The factors dealing with resin flow, however, raise several potentially serious material and design questions. These questions must be dealt with up front in order to minimize springback: viscosity of the resin, vacuum bagging of the part for cure, and the curing method selected. These factors directly affect design, material selection, and processing methods.

Benzie, M. A.↗
NASA NTRS1998

Damping Mechanisms for Microgravity Vibration Isolation (MSFC Center Director's Discretionary Fund Final Report, Project No. 94-07)

As a research facility for microgravity science, the International Space Station (ISS) will be used for numerous investigations such as protein crystal growth, combustion, and fluid mechanics experiments which require a quiescent acceleration environment across a broad spectrum of frequencies. These experiments are most sensitive to low-frequency accelerations and can tolerate much higher accelerations at higher frequency. However, the anticipated acceleration environment on ISS significantly exceeds the required acceleration level. The ubiquity and difficulty in characterization of the disturbance sources precludes source isolation, requiring vibration isolation to attenuate the anticipated disturbances to an acceptable level. This memorandum reports the results of research in active control methods for microgravity vibration isolation.

Whorton, M. S.↗
NASA NTRS1998

High Performance, Robust Control of Flexible Space Structures: MSFC Center Director's Discretionary Fund

Many spacecraft systems have ambitious objectives that place stringent requirements on control systems. Achievable performance is often limited because of difficulty of obtaining accurate models for flexible space structures. To achieve sufficiently high performance to accomplish mission objectives may require the ability to refine the control design model based on closed-loop test data and tune the controller based on the refined model. A control system design procedure is developed based on mixed H2/H(infinity) optimization to synthesize a set of controllers explicitly trading between nominal performance and robust stability. A homotopy algorithm is presented which generates a trajectory of gains that may be implemented to determine maximum achievable performance for a given model error bound. Examples show that a better balance between robustness and performance is obtained using the mixed H2/H(infinity) design method than either H2 or mu-synthesis control design. A second contribution is a new procedure for closed-loop system identification which refines parameters of a control design model in a canonical realization. Examples demonstrate convergence of the parameter estimation and improved performance realized by using the refined model for controller redesign. These developments result in an effective mechanism for achieving high-performance control of flexible space structures.

Whorton, M. S.↗
NASA NTRS1998

A Case Study for Probabilistic Methods Validation (MSFC Center Director's Discretionary Fund, Project No. 94-26)

Probabilistic method is not a universally accepted approach for the design and analysis of aerospace structures. The validity of this approach must be demonstrated to encourage its acceptance as it viable design and analysis tool to estimate structural reliability. The objective of this Study is to develop a well characterized finite population of similar aerospace structures that can be used to (1) validate probabilistic codes, (2) demonstrate the basic principles behind probabilistic methods, (3) formulate general guidelines for characterization of material drivers (such as elastic modulus) when limited data is available, and (4) investigate how the drivers affect the results of sensitivity analysis at the component/failure mode level.

Price J. M.↗
NASA NTRS1998

Solidification of Drops in the MSFC Drop Tube

Silver drops (99.9%, 7 mm diameter) were levitated, melted, and released to fall through the Marshall Space Flight Center's 105 m drop tube in an He-6% H atmosphere at 170 degrees superheat. The extent of solidification during the approx. 4.6 s of free fall time prior to impact was measured experimentally and computed numerically using a newly developed solidification heat transfer model. Comparison of the experimental observation of the fraction of liquid transformed with the numerical solutions showed reasonable agreement. Possible modifications of the model, in an attempt to close the gap between the experiment and the model comparison are discussed.

Brush, Lucien N.↗
NASA NTRS1998

High-Strength Aluminum Casting Alloy for High-Temperature Applications (MSFC Center Director's Discretionary Fund Final Project No. 97-10)

A new aluminum-silicon alloy has been successfully developed at Marshall Space Flight Center that has a significant improvement in tensile strength at elevated temperatures (550 to 700 F). For instance, the new alloy shows in average tensile strength of at least 90 percent higher than the current 390 aluminum piston alloy tested at 500 F. Compared to conventional aluminum alloys, automotive engines using the new piston alloy will have improved gas mileage, and may produce less air pollution in order to meet the future U.S. automotive legislative requirements for low hydrocarbon emissions. The projected cost for this alloy is less than $0.95/lb, and it readily allows the automotive components to be cast at a high production volume with a low, fully accounted cost. It is economically produced by pouring molten metal directly into conventional permanent steel molds or die casting.

Lee, J. A.↗
NASA NTRS1999

Measurement of Plastic Stress and Strain for Analytical Method Verification (MSFC Center Director's Discretionary Fund Project No. 93-08)

The analytical prediction of stress, strain, and fatigue life at locations experiencing local plasticity is full of uncertainties. Much of this uncertainty arises from the material models and their use in the numerical techniques used to solve plasticity problems. Experimental measurements of actual plastic strains would allow the validity of these models and solutions to be tested. This memorandum describes how experimental plastic residual strain measurements were used to verify the results of a thermally induced plastic fatigue failure analysis of a space shuttle main engine fuel pump component.

Price, J. M.↗
NASA NTRS1999

Containerless, Low-Gravity Undercooling of Ti-Ce Alloys in the MSFC Drop Tube

Previous tests of the classical nucleation theory as applied to liquid-liquid gap miscibility systems found a discrepancy between experiment and theory in the ability to undercool one of the liquids before the L1-L2 separation occurs. To model the initial separation process in a two-phase liquid mixture, different theoretical approaches, such as free-energy gradient and density gradient theories, have been put forth. If there is a large enough interaction between the critical liquid and the crucible, both models predict a wetting temperature (T(sub w)) above which the minority liquid perfectly wets and layers the crucible interface, but only on one side of the immiscibility dome. Materials with compositions on the other side of the dome will have simple surface adsorption by the minority liquid before bulk separation occurs when the coexistence (i.e., binoidal) line in reached. If the interaction between the critical liquid and the crucible were to decrease, T(sub w) would increase, eventually approaching the critical consolute temperature (T(sub cc)). If this situation occurs, then there could be large regions of the miscibility gap where non-perfect wetting conditions prevail resulting in droplets of L1 liquid at the surface having a non-zero contact angle. The resulting bulk structure will then depend on what happens on the surface and the subsequent processing conditions. In the past several decades, many experiments in space have been performed on liquid metal binary immiscible systems for the purpose of determining the effects that different crucibles may have on the wetting and separation process of the liquids. Potard performed experiments that showed different crucible materials could cause the majority phase to preferentially wet the container and thus produce a dispersed microstructure of the minority phase. Several other studies have been performed on immiscibles in a semi-container environment using an emulsion technique. Only one previous study was performed using completely containerless processing of immiscible metals and the results of that investigation are similar to some of the emulsion studies. In all the studies, surface wetting was attributed as the cause for the similar microstructures or the asymmetry in the ability to undercool the liquid below the binoidal on one side of the immiscibility dome. By removing the container completely from the separation process, it was proposed that the loss of the crucible/liquid interaction would produce a large shift in T(sub w) and thus change the wetting characteristics at the surface. By investigating various compositions across the miscibility gap, a change in the type and amount of liquid wetting at the surface of a containerless droplet should change the surface nucleating behavior of the droplet - whether it be the liquid-liquid wetting or the liquid-to-solid transition. Undercooling of the liquid into the metastable region should produce significant differences in the separation process and the microstructure upon solidification. In this study, we attempt to measure these transitions by monitoring the temperature of the sample by optical pyrometry. Microstructural analysis will be made to correlate with the degree of undercooling and the separation mechanisms involved.

Robinson, M. B.↗