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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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Environmental test program for superconducting materials and devices

A systematic approach to obtaining real time, superconducting YBa2Cu30(7-x) materials is presented. The work was carried out under the overall direction of Clemson University with tasks being performed at both Clemson and Westinghouse (Aiken, SC). Clemson prepared the tapecast superconducting 123 material and fabricated in into substrate-supported, environmentally-protected conducting links. Following this, all of the elements were individually tested for resistance vs. temperature and Tc; and then a portion of them were kept at Clemson for further testing while a randomly selected group was delivered to Westinghouse for specialized testing and evaluation in their low temperature/high vacuum and radiation facilities. In addition, a number of control samples (12 ea.) were put on the shelf at Clemson for further reference at the end of the testing period. The specific tests conducted at Clemson and Westinghouse/SRC are presented with a summary of the results.

Haertling, Gene↗
NASA NTRS1991

Environmental test program for superconducting materials and devices

This report is divided into two parts. The first dealing with work involved with Clemson University and the second with the results from Westinghouse/Savannah River. Both areas of work involved low noise, low thermal conductivity superconducting grounding links used in the NASA-sponsored Spectroscopy of the Atmosphere using Far Infrared Emission (SAFIRE) Project. Clemson prepared the links from YBa2Cu3O(7-x) superconductor tape that was mounted on a printed circuit board and encapsulated with epoxy resin. The Clemson program includes temperature vs. resistance, liquid nitrogen immersion, water immersion, thermal cycling, humidity, and radiation testing. The evaluation of the links under a long term environmental test program is described. The Savannah River program includes gamma irradiation, vibration, and long-term evaluation. The progress made in these evaluations is discussed.

Haertling, Gene↗
NASA NTRS1983

Accelerated degradation of silicon metallization systems

Clemson University has been engaged for the past five years in a program to determine the reliability attributes of solar cells by means of accelerated test procedures. The cells are electrically measured and visually inspected and then subjected for a period of time to stress in excess of that normally encountered in use, and then they are reinspected. Changes are noted and the process repeated. This testing has thus far involved 23 different unencapsulated cell types from 12 different manufacturers, and 10 different encapsulated cell types from 9 different manufacturers. Reliability attributes of metallization systems can be classified as major or minor, depending on the severity of the effects observed. As a result of the accelerated testing conducted under the Clemson program, major effects have been observed related to contact resistance and to mechanical adherence and solderability. This paper does not attempt a generalized survey of accelerated test results, but rather concentrates on one particular attribute of metallization that has been observed to cause electrical degradation - increased contact resistance due to Schottky barrier formation. In this example basic semiconductor theory was able to provide an understanding of the electrical effects observed during accelerated stress testing.

Lathrop, J. W.↗
NASA NTRS1988

Design and manufacture of solid ZrO2 electrolyte

The following project assignment was given to the students: 'design and build a suitable YSZ solid electrolyte cell. Describe advantages of the design and fabrication method. Finally, to the limits of available resources, fabricate the design. Explain why it would be superior to other designs.' Clemson University students definitely benefitted from this experience with USRA/NASA. The challenge that this project gave the students was both exciting and attention-getting. Students spent far more time per credit hour on this project than on their other course. This project advanced the art of making efficient oxygen generators as well. Clemson students are now well on the way to designing a solid electrolyte with a large active surface area and comparatively small volume. Previous devices have had to endure the limitation of using only simple shapes such as tubes. The results of this project have demonstrated that better configurations are not only possible but practical.

Source record↗
NASA NTRS1993

Windshear detection radar signal processing studies

This final report briefly summarizes research work at Clemson in the Radar Systems Laboratory under the NASA Langley Research Grant NAG-1-928 in support of the Antenna and Microwave Branch, Guidance and Control Division, program to develop airborne sensor technology for the detection of low altitude windshear. A bibliography of all publications generated by Clemson personnel is included. An appendix provides abstracts of all publications.

Baxa, Ernest G., Jr.↗
NASA NTRSDate not supplied

Mitigating Headward Fluid Shifts With Veno-Constrictive Thigh Cuffs During Spaceflight

Astronauts experience a chronic headward fluid shift in weightlessness as evidenced by increased cardiac output, decreased leg volume, a redistribution of venous fluid, and venous congestion in the upper body. Alterations in cerebrospinal fluid hydrodynamics and changes in cerebral venous pressure secondary to the headward fluid shift may contribute to ocular changes associated with spaceflight-associated neuro-ocular syndrome (SANS). Veno-constrictive thigh cuffs (VTC; Braslets) provided to Soyuz crewmembers alleviate symptoms of the headward fluid shift during the first week of spaceflight and have been documented to reduce internal jugular vein (IJV) distension during weightlessness. Application of VTCs designed collaboratively by NASA Johnson Space Center Cardiovascular and Vision Laboratory (CVL) and Clemson Textile Laboratory at Clemson University to improve fit and comfort was documented to mitigate changes in choroid thickness, intraocular pressure, and IJV area during posture-induced headward fluid shifts. VTC are demonstrated to reduce headward fluid shifts in both ground-based and spaceflight studies, and thus, may be a countermeasure against development of SANS. In addition, VTC are a simple mechanical countermeasure currently at a high technical readiness level (TRL) and are compact and lightweight, making them compatible with the spaceflight operations environment

Connor R. Ferguson↗
NASA NTRS1984

Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

Research on the reliability of terrestrial solar cells was performed to identify failure/degradation modes affecting solar cells and to relate these to basic physical, chemical, and metallurgical phenomena. Particular concerns addressed were the reliability attributes of individual single crystalline, polycrystalline, and amorphous thin film silicon cells. Results of subjecting different types of crystalline cells to the Clemson accelerated test schedule are given. Preliminary step stress results on one type of thin film amorphous silicon (a:Si) cell indicated that extraneous degradation modes were introduced above 140 C. Also described is development of measurement procedures which are applicable to the reliability testing of a:Si solar cells as well as an approach to achieving the necessary repeatability of fabricating a simulated a:Si reference cell from crystalline silicon photodiodes.

Lathrop, J. W.↗
NASA NTRS1987

Lunar fiberglass: Properties and process design

A Clemson University ceramic engineering design for a lunar fiberglass plant is presented. The properties of glass fibers and metal-matrix composites are examined. Lunar geology is also discussed. A raw material and site are selected based on this information. A detailed plant design is presented, and summer experiments to be carried out at Johnson Space Center are reviewed.

Dalton, Robert↗
NASA NTRS1993

Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented.

Buoncristiani, A. M.↗
NASA NTRS1993

Carbon and nitrogen in Type 2 supernova diamonds

Abundant diamonds found in meteorites seem either to have condensed within supernova interiors during their expansions and coolings or to have been present around those explosions. Either alternative allows implantation of Xe-HL prior to interstellar mixing. A puzzling feature is the near normalcy of the carbon isotopes, considering that the only C-rich matter, the He-burning shell, is pure C-12 in that region. That last fact has caused many to associate supernova carbon with C-12 carbon, so that its SUNOCONS have been anticipated as very C-12-rich. We show that this expectation is misleading because the C-13-rich regions of Type 2's have been largely overlooked in this thinking. We here follow the idea that the diamonds nucleated in the C-12-rich He shell, the only C-rich site for nucleation, but then attached C-13-rich carbon during turbulent encounters with overlying C-13-rich matter. That is, the initial diamonds continued to grow during the same collisional encounters that cause the Xe-HL implantation. Instead of interacting with the small carbon mass having 13/12 = 0.2 in the upper He zone, however, we have calculated the remnants of the initial H-burning core, which left behind C-13-rich matter as it receded during core hydrogen burning. Howard et al. described why the velocity mixing would be essential to understanding the implantation of both the Xe-H and Xe-L components. Velocity mixing is now known to occur from the X-ray and gamma-ray light curves of supernova 1987A. Using the stellar evolution code developed at Goettingen, we calculated at Clemson the evolution of a grid of massive stars up to the beginning of core He burning. We paid attention to all H-burning reactions throughout the star, to the treatment of both convection and semiconvection, and to the recession of the outer boundary of the convective H-burning core as the star expands toward a larger redder state. This program was to generate a careful map of the CNO isotope distribution as He burning begins. Our result for the 30 solar mass star is shown.

Clayton, Donald D.↗
NASA NTRS1995

Characterizing and testing a thermally isolating superconducting link for SAFIRE-like missions

The discovery of a new class of ceramic superconductors with transition temperatures above the boiling point of liquid nitrogen has opened the doors for several space applications. One important space application is the fabrication of an electrically conducting and thermally isolating link to replace manganin wires used in connecting IR detectors to data acquisition electronics on remote sensing platforms like SAFIRE and SIRTF. These NASA platforms designed to monitor the earth's atmosphere from space use infrared detectors which operate at liquid helium temperature (4.2K) for optimum performance. The SAFIRE mission employs hybrid dewars which combine both mechanical and cryogenic liquid cooling. The lifetime of such a mission is limited by the heat conducted through sensor array leads that connect the electronics (at approximately 80 K) to the sensors (at approximately 4 K). Currently these remoter sensing systems use manganin wires to connect the IR detectors to the data acquisition electronics. This link between a detector operating at 4 K and electronics operating at 80 K must be made of material that has high electrical conductivity and high thermal resistance. The YBCO superconductor with a transition temperature, Tc, of 93 K can achieve these conflicting requirements. A link with these characteristics will improve the thermal isolation of IR detectors and will increase the lifetime of the cryogen. The fabrication of an electrically conducting and thermally isolating link that replaces the manganin wires is an important application that will improve thermal isolation of IR detectors and will increase the lifetime of the cryogen. The link is made by screen printing superconducting lines on a low thermal conductivity ceramic substrate. Developing, modeling, and testing this high temperature superconducting link is a collaborative effort among NASA-Langley Research Center, Christopher Newport University (CNU), Clemson University and the industrial companies that have joined the Commercialization of Space Program for the purpose of developing and testing this link. CNU's effort in the development of this superconducting link included the following major efforts: (1) Development of a thermal conductivity measurement system for high temperature superconductors and ceramic materials which are potential candidates for use as substrates in this link. (2) Development of a mathematical model for the superconducting link that studies the effect of materials and geometry on the heat load and life time of missions. (3) Characterization of high Tc materials and assemblies made for space applications. Properties studied include humidity effects and aging effects on high Tc materials. This report summarizes the results of the research studies that were completed. Copies of publications detailing these findings are attached to this report.

Selim, Raouf R.↗
NASA NTRS1996

Smart Material Demonstrators Based on Shape Memory Alloys and Electroceramics

This paper describes the development and characterization of two technology demonstrators that were produced under the auspices of an ARPA sponsored smart materials synthesis and processing effort. The ARPA Smart Materials and Synthesis (SMS) Program was a 2 year, $10M partnership led by Martin Marietta Laboratories - Baltimore and included Lockheed Missiles & Space Co., NRL, AVX Corp., Martin Marietta Astronautics Groups, BDM Federal, Inc., Virginia Tech, Clemson, University of Maryland, Denver University, and The Johns Hopkins University. In order to demonstrate the usefulness of magnetron sputtered shape memory foil and the manufacturability of reliable, reproducible electrostrictive actuators, the team designed a broadband active vibration cancellation device for suppressing the vibration load on delicate instruments and precision pointing devices mounted on orbiting satellites and spacecraft. The results of extensive device characterization and bench testing are discussed. Initial simulation results show excellent control authority and amplitude attenuation over the range of anticipated disturbance frequencies. The SMS Team has also developed an active 1-3 composite comprising micro-electrostrictive actuators embedded in a polymeric matrix suitable for underwater applications such as sonar quieting and listening arrays, and for medical imaging. Follow-on programs employing these technologies are also described.

Cooke, Arther V.↗
NASA NTRS1999

Multidisciplinary Design and Analysis for Commercial Aircraft

Multidisciplinary design and analysis (MDA) has become the normal mode of operation within most aerospace companies, but the impact of these changes have largely not been reflected at many universities. On an effort to determine if the emergence of multidisciplinary design concepts should influence engineering curricula, NASA has asked several universities (Virginia Tech, Georgia Tech, Clemson, BYU, and Cal Poly) to investigate the practicality of introducing MDA concepts within their undergraduate curricula. A multidisciplinary team of faculty, students, and industry partners evaluated the aeronautical engineering curriculum at Cal Poly. A variety of ways were found to introduce MDA themes into the curriculum without adding courses or units to the existing program. Both analytic and educational tools for multidisciplinary design of aircraft have been developed and implemented.

Cummings, Russell M.↗
NASA NTRS1999

KNBD: A Remote Kernel Block Server for Linux

I am developing a prototype of a Linux remote disk block server whose purpose is to serve as a lower level component of a parallel file system. Parallel file systems are an important component of high performance supercomputers and clusters. Although supercomputer vendors such as SGI and IBM have their own custom solutions, there has been a void and hence a demand for such a system on Beowulf-type PC Clusters. Recently, the Parallel Virtual File System (PVFS) project at Clemson University has begun to address this need (1). Although their system provides much of the functionality of (and indeed was inspired by) the equivalent file systems in the commercial supercomputer market, their system is all in user-space. Migrating their 10 services to the kernel could provide a performance boost, by obviating the need for expensive system calls. Thanks to Pavel Machek, the Linux kernel has provided the network block device (2) with kernels 2.1.101 and later. You can configure this block device to redirect reads and writes to a remote machine's disk. This can be used as a building block for constructing a striped file system across several nodes.

Becker, Jeff↗
NASA NTRS2001

A Rocket Investigation of Mesospheric Eddy Diffusion Effects on Airglow and Oxygen Chemistry

A Terrier Orion rocket was launched at 0750 Z on 02/25/98 about seven minutes after the Clemson University chemical release rocket. Measurements made of the electron density by a dc probe calibrated by a capacitance probe showed several layers of electron density on a rocket ascent in the altitude range from 90 to 110 km. Rocket descent results showed several but not all of the ascent structure. From power spectral analysis of the measured electron densities, turbulent parameters are derived Measurements were made on rocket ascent and descent by an infrared radiometer of the OH Meinel (3-1) band and O2 singlet delta emissions. Profiles of the emissions are presented and discussed on both rocket ascent and descent an enhancement of the OH emission monitored by the OH radiometer was observed above 90 km. The glow was not defected by the O2 radiometer and was significantly reduced on rocket descent. Using these data and a mechanistic analysis, a profile proportional to atomic oxygen is obtained. This profile is compared to one from the ATOX probe on the rocket. A one-dimensional (1-D) photochemical model that solves the time-dependent continuity equations is used with the rocket data to investigate the odd-oxygen concentration in the near equatorial mesosphere.

Ulwick, James C.↗
NASA NTRS2003

A Sounding Rocket Investigation of the Fine Structure in the Mesopause Region in Conjunction with High Spatial Resolution Lidar Measurements

The grant funds were provided to carry out chemical tracer wind and turbulence measurements in the mesosphere and lower thermosphere as part of the Turbulent Oxygen Mixing Experiment (TOMEX) for which Dr. James Hecht of the Aerospace Corp. was the Principal Investigator. Clemson University designed, built, and tested two chemical tracer release payload sections for the 21.126 and 21.127 payloads which, in addition, had photometer and ionization gauge instrumentation. The tracer chemical was trimethyl aluminum (TMA). The experiment was carried out at White Sands Missile Range in New Mexico on October 26,2000. The location was chosen because of the proximity to the Starfire Optical Range (SOR) which hosted the powerful University of Illinois sodium lidar for an extended period prior to and also during the launch window. Since the SOR telescope is fully steerable, lidar measurements in the same volume sampled by the rocket were possible. The primary objective of the experiment was to measure the turbulent diffusion and mixing in the mesosphere and lower thermosphere, especially in layers characterized by convective and/or dynamical instabilities. The lidar, which is capable of measuring the sodium density, temperatures, and winds with good range and time resolution, provided the launch criteria, as well as context measurements for the in situ rocket observations.

Larsen, M. F.↗
NASA NTRS2003

CODA: Coordinated Observations of Dynamics in Aurora

The grant funds were provided to carry out chemical tracer wind and turbulence measurements in the mesosphere and lower thermosphere as part of the Coordinated Observations of Dynamics in Aurora (CODA) experiment for which Dr. Andy Christensen of the Aerospace Corp. was the Principal Investigator. Clemson University was a co-investigator institution on the project and was tasked with designing, building, and testing a total of four chemical tracer release payloads which were used to release trimethyl aluminum (TMA) to measure the winds and turbulent diffusion. All four payloads were flown from the rocket range at Poker Flat, Alaska, in support of instrumented payloads flown from the same location. The CODA experiment was designed to investigate the changes in the chemical composition in the lower thermosphere during an auroral substorm event. In particular, the objective was to determine the relative importance of two competing mechanisms. The first mechanism is associated with the advection of air from the polar cap into the auroral oval. A flow in that direction is typical in the postmidnight sector of the oval. As the air moves from the region of negligible forcing in the polar cap to the region of strong forcing and heating in the oval, changes in the composition are expected to occur. Alternatively, enhanced local mixing will also cause such changes. Since the auroral forcing accelerates the neutral winds in the lower E region, but not at lower altitudes, the forcing results in large shears that can be large enough to be unstable in the Richardson number sense. The unstable shears are expected to generate turbulence and therefore enhanced mixing. Such mixing will also create composition changes similar to what is observed. In the CODA experiment an instrumented payload designed and built by the Aerospace Corporation was used to measure the composition and plasma parameters needed to define the auroral forcing. In addition, three chemical tracer payloads were to be flown along three trajectories widely separated in azimuth to map out the winds and wind gradients. The measurements would thus provide information about the local composition changes above the launch site as well as detailed information about the advection and location of stable or unstable shears both locally and over a broader area in the vicinity of the launch site.

Larsen, M. F.↗
NASA NTRS2004

Measurements of Man-Made Spectrum Noise Floor

This report consolidates research carried out at Clemson University and Stanford University where a series of measurements were undertaken to identify the man-made radiation present in four bands used by rather different services, namely, L1 Band (1563.42 1587.42 MHz), the Unified S-Band (2025 2110 MHz), the 2.4 GHz Industrial, Scientific and Medical (ISM) Band (2400 2482.50 MHz), and the 23.6-24.0 GHz Passive Sensing Band. Results show that there were distinctive differences in the measurement data in the frequency bands, which should be expected based on the function/regulation associated with each. The GPS L1 Band had little to none terrestrial man-made sources, but the ISM 2.4 GHz Band had a large number of man-made sources regardless of the site and the time. The Unified S Band showed mixed results depending on the sites. The Passive Sensing Band does not contain appreciable man-made radiation.

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