Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “FURNACE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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

At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Consolidation of lunar regolith: Microwave versus direct solar heating

The production of construction materials on the lunar surface will require an appropriate fabrication technique. Two processing methods considered as being suitable for producing dense, consolidated products such as bricks are direct solar heating and microwave heating. An analysis was performed to compare the two processes in terms of the amount of power and time required to fabricate bricks of various size. The regolith was considered to be a mare basalt with an overall density of 60 pct. of theoretical. Densification was assumed to take place by vitrification since this process requires moderate amounts of energy and time while still producing dense products. Microwave heating was shown to be significantly faster compared to solar furnace heating for rapid production of realistic-size bricks.

Kunitzer, J.↗
NASA NTRS1991

Isothermal thermogravimetric data acquisition analysis system

The description of an Isothermal Thermogravimetric Analysis (TGA) Data Acquisition System is presented. The system consists of software and hardware to perform a wide variety of TGA experiments. The software is written in ANSI C using Borland's Turbo C++. The hardware consists of a 486/25 MHz machine with a Capital Equipment Corp. IEEE488 interface card. The interface is to a Hewlett Packard 3497A data acquisition system using two analog input cards and a digital actuator card. The system provides for 16 TGA rigs with weight and temperature measurements from each rig. Data collection is conducted in three phases. Acquisition is done at a rapid rate during initial startup, at a slower rate during extended data collection periods, and finally at a fast rate during shutdown. Parameters controlling the rate and duration of each phase are user programmable. Furnace control (raising and lowering) is also programmable. Provision is made for automatic restart in the event of power failure or other abnormal terminations. Initial trial runs were conducted to show system stability.

Cooper, Kenneth, Jr.↗
NASA NTRS1990

Extraterrestrial resource utilization for economy in space missions

The NASA/University of Arizona Space Engineering Research Center is dedicated to research on the discovery, characterization, mapping, beneficiation, extraction, processing, and fabrication of useful products from extraterrestrial material. Schemes for the automated production of low-technology products that are likely to be desired in large quantities in the early stages of any large-scale space activity are identified and developed. This paper summarizes the research program, concentrating upon the production of (1) propellants, both cryogenic and storable, (2) volatiles such as water, nitrogen, and carbon dioxide for use in life-support systems (3) structural metals, and (4) refractories for use in aerobrakes and furnace linings.

Lewis, J. S.↗
NASA NTRS1990

The Marshall Space Flight Center Drop Tube Facility

The structural and instrumentation hardware and the improved experimental capabilities of a 105-m Drop Tube Facility are described. The structure is designed to provide a high-vacuum facility in a vertical orientation. The low-gravity environment obtained during free-fall and the containerless materials processing capabilities are discussed. Two furnaces, an electron-beam and an electromagnetic levitator, are used to melt metallic samples in a process environment ranging from 10 to the -6th torr to 1 atm. Specifics of the vacuum control and gas delivery systems are provided. The experimental instrumentation and data acquisition systems used to perform predrop and in-flight measurements of the melting and solidification process are discussed. Typical experimental results are presented as an indicator of the performance of the Drop Tube Facility.

Rathz, Thomas J.↗
NASA NTRS1991

Ground based preparation for microgravity growth of alloy semiconductors

Ground-based research conducted in order to prepare a microgravity space flight experiment is presented. The thermophysical properties of a PbSnTe alloy used for semiconductors are investigated, and furnace calibration and fluid-flow measurements are performed. The alloy has a zero energy crossing at approximately 40 percent SnTe in its band-gap vs composition diagram, which facilitates the design of long-wavelength IR detectors and lasers. The uniformity of devices made from this material depends on the ratio of PbTe and SnTe and requires the composition of the crystal growth to be closely controlled. The main obstacle to such control is the fact that liquid of this material is always solutally or thermally unstable, and, in a high-temperature gradient, the double convective instability cannot be made stable by balancing thermal and solutal expansion. In order to extend the science of crystal growth, the limits of suppression of convection have to be tested in low earth orbit.

Fripp, Archibald L.↗
NASA NTRS1991

The integration of microgravity science experiments into shared or previously existing experiment facilities

The overall flow for integrating a sample into an experiment facility, specifically materials science is discussed using the Crystal Growth Furnace as an example. A typical preflight timeline for an experiment is discussed, including identification of all documentation and hardware deliveries. Each of the items presented is discussed in detail including the experiment requirements document, the announcement opportunity response, the experiment specific equipment, safety reviews, mission plan, and hardware integration plan. These items are addressed both individualy and with respect to their relevance to the program as a whole.

Baer-Peckham, M. S.↗
NASA NTRS1990

Growth and characterization of CdS crystals

A growth method for the physical vapor transport of compound semiconductors in closed ampoules is described. With the unique techniques applied in the heat treatment of the starting materials and the temperature profiles provided by the three-zone translational furnace, large crystals of CdS have been grown successfully by the method at lower temperatures than previously used. Both unseeded and seeded growth have been investigated. The CdS crystals were examined using optical and scanning electron microscopies (SEM) to study the microstructure and the dislocation etch-pits. The crystals were further characterized by infrared (IR) and ultraviolet (UV) transmission measurements.

Su, Ching-Hua↗
NASA NTRS1991

Crystallization kinetics of a lithia-silica glass - Effect of sample characteristics and thermal analysis measurement techniques

DTA and both isothermal and nonisothermal DSC techniques are presently used to investigate the crystallization kinetics of a 40 (mol) percent Li2O-60 percent SiO2 glass as a function of glass powder particle size, the use of either alumina or Pt as the crucible material, the use of N, O, or Ar atmospheres, and surface pretreatments of the glass powder with deionized water, HCl, or HF. Neither the furnace atmosphere nor the crucible material had a significant effect on activation energy, frequency factor, or Avrami exponent. Washings of the glass with the three different fluids decreased the crystallization temperature by 25 to 30 C.

Ray, Chandra S.↗
NASA NTRS1990

Development of experimental facilities for processing metallic crystals in orbit

This paper discusses the evolution, current status, and planning for facilities to exploit the microgravity environment of earth orbit in applied metallic materials science. Space-Shuttle based facilities and some precursor flight programs are reviewed. Current facility development programs and planned Space Station furnace capabilities are described. The reduced gravity levels available in earth orbit allow the processing of metallic materials without the disturbing influence of gravitationally induced thermal convection, stratification due to density differences in sample components, or the effects of hydrostatic pressure.

Duncan, Bill J.↗
NASA NTRS1990

Preparation of 110K (Bi, Pb)-Sr-Ca-Cu-O superconductor from glass precursor

The Bi1.5Pb0.5Sr2Ca2Cu3O(x) glass, prepared by rapid quenching of the melt, showed T(sub g) of 383 C, crystallization temperature of approx. 446 C, melting temperature of approx. 855 C, and bulk density of 5.69 g/cu. cm. in air. The as-quenched glass was oxygen deficient. On heating in O2, it showed a slow, irreversible, and continuous weight gain starting at approx. 530 C. The influence of annealing conditions on the formation of various phases was investigated by XRD and electrical resistivity measurements. The 110K-T(sub c) phase did not form below 840 C. The amount of this phase increased with the sintering time at 840 C. A sample annealed at 840 C for 243 h in air and furnace cooled showed the highest T(sub c) (R=0) of 107.2 K and transition width delta T(sub c) (10 to 90 percent) of approx. 2 K.

Bansal, Narottam P.↗
NASA NTRS1991

Oscillation phase relations in a Bridgman system

The thermal conditions under which convection in a tin melt undergoes the transition from steady flow to time-dependent flow are investigated. Previously, it has been shown that crystals that are directionally solidified from a time-dependent melt will have a larger defect density and increased chance of compositional striations. Thus, it is important for this transition to be well characterized. The experimental results to be presented were obtained from a two-zone Bridgman furnace with a middle insulation zone. Thermocouples were placed on the axis and on the outer wall of a cylindrical vitreous silica tube which contained molten tin. The phase relations between temperature oscillations measured at different positions in the cell are discussed. Fourier transforms are used to investigate the increasing complexity of convection as the temperature gradient is increased.

Knuteson, David J.↗
NASA NTRS1991

Computed stress fields in GaAs during vertical Bridgman growth

The thermoelastic stress field of GaAs crystals grown by the vertical Bridgman method has been approximated using a linear elastic, axisymmetric stress model. The model included the effects due to the thermal field and the gravitational field, as well as the interaction with the ampoule, but did not fully account for the elastic anisotropy of the crystal. Realistic thermal fields for different furnace temperatures and insulation zone thicknesses were computed with a similar model. The difference between the Von Mises stress and the critical resolved shear stress (CRSS) was used as a measure of the number of dislocations present. Different sets of growth parameters were examined to determine which produced the lowest amount of stress in the crystal. Results show that the crystal-ampoule interaction is the most important parameter in dislocation generation. In addition, for the same sticking boundary conditions, concave interfaces have lower stress than convex interfaces.

Rosch, William↗
NASA NTRS1990

Low-gravity materials experiments in the Space Station Freedom

The science and hardware programs laying the science and technology framework for experiments to be conducted aboard SSF are described. Six microgravity facilities planned for the Laboratory Module encompass the Fluid Physics/Dynamics Facility, investigating fundamental fluid behavior; the Advanced Protein Crystal Growth Facility, growing high-quality crystals for pharmaceutical, medical, chemical, and biotechnology applications; the Biotechnology Facility, investigating microgravity effects on biological processes and living organisms at the cellular level and on the purification and production of biological materials; the Space Station Furnace Facility, conducting metal and alloy solidification experiments; the Modular Containerless Processing Facility, supporting experiments through levitation techniques; and the Modular Combustion Facility, performing studies of fundumental combustion processes.

Chassay, Roger P.↗
NASA NTRS1991

An apparatus for the specific heat measurement of undercooled liquids

This paper describes a drop calorimeter with an electromagnetic levitator that was specifically built for enthalpy measurements of undercooled liquids, including high-melting-point metals. Design diagrams of this device and of a furnace for making a suspended drop are presented together with results of measurements on an aluminum sample.

Ohsaka, K.↗
NASA NTRS1991

Development of nuclear fuels and materials for propulsion systems for SEI

A panel was organized by NASA/DOE/DOD to study nuclear fuels, materials, and related nuclear propulsion technologies for SEI, and the panel findings are discussed. The fuels/materials requirements for nuclear thermal propulsion and nuclear electric propulsions are reviewed, and the development items such as 'element' development and characterization, fabrication process development, nuclear capsule tests, nuclear loop tests, and nuclear furnace tests are examined for selected classes of fuels.

Bhattacharyya, S. K.↗
NASA NTRS1992

Electronic Control Of Slow Rotations

Digital/analog circuit controls both angular position and speed of rotation of motor shaft with high precision. Locks angular position of motor to phase of rotation-command clock signal at binary submultiple of master clock signal. Circuit or modified version used to control precisely position and velocity of robotic manipulator, to control translation mechanism of crystal-growing furnace, to position hands of mechanical clock, or to control angular position and rate of rotation in any of large variety of rotating mechanisms.

Howard, David E.↗
NASA NTRS1992

Dynamic, High-Temperature, Flexible Seals

Dynamic, flexible ceramic seals developed for use at high temperatures in high-performance, variable-geometry, hypersonic airplane engines. Stacked ceramic wafers pressed against stationary sidewall by pressure in one or more metal bellows. Seals also used in hypersonic engines, two-dimensional convergent/divergent and vectored-thrust exhaust nozzles, airframes of reentry vehicles, casings of rocket motors furnaces, and other applications.

Steinetz, Bruce M.↗
NASA NTRS1992

Porous Barrier To Flow Of Hot Gas

Porous, ropelike barrier prevents recirculating flow of hot, hydrogen-rich steam from reaching nickel-alloy bellows seal located deep in gap in wall of combustion chamber. Proven successful protecting bellows seal at different values of protrusion of coolant tubes giving rise to recirculating hot flow. Similar barriers help block deleterious recirculating flow of hot gases in other combustion chambers such as furnaces and turbomachines.

Onstott, Joseph W.↗