SEARCH · Engineering Papers

Results for “FeP”

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 181 records · Page 10

All sources NASA NTRS DOE OSTI

NASA NTRS1972

Current drainage to a high voltage probe in a dilute plasma.

The current drainage from a plasma through approximately 0.05 cm diameter holes in Kapton H polymide film, FEP type C, and quartz (7940 Corning glass) placed on a probe at voltages up to 2000 volts dc have been determined both analytically and experimentally. A Laplace field was used to numerically predict an upper limit for the drainage current. The measured current was less than the calculated current for the FEP and quartz, and the two were approximately in agreement for Kapton H. The measured currents were on the order of 5 microamperes with the calculated currents on the order of 10 microamperes.

Grier, N. T.↗

NASA NTRS1972

Design and development of pressure and repressurization purge system for reusable space shuttle multilayer insulation system

The experimental determination of purge bag materials properties, development of purge bag manufacturing techniques, experimental evaluation of a subscale purge bag under simulated operating conditions and the experimental evaluation of the purge pin concept for MLI purging are discussed. The basic purge bag material, epoxy fiberglass bounded by skins of FEP Teflon, showed no significant permeability to helium flow under normal operating conditions. Purge bag small scale manufacturing tests were conducted to develop tooling and fabrication techniques for use in full scale bag manufacture. A purge bag material layup technique was developed whereby the two plys of epoxy fiberglass enclosed between skins of FEP Teflon are vacuum bag cured in an oven in a single operation. The material is cured on a tool with the shape of a purge bag half. Plastic tooling was selected for use in bag fabrication. A model purge bag 0.6 m in diameter was fabricated and subjected to a series of structural and environmental tests simulating various flight type environments. Pressure cycling tests at high (450 K) and low (200 K) temperature as well as acoustic loading tests were performed. The purge bag concept proved to be structurally sound and was used for the full scale bag detailed design model.

Source record↗

NASA NTRS1975

Method of producing a storage bulb for an atomic hydrogen maser

A storage bulb for an atomic hydrogen maser is produced by coating its internal surface with an emulsion containing both TFE and FEP particles. The emulsion is produced by mixing a first quantity of TFE in an aqueous dispersion with a second quantity of FEP in an aqueous dispersion, with a third quantity of distilled water. The emulsion is poured into the bulb to coat it uniformly so as to form a thin film of emulsion on the bulb's internal surface. After excess emulsion is drained out of the bulb the emulsion in the bulb is dried to remove the water and most of the aqueous matter therefrom. The remaining emulsion is then cured by heating the bulb to a temperature of at least 380 C.

Erpenbach, H.↗

NASA NTRS1975

Early results of the ATS-6 solar cell flight experiment

This paper presents preliminary ATS-6 solar-cell flight-experiment data through the first 247 days in synchronous orbit. The experiment is transmitting data on forty 2 x 2-cm solar cells representing 16 solar-cell configurations. The experiment is designed to study the effect of this orbit on select solar cells and cover-glass parameters such as solar-cell thickness and base resistivity, cover-glass thickness variation, new cover processes, and materials such as 7940 and 7070 integral covers as well as the FEP covers, the COMSAT 'violet' cell, and backside irradiation effects. The in-space solar-cell data indicate short-circuit currents are running higher by 1% to 8% than in measurements made with solar simulations; maximum power varied between -1% and +6%. Degradation of short-circuit current due to ultraviolet effects was determined to be about 2% after 50 days in orbit. All cells performed well through 247 days in orbit except the FEP-covered cells, which appear to have increased their rate of degradation during the eclipse season.

Goldhammer, L. J.↗

NASA NTRS1977

Preliminary results of accelerated exposure testing of solar cell system components

Plastic samples and solar cell sub modules were exposed to an accelerated outdoor environment in Arizona and an accelerated simulated environment in a cyclic ultraviolet exposure tester which included humidity exposure. These tests were for preliminary screening of materials suitable for use in the manufacture of solar cell modules which are to have a 20-year lifetime. The samples were exposed for various times up to six months, equivalent to a real time exposure of four years. Suitable materials were found to be FEP-A, FEP-C, PFA, acrylic, silicone compounds and adhesives and possibly parylene. The method of packaging the sub modules was also found to be important to their performance.

Anagnostou, E.↗

NASA NTRS1977

Optical and electrical properties of ion beam textured Kapton and Teflon

An electron bombardment argon ion source was used to ion etch polyimide (Kapton) and fluorinated ethylene, FEP (Teflon). Samples of polyimide and FEP were exposed to (0.5-1.0) keV Ar ions at ion current densities of (1.0-1/8) mA/sq cm for various exposure times. Changes in the optical and electrical properties of the samples were used to characterize the exposure. Spectral reflectance and transmittance measurements were made between 0.33 and 2.16 micron m using an integrating sphere after each exposure. From these measurements, values of solar absorptance were obtained. Total emittance measurements were also recorded for some samples. Surface resistivity was used to determine changes in the electrical conductivity of the etched samples. A scanning electron microscope recorded surface structure after exposure. Spectral optical data, resistivity measurements, calculated absorptance and emittance measurements are presented along with photomicrographs of the surface structure for the various exposures to Ar ions.

Mirtich, M. J.↗

NASA NTRS1981

The SYSGEN user package

The user documentation of the SYSGEN model and its links with other simulations is described. The SYSGEN is a production costing and reliability model of electric utility systems. Hydroelectric, storage, and time dependent generating units are modeled in addition to conventional generating plants. Input variables, modeling options, output variables, and reports formats are explained. SYSGEN also can be run interactively by using a program called FEPS (Front End Program for SYSGEN). A format for SYSGEN input variables which is designed for use with FEPS is presented.

Carlson, C. R.↗

NASA NTRS1980

Accelerated Alpha-s deterioration in a geostationary orbit

Between the Teflon substrate and the interference filter a 2 micron varnish layer was sandwiched in. The bending radius of the SSM, measured on a cone, decreased from about 13 mm to 6 mm prior to interference filter fracture, due to increased tensile strength of its substrate. These samples, and for comparison samples of the same make but without varnish and a conductive layer were included in the test. Additionally 2 Teflon FEP samples without the protective interference filter, one of them with a conductive layer, were tested. The sample substrate was 125 micron Teflon FEP, with vapor deposited silver reflector and a thin Inconel film for corrosion protection.

Husmann, O. K.↗

NASA NTRS1982

Solar array system for solar maximum mission

The paper describes the design of the solar array system (SAS) for the Solar Maximum Mission, the unique features of the SAS, and the results of its successful in-orbit operation. It is noted that the array was unique in that: (1) major weight concessions were made to produce a dynamically stiff array; (2) it was the first array designed to be compatible with the NASA Multimission Modular Spacecraft; (3) it is the first jettisonable solar array; and (4) it represents the first use of FEP-bonded overslides on a prime power array. It is concluded that the array performed as predicted with no evidence of the FEP causing any unusual array power degradations. In addition, the deployment and telemetry systems performed as designed.

Meese, R. A.↗

NASA NTRS1986

Thermal components for 1.8 K space cryogenics

Work of the summer 1986 is summarized in three areas. First, conceptual design of a laboratory system for heat exchanger evaluation in conjunction with the operation of a thermally activated fountain effect pump (FEP) is presented. Second, Knudsen effect evaluation of fine porous media useful for the pressurization plug which forms the main component of the FEP is described. Third, proof-of-principle test of the lab system selected on the basis of the evaluation is summarized.

Chen, W. E. W.↗

NASA NTRS1988

Temperature rise in superfluid helium pumps

The temperature rise of a fountain effect pump (FEP) and of a centrifugal pump (CP) are compared. Calculations and estimates presented here show that under the operating conditions expected during the resupply of superfluid helium in space, a centrifugal pump will produce a smaller temperature rise than will a fountain effect pump. The temperature rise for the FEP is calculated assuming an ideal pump, while the temperature rise of the CP is estimated from the measured performance of a prototype pump. As a result of this smaller temperature rise and of the different operating characteristics of the two types of pumps, transfers will be more effective using a centrifugal pump.

Kittel, Peter↗

NASA NTRS1987

Performance test of a laboratory pump liquid transfer based on the fountain effect

A laboratory scale pump has been tested in detail in order to determine the flow characteristics of a heater-activated all-metal thermomechanical pump (fountain effect pump, FEP). The emphasis is on the functional dependence of the fountain pressure difference versus mass throughput. A modified Vote et al. (1971) power law approximation is employed for a simplified description of the flow rate as a function of the driving force. Flow rates of up to 10 liters/(hr/sq cm) have been obtained despite a large nominal pore size of the porous plug of 2 microns (filtration rating) used for the FEP.

Chen, W. E. W.↗

NASA NTRS1988

Performance test of a laboratory pump for liquid transfer based on the fountain effect

A laboratory scale pump which determines the flow characteristics of a heater-activated all-metal thermomechanical fountain-effect pump (FEP) is evaluated. Results are presented on the functional dependence of the fountain pressure difference versus mass throughput. A modified Vote et al. (1971) power law approximation is used to obtain the flow rate as a function of the driving force. Despite a large nominal pore size of the porous plug used for the FEP, flow rates of up to 10 liter/hr sq cm have been obtained.

Chen, W. E. W.↗

NASA NTRS1989

A message passing kernel for the hypercluster parallel processing test bed

A Message-Passing Kernel (MPK) for the Hypercluster parallel-processing test bed is described. The Hypercluster is being developed at the NASA Lewis Research Center to support investigations of parallel algorithms and architectures for computational fluid and structural mechanics applications. The Hypercluster resembles the hypercube architecture except that each node consists of multiple processors communicating through shared memory. The MPK efficiently routes information through the Hypercluster, using a message-passing protocol when necessary and faster shared-memory communication whenever possible. The MPK also interfaces all of the processors with the Hypercluster operating system (HYCLOPS), which runs on a Front-End Processor (FEP). This approach distributes many of the I/O tasks to the Hypercluster processors and eliminates the need for a separate I/O support program on the FEP.

Blech, Richard A.↗

NASA NTRS1991

Space environmental effects on silvered Teflon thermal control surfaces

Cumulative space environment effects on Ag/fluorinated ethylene propylene (FEP) were a function of exposure orientation. Samples from nineteen silvered Teflon (Ag/FEP) thermal control surfaces recovered from the Long Duration Exposure Facility (LDEF) were analyzed to determine changes in this material as a function of position on the spacecraft. Although solar absorptance and infrared emittance of measured thermal blanket specimens are relatively unchanged from control specimen values, significant changes in surface morphology, composition and chemistry were observed. Researchers hypothesize that the FEP surfaces on LDEF were degraded by ultraviolet radiation exposure at all orientations, but that the damaged material had been removed by erosion from the blankets exposed to atomic oxygen flux and that contamination is masking the damage on trays flanking the trailing edge.

Hemminger, C. S.↗

NASA NTRS1991

Atomic oxygen testing with thermal atom systems - A critical evaluation

The use of thermal atom (kinetic energy near 0.04 eV) test methods as a materials selection and screening technique for LEO spacecraft is critically evaluated in this paper. The physics and chemistry of the thermal atom environments are shown to produce specific mass loss rates (mg/sq cm per min) and reaction efficiencies (Re) radically different from those produced in the LEO environment. A response surface study shows that specific mass loss rates change rapidly with plasma-asher parameters and seldom agree with flight data. FEP Teflon is shown to react by a different mechanism than Kapton, polyethylene, or graphite. The Re (Re = volume of material removed/oxygen atom) of Kapton, polyethylene, Mylar, Tedlar, FEP Teflon, and graphite measured in a flowing afterglow apparatus are 0.001 to 0.0001 those measured with high-energy atoms (kinetic energy 1.5 eV or greater) in beam systems or in LEO. The effect of sample temperature and atom impact energy on Re is discussed. A simple kinetic model describing the reaction of atomic oxygen with polymer surfaces is developed. Guidelines and recommendations for thermal atom testing and interpretation of test results are presented.

Koontz, Steven L.↗

NASA NTRS1992

Results of examination of silvered Teflon from the Long Duration Exposure Facility

A significant effort to determine the effects of low earth orbit (LEO) exposure on silver backed fluorinated ethylene-propylene (FEP) blankets from the Long Duration Exposure Facility (LDEF) was performed, and the results of this investigation are described. Extensive measurements of surface, optical, chemical, and mechanical properties were conducted. Effects of contamination and erosion rates of the FEP layer were determined. Specific results are reported on solar absorptance, thermal emittance, diffuse reflectance, cross sectional microphotography, secondary ion mass spectroscopy, electron scattering for chemical analysis, scanning electron microscopy, percent elongation, and tensile strength. These measurements show the effects of two distinctly different exposure environments, solar exposure, and simultaneous atomic oxygen (AO) and solar exposure.

Rousslang, Ken↗

NASA NTRS1990

Experimental verification of a tank to tank He II transfer model with trade study results

A computer program has been developed to study the thermodynamics of tank to tank superfluid helium transfer. The model includes a supply and a receiver tank connected by a transfer line. The convey of He II from one tank to the other is controlled by a fountain effect pump (FEP). Phase separators are present in both the supply and receiver tank to regulate the bath temperature. Description of this model has been published elsewhere. In the present paper, data from a transfer experiment are used to verify the accuracy of this model. The experiment consisted of an FEP made of a 2-micron sintered stainless steel porous plug. Superfluid has been transferred from a liquid helium bath into a glass beaker. Bath temperatures, flowrate and heater power records are available. These results are compared to the predictions of the computer program and good agreement is found between the two. This model is very useful for the study and design of superfluid transfer systems, e.g., the Superfluid Helium Tanker (SFHT) and the Particle Astrophysics Magnet Facility (ASTROMAG).

Yuan, S. W. K.↗