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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

An Innovative Manufacturing of CCC Ion Thruster Grids by North Carolina A&T's RTM Carbon/Carbon Process

Electric ion thrusters are the preferred engines for deep space missions, because of very high specific impulse. The ion engine consists of screen and accelerator grids containing thousands of concentric very small holes. The xenon gas accelerates between the two grids, thus developing the impulse force. The dominant life-limiting mechanism in the state-of-the-art molybdenum thrusters is the xenon ion sputter erosion of the accelerator grid. Carbon/carbon composites (CCC) have shown to be have less than 1/7 the erosion rates than the molybdenum, thus for interplanetary missions CCC engines are inevitable. Early effort to develop CCC composite thrusters had a limited success because of limitations of the drilling technology and the damage caused by drilling. The proposed is an in-situ manufacturing of holes while the CCC is made. Special low CTE molds will be used along with the NC A&T s patented resin transfer molding (RTM) technology to manufacture the CCC grids. First, a manufacture process for 10-cm diameter thruster grids will be developed and verified. Quality of holes, density, CTE, tension, flexure, transverse fatigue and sputter yield properties will be measured. After establishing the acceptable quality and properties, the process will be scaled to manufacture 30-cm diameter grids. The properties of the two grid sizes are compared with each other.

Haag, Thomas W.↗
NASA NTRS2002

Design of a Modular 5-kW Power Processing Unit for the Next-Generation 40-cm Ion Engine

NASA Glenn Research Center is developing a 5/10-kW ion engine for a broad range of mission applications. Simultaneously, a 5-kW breadboard poster processing unit is being designed and fabricated. The design includes a beam supply consisting of four 1.1 kW power modules connected in parallel, equally sharing the output current. A novel phase-shifted/pulse-width-modulated dual full-bridge topology was chosen for its soft-switching characteristics. The proposed modular approach allows scalability to higher powers as well as the possibility of implementing an N+1 redundant beam supply. Efficiencies in excess of 96% were measured during testing of a breadboard beam power module. A specific mass of 3.0 kg/kW is expected for a flight PRO. This represents a 50% reduction from the state of the art NSTAR power processor.

Pinero, Luis R.↗
NASA NTRS1980

Tailored emitter, low-resistivity, ion-implanted silicon solar cells

Open-circuit voltages as high as 0.645 V (AM0, 25 C) have been obtained by a new process developed for low-resistivity silicon. The process utilizes high-dose phosphorus implantation followed by furnace annealing and simultaneous oxide growth. The effect of the thermally grown oxide is a reduction of surface recombination velocity; the oxide also acts as a moderately efficient antireflection (AR) coating. Boron-doped, float-zone silicon with resistivities from 0.1 to 1.0 (omega)(cm) has been processed according to this sequence; results show that the highest open-circuit voltage is obtained with 0.1(omega)(cm) starting material. The effects of Auger recombination and bandgap narrowing caused by high doping concentrations in the n(+)junction region have been investigated by implanting phosphorus over a wide range of dose levels. The effects of emitter-phosphorus concentrations tailored to optimize electric fields in the emitter have also been investigated.

Minnucci, J. A.↗
NASA NTRS2006

Daily Planet Redesign: eZ Publish Web Content Management Implementation

This viewgraph presentation reviews the process of the redesign of the Daily . Planet news letter as a content management implementation project. This is a site that is an internal news site that acts as a communication vehicle for a large volume of content. The Objectives for the site redesign was: (1) Clean visual design, (2) Facilitation of publication processes, (3) More efficient maintenance mode, (4) Automated publishing to internal portal, (5) Better navigation through improved site IA, (6) Archiving and retrieval functionality, (7) Back to basics on fundamental business goals. The CM is a process not a software package

web content management↗
NASA NTRS1979

Automated Array Assembly, Phase 2

The Automated Array Assembly Task, Phase 2 of the Low Cost Silicon Solar Array Project is a process development task. The contract provides for the fabrication of modules from large area tandem junction cells (TJC). During this quarter, effort was focused on the design of a large area, approximately 36 sq cm, TJC and process verification runs. The large area TJC design was optimized for minimum I squared R power losses. In the TJM activity, the cell-module interfaces were defined, module substrates were formed and heat treated and clad metal interconnect strips were fabricated.

Carbajal, B. G.↗
NASA NTRS1989

Ion optics for high power 50-cm-diam ion thrusters

The process used at the NASA-Lewis to fabricate 30 and 50-cm-diameter ion optics is described. The ion extraction capabilities of the 30 and 50-cm diameter ion optics were evaluated on divergent field and ring-cusp discharge chambers and compared. Perveance was found to be sensitive to the effects of the type and power of the discharge chamber and to the accelerator electrode hole diameter. Levels of up to 0.64 N and 20 kW for thrust and input power, respectively, were demonstrated with the divergent-field discharge chamber. Thruster efficiencies and specific impulse values up to 79 percent and 5000 sec., respectively, were achieved with the ring-cusp discharge chamber.

Rawlin, Vincent K.↗
NASA NTRS1980

Silicon solar cells with high open-circuit voltage

Open-circuit voltages as high as 0.645 V (AM0-25 C) have been obtained by a new process developed for low-resistivity silicon. The method utilizes high-dose phosphorus implantation, followed by furnace annealing and simultaneous oxide growth to form high-efficiency, shallow junctions. The effect of the thermally grown oxide is a reduction of surface recombination velocity; the oxide also acts as a moderately efficient AR coating. Boron doped silicon with resistivities from 0.1 to 0.3 ohm-cm has been processed according to this sequence; results show highest open-circuit voltage is attained with 0.1-ohm-cm starting material. The effects of bandgap narrowing, caused by high doping concentrations in the junction, were also investigated by implanting phosphorus over a wide range of dose levels.

Minnucci, J. A.↗
NASA NTRS1989

Ion optics for high power 50-cm-dia ion thrusters

The process used at the NASA Lewis Research Center to fabricate 30 and 50-cm-diameter ion optics is described. The ion extraction capabilities of the 30 and 50-cm diameter ion optics were evaluated on divergent field and ring-cusp discharge chambers and compared. Perveance was found to be sensitive to the effects of the type and power of the discharge chamber and to the accelerator electrode hole diameter. Levels of up to 0.64 N and 20 kW for thrust and input power, respectively, were demonstrated with the divergent-field discharge chamber. Thruster efficiencies and specific-impulse values up to 79 percent and 5000 seconds, respectively, were achieved with the ring-cusp discharge chamber.

Rawlin, Vincent K.↗
NASA NTRS1994

Formation of thin sulfide rinds on the CM parent body

Many of the textures that are observed in CM chondrites have been alternately assigned nebular, parent-body, or combined nebular-parent body origins. Since it is very difficult to substantiate the production of complex textures in the nebula, an alternate approach to this problem is to rigorously determine which of the observable textures could have been produced by reasonable aqueous alteration processes on the CM parent body. Potential parent body reactions involving S deserve special attention because S-bearing phase define many important CM textures, such as rims. We have examined the possibility that the thin (about 5 microns) rinds of sulfides observed around some partially dissolved olivines within the chondrules and matrixes of CM chondrites were formed by the preferential precipitation of sulfides at or near dissolving olivine boundaries during parent-body alteration. Our model defines two infinite and parallel planes of olivine that are separated by pure water. Average separation distances between olivine grains in CM chondrites at the time of accretion (about 100-200 microns) were estimated by assuming a closed system fluid/rock ratio of 45% and varying the bimodal grain-size distribution. We restrict our calculations to the case of an isochemical system with sufficient bisulfide in solution to account for precipitation of pyrrhotite at STP. Our model examines the possibility that dissolving olivines with compositions between Fo(sub 0.9) and Fo(sub 0.4) can produce a strong gradient of Fe(2+) at pHs from 7 to 12 such that the precipitation of pyrrhotite will be initiated at the olivine-fluid boundary. Since CM phase equilibria is consistent with highly reducing conditions, Fe released by olivines would largely remain in solution as Fe(2+) until the solubility product of a Fe(2+) bearing phase was exceeded. Our calculations indicate that all examined combinations of olivine composition and pH yield a strong Fe(2+) gradient at the time the pyrrhotite solubility is exceeded near the olivine-fluid boundary. This favors the initiation of sulfide precipitation around dissolving olivines. However, sulfide rinds are not observed around all partially dissolved olivine grains in CM chondrites, which suggests that the availability of aqueous sulfide species limits the production of the thin sulfide rinds.

Browning, L. B.↗
NASA NTRS1979

A continuous silicon-coating facility

Automatic continuous silicon-coating facility is used to process 100 by 10 cm graphite-coated ceramic substrates for silicon solar cells. Process reduces contamination associated with conventional dip-coating processes, improving material service life.

Butter, C.↗
NASA NTRS1977

Cross sections for charge transfer between mercury ions and other metals

Cross sections for charge transfer between several ions and metals of interest to the NASA electro propulsion program have been measured. Specifically, the ions considered were Hg(+), Xe(+) and Cs(+) and the metals Mo, Fe, Al, Ti, Ta, and C. Measurements were made in the energy regime from 1 to 5,000 eV. In general, the cross sections for charge transfer were found to be less than 10 to the minus 15 power sq cm for most processes over the total energy range. Exceptions are Hg(+) in collision with Ti and Ta. The results obtained for each reaction are given in both graphical and numerical form in the text. For quick reference, the data at several ion velocities are condensed into one table given in the summary.

Vroom, D. A.↗
NASA NTRS1985

Dissociation of metastable O2 as a potential source of atmospheric odd oxygen

An analysis of the possible dissociation of metastable oxygen molecules subject ot constraints imposed by selection rules for molecular transitions, airglow observations, and atmospheric chemistry leads to the following conclusions. Dissociation of O2(b1Sigma g +) must produce a negligible number of oxygen atoms at all altitudes in the earth's atmosphere. However, if the dissociation cross section of O2(a1Delta g) has a maximum value in the range 10 to the -20th to 10 to the -19th/sq cm, then the process O2(a1Delta g) + h(nu) yields O2(C3Delta u) yields O(3P) + O(3P) will constitute a significant, and potentially the major, source of odd oxygen in the uppermost stratosphere and mesosphere.

Frederick, J. E.↗
NASA NTRS2005

Contingency Management Requirements Document: Preliminary Version. Revision F

This is the High Altitude, Long Endurance (HALE) Remotely Operated Aircraft (ROA) Contingency Management (CM) Functional Requirements document. This document applies to HALE ROA operating within the National Airspace System (NAS) limited at this time to enroute operations above 43,000 feet (defined as Step 1 of the Access 5 project, sponsored by the National Aeronautics and Space Administration). A contingency is an unforeseen event requiring a response. The unforeseen event may be an emergency, an incident, a deviation, or an observation. Contingency Management (CM) is the process of evaluating the event, deciding on the proper course of action (a plan), and successfully executing the plan.

Source record↗
NASA NTRS2008

Navigation Ground Data System Engineering for the Cassini/Huygens Mission

The launch of the Cassini/Huygens mission on October 15, 1997, began a seven year journey across the solar system that culminated in the entry of the spacecraft into Saturnian orbit on June 30, 2004. Cassini/Huygens Spacecraft Navigation is the result of a complex interplay between several teams within the Cassini Project, performed on the Ground Data System. The work of Spacecraft Navigation involves rigorous requirements for accuracy and completeness carried out often under uncompromising critical time pressures. To support the Navigation function, a fault-tolerant, high-reliability/high-availability computational environment was necessary to support data processing. Configuration Management (CM) was integrated with fault tolerant design and security engineering, according to the cornerstone principles of Confidentiality, Integrity, and Availability. Integrated with this approach are security benchmarks and validation to meet strict confidence levels. In addition, similar approaches to CM were applied in consideration of the staffing and training of the system administration team supporting this effort. As a result, the current configuration of this computational environment incorporates a secure, modular system, that provides for almost no downtime during tour operations.

Beswick, R. M.↗
NASA NTRS1981

Electric power needs in space

The power requirements for specific float zone experiments in space are presented. Power figures for the Space Shuttle and projected available power for advanced vehicles are given. The following power related trends are derived: (1) float zone processing of up to 5 cm diameter silicon and 16.0 cm diameter cadmium telluride can be conducted on a Shuttle pallet mission; (2) float zone processing of up to 8.5 cm diameter silicon for 70% total heating efficiency can be conducted on the initial MEC/space platform; (3) projected available host vehicle power for float zone sample heating; (4) induction heating is found to be the most promising heating method; (5) process control and ease of equipment integration into the host vehicle influence heating method selection.

Waltz, D. M.↗
NASA NTRS2012

Processing and Damage Tolerance of Continuous Carbon Fiber Composites Containing Puncture Self-Healing Thermoplastic Matrix

Research at NASA Langley Research Center (NASA LaRC) has identified several commercially available thermoplastic polymers that self-heal after ballistic impact and through-penetration. One of these resins, polybutadiene graft copolymer (PB(sub g)), was processed with unsized IM7 carbon fibers to fabricate reinforced composite material for further evaluation. Temperature dependent characteristics, such as the degradation point, glass transition (T(sub g)), and viscosity of the PBg polymer were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic parallel plate rheology. The PBg resin was processed into approximately equal to 22.0 cm wide unidirectional prepreg tape in the NASA LaRC Advanced Composites Processing Research Laboratory. Data from polymer thermal characterization guided the determination of a processing cycle used to fabricate quasi-isotropic 32-ply laminate panels in various dimensions up to 30.5cm x 30.5cm in a vacuum press. The consolidation quality of these panels was analyzed by optical microscopy and acid digestion. The process cycle was further optimized based on these results and quasi-isotropic, [45/0/-45/90]4S, 15.24cm x 15.24cm laminate panels were fabricated for mechanical property characterization. The compression strength after impact (CAI) of the IM7/pBG composites was measured both before and after an elevated temperature and pressure healing cycle. The results of the processing development effort of this composite material as well as the results of the mechanical property characterization are presented in this paper.

Grimsley, Brian W.↗
NASA NTRS1990

New directions in InP solar cell research

Recent research efforts representing new directions in InP solar cell research are reviewed. These include heteroepitaxial growth on silicon and gallium arsenide substrates, V-grooved cells, large area high efficiency cells, and surface passivation. Improvements in heteroepitaxial cell efficiency are described together with processing of 19.1 percent, 4 sq cm cells. Recommendations are made for improvements in processing leading to increased efficiencies.

Weinberg, I.↗
NASA NTRS1990

New directions in InP solar cell research

Recent research efforts representing new directions in InP solar cell research are reviewed. These include heteroepitaxial growth on silicon and gallium arsenide substrates, V-grooved cells, large-area high efficiency cells, and surface passivation. Improvements in heteroepitaxial cell efficiency are described together with processing of 19.1 percent, 4 sq cm cells. Recommendations are made for improvements in processing leading to increased efficiencies.

Weinberg, I.↗