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  • 1
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    Evaluation of Thermal Control Coatings for Flexible Ceramic Thermal Protection Systems (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report summarizes the evaluation and testing of high emissivity protective coatings applied to flexible insulations for the Reusable Launch Vehicle technology program. Ceramic coatings were evaluated for their thermal properties, durability, and potential for reuse. One of the major goals was to determine the mechanism by which these coated blanket surfaces become brittle and try to modify the coatings to reduce or eliminate embrittlement. Coatings were prepared from colloidal silica with a small percentage of either SiC or SiB6 as the emissivity agent. These coatings are referred to as gray C-9 and protective ceramic coating (PCC), respectively. The colloidal solutions were either brushed or sprayed onto advanced flexible reusable surface insulation blankets. The blankets were instrumented with thermocouples and exposed to reentry heating conditions in the Ames Aeroheating Arc Jet Facility. Post-test samples were then characterized through impact testing, emissivity measurements, chemical analysis, and observation of changes in surface morphology. The results show that both coatings performed well in arc jet tests with backface temperatures slightly lower for the PCC coating than with gray C-9. Impact testing showed that the least extensive surface destruction was experienced on blankets with lower areal density coatings.
    Keywords: Nonmetallic Materials
    Type: NASA-TM-112199 , NAS 1.15:112199 , A-976757
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Materials Testing on the DC-X and DC-XA (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Flight testing of thermal protection materials has been carried out over a two year period on the base heat shield of the Delta Clipper (DC-X and DC-XA), as well on a body flap. The purpose was to use the vehicle as a test bed for materials and more efficient repair or maintenance processes which would be potentially useful for application on new entry vehicles (i.e., X-33, RLV, planetary probes), as well as on the existing space shuttle orbiters. Panels containing Thermal Protection Systems (TPS) and/or structural materials were constructed either at NASA Ames Research Center or at McDonnell Douglas Aerospace (MDA) and attached between two of the four thrusters in the base heat shield of the DC-X or DC-XA. Three different panels were flown on DC-X flights 6, 7, and 8. A total of 7 panels were flown on DC-XA flights 1, 2, and 3. The panels constructed at Ames contained a variety of ceramic TPS including flexible blankets, tiles with high emissivity coatings, lightweight ceramic ablators and other ceramic composites. The MDS test panels consisted primarily of a variety of metallic composites. This report focuses on the ceramic TPS test results.
    Keywords: Chemistry and Materials (General)
    Type: NASA-TM-110430 , NAS 1.15:110430 , A-975493
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    NASA TECHNICAL REPORTS
  • 3
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    A Theoretical Study of the Interaction of Water and Imidazole with Iron and Nickel Dications (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The structures, the harmonic frequencies, and the energies of Fe2+(H2O)n(imid)m and Ni2+(H2O)n(imid)m complexes are computed using density functional theory with the B3LYP functional. A CSOV analysis shows that the bonding is mostly electrostatic in nature. Imidazole forms a stronger bond than water with both metal dications due to its larger dipole moment and polarizability. The reactions for the exchange of one water molecule by one imidazole are exothermic and up to six water molecules can be replaced by imidazoles. The trends are very similar for both metals with the displacement reactions being slightly more favorable for Ni(2+).
    Keywords: Inorganic, Organic and Physical Chemistry
    Format: text
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  • 4
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    Feature Profile Evolution of SiO2 Trenches In Fluorocarbon Plasmas (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Etching of silicon microstructures for semiconductor manufacturing in chlorine plasmas has been well characterized. The etching proceeds in a two-part process, where the chlorine neutrals passivate the Si surface and then the ions etch away SiClx. However, etching in more complicated gas mixtures and materials, such as etching of SiO2 in Ar/C4F8, requires knowledge of the ion and neutral distribution functions as a function of angle and velocity, in addition to modeling the gas surface reactions. In order to address these needs, we have developed and integrated a suite of models to simulate the etching process from the plasma reactor level to the feature profile evolution level. This arrangement allows for a better understanding, control, and prediction of the influence of equipment level process parameters on feature profile evolution. We are currently using the HPEM (Hybrid Plasma Equipment Model) and PCMCM (Plasma Chemistry Monte Carlo Model) to generate plasma properties and ion and neutral distribution functions for argon/fluorocarbon discharges in a GEC Reference Cell. These quantities are then input to the feature scale model, Simulation of Profile Evolution by Level Sets (SPELS). A surface chemistry model is used to determine the interaction of the incoming species with the substrate material and simulate the evolution of the trench profile. The impact of change of gas pressure and inductive power on the relative flux of CFx and F to the wafer, the etch and polymerization rates, and feature profiles will be examined. Comparisons to experimental profiles will also be presented.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: 46th International Symposium of American Vacuum Society International Symposium; Oct 01, 1999; Seattle, WA; United States
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  • 5
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    Reliability-Based Design of a Safety-Critical Automation System: A Case Study (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: In 1986, NASA funded a project to modernize the NASA Ames Research Center Unitary Plan Wind Tunnels, including the replacement of obsolescent controls with a modern, automated distributed control system (DCS). The project effort on this system included an independent safety analysis (ISA) of the automation system. The purpose of the ISA was to evaluate the completeness of the hazard analyses which had already been performed on the Modernization Project. The ISA approach followed a tailoring of the risk assessment approach widely used on existing nuclear power plants. The tailoring of the nuclear industry oriented risk assessment approach to the automation system and its role in reliability-based design of the automation system is the subject of this paper.
    Keywords: Research and Support Facilities (Air)
    Type: A Bridge Into the 21st Century; Unknown
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Enabling Exploration: NASA's Technology Needs (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Deputy Director of Science, Carol W. Carroll has been invited by University of Oregon's Materials Science Institute to give a presentation. Carol's Speech explains NASA's Technologies that are needed where NASA was, what NASA's current capabilities are. Carol will highlight many of NASA's high profile projects and she will explain what NASA needs for its future by focusing on the next steps in space exploration. Carol's audience will be University of Oregon's future scientists and engineer's and their professor's along with various other faculty members.
    Keywords: Space Sciences (General); General
    Type: ARC-E-DAA-TN4699
    Format: application/pdf
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  • 7
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    Characterization of Showerhead Performance At Low Pressure (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The overall objective of this work is to characterize the flow to rough showerheads by deriving pressure drop versus velocity correlations to at can be then used in reactor scale simulations where the showerhead is approximated as a porous medium. At relatively low Reynolds numbers (less than 1-10 based on the hole length scale) and in the absence of slip flow, Darcy's Law, grad P = mu U/k, can be used to express the relation between the pressure drop and velocity where @mu@ is the fluid viscosity and it is the permeability that can be theoretically predicted as k= e R^2 /8, where e is the porosity. However, at sufficiently small hole diameters and decreased pressures (less than 5 Torr), the Knudsen number based on showerhead tube radius increases, and the flow may be in a transition regime. Different expressions have been proposed to account for this effect in the permeability by expressing k as a function of either pressure or Knudsen number. But at even higher Knudsen numbers, the pressure drop - velocity dependence is non-linear, and Darcy's Law no longer holds such that a permeability cannot be defined. The direct simulation Monte Carlo method is used along side conventional CFD techniques to determine the extent to which the CFD technique is appropriate and helps to derive correlations for the more rarefied cases of interest in these showerhead flows.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: 46th American Vacuum Society International Symposium; Oct 01, 1999; Seattle, WA; United States
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  • 8
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    A New Way of Doing Business: Reusable Launch Vehicle Advanced Thermal Protection Systems Technology Development: NASA Ames and Rockwell International Partnership (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: NASA Ames Research Center and Rockwell International are partners in a Cooperative Agreement (CA) for the development of Thermal Protection Systems (TPS) for the Reusable Launch Vehicle (RLV) Technology Program. This Cooperative Agreement is a 30 month effort focused on transferring NASA innovations to Rockwell and working as partners to advance the state-of-the-art in several TPS areas. The use of a Cooperative Agreement is a new way of doing business for NASA and Industry which eliminates the traditional customer/contractor relationship and replaces it with a NASA/Industry partnership.
    Keywords: Launch Vehicles and Launch Operations
    Type: Technology 2005 Conference; Oct 24, 1995 - Oct 26, 1995; Chicago, IL; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    In-Space Propulsion Program Overview and Status (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-08-14
    Description: NASA's In-Space Propulsion (ISP) Program is designed to develop advanced propulsion technologies that can enable or greatly enhance near and mid-term NASA science missions by significantly reducing cost, mass, and/or travel times. These technologies include: Electric Propulsion (Solar and Nuclear Electric) [note: The Nuclear Electric Propulsion work will be transferred to the NSI program in FY03]; Propellantless Propulsion (aerocapture, solar sails, plasma sails, and momentum exchange tethers); Advanced Chemical Propulsion. The ISP approach to identifying and prioritizing these most promising technologies is to use mission analysis and subsequent peer review. These technologies under consideration are mid-Technology Readiness Level (TRL) up to TRL-6 for incorporation into mission planning within three - five years of initiation. In addition, maximum use of open competition is encouraged to seek optimum solutions under ISP. Several NASA Research Announcements (NRAs) have been released asking industry, academia and other organizations to propose propulsion technologies designed to improve our ability to conduct scientific study of the outer planets and beyond. The ISP Program is managed by NASA HQ (Headquarters) and implemented by the Marshall Space Flight Center in Huntsville, Alabama.
    Keywords: Spacecraft Propulsion and Power
    Type: 28th International Electric Propulsion Conference (IEPC); Mar 17, 2003 - Mar 21, 2003; Toulouse; France
    Format: text
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