Engineering topics

Carroll, Carol W.

Publications and source records attributed to Carroll, Carol W..

6 records

NASA NTRS2012

Enabling Exploration: NASA's Technology Needs

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.

Capabilities↗

NASA NTRS2001

A Theoretical Study of the Interaction of Water and Imidazole with Iron and Nickel Dications

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+).

Ricca, Alessandra↗

NASA NTRS1999

Characterization of Showerhead Performance At Low Pressure

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.

Hash, David B.↗

NASA NTRS1999

Feature Profile Evolution of SiO2 Trenches In Fluorocarbon Plasmas

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.

Hwang, Helen↗

NASA NTRS1995

A New Way of Doing Business: Reusable Launch Vehicle Advanced Thermal Protection Systems Technology Development: NASA Ames and Rockwell International Partnership

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.

Carroll, Carol W.↗

NASA NTRS1994

Reliability-Based Design of a Safety-Critical Automation System: A Case Study

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.

Carroll, Carol W.↗