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All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

The atmospheres of Uranus and Neptune

The atmospheres of Uranus and Neptune are discussed in the light of the Voyager 2 flybys of these planets. A basic overview of their atmospheres is presented, with emphasis on thermal structure, composition, energy and opacity sources, cloud structure, and the horizontal structure of the atmospheres. The nature and implications of the different internal heat flows on the two planets, and the implications of the deuterium and helium abundances for the origin and evolution of these ice giants, as distinct from Jupiter and Saturn, are discussed. Selected chemical and physical processes in the atmospheres of Uranus and Neptune are illustrated.

Lunine, Jonathan I.↗
NASA NTRS1994

Integrated design and manufacturing for the high speed civil transport

In June 1992, the School of Aerospace Engineering at Georgia Tech was awarded a three year NASA University Space Research Association (USRA) Advanced Design Program (ADP) grant to address issues associated with the Integrated Design and Manufacturing of High Speed Civil Transport (HSCT) configurations in its graduate Aerospace Systems Design courses. This report provides an overview of the on-going Georgia Tech initiative to address these design/manufacturing issues during the preliminary design phases of an HSCT concept. The new design methodology presented here has been incorporated in the graduate aerospace design curriculum and is based on the concept of Integrated Product and Process Development (IPPD). The selection of the HSCT as a pilot project was motivated by its potential global transportation payoffs; its technological, environmental, and economic challenges; and its impact on U.S. global competitiveness. This pilot project was the focus of each of the five design courses that form the graduate level aerospace systems design curriculum. This year's main objective was the development of a systematic approach to preliminary design and optimization and its implementation to an HSCT wing/propulsion configuration. The new methodology, based on the Taguchi Parameter Design Optimization Method (PDOM), was established and was used to carry out a parametric study where various feasible alternative configurations were evaluated. The comparison criterion selected for this evaluation was the economic impact of this aircraft, measured in terms of average yield per revenue passenger mile ($/RPM).

Lee, Jae Moon↗
NASA NTRS1995

Next generation fire suppressants

Spectrex, Inc., located in Cedar Grove, NJ is a manufacturer of fire detection and suppression equipment. Spectrex is one of the original pioneers in high speed fire detection and suppression systems for combat vehicles. Spectrex has installed fire suppressions systems in thousands of combat vehicles and ships throughout the world. Additionally, they manufacture flame explosion detectors, ship damage control systems, and optical gas and vapor detectors. The culmination of several years of research and development has recently produced an innovative electro-optical continuous monitoring systems called SharpEye 20/20I IR(sup 3) and SAFEYE that provide fast and reliable gas, vapor, aerosol, flame, and explosion detection. SharpEye 20/20I IR(sup 3) is a self-contained triple spectrum flame detector which scans for oscillating IR radiation (1 to 10 Hz) in the spectral bands ranging from 4.0 to 5.0 microns and uses programmed algorithms to check the ratio and correlation of data received by the three sensors to make the system highly immune to false alarms. It is extremely sensitive as it can detect a 1 x 1 square foot gasoline pan fire at 200 feet in less than 3 seconds. The sensitivity is user programmable, offering 4 ranges of detection. SAFEYE is comprised of a selected number of multispectral ban microprocessors controlled detectors which are in communication with one or more radiation sources that is projected along a 600 feet optical path. The signals from the selected narrow bands are processed and analyzed by highly sophisticated algorithms. It is ideal for high risk, remote, large areas such as petroleum and chemical manufacturing sites, waste dumps, aircraft cargo bays, and ship compartments. The SAFEYE will perform direct readings of the presence or rate of rise of concentrations of gases, vapors, or aerosols at the range of parts per million and provide alarms at various set points at different levels of concentrations.

Brown, Jerry A.↗
NASA NTRS1994

A study of Type I polar stratospheric cloud formation

Mechanisms for the formation of Type I (nitric acid-based) polar stratospheric clouds (PSCs) are discussed. If the pre-existing sulfate aerosols are liquid prior to PSC formation, then nitric acid particles (Type Ib) form by HNO3 dissolution in aqueous H2SO4 solution droplets. This process does not require a nucleation step for the formation of HNO3 aerosols, so most pre-existing aerosols grow to become relatively small HNO3-containing particles. At significantly lower temperatures, the resulting supercooled solutions (Type Ib) may freeze to form HNO3 ice particles (Type Ia). If the pre-existing sulfate aerosols are initially solid before PSC formation, then HNO3 vapor can be deposited directly on the frozen sulfate particles. However, because an energy barrier to the condensation exists a nucleation mechanism is involved. Here, we suggest a unique nucleation mechanism that involves formation of HNO3/H20 solutions on the sulfate ice particles. These nucleation processes may be highly selective, resulting in the formation of relatively small number of large particles.

Tabazadeh, A.↗
NASA NTRS1997

NASA Aerospace Flight Battery Systems Program Update

The objectives of NASA's Aerospace Flight Battery Systems Program is to: develop, maintain and provide tools for the validation and assessment of aerospace battery technologies; accelerate the readiness of technology advances and provide infusion paths for emerging technologies; provide NASA projects with the required database and validation guidelines for technology selection of hardware and processes relating to aerospace batteries; disseminate validation and assessment tools, quality assurance, reliability, and availability information to the NASA and aerospace battery communities; and ensure that safe, reliable batteries are available for NASA's future missions.

Manzo, Michelle↗
NASA NTRS1998

Evaluation of Chemical Coating Processes for AXAF

The need existed at MSFC for the development and fabrication of radioisotope calibration sources of cadmium 109 and iron 55 isotopes. This was in urgent response to the AXA-F program. Several issues persisted in creating manufacturing difficulties for the supplier. In order to meet the MSFC requirements very stringent control needed to be maintained for the coating quality, specific activity and thickness. Due to the difficulties in providing the precisely controlled devices for testing, the delivery of the sources was seriously delayed. It became imperative that these fabrication issues be resolved to avoid further delays in this AXA-F observatory key component. The objectives are: 1) Research and provide expert advice on coating materials and procedures. 2) Research and recommend solutions to problems that have been experienced with the coating process. 3) Provide recommendations on the selection and preparation of substrates. 4) Provide consultation on the actual coating process including the results of the qualification and acceptance test programs. 5) Perform independent tests at UAH or MSFC as necessary.

Engelhaupt, Darell↗
NASA NTRS1996

Specialization of the DNA-Cleaving Activity of a Group I Ribozyme Through In Vitro Evolution

In an earlier study, an in vitro evolution procedure was applied to a large population of variants of the Tetrahymena group 1 ribozyme to obtain individuals with a 10(exp 5)-fold improved ability to cleave a target single-stranded DNA substrate under simulated physiological conditions. The evolved ribozymes also showed a twofold improvement, compared to the wild-type, in their ability to cleave a single-stranded RNA substrate. Here, we report continuation of the in vitro evolution process using a new selection strategy to achieve both enhanced DNA and diminished RNA-cleavage activity. Our strategy combines a positive selection for DNA cleavage with a negative selection against RNA binding. After 36 "generations" of in vitro evolution, the evolved population showed an approx. 100-fold increase in the ratio of DNA to RNA-cleavage activity. Site-directed mutagenesis experiment confirmed the selective advantage of two covarying mutations within the catalytic core of ribozyme that are largely responsible for this modified behavior. The population of ribozymes has now undergone a total of 63 successive generations of evolution, resulting in an average 28 mutations relative to the wild-type that are responsible for the altered phenotype.

Tsang, Joyce↗
NASA NTRS1960

Evaluation of Blended Wing-Body Combinations with Curved Plan Forms at Mach Numbers Up to 3.50

This investigation is a continuation of the experimental and theoretical evaluation of the effects of wing plan-form variations on the aerodynamic performance characteristics of blended wing-body combinations. The present report compares previously tested straight-edged delta and arrow models which have leading-edge sweeps of 59.04 and 70-82 deg., respectively, with related models which have plan forms with curved leading and trailing edges designed to result in the same average sweeps in each case. All the models were symmetrical, without camber, and were generally similar having the same span, length, and aspect ratios. The wing sections had an average value of maximum thickness ratio of about 4 percent of the local wing chords in a streamwise direction. The wing sections were computed by varying their shapes along with the body radii (blending process) to match the selected area distribution and the given plan form. The models were tested with transition fixed at Reynolds numbers of roughly 4,000,000 to 9,000,000, based on the mean aerodynamic chord of the wing. The characteristic effect of the wing curvature of the delta and arrow models was an increase at subsonic and transonic speeds in the lift-curve slopes which was partially reflected in increased maximum lift-drag ratios. Curved edges were not evaluated on a diamond plan form because a preliminary investigation indicated that the curvature considered would increase the supersonic zero-lift wave drag. However, after the test program was completed, a suitable modification for the diamond plan form was discovered. The analysis presented in the appendix indicates that large reductions in the zero-lift wave drag would be obtained at supersonic Mach numbers if the leading- and trailing-edge sweeps are made to differ by indenting the trailing edge and extending the root of the leading edge.

Holdaway, George H.↗
NASA NTRS1959

Investigation at Mach Numbers of 0.20 to 3.50 of a Blended Diamond Wing and Body Combination of Sonic Design but with Low Wave-Drag Increase with Increasing Mach Number

A diamond wing and body combination was designed to have an area distribution which would result in near optimum zero-lift wave-drag coefficients at a Mach number of 1.00, and decreasing wave-drag coefficient with increasing Mach number up to near sonic leading-edge conditions for the wing. The airfoil section were computed by varying their shape along with the body radii (blending process) to match the selected area distribution and the given plan form. The exposed wing section had an average maximum thickness of about 3 percent of the local chords, and the maximum thickness of the center-line chord was 5.49 percent. The wing had an aspect ratio of 2 and a leading-edge sweep of 45 deg. Test data were obtained throughout the Mach number range from 0.20 to 3.50 at Reynolds numbers based on the mean aerodynamic chord of roughly 6,000,000 to 9,000,000. The zero-lift wave-drag coefficients of the diamond model satisfied the design objectives and were equal to the low values for the Mach number 1.00 equivalent body up to the limit of the transonic tests. From the peak drag coefficient near M = 1.00 there was a gradual decrease in wave-drag coefficient up to M = 1.20. Above sonic leading-edge conditions of the wing there was a rise in the wave-drag coefficient which was attributed in part to the body contouring as well as to the wing geometry. The diamond model had good lift characteristics, in spite of the prediction from low-aspect-ratio theory that the rear half of the diamond wing would carry little lift. The experimental lift-curve slope obtained at supersonic speeds were equal to or greater than the values predicted by linear theory. Similarly the other basic aerodynamic parameters, aerodynamic center position, and maximum lift-drag ratios were satisfactorily predicted at supersonic speeds.

Holdaway, George H.↗
NASA NTRS1999

An Adaptive Kalman Filter Using a Simple Residual Tuning Method

One difficulty in using Kalman filters in real world situations is the selection of the correct process noise, measurement noise, and initial state estimate and covariance. These parameters are commonly referred to as tuning parameters. Multiple methods have been developed to estimate these parameters. Most of those methods such as maximum likelihood, subspace, and observer Kalman Identification require extensive offline processing and are not suitable for real time processing. One technique, which is suitable for real time processing, is the residual tuning method. Any mismodeling of the filter tuning parameters will result in a non-white sequence for the filter measurement residuals. The residual tuning technique uses this information to estimate corrections to those tuning parameters. The actual implementation results in a set of sequential equations that run in parallel with the Kalman filter. A. H. Jazwinski developed a specialized version of this technique for estimation of process noise. Equations for the estimation of the measurement noise have also been developed. These algorithms are used to estimate the process noise and measurement noise for the Wide Field Infrared Explorer star tracker and gyro.

Harman, Richard R.↗
NASA NTRS1999

An Adaptive Kalman Filter using a Simple Residual Tuning Method

One difficulty in using Kalman filters in real world situations is the selection of the correct process noise, measurement noise, and initial state estimate and covariance. These parameters are commonly referred to as tuning parameters. Multiple methods have been developed to estimate these parameters. Most of those methods such as maximum likelihood, subspace, and observer Kalman Identification require extensive offline processing and are not suitable for real time processing. One technique, which is suitable for real time processing, is the residual tuning method. Any mismodeling of the filter tuning parameters will result in a non-white sequence for the filter measurement residuals. The residual tuning technique uses this information to estimate corrections to those tuning parameters. The actual implementation results in a set of sequential equations that run in parallel with the Kalman filter. Equations for the estimation of the measurement noise have also been developed. These algorithms are used to estimate the process noise and measurement noise for the Wide Field Infrared Explorer star tracker and gyro.

Harman, Richard R.↗
NASA NTRS1998

Space Product Development of Commercial NLO Materials

Growth on selected substrates under various processing conditions have been useful for preparing highly oriented and otherwise promising films of organic compounds for optical thin films and waveguides. The significance of processing conditions to uniformity in thickness, degree of orientation, film quality, and optical properties for a specific processing technique is the general focus of work in this area. A study on the effect of processing conditions relevant to thin-film deposition by various techniques is particularly difficult because of the possibility that convection may play a major role in some cases. It is a goal of some researchers to produce good quality anisotropic films, therefore, an important, yet understudied, requirement should be to assess the role of gravity during certain processing methods. This may be particularly true for the vapor deposition of diacetylenes where subsequent polymerization in the crystal is topochemical and occurs readily only when neighboring monomer molecules are sufficiently close and suitably oriented. Likewise, this requirement is equally viable for the vapor deposition of certain materials such as Pcs in view of the results of microgravity experiments by 3M Corporation involving the preparation of thin films of copper Pc (CuPc). Microgravity-grown CuPc had several desirable features which indicate that the vapor growth of organic films in low-g may result in better quality films for optical and electrical applications. Indeed, other materials vapor deposited onto specific substrates in microgravity produce films potentially beneficial for electro-optic applications. A novel technique, recently discovered, for growing polydiacetylene thin films involves exposing a transparent substrate, in contact with diacetylene monomer solution, to ultraviolet (LTV) light. A polymer film deposits on the side of the substrate in contact with monomer in solution, and there are distinct gravitational effects, which influence film quality. Good quality thin films elude growth from solutions absent of uniform flow fields and homogeneous temperature distributions near the substrate surfaces. The flow fields and temperature distributions during the polymerization process by exposure to UV light details the nature of gravitational influences on this process.

Frazier, Donald O.↗
NASA NTRS2000

Materials Science Research Hardware for Application on the International Space Station: an Overview of Typical Hardware Requirements and Features

NASA's Marshall Space Flight Center (MSFC) is the lead center for Materials Science Microgravity Research. The Materials Science Research Facility (MSRF) is a key development effort underway at MSFC. The MSRF will be the primary facility for microgravity materials science research on board the International Space Station (ISS) and will implement the NASA Materials Science Microgravity Research Program. It will operate in the U.S. Laboratory Module and support U. S. Microgravity Materials Science Investigations. This facility is being designed to maintain the momentum of the U.S. role in microgravity materials science and support NASA's Human Exploration and Development of Space (HEDS) Enterprise goals and objectives for Materials Science. The MSRF as currently envisioned will consist of three Materials Science Research Racks (MSRR), which will be deployed to the International Space Station (ISS) in phases, Each rack is being designed to accommodate various Experiment Modules, which comprise processing facilities for peer selected Materials Science experiments. Phased deployment will enable early opportunities for the U.S. and International Partners, and support the timely incorporation of technology updates to the Experiment Modules and sensor devices.

Schaefer, D. A.↗
NASA NTRS2003

Durability of Membrane Electrode Assemblies (MEAs) in PEM Fuel Cells Operated on Pure Hydrogen and Oxygen

Proton exchange membrane (PEM) fuel cells are energy sources that have the potential to replace alkaline fuel cells for space programs. Broad power ranges, high peak-to-nominal power capabilities, low maintenance costs, and the promise of increased life are the major advantages of PEM technology in comparison to alkaline technology. The probability of PEM fuel cells replacing alkaline fuel cells for space applications will increase if the promise of increased life is verified by achieving a minimum of 10,000 hours of operating life. Durability plays an important role in the process of evaluation and selection of MEAs for Teledyne s Phase I contract with the NASA Glenn Research Center entitled Proton Exchange Membrane Fuel cell (PEMFC) Power Plant Technology Development for 2nd Generation Reusable Launch Vehicles (RLVs). For this contract, MEAs that are typically used for H2/air operation were selected as potential candidates for H2/O2 PEM fuel cells because their catalysts have properties suitable for O2 operation. They were purchased from several well-established MEA manufacturers who are world leaders in the manufacturing of diverse products and have committed extensive resources in an attempt to develop and fully commercialize MEA technology. A total of twelve MEAs used in H2/air operation were initially identified from these manufacturers. Based on the manufacturers specifications, nine of these were selected for evaluation. Since 10,000 hours is almost equivalent to 14 months, it was not possible to perform continuous testing with each MEA selected during Phase I of the contract. Because of the lack of time, a screening test on each MEA was performed for 400 hours under accelerated test conditions. The major criterion for an MEA pass or fail of the screening test was the gas crossover rate. If the gas crossover rate was higher than the membrane intrinsic permeability after 400 hours of testing, it was considered that the MEA had failed the test. Three types of MEAs out of the nine total membranes failed the test. The evaluation results showed that fuel cell operating conditions (current, pressure, stoichiometric flow rates) were the parameters that influenced the durability of MEAs. In addition, the durability test results indicated that the type of membrane was also an important parameter for MEA durability. At accelerated test conditions, the MEAs with casted membranes failed during the 400 hour test. However, the MEAs prepared from the casted membrane with support as well as extruded membranes, both passed the 400h durability test at accelerated operating test conditions. As a result of the MEA accelerated durability tests, four MEAs were selected for further endurance testing. These tests are being carried out with four-cell stacks under nominal fuel cell operating conditions.

Stanic, Vesna↗
NASA NTRS2002

Packaging Technology for SiC High Temperature Circuits Operable up to 500 Degrees Centigrade

New high temperature low power 8-pin packages have been fabricated using commercial fabrication service. These packages are made of aluminum nitride and 96 percent alumina with Au metallization. The new design of these packages provides the chips inside with EM shielding. Wirebond geometry control has been achieved for precise mechanical tests. Au wirebond samples with 45 degree heel-angle have been tested using wireloop test module. The geometry control improves the consistency of measurement of the wireloop breaking point.Also reported on is a parametric study of the thermomechanical reliability of a Au thick-film based SiC die-attach assembly using nonlinear finite element analysis (FEA) was conducted to optimize the die-attach thermo-mechanical performance for operation at temperatures from room temperature to 500 degrees Centigrade. This parametric study centered on material selection, structure design and process control.

Chen, Lian-Yu↗
NASA NTRS1997

Structural and functional analyses of human cerebral cortex using a surface-based atlas

We have analyzed the geometry, geography, and functional organization of human cerebral cortex using surface reconstructions and cortical flat maps of the left and right hemispheres generated from a digital atlas (the Visible Man). The total surface area of the reconstructed Visible Man neocortex is 1570 cm2 (both hemispheres), approximately 70% of which is buried in sulci. By linking the Visible Man cerebrum to the Talairach stereotaxic coordinate space, the locations of activation foci reported in neuroimaging studies can be readily visualized in relation to the cortical surface. The associated spatial uncertainty was empirically shown to have a radius in three dimensions of approximately 10 mm. Application of this approach to studies of visual cortex reveals the overall patterns of activation associated with different aspects of visual function and the relationship of these patterns to topographically organized visual areas. Our analysis supports a distinction between an anterior region in ventral occipito-temporal cortex that is selectively involved in form processing and a more posterior region (in or near areas VP and V4v) involved in both form and color processing. Foci associated with motion processing are mainly concentrated in a region along the occipito-temporal junction, the ventral portion of which overlaps with foci also implicated in form processing. Comparisons between flat maps of human and macaque monkey cerebral cortex indicate significant differences as well as many similarities in the relative sizes and positions of cortical regions known or suspected to be homologous in the two species.

NASA Discipline Neuroscience↗
NASA NTRS2002

Miniature Heat Transport System for Spacecraft Thermal Control

Loop heat pipes (LHP) are efficient devices for heat transfer and use the basic principle of a closed evaporation-condensation cycle. The advantage of using a loop heat pipe over other conventional methods is that large quantities of heat can be transported through a small cross-sectional area over a considerable distance with no additional power input to the system. By using LHPs, it seems possible to meet the growing demand for high-power cooling devices. Although they are somewhat similar to conventional heat pipes, LHPs have a whole set of unique properties, such as low pressure drops and flexible lines between condenser and evaporator, that make them rather promising. LHPs are capable of providing a means of transporting heat over long distances with no input power other than the heat being transported because of the specially designed evaporator and the separation of liquid and vapor lines. For LHP design and fabrication, preliminary analysis on the basis of dimensionless criteria is necessary because of certain complicated phenomena that take place in the heat pipe. Modeling the performance of the LHP and miniaturizing its size are tasks and objectives of current research. In the course of h s work, the LHP and its components, including the evaporator (the most critical and complex part of the LHP), were modeled with the corresponding dimensionless groups also being investigated. Next, analysis of heat and mass transfer processes in the LHP, selection of the most weighted criteria from known dimensionless groups (thermal-fluid sciences), heat transfer rate limits, (heat pipe theory), and experimental ratios which are unique to a given heat pipe class are discussed. In the third part of the report, two-phase flow heat and mass transfer performances inside the LHP condenser are analyzed and calculated for Earth-normal gravity and microgravity conditions. On the basis of recent models and experimental databanks, an analysis for condensing two-phase flow regimes, pressure gradients, and local heat transfer coefficients using ammonia, propylene, and R134, are carried out.

Ochterbeck, Jay M.↗
NASA NTRS1997

Visual Computing Environment

The Visual Computing Environment (VCE) is a NASA Lewis Research Center project to develop a framework for intercomponent and multidisciplinary computational simulations. Many current engineering analysis codes simulate various aspects of aircraft engine operation. For example, existing computational fluid dynamics (CFD) codes can model the airflow through individual engine components such as the inlet, compressor, combustor, turbine, or nozzle. Currently, these codes are run in isolation, making intercomponent and complete system simulations very difficult to perform. In addition, management and utilization of these engineering codes for coupled component simulations is a complex, laborious task, requiring substantial experience and effort. To facilitate multicomponent aircraft engine analysis, the CFD Research Corporation (CFDRC) is developing the VCE system. This system, which is part of NASA's Numerical Propulsion Simulation System (NPSS) program, can couple various engineering disciplines, such as CFD, structural analysis, and thermal analysis. The objectives of VCE are to (1) develop a visual computing environment for controlling the execution of individual simulation codes that are running in parallel and are distributed on heterogeneous host machines in a networked environment, (2) develop numerical coupling algorithms for interchanging boundary conditions between codes with arbitrary grid matching and different levels of dimensionality, (3) provide a graphical interface for simulation setup and control, and (4) provide tools for online visualization and plotting. VCE was designed to provide a distributed, object-oriented environment. Mechanisms are provided for creating and manipulating objects, such as grids, boundary conditions, and solution data. This environment includes parallel virtual machine (PVM) for distributed processing. Users can interactively select and couple any set of codes that have been modified to run in a parallel distributed fashion on a cluster of heterogeneous workstations. A scripting facility allows users to dictate the sequence of events that make up the particular simulation.

Lawrence, Charles↗