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At least 271 records · Page 15

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NASA NTRS1990

Towards a mature measurement environment: Creating a software engineering research environment

Software engineering researchers are building tools, defining methods, and models; however, there are problems with the nature and style of the research. The research is typically bottom-up, done in isolation so the pieces cannot be easily logically or physically integrated. A great deal of the research is essentially the packaging of a particular piece of technology with little indication of how the work would be integrated with other prices of research. The research is not aimed at solving the real problems of software engineering, i.e., the development and maintenance of quality systems in a productive manner. The research results are not evaluated or analyzed via experimentation or refined and tailored to the application environment. Thus, it cannot be easily transferred into practice. Because of these limitations we have not been able to understand the components of the discipline as a coherent whole and the relationships between various models of the process and product. What is needed is a top down experimental, evolutionary framework in which research can be focused, logically and physically integrated to produce quality software productively, and evaluated and tailored to the application environment. This implies the need for experimentation, which in turn implies the need for a laboratory that is associated with the artifact we are studying. This laboratory can only exist in an environment where software is being built, i.e., as part of a real software development and maintenance organization. Thus, we propose that Software Engineering Laboratory (SEL) type activities exist in all organizations to support software engineering research. We describe the SEL from a researcher's point of view, and discuss the corporate and government benefits of the SEL. The discussion focuses on the benefits to the research community.

Basili, Victor R.↗

NASA NTRS1993

Mixing model analysis of telescopic lunar spectra

We have analyzed very high quality reflectance spectra of the lunar surface from the University of Hawaii lunar spectral data collection using a spectral mixing model. The spectra analyzed are those of 45 mare sites and 75 highland sites. The spectra were selected on the basis of very high signal to noise ratios based on error bars and point to point scatter, and on quality of removal of telluric water bands. The spectral mixing model used 7 components, not all of which were used in each fit. Four of the components were mineral spectra of the orthopyroxene, a clinopyroxene, an olivine and an anorthite, measured at the Brown University's RELAB. All of the minerals were 45-90 micron splits. Lunar soil contains other components which have the effect of reddening and darkening the soil as well as reducing spectral contrast. In addition, lunar soil contains spectral neutral bright material (likely very fine grained feldspar) which serves to reduce spectral contrast and brighten soils. Early attempts to fit many of the spectra pointed out the need for a component which has a very broad smooth absorption feature centered near 1.1 microns. Glass is a good candidate for this component. For the bright component we used a flat reflectance of 70 percent to represent fine grained feldspar. For the 'glass' component we used a telescopic spectrum of a pyroclastic glass present on the Aristarchus plateau which is characterized by a strong smooth band centered at 1.07 microns. In addition to exhibiting the glass band this spectrum is very red and has a low albedo. On the assumption that the dark component and the red component are agglutinates, which is reasonable but not necessarily true, we sought a dark red component. To derive its properties we modelled the spectrum of an Apollo 16 soil (16xxx) and assumed the dark red component to comprise 60 percent of the soil, appropriate to agglutinate abundance in mature soil. We adjusted the albedo and slope of a straight line representing the dark red component until the contrast and albedo of the model spectrum matched the soil spectrum. The mixing was done after conversion to a single scattering albedo.

Lucey, Paul G.↗

NASA NTRS2019

Modeled Microgravity Induces Neutrophil Extracellular Trap (NET)osis Formation and Reduced Phagocytosis of Polymorphonuclear Neutrophils

Spaceflight can dysregulate immunity, by way of increasing granulocytes numbers with impaired function. Polymorphonuclear neutrophils (PMN) are granulocytes that are first responders to infection or injury, and consist of the largest pool of immune cells in humans. PMNs function during innate immunity, through phagocytosis and promotion of inflammation, via the release of reactive oxygen species (ROS) mediators and granule-containing enzymes, such as myeloperoxidase (MPO) and NADPH oxidase-2 (NOX-2). In addition, neutrophil extracellular trap (NET) formation is another mechanism of PMN surveillance that works independently of engulfment phagocytosis, and is a last resort function that can induce NETosis or PMN-specific cell death. Previous studies in our lab have identified increased mature neutrophils, ROS and MPO production, and reduced phagocytosis in granulocytes in simulated microgravity (sug) models of hindlimb unloading (HU) in adult mice and leukocytes cultured in high-aspect rotating wall vessels (HARV-RWV). Since sug impaired phagocytosis, but improved enzymatic mediator production of MPO and redox molecules, we sought to address the third known function of PMNs, NETosis. For this, PMNs were culture in the presence or absence of the anti-oxidant N-acetyl cysteine (NAC), which rescued impaired phagocytosis that was present in sug without NAC treatment. Further, NETosis was induced in sug that was no different in the presence of NAC, suggesting NAC targets independent functions of PMNs under sug. Collectively, these results suggest modeled microgravity induced NETosis, which opens a new avenue for spaceflight studies in immune dysfunction.

Paul, Amber M.↗

NASA NTRS1999

Modeling the Atmospheric Structure and Dynamics of the Martian Atmosphere

Models of the general circulation and climate system of Mars have reached a high level of maturity, but observations to validate them have lacked the kind of global and temporal coverage required. However, we are now on the verge of a new era in Mars exploration as Mars Global Surveyor, and the now enroute Mars Climate Orbiter, will provide daily global coverage of the atmosphere for two Mars years. In the coming years, data from these missions will test the predictions of general circulation models (GCM's) whose results have perhaps become too accepted as truth. This talk will review what GCM's tell us about Mars, what their weaknesses are, and what the latest results imply for their future. Additional information is contained in the original extended abstract.

Haberle, R. M.↗

NASA NTRS1973

Evolution of lunar soil grain-size and shape parameters

Substrates at the Apollo 15 and 16 sites were analyzed and showed essentially the same graphic mean, graphic standard deviation, and graphic skewness. The graphic kurtosis of Apollo 16 soils is slightly smaller than that of Apollo 15. In Apollo 15 soil samples, grain size and graphic standard deviation increase with depth, while the trend is reversed in Apollo 16 soil samples. Lower sphericity values for Apollo 15 samples coincide with concentrations of highly irregularly shaped glass particles. Two-dimensional sphericity of Apollo 15 samples is contoured as a function of particle size and depth below lunar surface. The results are consistent with an overall model for soil development in which samples closer to the surface are more mature in response to more prolonged reworking of meteorite impact.

Lindsay, J. F.↗

NASA NTRS1982

Variation of directional reflectance factors with structural changes of a developing alfalfa canopy

Directional reflectance factors of an alfalfa canopy were determined and related to canopy structure, agronomic variables, and irradiance conditions at four periods during a cutting cycle. Nadir and off-nadir reflectance factors decreased with increasing biomass in Thematic Mapper band 3(0.63-0.69 micrometer) and increased with increasing biomass in band 4(0.76-0.90 micrometer). The sensor view angle had less impact on perceived reflectance as the alfalfa progressed from an erectophile canopy of stems after harvest to a near planophile canopy of leaves at maturity. Studies of directional reflectance are needed for testing and upgrading vegetation canopy models and to aid in the complex interpretation problems presented by aircraft scanners and pointable satellites where illumination and viewing geometries may vary widely. Distinct changes in the patterns of radiance observed by a sensor as structural and biomass changes occur are keys to monitoring the growth and condition of crops.

Kirchner, J. A.↗

NASA NTRS1988

Predicting Temperatures In Ball Bearings

Computer simulations speed design studies. Analyses performed in two or three dimensions. Sizes and shapes of components approximated by zones or nodes connected by gridlines. From geometric information about grids and boundary conditions, properties of bearing and lubricant materials, and information supplied by users, thermal-analysis programs generate mathematical models for thermal transport. Thermal analysis of high-speed rolling contact bearings matured so much that computerized numerical simulations replace expensive time consuming full scale experiments.

Wagner, William R.↗

NASA NTRS1993

Application of fuzzy set and Dempster-Shafer theory to organic geochemistry interpretation

An application of fuzzy sets and Dempster Shafter Theory (DST) in modeling the interpretational process of organic geochemistry data for predicting the level of maturities of oil and source rock samples is presented. This was accomplished by (1) representing linguistic imprecision and imprecision associated with experience by a fuzzy set theory, (2) capturing the probabilistic nature of imperfect evidences by a DST, and (3) combining multiple evidences by utilizing John Yen's generalized Dempster-Shafter Theory (GDST), which allows DST to deal with fuzzy information. The current prototype provides collective beliefs on the predicted levels of maturity by combining multiple evidences through GDST's rule of combination.

Kim, C. S.↗

NASA NTRS2006

A Fast Technology Infusion Model for Aerospace Organizations

A multi-year Fast Technology Infusion initiative proposes a model for aerospace organizations to improve the cost-effectiveness by which they mature new, in-house developed software and hardware technologies for space mission use. The first year task under the umbrella of this initiative will provide the framework to demonstrate and document the fast infusion process. The viability of this approach will be demonstrated on two technologies developed in prior years with internal Jet Propulsion Laboratory (JPL) funding. One hardware technology and one software technology were selected for maturation within one calendar year or less. The overall objective is to achieve cost and time savings in the qualification of technologies. At the end of the recommended three-year effort, we will have demonstrated for six or more in-house developed technologies a clear path to insertion using a documented process that permits adaptation to a broad range of hardware and software projects.

technology readiness level↗

NASA NTRS2023

An In-time Aviation Safety Management System (IASMS) Concept of Operations for Vertiport Design and Operations

The National Airspace System is foreseen to undergo revolutionary change with Urban Air Mobility (UAM) and its use of vertiports to transport passengers and cargo. To assure safety with UAM and more broadly with Advanced Air Mobility (AAM), the National Academies recommended an In-time Aviation Safety Management System (IASMS) that is extensible to the design and operation of vertiports. Vertiport designs will scale in several dimensions including physical size and infrastructure depending upon location and in the Services, Functions, and Capabilities required for assuring safety with increasingly complex vertiport designs and operations. These operations will be enabled by evolving technologies including electric vertical takeoff and landing (eVTOL) aircraft for passenger-and cargo-carrying commercial transportation. Within this construct, safety hazards and risk mitigations involving predictive data analytics and modeling will be used. Use cases and future challenges are examined to guide maturation of the IASMS ConOps for vertiports.

K Ellis↗

NASA NTRSDate not supplied

Laser Beam Welding Advancements for In-Space Servicing, Assembly, and Manufacturing

NASA is currently working to develop in-space servicing, assembly, and manufacturing (ISAM) capabilities for low Earth orbit and the lunar surface. One crucial technology for this effort is laser beam welding. Laser systems can perform joining, cleaning, cutting, and repair activities, which will enable the construction of large in-space structures that could not fit on a single launch vehicle, such as trusses for solar panels, radiators, or communications infrastructure. Multiple projects studying laser welding for space applications are currently underway at NASA Marshall Space Flight Center. One of these, the DIsk-Shaped Configurable and Modular vAcuum uNit (DISCMAN), is a compact vacuum chamber designed to support parameter development for laser welding in microgravity. It contains a rotating platen with weld samples made from aluminum, steel, and titanium, a high-power infrared laser, and integrated pumps for pulling vacuum inside the sample cartridge. The DISCMAN payload is planned to launch to the International Space Station, where welds will be performed under sustained microgravity inside the Bishop Airlock. Another effort underway at Marshall is the Lunar Assembly and Servicing by Autonomous Robotics (LASAR) initiative. This project uses a space-rated robotic arm equipped with a laser weld head, wire feeder, and multiple cameras to perform welds in a thermal vacuum chamber simulating the lunar surface environment. Some of these welds are done on snowflake joints, which are specially designed to slot together to join segments of trussN structures, allowing for the construction of tall surface infrastructure. DISCMAN, LASAR, and other projects are being carried out to advance the technological maturity of in-space laser beam welding, collect data to inform computational models, and learn reliable processes for creating weld joints in space. This work supports NASA’s greater goals to expand humanity’s presence in low Earth orbit, establish a permanent moon base, and eventually send crewed missions to Mars and beyond.

Manufacturing↗

NASA NTRSDate not supplied

Laser Beam Welding Advancements for In-Space Servicing, Assembly, and Manufacturing

Robotics↗

NASA NTRS2012

Status of Turbulence Modeling for Hypersonic Propulsion Flowpaths

This report provides an assessment of current turbulent flow calculation methods for hypersonic propulsion flowpaths, particularly the scramjet engine. Emphasis is placed on Reynolds-averaged Navier-Stokes (RANS) methods, but some discussion of newer meth- ods such as Large Eddy Simulation (LES) is also provided. The report is organized by considering technical issues throughout the scramjet-powered vehicle flowpath including laminar-to-turbulent boundary layer transition, shock wave / turbulent boundary layer interactions, scalar transport modeling (specifically the significance of turbulent Prandtl and Schmidt numbers) and compressible mixing. Unit problems are primarily used to conduct the assessment. In the combustor, results from calculations of a direct connect supersonic combustion experiment are also used to address the effects of turbulence model selection and in particular settings for the turbulent Prandtl and Schmidt numbers. It is concluded that RANS turbulence modeling shortfalls are still a major limitation to the accuracy of hypersonic propulsion simulations, whether considering individual components or an overall system. Newer methods such as LES-based techniques may be promising, but are not yet at a maturity to be used routinely by the hypersonic propulsion community. The need for fundamental experiments to provide data for turbulence model development and validation is discussed.

Georgiadis, Nicholas J.↗

NASA NTRS2003

Physiological Maturation of Regenerating Hair Cells

The bullfrog saccule, a sensor of gravity and substrate-borne vibration, is a model system for hair cell transduction. Saccular hair cells also increase in number throughout adult life and rapidly recover after hair cell damage, making this organ an ideal system for studying hair cell development, repair, and regeneration. We have used of hair cell and supporting cell immunocytochemical markers to identify damaged hair cells and hair cell precursors in organotypic cultures of the bullfrog saccule. We then used an innovative combination of confocal, electron, and time-lapse microscopy to study the fate of damaged hair cells and the origin of new hair cells after gentamicin ototoxicity in normal and mitotically blocked saccular cultures. These studies have shown that gentamicin ototoxicity produces both lethal and sublethal hair cell damage. They have also shown that hair cell recovery in this organ takes place by both the repair of sublethally damaged hair cells and by the replacement of lost hair cells by mitotic regeneration. In parallel studies, we have used biophysical and molecular biological techniques to study the differentiation and innervation of developing, repairing, and regenerating hair cells. More specifically, we have used RT-PCR to obtain the bullfrog homologues of L-type voltage- gated calcium (L-VGCC) and large-conductance Ca(2+)-activated potassium (BK) channel genes. We have then obtained probes for these genes and, using in situ hybridization, begun to examine their expression in the bullfrog saccule and amphibian papilla. We have also used fluorescent-labeled channel toxins and channel toxin derivatives to determine the time of appearance of L-type voltage-gated calcium (L-VGCC) and Ca(2+)-activated potassium (BK) channels and to study dynamic changes in the number, distribution, and co-localization of these proteins in developing, repairing, and regenerating hair cells. Using time-lapse microscopy, we are also studying the dynamic relationship between ion channel clustering and synaptic formation in hair cells and afferent neurons. In future studies, we will determine when hair cell precursors acquire electrical tuning, and, using whole-cell patch-clamp techniques, identify and characterize their L-VGCC and BK currents. We will also use biophysical techniques to determine the number of L-VGCC and BK channels and the size and gating kinetics of their underlying L-VGCC and BK conductances, correlating these variables with the amplitude and frequency of membrane oscillations produced by intracellular current steps. We expect these studies to determine how hair cells regulate ion channel expression to achieve specific physiological responses.

Baird, Richard A.↗

NASA NTRSDate not supplied

Psyche Hardware Abstraction Simulation Environment (PHASE): Development of High-Fidelity Downlink Model for Flight Software Performance Testing

NASA’s Katherine Johnson Independent Verification and Validation (IV&V) Independent Test Capability (ITC) Team develops high fidelity software-only simulations (or “digital-twins”) of NASA’s most critical missions that are then used for software verification and validation (V&V). One such digital-twin simulator nearing maturity is the Psyche Hardware Abstraction Simulation Environment (PHASE). PHASE utilizes an instruction set simulator along with ITC-developed avionics models. PHASE includes a newly-developed model of the telecom hardware with a high-fidelity downlink interface, capable of supporting reconfigurable downlink data rates and transmission modes. The different downlink transmission modes allow more processing to be ceded from software onto the telecom hardware. Thus, we are able to monitor the performance of the downlink software module in the time-partitioned OS and perform more realistic dynamic testing based on software’s resource utilization. This presentation will cover PHASE, avionics modeling, the downlink model, and its usage for flight software performance testing.

modeling↗

NASA NTRSDate not supplied

Evaluation of Preliminary Buffet Forcing Function Development based on Wind-Tunnel Tests of Geometrically-similar Models

The current state-of-the-art for launch vehicle buffet load estimation involves wind tunnel testing of highly instrumented rigid models and data processing of experimental unsteady pressure measurements to estimate the fluctuating aerodynamic loads. The model and instrumentation requirements to accomplish this type of testing are significant. The rigid model, in particular, must be built with relatively high geometric fidelity to approximate similar aerodynamic phenomena that will occur during the full-scale vehicle flight. Due to this requirement, several iterative wind tunnel tests are often required during the design maturation of the vehicle. For preliminary buffet load estimation, however, data from previous launch vehicle wind tunnel tests of geometrically similar models can be used to provide initial buffet environment estimates before a high geometric fidelity wind tunnel test has been conducted. In this paper, two components of this preliminary buffet estimation process are described: (1) assembly of buffet forcing functions from multiple data sources and (2) scaling of these buffet forcing functions to geometrically-similar components of a target vehicle configuration. The impacts of these estimation methods on the full-vehicle buffet forcing functions, including their longitudinal distribution along the vehicle, frequency-content at individual stations, and station-to-station coherence, are investigated. Considerations for using these methods to extrapolate wind tunnel data to geometrically similar models are also discussed.

Patrick S Heaney↗

NASA NTRSDate not supplied

Strategy for Developing Technologies for Megawatt-class Nuclear Electric Propulsion Systems

A strategy for maturing the technologies required for a megawatt-class nuclear electric propulsion (NEP) system is presented. The effort is responsive to recent non-advocate reviews stating high-power NEP technologies were relatively immature and significant maturation was required before contemplating the use of NEP on a flight mission. The maturation strategy presented accomplishes this through hardware test and evaluation at the sizes, scales, and conditions expected during high-power NEP missions. The development effort is accompanied by modeling of such a system to demonstrate thorough understanding and verification of the performance, lifetime, and failure modes. The proposed effort uses a building-block approach, maturing technologies for a 1 MWe block under the assumption that a future high-power NEP mission will have requirements that can be met either through straightforward scaling of this building block to the levels required or through the use of multiple blocks to meet the overall power needs. The plan is outlined for maturation to technology readiness level 5, characterized by test and evaluation using brassboard-fidelity hardware in a relevant environment and by demonstration of agreement between test data and analytical predictions.

Kurt A. Polzin↗

NASA NTRS1993

A Data Base of Crop Nutrient Use, Water Use, and Carbon Dioxide Exchange in a 20 Square Meter Growth Chamber: Wheat as a Case Study - Part 1

A data set is given describing the daily nutrient uptake, gas exchange, environmental conditions, and carbon (C), and nutrient partitioning at harvest for the entire canopy and root system of a wheat crop (Triticum aestivum, cv. Yecora Rojo). The data were obtained from a 20 sq m stand of wheat plants grown from planting to maturity in a closed, controlled environment, and include daily nutrient uptake [macronutrients, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S); and micronutrients, iron (Fe), boron (B), manganese (Mn), zinc (Zn), copper (Cu), and molybdenum (Mo)], canopy carbon dioxide (CO2) exchange rates, and transpiration. Environmental factors such as relative humidity, air temperature, nutrient solution temperature, pH and electrical conductivity, and photoperiod were controlled in the chamber to specific set points. A detailed description of biomass yield for each of the 64 plant growth trays comprising the 20 sq m of growth area is also provided, and includes dry weights of grain, straw, chaff, and roots, along with the concentration of nutrients in different plant tissues and the percent carbohydrate, fat, and protein. To our knowledge, this information represents one of the most extensive data sets available for a canopy of wheat grown from seed to maturity under controlled environmental and nutritional conditions, and thus may provide useful information for model development and validation. A methods section is included to qualify any assumptions that might he required for the use of the data in plant growth models, along with a daily event calendar indicating when adjustments in set points and occasional equipment or sensor failures occurred.

Wheeler, Raymond M.↗