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NASA NTRS2015

Viking GCMS Data Restoral and Perceiving Temperature on Other Worlds: Astrobiology Projects at NASA Ames

The primary task for the summer was to procure the GCMS data from the National Space Science Data Coordinated Archive (NSSDCA) and to assess the current state of the data set for possible reanalysis opportunities. After procurement of the Viking GCMS data set and analysis of its current state, the internship focus shifted to preparing a plan for restoral and archiving of the GCMS data set. A proposal was prepared and submitted to NASA Headquarters to restore and make available the 8000 mass chromatographs that are the basic data generated by the Viking GCMS instrument. The relevance of this restoral and the methodology we propose for restoral is presented. The secondary task for the summer is to develop a thermal model for the perceived temperature of a human standing on Mars, Titan, or Europa. Traditionally, an equation called "Fanger's comfort equation" is used to measure the perceived temperature by a human in a given reference environment. However, there are limitations to this model when applied to other planets. Therefore, the approach for this project has been to derive energy balance equations from first principles and then develop a methodology for correlating "comfort" to energy balance. Using the -20 C walk-in freezer in the Space Sciences building at NASA Ames, energy loss of a human subject is measured. Energy loss for a human being on Mars, Titan and Europa are calculated from first principles. These calculations are compared to the freezer measurements, e.g. for 1 minute on Titan, a human loses as much energy as x minutes in a -20 C freezer. This gives a numerical comparison between the environments. These energy calculations are used to consider the physiological comfort of a human based on the calculated energy losses.

FangeraEuro(TM)s comfort equation↗
NASA NTRS2010

The Solar Dynamics Observatory: Your Eye on the Sun

The Solar Dynamics Observatory (SDO) was launched on February 11,2010 into partly cloudy skies over Cape Canaveral, Florida. SDO moved into a 28 degree inclined geosynchronous orbit over the longitude of the ground station in New Mexico. SDO is the first Space Weather Mission in NASA's Living With a Star Program. SDO's main goal is to understand and predict those solar variations that influence life on Earth and our technological systems. The SDO science investigations will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere as the solar wind, energetic particles, and variations in the solar irradiance. The SDO mission consists of three scientific investigations (AIA, EVE, and HMI), a spacecraft bus, and a dedicated Ka-band ground station to handle the 150 Mbps data flow. SDO continues a long tradition of NASA missions providing calibrated solar spectral irradiance data, in this case using multiple measurements of the irradiance and rocket underflights of the spacecraft. The other instruments on SDO will be used to explain and develop predictive models of the solar spectral irradiance in the extreme ultraviolet. Science teams at LMSAL, LASP, and Stanford are responsible for processing, analyzing, distributing, and archiving the science data. We will talk about the building of SDO, its launch, and the data and science it will provide to NASA.

Pesnell, William Dean↗
NASA NTRS2010

Test Rack Development for Extended Operation of Advanced Stirling Convertors at NASA Glenn Research Center

The U.S. Department of Energy, Lockheed Martin Space Systems Company, Sunpower Inc., and NASA Glenn Research Center (GRC) have been developing an Advanced Stirling Radioisotope Generator (ASRG) for use as a power system on space science missions. This generator will make use of free-piston Stirling convertors to achieve higher conversion efficiency than with currently available alternatives. One part of NASA GRC's support of ASRG development includes extended operation testing of Advanced Stirling Convertors (ASCs) developed by Sunpower Inc. and GRC. The ASC consists of a free-piston Stirling engine integrated with a linear alternator. NASA GRC has been building test facilities to support extended operation of the ASCs for several years. Operation of the convertors in the test facility provides convertor performance data over an extended period of time. One part of the test facility is the test rack, which provides a means for data collection, convertor control, and safe operation. Over the years, the test rack requirements have changed. The initial ASC test rack utilized an alternating-current (AC) bus for convertor control; the ASRG Engineering Unit (EU) test rack can operate with AC bus control or with an ASC Control Unit (ACU). A new test rack is being developed to support extended operation of the ASC-E2s with higher standards of documentation, component selection, and assembly practices. This paper discusses the differences among the ASC, ASRG EU, and ASC-E2 test racks.

Dugala, Gina M.↗
NASA NTRS1993

Production of long-term global water vapor and liquid water data set using ultra-fast methods to assimilate multi-satellite and radiosonde observations

During the next decade, many programs and experiments under the Global Energy and Water Cycle Experiment (GEWEX) will utilize present day and future data sets to improve our understanding of the role of moisture in climate, and its interaction with other variables such as clouds and radiation. An important element of GEWEX will be the GEWEX Water Vapor Project (GVaP), which will eventually initiate a routine, real-time assimilation of the highest quality, global water vapor data sets including information gained from future data collection systems, both ground and space based. The comprehensive global water vapor data set being produced by METSAT Inc. uses a combination of ground-based radiosonde data, and infrared and microwave satellite retrievals. This data is needed to provide the desired foundation from which future GEWEX-related research, such as GVaP, can build. The first year of this project was designed to use a combination of the best available atmospheric moisture data including: radiosonde (balloon/acft/rocket), HIRS/MSU (TOVS) retrievals, and SSM/I retrievals, to produce a one-year, global, high resolution data set of integrated column water vapor (precipitable water) with a horizontal resolution of 1 degree, and a temporal resolution of one day. The time period of this pilot product was to be det3ermined by the availability of all the input data sets. January 1988 through December 1988 were selected. In addition, a sample of vertically integrated liquid water content (LWC) was to be produced with the same temporal and spatial parameters. This sample was to be produced over ocean areas only. Three main steps are followed to produce a merged water vapor and liquid water product. Input data from Radiosondes, TOVS, and SSMI/I is quality checked in steps one and two. Processing is done in step two to generate individual total column water vapor and liquid water data sets. The third step, and final processing task, involves merging the individual output products to produce the integrated water vapor product. A final quality control is applied to the merged data sets.

Vonderhaar, T. H.↗
NASA NTRS2009

Development of a Compact, Pulsed, 2-Micron, Coherent-Detection, Doppler Wind Lidar Transceiver; and Plans for Flights on NASA's DC-8 and WB-57 Aircraft

We present results of a recently completed effort to design, fabricate, and demonstrate a compact lidar transceiver for coherent-detection lidar profiling of winds. The novel high-energy, 2-micron, Ho:Tm:LuLiF laser technology developed at NASA Langley was employed to permit study of the laser technology currently envisioned by NASA for global coherent Doppler lidar measurement of winds in the future. The 250 mJ, 10 Hz compact transceiver was also designed for future aircraft flight. Ground-based wind profiles made with this transceiver will be presented. NASA Langley is currently funded to build complete Doppler lidar systems using this transceiver for the DC-8 and WB-57 aircraft. The WB-57 flights will present a more severe environment and will require autonomous operation of the lidar system. The DC-8 lidar system is a likely component of future NASA hurricane research. It will include real-time data processing and display, as well as full data archiving. We will attempt to co-fly on both aircraft with a direct-detection Doppler wind lidar system being prepared by NASA Goddard Space Flight Center.

Kavaya, Michael J.↗
NASA NTRS2012

Coordinated STEM/FIB/NanoSIMS Analyses of Presolar Silicates in Comet Dust and Primitive Meteorites

Silicate grains were among the most abundant mineralogical building blocks of our Solar System. These grains were the detritus from earlier generations of stars that have been recycled in the early solar nebula. Rare sub-micrometer survivors of this processing have been identified in meteorites, micrometeorites and interplanetary dust particles (IDPs). These silicate grains are recognized as presolar in origin because of their extremely anomalous isotopic compositions that reflect nucleosynthetic processes in their stellar sources (evolved stars, novae and supernovae). We perform coordinated chemical, mineralogical and isotopic studies of these grains to determine their origins and histories. We examine the complex mineralogy and petrography of presolar silicates using imaging, diffraction and chemical data obtained from thin sections with the JSC JEOL 2500 field-emission STEM equipped with a Noran thin window energy dispersive x-ray (EDX) spectrometer and a Gatan Tridiem GIF. Quantitative element x-ray maps (spectrum images) are acquired by rastering a 4 nm incident probe whose dwell time is minimized to avoid beam damage and element diffusion during mapping. Successive image layers are acquired and combined in order to achieve approx 1% counting statistics for major elements. The IDP samples are prepared by ultramicrotomy of particles embedded in epoxy or elemental sulfur. After EDX mapping, the sections are subjected to C, N, and O isotopic imaging with the JSC NanoSIMS 50L ion microprobe. We prepare sections of some meteorite grains using the JSC FEI Quanta 3D focused ion beam (FIB) instrument. The specimen surface is protected from the FIB milling process by layers of electron beam-deposited C and Pt followed by an ion-deposited Pt layer. We also use the FIB to preferentially remove surrounding grains to reduce the background in subsequent NanoSIMS measurements. For mineralogical studies, we again employ the FIB instrument to deposit a protective cap over the grain of interest and then extract the grain and thin it to electron transparency for TEM analysis.

Keller, Lindsay↗
NASA NTRS2002

Containerless Ripple Turbulence

One of the longest standing unsolved problems in physics relates to the behavior of fluids that are driven far from equilibrium such as occurs when they become turbulent due to fast flow through a grid or tidal motions. In turbulent flows the distribution of vortex energy as a function of the inverse length scale [or wavenumber 'k'] of motion is proportional to 1/k(sup 5/3) which is the celebrated law of Kolmogorov. Although this law gives a good description of the average motion, fluctuations around the average are huge. This stands in contrast with thermally activated motion where large fluctuations around thermal equilibrium are highly unfavorable. The problem of turbulence is the problem of understanding why large fluctuations are so prevalent which is also called the problem of 'intermittency'. Turbulence is a remarkable problem in that its solution sits simultaneously at the forefront of physics, mathematics, engineering and computer science. A recent conference [March 2002] on 'Statistical Hydrodynamics' organized by the Los Alamos Laboratory Center for Nonlinear Studies brought together researchers in all of these fields. Although turbulence is generally thought to be described by the Navier-Stokes Equations of fluid mechanics the solution as well as its existence has eluded researchers for over 100 years. In fact proof of the existence of such a solution qualifies for a 1 M$ millennium prize. As part of our NASA funded research we have proposed building a bridge between vortex turbulence and wave turbulence. The latter occurs when high amplitude waves of various wavelengths are allowed to mutually interact in a fluid. In particular we have proposed measuring the interaction of ripples [capillary waves] that run around on the surface of a fluid sphere suspended in a microgravity environment. The problem of ripple turbulence poses similar mathematical challenges to the problem of vortex turbulence. The waves can have a high amplitude and a strong nonlinear interaction. Furthermore, the steady state distribution of energy again follows a Kolmogorov scaling law; in this case the ripple energy is distributed according to 1/k (sup 7/4). Again, in parallel with vortex turbulence ripple turbulence exhibits intermittency. The problem of ripple turbulence presents an experimental opportunity to generate data in a controlled, benchmarked system. In particular the surface of a sphere is an ideal environment to study ripple turbulence. Waves run around the sphere and interact with each other, and the effect of walls is eliminated. In microgravity this state can be realized for over 2 decades of frequency. Wave turbulence is a physically relevant problem in its own right. It has been studied on the surface of liquid hydrogen and its application to Alfven waves in space is a source of debate. Of course, application of wave turbulence perspectives to ocean waves has been a major success. The experiment which we plan to run in microgravity is conceptually straightforward. Ripples are excited on the surface of a spherical drop of fluid and then their amplitude is recorded with appropriate photography. A key challenge is posed by the need to stably position a 10cm diameter sphere of water in microgravity. Two methods are being developed. Orbitec is using controlled puffs of air from at least 6 independent directions to provided the positioning force. This approach has actually succeeded to position and stabilize a 4cm sphere during a KC 135 segment. Guigne International is using the radiation pressure of high frequency sound. These transducers have been organized into a device in the shape of a dodecahedron. This apparatus 'SPACE DRUMS' has already been approved for use for combustion synthesis experiments on the International Space Station. A key opportunity presented by the ripple turbulence data is its use in driving the development of codes to simulate its properties.

Putterman, Seth↗
NASA NTRS2008

Satellite-based Assessment of Fire Impacts on Ecosystem Changes in West Africa

Fires bum many vegetated regions of the world to a variety of degrees and frequency depending on season. Extensive biomass burning occurs in most parts of sub-Saharan Africa, posing great threat to ecosystem stability among other real and potential adverse impacts. In Africa, such landscape-scale fires are used for various agricultural purposes, including land clearing and hunting, although there may be a limited number of cases of fires ignited by accident or due to arson. Satellite remote sensing provides the most practical means of mapping fires, because of their sudden and aggressive nature coupled with the tremendous heat they generate. Recent advancements in satellite technology has enabled, not only the identification of fire locations, but also the measurement of fire radiative energy (FRE) release rate or power (FRP), which has been found to have a direct linear relationship with the rate of biomass combustion. A recent study based on FRP measurements from the Moderate-resolution imaging Spectro-radiometer (MODIS) sensor aboard the Terra and Aqua satellites revealed that, among all the regions of the world where fires occur, African regions rank the highest in the intensity of biomass burning per unit area of land during the peak of the burning season. In this study, we will analyze the burning patterns in West Africa during the last several years and examine the extent of their impacts on the ecosystem dynamics, using a variety of satellite data. The study introduces a unique methodology that can be used to build up the knowledge base from which decision makers can obtain scientific information in fomulating policies for regulating biomass burning in the region.

Ichoku, Charles↗
NASA NTRSDate not supplied

Metal Additive Manufacturing Process Selection and Development Lifecycle for Propulsion Components

Metal additive manufacturing (AM) is a generic term that captures a variety of fabrication processes. Each of these manufacturing process has unique advantages and challenges for use in aerospace propulsion applications. The most commonly used AM processes include Powder Bed Fusion (PBF), Directed Energy Deposition (DED), and solid-state processes as in Cold Spray, Ultrasonic Additive Manufacturing, and Additive Friction Stir Deposition. While detailed research has been conducted among many of the AM processes to mature processing parameters and material properties, navigating which processes are best to select is difficult as it is based on specific component requirements. The focus of this presentation is to provide an overview of considerations for each of metal AM process selection for aerospace components based on various key attributes. These key attributes include geometric considerations, metallurgical characteristics, cost basis, post-processing and maturity of the processes. The data for these trade selections are based on studies that NASA as performed internally and with academic and industry partners. These studies include multiple AM build experiments to evaluate (1) geometric variations and constraints within the processes, (2) alloy characterization and mechanical testing, (3) pathfinder component development and hot-fire evaluations, and (4) certification approaches. This presentation summarizes these results and is meant to introduce specific examples which show what to consider when designing a metal AM component for aerospace propulsion applications.

Paul Gradl↗
NASA NTRS1991

Ignition transient analysis of solid rocket motor

Measurement data on the performance of Space Shuttle Solid Rocket Motor show wide variations in the head-end pressure changes and the total thrust build-up during the ignition transient periods. To analyze the flow and thermal behavior in the tested solid rocket motors, a 1-dimensional, ideal gas flow model via the SIMPLE algorithm was developed. Numerical results showed that burning patterns in the star-shaped head-end segment of the propellant and the erosive burning rate are two important factors controlling the ignition transients. The objective of this study is to extend the model to include the effects of aluminum particle commonly used in solid propellants. To treat the effects of aluminum-oxide particles in the combustion gas, conservation of mass, momentum, and energy equations for the particles are added in the numerical formulation and integrated by an inter-phase-slip algorithm.

Han, Samuel S.↗
NASA NTRS2001

Remote Sensing of Atlanta's Urban Sprawl and the Distribution of Land Cover and Surface Temperatures

Between 1973 and 1992, an average of 20 ha of forest was lost each day to urban expansion of Atlanta, Georgia. Urban surfaces have very different thermal properties than natural surfaces-storing solar energy throughout the day and continuing to release it as sensible heat well after sunset. The resulting heat island effect serves as catalysts for chemical reactions from vehicular exhaust and industrialization leading to a deterioration in air quality. In this study, high spatial resolution multispectral remote sensing data has been used to characterize the type, thermal properties, and distribution of land surface materials throughout the Atlanta metropolitan area. Ten-meter data were acquired with the Advanced Thermal and Land Applications Sensor (ATLAS) on May 11 and 12, 1997. ATLAS is a 15-channel multispectral scanner that incorporates the Landsat TM bands with additional bands in the middle reflective infrared and thermal infrared range. The high spatial resolution permitted discrimination of discrete surface types (e.g., concrete, asphalt), individual structures (e.g., buildings, houses) and their associated thermal characteristics. There is a strong temperature contrast between vegetation and anthropomorphic features. Vegetation has a modal temperature at about 20 C, whereas asphalt shingles, pavement, and buildings have a modal temperature of about 39 C. Broad-leaf vegetation classes are indistinguishable on a thermal basis alone. There is slightly more variability (plus or minus 5 C) among the urban surfaces. Grasses, mixed vegetation and mixed urban surfaces are intermediate in temperature and are characterized by broader temperature distributions with modes of about 29 C. Thermal maps serve as a basis for understanding the distribution of "hotspots", i.e., how landscape features and urban fabric contribute the most heat to the lower atmosphere.

Laymon, Charles A.↗
NASA NTRS2001

Remote Sensing of Atlanta's Urban Sprawl and the Distribution of Land Cover and Surface Temperature

Between 1973 and 1992, an average of 20 ha of forest was lost each day to urban expansion of Atlanta, Georgia. Urban surfaces have very different thermal properties than natural surfaces-storing solar energy throughout the day and continuing to release it as sensible heat well after sunset. The resulting heat island effect serves as catalysts for chemical reactions from vehicular exhaust and industrialization leading to a deterioration in air quality. In this study, high spatial resolution multispectral remote sensing data has been used to characterize the type, thermal properties, and distribution of land surface materials throughout the Atlanta metropolitan area. Ten-meter data were acquired with the Advanced Thermal and Land Applications Sensor (ATLAS) on May 11 and 12, 1997. ATLAS is a 15-channel multispectral scanner that incorporates the Landsat TM bands with additional bands in the middle reflective infrared and thermal infrared range. The high spatial resolution permitted discrimination of discrete surface types (e.g., concrete, asphalt), individual structures (e.g., buildings, houses) and their associated thermal characteristics. There is a strong temperature contrast between vegetation and anthropomorphic features. Vegetation has a modal temperature at about 20 C, whereas asphalt shingles, pavement, and buildings have a modal temperature of about 39 C. Broad-leaf vegetation classes are indistinguishable on a thermal basis alone. There is slightly more variability (+/-5 C) among the urban surfaces. Grasses, mixed vegetation and mixed urban surfaces are intermediate in temperature and are characterized by broader temperature distributions with modes of about 29 C. Thermal maps serve as a basis for understanding the distribution of "hotspots", i.e., how landscape features and urban fabric contribute the most heat to the lower atmosphere.

Laymon, Charles A.↗
NASA NTRS1980

Solar heating and hot water system installed at Saint Louis, Missouri

The solar heating and hot water system installed at the William Tao & Associates, Inc., office building in St. Louis, Missouri is described, including maintenance and construction problems, final drawings, system requirements, and manufacturer's component data. The solar system was designed to provide 50 percent of the hot water requirements and 45 percent of the space heating needs for a 900 sq ft office space and drafting room. The solar facility has 252 sq ft of glass tube concentrator collectors and a 1000 gallon steel storage tank buried below a concrete slab floor. Freeze protection is provided by a propylene glycol/water mixture in the collector loop. The collectors are roof mounted on a variable tilt array which is adjusted seasonally and is connected to the solar thermal storage tank by a tube-in-shell heat exchanger. Incoming city water is preheated through the solar energy thermal storage tank.

Source record↗
NASA NTRS2022

The Lithophile Element Budget of Earth’s Core

The relative composition of Earth’s core and mantle were set during core formation. By determining how elements partition between metal and silicate at high pressures and temperatures, measurements of the mantle composition and geophysical observations of the core can be used to understand the mechanisms by which Earth formed. Here we present the results of metal–silicate partitioning experiments for a range of nominally lithophile elements (Al, Ca, K, Mg, O, S, Si, Th, U) and S to 85 GPa and up to 5400 K. With our results and a compilation of literature data, we developed a parameterization for partitioning that accounts for compositional dependencies in both the metal and silicate phases. Using this parameterization in a range of planetary growth models, we find that, in general, lithophile element partitioning into the metallic phase is enhanced at high temperatures. The relative abundances of FeO, SiO2 and MgO in the mantle vary significantly between planetary growth models, and the mantle abundances of these elements can be used to provide important constraints on Earth’s accretion. To match Earth’s core mass and mantle composition, Earth’s building blocks must have been enriched in Fe and depleted in Si compared with CI chondrites. Finally, too little Mg, Si and O are partitioned into the core for precipitation of oxides to be a major source of energy for the geodynamo. In contrast, several ppb of U can be partitioned into the core at high temperatures, and this energy source must be accounted for in thermal evolution models.

dynamo↗
NASA NTRS2025

Airports as Energy Nodes Activity Summary

Advanced aircraft concepts that use non-traditional aviation energy storage methods such as batteries or cryogenic hydrogen are in development and expected to enter regular service at airports worldwide within the next decade. The energy needs for these aircraft may quickly overwhelm the existing energy infrastructure at airports, particularly at smaller and more remote facilities. Without energy upgrades, these airports will not be able to host these advanced vehicles, but without the advanced vehicle traffic, these airports will not have the rationale or funding to build up their energy infrastructure. The Airports as Energy Nodes (ÆNodes) activity, a collaboration between the National Aeronautics and Space Administration (NASA) and the National Renewable Energy Laboratory (NREL), was executed to understand and model the energy needs that advanced aircraft concepts may levy on these smaller airports, determine cost-effective approaches to enhance the airport energy infrastructure, and demonstrate the enhanced resilience of these energy infrastructure upgrades to the airport and surrounding community via “digital twin” simulation at relevant energy and dynamic time scales. The ÆNodes team also investigated future reference aircraft designs and materials to enable cryogenic hydrogen storage for aircraft. The ÆNodes team conducted analysis at two U.S. airport partner sites — Winchester Regional Airport in Winchester, Virginia, and Tweed/New Haven Airport in New Haven, Connecticut. The goal of this partnership was to develop data and reference infrastructure designs that could accommodate advanced aircraft in the future at these airports while also enhancing the resiliency of the energy supply to the surrounding airport community, which could be used to capture funding to enable the infrastructure upgrades. Over the course of the study, a method was developed to estimate air traffic requiring advanced energy services over the course of a year using a mix of historical data and companion studies on advanced aircraft transportation networks. The study has concluded at NASA but continues at NREL, who will develop a final report discussing the energy infrastructure upgrades and digital twin results. Preliminary results indicate that unrestricted adoption of advanced battery-electric aircraft may double traffic at these airports and increase peak daily power usage by an order of magnitude, while increase electricity energy needs by a factor of two to four. The infrastructure upgrades necessary to accommodate these increased energy needs could be used to provide enhanced energy services to the airport community to offset the cost and increase the utility of the upgrades, which will be described in the NREL final report.

Airports↗
NASA NTRS1980

Active nutation controller

An apparatus is described for controlling nutation motion in a spinning body, comprised of an angular accelerometer with its input axis perpendicular to the spin axis of the body, a flywheel with an axis of rotation perpendicular to the axis of the accelerometer and to the spin axis of the body, and a motor for driving the flywheel to attenuate or build nutation. The motor is controlled by circuitry that monitors the output of the angular accelerometer and drives the motor clockwise or counterclockwise during predetermined nutation angles synchronized to the zero crossover points of the accelerometer signal centered about the nutation peaks. The motor drive is phased to damp nutation motion to zero for stabilization. To increase the noise immunity of the system, when the output of the accelerometer falls below a threshold level, the circuitry operates in an open loop, beat mode where data representing the last accelerometer signal that exceeded that threshold level is stored, and the motor drive is controlled by the stored data. In a second version, the motor is controlled to supply a predetermined amount of nutation motion to a body undergoing testing on a spin table for energy dissipation evaluation. In each version, the use of an angular accelerometer rather than a linear accelerometer or gyro to monitor nutation enables placement of the nutation control apparatus at any location relative to the spin axis of the body requiring only crude orientation and no calibration.

Hoffman, H. C.↗
NASA NTRS2016

Study of Material Densification of In718 in the Higher Throughput Parameter Regime

Selective Laser Melting (SLM) is a powder bed fusion additive manufacturing process used increasingly in the aerospace industry to reduce the cost, weight, and fabrication time for complex propulsion components. Previous optimization studies for SLM using the Concept Laser M1 and M2 machines at NASA Marshall Space Flight Center have centered on machine default parameters. The objective of this project is to characterize how heat treatment affects density and porosity from a microscopic point of view. This is performs using higher throughput parameters (a previously unexplored region of the manufacturing operating envelope for this application) on material consolidation. Density blocks were analyzed to explore the relationship between build parameters (laser power, scan speed, and hatch spacing) and material consolidation (assessed in terms of density and porosity). The study also considers the impact of post-processing, specifically hot isostatic pressing and heat treatment, as well as deposition pattern on material consolidation in the higher energy parameter regime. Metallurgical evaluation of specimens will also be presented. This work will contribute to creating a knowledge base (understanding material behavior in all ranges of the AM equipment operating envelope) that is critical to transitioning AM from the custom low rate production sphere it currently occupies to the world of mass high rate production, where parts are fabricated at a rapid rate with confidence that they will meet or exceed all stringent functional requirements for spaceflight hardware. These studies will also provide important data on the sensitivity of material consolidation to process parameters that will inform the design and development of future flight articles using SLM.

Cordner, Samuel↗
NASA NTRS1997

Effects of FU Orionis Outbursts on Protoplanetary Disks

In the early stages of work under this grant, we developed simulations to match the light curves of the three best studied systems: FU Ori, V1515 Cyg, & V1057 Cyg (Bell et al. 1995). We compared the details of model results to observations to test the validity of the thermal ionization instability model for outburst. In this paper, we were able to answer several of the key objections to the accretion disk outburst model for the FU Orionis phenomenon (eg. Herbig 1989). The declines in line width and reddening observed in V1057 Cyg following peak light had been used as arguments against the disk instability model. We showed these effects to be natural consequences of the slow outward progression and limited radial excursion of the ionization front during outburst. By the end of the grant period, we had begun combining the inner and outer disk models to derive the radiation expected in the planet forming region of the disk. A crucial step in this was the development of a radiative transfer model of the complete inner and outer disk system (Turner, Bodenheimer, & Bell 1997). In this work, wavelength dependent opacities were used to synthesize images and spectral energy distributions of FU Ori objects. New detailed opacities provided by Alexander (1995) allowed the resolution of coarse features such as silicate emission lines. Data for the fits were taken from the time dependent simulations in Bell et al. (1995) to which was added the effect of disk to disk or "self"-reprocessing which accounts for the illumination of the outer disk by the inner disk (Bell 1998). Through the course of work on this grant we have made considerable progress in computing detailed models of both the active outburst region of the disk and the outer quiescent disk. We have begun an investigation into the effects of a cocooning envelope. Direct comparisons with observations lend confidence that the basic underlying assumptions of the outburst model are reasonable. We are now ready to build upon these results to investigate the effects of outbursts on the central star and on the accumulation of small particles in the planet-forming regions.

Bodenheimer, Peter↗