NASA's space platform technology program and planning

As part of the Civil Space Technology Initiative, NASA has established a space platform technology program which encompasses two ongoing programs as well as active planning for new platform initiatives in such areas as advanced heat rejection technologies, advanced space suits, advanced life support, and better support equipment (refrigerators, furnaces, etc.). Platform technology is extremely important because it provides both the basis for future missions and enhanced national competitiveness in space

Thermographic Qualification of Graphite/Epoxy Instrumentation Racks

A nondestructive evaluation method is desired for ensuring the 'as manufactured' and 'post service' quality of graphite/epoxy instrumentation rack shells. The damage tolerance and geometry of the racks dictate that the evaluation method be capable of identifying defects, as small as 0.25 inch 2 in area, over large acreage regions, tight compound radii and thickness transition zones. The primary defects of interest include voids, inclusions, delaminations and porosity. The potential for an infrared thermographic inspection to replace ultrasonic testing, for qualifying the racks as 'defect free' is under investigation. The inspection process is validated by evaluating defect standard panels built to the same specifications as the racks, except for the insertion of artificial fabricated defects. The artificial defects are designed to match those which are most prevalent in the actual instrumentation racks. A target defect area of 0.0625 inch 2 (a square with 0.25 inch on a side) was chosen for the defect standard panels to ensure the ability to find all defects of the critical (0.25 inch squared) size

Symmetric Equations on the Surface of a Sphere as Used by Model GISS:IB

Standard vector calculus formulas of Cartesian three space are projected onto the surface of a sphere. This produces symmetric equations with three nonindependent horizontal velocity components. Each orthogonal axis has a velocity component that rotates around its axis (eastward velocity rotates around the northsouth axis) and a specific angular momentum component that is the product of the velocity component multiplied by the cosine of axis latitude. Angular momentum components align with the fixed axes and simplify several formulas, whereas the rotating velocity components are not orthogonal and vary with location. Three symmetric coordinates allow vector resolution and calculus operations continuously over the whole spherical surface, which is not possible with only two coordinates. The symmetric equations are applied to one-layer shallow water models on cubed-sphere and icosahedral grids, the latter being computationally simple and applicable to an ocean domain. Model results are presented for three different initial conditions and five different resolutions

Small‐scale nutrient patchiness: Some consequences and a new encounter mechanism

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109816/1/lno19842940785.pd

Summary of data concerning radiological contamination at well PM-2, Nevada Test Site, Nye County, Nevada

Analysis of water from well Pahute Mesa No. 2 (PM-2), on Pahute Mesa in the extreme northwestern part of the Nevada Test Site, indicated tritium concentrations above background levels in August 1993. A coordinated investigation of the tritium occurrence in well PM-2 was undertaken by the Hydrologic Resources Management Program of the US Department of Energy. Geologic and hydrologic properties of the hydrogeologic units were characterized using existing information. Soil around the well and water quality in the well were characterized during the investigation. The purpose of this report is to present existing information and results from a coordinated investigation of tritium occurrence. The objectives of the overall investigation include: (1) determination of the type and concentration of contamination; (2) identification of the source and mechanism of contamination; (3) estimation of the extent of radiological contamination; (4) initiation of appropriate monitoring of the contamination; and (5) reporting of investigation results. Compiled and tabulated data of the area are presented. The report also includes characterization of geology, soil, hydrology, and water quality data

A Neural Network/Acoustic Emission Analysis of Impact Damaged Graphite/Epoxy Pressure Vessels

Acoustic emission (AE) signal analysis has been used to measure the effects of impact damage on burst pressure in 5.75 inch diameter, inert propellant filled, filament wound pressure vessels. The AE data were collected from fifteen graphite/epoxy pressure vessels featuring five damage states and three resin systems. A burst pressure prediction model was developed by correlating the AE amplitude (frequency) distribution, generated during the first pressure ramp to 800 psig (approximately 25% of the average expected burst pressure for an undamaged vessel) to known burst pressures using a four layered back propagation neural network. The neural network, trained on three vessels from each resin system, was able to predict burst pressures with a worst case error of 5.7% for the entire fifteen bottle set

Future Climate Change under SSP Emission Scenarios with GISS-E2.1

Abstract This paper presents the response to anthropogenic forcing in the GISS-E2.1 climate models for the 21st century Shared Socioeconomic Pathways (SSPs) emission scenarios within the Coupled Model Intercomparison Project phase 6 (CMIP6). The experiments were performed using an updated and improved version of the NASA Goddard Institute for Space Studies (GISS) coupled general circulation model that includes two different versions for atmospheric composition: a non-interactive version (NINT) with prescribed composition and a tuned aerosol indirect effect (AIE) and the One-Moment Aerosol model (OMA) version with fully interactive aerosols which includes a parameterized first indirect aerosol effect on clouds. The effective climate sensitivities are 3.0ºC and 2.9ºC for the NINT and OMA models, respectively. Each atmospheric version is coupled to two different ocean general circulation models: the GISS ocean model (E2.1-G) and HYCOM (E2.1-H). We describe the global mean responses for all future scenarios and spatial patterns of change for surface air temperature and precipitation for four of the marker scenarios: SSP1-2.6, SSP2-4.5, SSP4-6.0, and SSP5-8.5. By 2100, global mean warming ranges from 1.5ºC to 5.2ºC relative to 1850-1880 mean temperature. Two high-mitigation scenarios SSP1-1.9 and SSP1-2.6 limit the surface warming to below 2°C by the end of the 21st century, except for the NINT E2.1-H model that simulates 2.2°C of surface warming. For the high emission scenario SSP5-8.5, the range is 4.6-5.2ºC at 2100. Due to about 15\% larger effective climate sensitivity (ECS) and stronger transient climate response (TCR) in both NINT and OMA CMIP6 models compared to CMIP5 versions, there is a stronger warming by 2100 in the SSP emission scenarios than in the comparable RCP scenarios in CMIP5. Changes in sea ice area are highly correlated to global mean surface air temperature anomalies and show steep declines in both hemispheres, with the largest sea ice area decreases occurring during September in the Northern Hemisphere in both E2.1-G (-1.21×106 km2/°C) and E2.1-H models (-0.94×106 km2/°C). Both coupled models project decreases in the Atlantic overturning stream function by 2100. The largest decrease of 56-65\% in the 21st century overturning stream function is produced in the warmest scenario SSP5-8.5 in the E2.1-G model, comparable to the reduction in the corresponding CMIP5 GISS-E2 RCP8.5 simulation. Both low-end scenarios SSP1-1.9 and SSP1-2.6 also simulate substantial reductions of the overturning (9-37\%) with slow recovery of about 10\% by the end of the 21st century (relative to the maximum decrease at the middle of the 21st century)Development of GISS-E2.1 was supported by the NASA Modeling, Analysis, and Prediction (MAP) Program. CMIP6 simulations with GISS-E2.1 were made possible by the NASA High-End Computing (HEC) Program through the NASA Center for Climate Simulation (NCCS) at Goddard Space Flight Center. We thank Ellen Salmon and the NCCS staff for hosting and providing convenient access to the model output. CMIP6 standard variables analyzed in this study are available through the Earth System Grid Federation and from https://portal.nccs.nasa.gov/datashare/giss_cmip6.Peer Reviewed"Article signat per 46 autors/es: Larissa S. Nazarenko, Nick Tausnev, Gary L. Russell, David Rind, Ron L. Miller, Gavin A. Schmidt, Susanne E. Bauer, Maxwell Kelley, Reto Ruedy, Andrew S. Ackerman, Igor Aleinov, Michael Bauer, Rainer Bleck, Vittorio Canuto, Grégory Cesana, Ye Cheng, Thomas L. Clune, Ben I. Cook, Carlos A. Cruz, Anthony D. Del Genio, Gregory S. Elsaesser, Greg Faluvegi, Nancy Y. Kiang, Daehyun Kim, Andrew A. Lacis, Anthony Leboissetier, Allegra N. LeGrande, Ken K. Lo, John Marshall, Elaine E. Matthews, Sonali McDermid, Keren Mezuman, Lee T. Murray, Valdar Oinas, Clara Orbe, Carlos Pérez García-Pando, Jan P. Perlwitz, Michael J. Puma, Anastasia Romanou, Drew T. Shindell, Shan Sun, Kostas Tsigaridis, George Tselioudis, Ensheng Weng, Jingbo Wu, Mao-Sung Yao "Postprint (author's final draft

A General Circulation Model Study of Atmospheric Carbon Monoxide

The carbon monoxide cycle is studied by incorporating the known and hypothetical sources and sinks in a tracer model that uses the winds generated by a general circulation model. Photochemical production and loss terms, which depend on OH radical concentrations, are calculated in an interactive fashion. The computed global distribution and seasonal variations of CO are compared with observations to obtain constraints on the distribution and magnitude of the sources and sinks of CO, and on the tropospheric abundance of OH. The simplest model that accounts for available observations requires a low latitude plant source of about 1.3×10^(15) g yr^(−1), in addition to sources from incomplete combustion of fossil fuels and oxidation of methane. The globally averaged OH concentration calculated in the model is 7×10^5 cm^(−3). Models that calculate globally averaged OH concentrations much lower than our nominal value are not consistent with the observed variability of CO. Such models are also inconsistent with measurements of CO isotopic abundances, which imply the existence of plant sources

Fast Atmosphere-Ocean Model Runs with Large Changes in CO2

How does climate sensitivity vary with the magnitude of climate forcing? This question was investigated with the use of a modified coupled atmosphere-ocean model, whose stability was improved so that the model would accommodate large radiative forcings yet be fast enough to reach rapid equilibrium. Experiments were performed in which atmospheric CO2 was multiplied by powers of 2, from 1/64 to 256 times the 1950 value. From 8 to 32 times, the 1950 CO2, climate sensitivity for doubling CO2 reaches 8 C due to increases in water vapor absorption and cloud top height and to reductions in low level cloud cover. As CO2 amount increases further, sensitivity drops as cloud cover and planetary albedo stabilize. No water vapor-induced runaway greenhouse caused by increased CO2 was found for the range of CO2 examined. With CO2 at or below 1/8 of the 1950 value, runaway sea ice does occur as the planet cascades to a snowball Earth climate with fully ice covered oceans and global mean surface temperatures near 30 C