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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Beta-Adrenergic Blockade Does not Prevent Polycythemia or Decrease in Plasma Volume in Men at 4300 m Altitude

When humans ascend to high altitude (ALT) their plasma volume (PV) and total blood volume (BV) decrease during the first few days. With continued residence over several weeks, the hypoxia-induced stimulation of erythropoietin increases red cell production which tends to restore BV. Because hypoxia also activates the beta-adrenergic system, which stimulates red blood cell production, we investigated the effect of adrenergic beta-receptor inhibition with propranolol on fluid volumes and the polycythemic response in 11 healthy unacclimatized men (21-33 years old exposed to an ALT of 4300 m (barometric pressure 460 Torr) for 3 weeks on Pikes Peak, Colorado. PV was determined by the Evans blue dye method (PV(sub EB)), BV by the carbon monoxide method (BV(sub CO)), red cell volume (RCV)was calculated from hematocrit (Hct) and BV(sub CO), and serum erythropoietin concentration ([EPO]) and reticulocyte count, were also determined. All determinations were made at sea level and after 9-11 (ALT-10) and 9-20 (ALT-20) days at ALT. At sea level and ALT, six men received propranolol (pro, 240 mg/day), and five received a placebo (pla). Effective beta-blockade did not modify the mean (SE) maximal values of [EPO] [pla: 24.9 (3.5) vs pro: 24.5 (1.5) mU/ml] or reticulocyte count [pla: 2.7 (0.7) vs pro: 2.2 (0.5)%]; nor changes in PV(sub EB)[pla: -15.8 (3.8) vs pro: -19.9 (2.8)%], RCV(sub CO) [pla: +7.0 (6.7) vs pro: +10.1 (6.1)%], or BV(sub CO) [pla: -7.3 (2.3) vs pro: -7.1 (3.9)%]. In the absence of weight loss, a redistribution of body water with no net loss is implied. Hence, activation of the beta-adrenergic system did not appear to affect the hypovolemic or polycythemic responses that occurred during 3 weeks at 4300 m ALT in these subjects.

Grover, R. F.↗
NASA NTRS2002

Spectral (Finite) Volume Method for Conservation Laws on Unstructured Grids II: Extension to Two Dimensional Scalar Equation

The framework for constructing a high-order, conservative Spectral (Finite) Volume (SV) method is presented for two-dimensional scalar hyperbolic conservation laws on unstructured triangular grids. Each triangular grid cell forms a spectral volume (SV), and the SV is further subdivided into polygonal control volumes (CVs) to supported high-order data reconstructions. Cell-averaged solutions from these CVs are used to reconstruct a high order polynomial approximation in the SV. Each CV is then updated independently with a Godunov-type finite volume method and a high-order Runge-Kutta time integration scheme. A universal reconstruction is obtained by partitioning all SVs in a geometrically similar manner. The convergence of the SV method is shown to depend on how a SV is partitioned. A criterion based on the Lebesgue constant has been developed and used successfully to determine the quality of various partitions. Symmetric, stable, and convergent linear, quadratic, and cubic SVs have been obtained, and many different types of partitions have been evaluated. The SV method is tested for both linear and non-linear model problems with and without discontinuities.

Wang, Z. J.↗
NASA NTRS2003

Finite Volume Methods: Foundation and Analysis

Finite volume methods are a class of discretization schemes that have proven highly successful in approximating the solution of a wide variety of conservation law systems. They are extensively used in fluid mechanics, porous media flow, meteorology, electromagnetics, models of biological processes, semi-conductor device simulation and many other engineering areas governed by conservative systems that can be written in integral control volume form. This article reviews elements of the foundation and analysis of modern finite volume methods. The primary advantages of these methods are numerical robustness through the obtention of discrete maximum (minimum) principles, applicability on very general unstructured meshes, and the intrinsic local conservation properties of the resulting schemes. Throughout this article, specific attention is given to scalar nonlinear hyperbolic conservation laws and the development of high order accurate schemes for discretizing them. A key tool in the design and analysis of finite volume schemes suitable for non-oscillatory discontinuity capturing is discrete maximum principle analysis. A number of building blocks used in the development of numerical schemes possessing local discrete maximum principles are reviewed in one and several space dimensions, e.g. monotone fluxes, E-fluxes, TVD discretization, non-oscillatory reconstruction, slope limiters, positive coefficient schemes, etc. When available, theoretical results concerning a priori and a posteriori error estimates are given. Further advanced topics are then considered such as high order time integration, discretization of diffusion terms and the extension to systems of nonlinear conservation laws.

Barth, Timothy↗
NASA NTRS2003

Columbia Accident Investigation Board Report. Volume Two

Volume II of the Report contains appendices that were cited in Volume I. The Columbia Accident Investigation Board produced many of these appendices as working papers during the investigation into the February 1, 2003 destruction of the Space Shuttle Columbia. Other appendices were produced by other organizations (mainly NASA) in support of the Board investigation. In the case of documents that have been published by others, they are included here in the interest of establishing a complete record, but often at less than full page size. Contents include: CAIB Technical Documents Cited in the Report: Reader's Guide to Volume II; Appendix D. a Supplement to the Report; Appendix D.b Corrections to Volume I of the Report; Appendix D.1 STS-107 Training Investigation; Appendix D.2 Payload Operations Checklist 3; Appendix D.3 Fault Tree Closure Summary; Appendix D.4 Fault Tree Elements - Not Closed; Appendix D.5 Space Weather Conditions; Appendix D.6 Payload and Payload Integration; Appendix D.7 Working Scenario; Appendix D.8 Debris Transport Analysis; Appendix D.9 Data Review and Timeline Reconstruction Report; Appendix D.10 Debris Recovery; Appendix D.11 STS-107 Columbia Reconstruction Report; Appendix D.12 Impact Modeling; Appendix D.13 STS-107 In-Flight Options Assessment; Appendix D.14 Orbiter Major Modification (OMM) Review; Appendix D.15 Maintenance, Material, and Management Inputs; Appendix D.16 Public Safety Analysis; Appendix D.17 MER Manager's Tiger Team Checklist; Appendix D.18 Past Reports Review; Appendix D.19 Qualification and Interpretation of Sensor Data from STS-107; Appendix D.20 Bolt Catcher Debris Analysis.

CAIB (COLUMBIA ACCIDENT INVESTIGATION BOARD)↗
NASA NTRS2003

SeaWiFS Postlaunch Technical Report Series Cumulative Index: Volumes 1-23

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is the follow-on ocean color instrument to the Coastal Zone Color Scanner (CZCS), which ceased operations in 1986, after an eight-year mission. SeaWiFS was launched on 1 August 1997, onboard the OrbView-2 satellite, built by Orbital Sciences Corporation (OSC). The SeaWiFS Project at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), undertook the responsibility of documenting all aspects of this mission, which is critical to the ocean color and marine science communities. The start of this documentation was titled the SeaWiFS Technical Report Series, which ended after 43 volumes were published. A follow-on series was started, titled the Sea WiFS Postlaunch Technical Report Series. This particular volume of the so-called Postlaunch Series serves as a reference, or guidebook, to the previous 23 volumes and consists of 4 sections including an errata, an index to key words and phrases, a list of acronyms used, and a list of all references cited. The editors will publish a cumulative index of this type after every five volumes.

Hooker, Stanford B.↗
NASA NTRS2003

Three-dimensional visual guidance improves the accuracy of calculating right ventricular volume with two-dimensional echocardiography

Three-dimensional guidance programs have been shown to increase the reproducibility of 2-dimensional (2D) left ventricular volume calculations, but these systems have not been tested in 2D measurements of the right ventricle. Using magnetic fields to identify the probe location, we developed a new 3-dimensional guidance system that displays the line of intersection, the plane of intersection, and the numeric angle of intersection between the current image plane and previously saved scout views. When used by both an experienced and an inexperienced sonographer, this guidance system increases the accuracy of the 2D right ventricular volume measurements using a monoplane pyramidal model. Furthermore, a reconstruction of the right ventricle, with a computed volume similar to the calculated 2D volume, can be displayed quickly by tracing a few anatomic structures on 2D scans.

Non-NASA Center↗
NASA NTRS2004

Volume and Mass Estimation of Three-Phase High Power Transformers for Space Applications

Spacecraft historically have had sub-1kW(sub e), electrical requirements for GN&C, science, and communications: Galileo at 600W(sub e), and Cassini at 900W(sub e), for example. Because most missions have had the same order of magnitude power requirements, the Power Distribution Systems (PDS) use existing, space-qualified technology and are DC. As science payload and mission duration requirements increase, however, the required electrical power increases. Subsequently, this requires a change from a passive energy conversion (solar arrays and batteries) to dynamic (alternator, solar dynamic, etc.), because dynamic conversion has higher thermal and conversion efficiencies, has higher power densities, and scales more readily to higher power levels. Furthermore, increased power requirements and physical distribution lengths are best served with high-voltage, multi-phase AC to maintain distribution efficiency and minimize voltage drops. The generated AC-voltage must be stepped-up (or down) to interface with various subsystems or electrical hardware. Part of the trade-space design for AC distribution systems is volume and mass estimation of high-power transformers. The volume and mass are functions of the power rating, operating frequency, the ambient and allowable temperature rise, the types and amount of heat transfer available, the core material and shape, the required flux density in a core, the maximum current density, etc. McLyman has tabulated the performance of a number of transformers cores and derived a "cookbook" methodology to determine the volume of transformers, whereas Schawrze had derived an empirical method to estimate the mass of single-phase transformers. Based on the work of McLyman and Schwarze, it is the intent herein to derive an empirical solution to the volume and mass estimation of three-phase, laminated EI-core power transformers, having radiated and conducted heat transfer mechanisms available. Estimation of the mounting hardware, connectors, etc. is not included.

Kimnach, Greg L.↗
NASA NTRS2005

Development of Parametric Mass and Volume Models for an Aerospace SOFC/Gas Turbine Hybrid System

In aerospace power systems, mass and volume are key considerations to produce a viable design. The utilization of fuel cells is being studied for a commercial aircraft electrical power unit. Based on preliminary analyses, a SOFC/gas turbine system may be a potential solution. This paper describes the parametric mass and volume models that are used to assess an aerospace hybrid system design. The design tool utilizes input from the thermodynamic system model and produces component sizing, performance, and mass estimates. The software is designed such that the thermodynamic model is linked to the mass and volume model to provide immediate feedback during the design process. It allows for automating an optimization process that accounts for mass and volume in its figure of merit. Each component in the system is modeled with a combination of theoretical and empirical approaches. A description of the assumptions and design analyses is presented.

Tornabene, Robert↗
NASA NTRS2005

Parallel Rendering of Large Time-Varying Volume Data

Interactive visualization of large time-varying 3D volume datasets has been and still is a great challenge to the modem computational world. It stretches the limits of the memory capacity, the disk space, the network bandwidth and the CPU speed of a conventional computer. In this SURF project, we propose to develop a parallel volume rendering program on SGI's Prism, a cluster computer equipped with state-of-the-art graphic hardware. The proposed program combines both parallel computing and hardware rendering in order to achieve an interactive rendering rate. We use 3D texture mapping and a hardware shader to implement 3D volume rendering on each workstation. We use SGI's VisServer to enable remote rendering using Prism's graphic hardware. And last, we will integrate this new program with ParVox, a parallel distributed visualization system developed at JPL. At the end of the project, we Will demonstrate remote interactive visualization using this new hardware volume renderer on JPL's Prism System using a time-varying dataset from selected JPL applications.

Garbutt, Alexander E.↗
NASA NTRS2007

The Human as a System - Monitoring Spacecraft Net Habitable Volume throughout the Design Lifecycle

Spacecraft design has historically allocated specific volume and mass "not to exceed" requirements upon individual systems and their accompanying hardware (e.g., life support, avionics) early in their conceptual design in an effort to align the spacecraft with propulsion capabilities. If the spacecraft is too heavy or too wide for the launch stack - it does not get off the ground. This approach has predictably ended with the crew being allocated whatever open, pressurized volume remains. With the recent inauguration of a new human-rated spacecraft - NASA human factors personnel have found themselves in the unique position to redefine the human as a system from the very foundation of design. They seek to develop and monitor a "not to fall below" requirement for crew net habitable volume (NHV) - balanced against the "not to exceed" system volume requirements, with the spacecraft fitting the crew versus the crew having to fit inside the spacecraft.

Szabo, Richard↗
NASA NTRS2007

Liquid Metering Centrifuge Sticks (LMCS): A Centrifugal Approach to Metering Known Sample Volumes for Colorimetric Solid Phase Extraction (C-SPE)

Phase separation is one of the most significant obstacles encountered during the development of analytical methods for water quality monitoring in spacecraft environments. Removing air bubbles from water samples prior to analysis is a routine task on earth; however, in the absence of gravity, this routine task becomes extremely difficult. This paper details the development and initial ground testing of liquid metering centrifuge sticks (LMCS), devices designed to collect and meter a known volume of bubble-free water in microgravity. The LMCS uses centrifugal force to eliminate entrapped air and reproducibly meter liquid sample volumes for analysis with Colorimetric Solid Phase Extraction (C-SPE). C-SPE is a sorption-spectrophotometric platform that is being developed as a potential spacecraft water quality monitoring system. C-SPE utilizes solid phase extraction membranes impregnated with analyte-specific colorimetric reagents to concentrate and complex target analytes in spacecraft water samples. The mass of analyte extracted from the water sample is determined using diffuse reflectance (DR) data collected from the membrane surface and an analyte-specific calibration curve. The analyte concentration can then be calculated from the mass of extracted analyte and the volume of the sample analyzed. Previous flight experiments conducted in microgravity conditions aboard the NASA KC-135 aircraft demonstrated that the inability to collect and meter a known volume of water using a syringe was a limiting factor in the accuracy of C-SPE measurements. Herein, results obtained from ground based C-SPE experiments using ionic silver as a test analyte and either the LMCS or syringes for sample metering are compared to evaluate the performance of the LMCS. These results indicate very good agreement between the two sample metering methods and clearly illustrate the potential of utilizing centrifugal forces to achieve phase separation and metering of water samples in microgravity.

Gazda, Daniel B.↗
NASA NTRS2009

Right Ventricular Tissue Doppler Assessment in Space During Circulating Volume Modification using the Braslet-M Device

This joint U.S. - Russian work aims to establish a methodology for assessing cardiac function in microgravity in association with manipulation of central circulating volume. Russian Braslet-M occlusion cuffs were used to temporarily increase the volume of blood in the lower extremities, which effectively reduces the volume returning to the heart in the central circulation. A novel methodology was tested on the International Space Station (ISS) to assess the volume status of crewmembers by evaluating the responses to application and release of the Braslet-on-occlusion cuffs, as well as to modified Valsalva and Mueller maneuvers. Baseline echocardiographic tissue Doppler imaging (TDI) of the right ventricular free wall with no Braslet applied shows early diastolic E' (16 cm/sec), late diastolic A' (14 cm/sec), and systolic (12 cm/sec) velocities compatible with normal subjects on Earth. TDI of the RV free wall with Braslet applied shows that early diastolic E' decreased by 50% (8 cm/sec), late diastolic A' increased by 45%, and systolic S' remains unchanged. TDI of the RV free wall approximately 8 beats after the Braslet was released shows early diastolic E' (8 cm/sec), late diastolic A' (12 cm/sec), and systolic S' (13 cm/sec) velocities. During this portion of the release, early diastolic E' did not recover to baseline values but late diastolic A' and systolic S' recovered to pre-Braslet values. The pre-systolic cross-sectional area of the internal jugular vein with Braslet off was 1.07 cm(sup 2) and 1.13 cm(sup 2) 10 min after the Braslet was applied. The presystolic cross-sectional area of the common femoral vein with Braslet off was 0.50 cm(sup 2), and was 0.54 cm(sup 2) 10 min after the Braslet was applied. The right ventricular myocardial performance Tei index also was calculated for comparison with typical values found in healthy subjects on Earth. Baseline and Braslet-on values for Tei index were 0.25 and 0.22 respectively. Braslet Tei indices are within normal ranges found in healthy subjects and temporarily become greater than 0.4 during the dynamic Braslet release portion of this study. Tissue Doppler imaging of the right ventricle revealed that the Braslet influenced cardiac preload and that fluid was sequestered in the lower-extremity interstitial and vascular space after only 10 minutes of application. This report demonstrates that Braslet application affects right ventricular physiology in long-duration space flight based on TDI and that this effect is in part due to venous hemodynamics.

Hamilton, D. R.↗
NASA NTRS2010

Ground and Space Radar Volume Matching and Comparison Software

This software enables easy comparison of ground- and space-based radar observations. The software was initially designed to compare ground radar reflectivity from operational, ground based Sand C-band meteorological radars with comparable measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite s Precipitation Radar (PR) instrument. The software is also applicable to other ground-based and space-based radars. The ground and space radar volume matching and comparison software was developed in response to requirements defined by the Ground Validation System (GVS) of Goddard s Global Precipitation Mission (GPM) project. This software innovation is specifically concerned with simplifying the comparison of ground- and spacebased radar measurements for the purpose of GPM algorithm and data product validation. This software is unique in that it provides an operational environment to routinely create comparison products, and uses a direct geometric approach to derive common volumes of space- and ground-based radar data. In this approach, spatially coincident volumes are defined by the intersection of individual space-based Precipitation Radar rays with the each of the conical elevation sweeps of the ground radar. Thus, the resampled volume elements of the space and ground radar reflectivity can be directly compared to one another.

Morris, Kenneth↗
NASA NTRS2011

Characterization of Volume F Trash from Four Recent STS Missions: Weights, Categorization, Water Content

The fate of space-generated solid wastes, including trash, for future missions is under consideration by NASA. Several potential treatment options are under consideration and active technology development. Potential fates for space-generated solid wastes are: Storage without treatment; storage after treatment(s) including volume reduction, water recovery, sterilization, and recovery plus recycling of waste materials. Recycling might be important for partial or full closure scenarios because of the prohibitive costs associated with resupply of consumable materials. For this study, we determined the composition of trash returned from four recent STS missions. The trash material was 'Volume F' trash and other trash, in large zip-lock bags, that accompanied the Volume F trash. This is the first of two submitted papers on these wastes. This one will cover trash content, weight and water content. The other will report on the microbial Characterization of this trash. STS trash was usually made available within 2 days of landing at KSC. The Volume F bag was weighed, opened and the contents were catalogued and placed into one of the following categories: food waste (and containers), drink containers, personal hygiene items - including EVA maximum absorbent garments (MAGs)and Elbow packs (daily toilet wipes, etc), paper, and packaging materials - plastic firm and duct tape. Trash generation rates for the four STS missions: Total wet trash was 0.602 plus or minus 0.089 kg(sub wet) crew(sup -1) d(sup -1) containing about 25% water at 0.154 plus or minus 0.030 kg(sub water) crew(sup -1) d(sup -1) (avg plus or minus stdev). Cataloguing by category: personal hygiene wastes accounted for 50% of the total trash and 69% of the total water for the four missions; drink items were 16% of total weight and 16% water; food wastes were 22% of total weight and 15% of the water; office waste and plastic film were 2% and 11% of the total waste and did not contain any water. The results can be used by NASA to determine requirements and criteria for Waste Management Systems on future missions.

Strayer, Richard F.↗
NASA NTRS2011

A CFD Analysis of Hydrogen Leakage During On-Pad Purge in the ORION/ARES I Shared Volume

A common open volume is created by the stacking of the Orion vehicle onto the Ares I Upper Stage. Called the Shared Volume, both vehicles contribute to its gas, fluid, and thermal environment. One of these environments is related to hazardous hydrogen gas. While both vehicles use inert purge gas to mitigate any hazardous gas buildup, there are concerns that hydrogen gas may still accumulate and that the Ares I Hazardous Gas Detection System will not be sufficient for monitoring the integrated volume. This Computational Fluid Dynamics (CFD) analysis has been performed to examine these topics. Results of the analysis conclude that the Ares I Hazardous Gas Detection System will be able to sample the vent effluent containing the highest hydrogen concentrations. A second conclusion is that hydrogen does not accumulate under the Orion Service Module (SM) avionics ring as diffusion and purge flow mixing sufficiently dilute the hydrogen to safe concentrations. Finally the hydrogen concentrations within the Orion SM engine nozzle may slightly exceed the 1 percent volume fraction when the entire worse case maximum full leak is directed vertically into the engine nozzle.

Ajmani, Kumud↗
NASA NTRS2014

Volume Measurements of Laser-generated Pits for In Situ Geochronology using KArLE (Potassium-Argon Laser Experiment)

The Potassium-Argon Laser Experiment( KArLE), is composed of two main instruments: a spectrometer as part of the Laser-Induced Breakdown Spectroscopy (LIBS) method and a Mass Spectrometer (MS). The LIBS laser ablates a sample and creates a plasma cloud, generating a pit in the sample. The LIBS plasma is measured for K abundance in weight percent and the released gas is measured using the MS, which calculates Ar abundance in mols. To relate the K and Ar measurements, total mass of the ablated sample is needed but can be difficult to directly measure. Instead, density and volume are used to calculate mass, where density is calculated based on the elemental composition of the rock (from the emission spectrum) and volume is determined by pit morphology. This study aims to reduce the uncertainty for KArLE by analyzing pit volume relationships in several analog materials and comparing methods of pit volume measurements and their associated uncertainties.

French, R. A.↗
NASA NTRS2013

Navigation Performance of Global Navigation Satellite Systems in the Space Service Volume

GPS has been used for spacecraft navigation for many years center dot In support of this, the US has committed that future GPS satellites will continue to provide signals in the Space Service Volume center dot NASA is working with international agencies to obtain similar commitments from other providers center dot In support of this effort, I simulated multi-constellation navigation in the Space Service Volume In this presentation, I extend the work to examine the navigational benefits and drawbacks of the new constellations center dot A major benefit is the reduced geometric dilution of precision (GDOP). I show that there is a substantial reduction in GDOP by using all of the GNSS constellations center dot The increased number of GNSS satellites broadcasting does produce mutual interference, raising the noise floor. A near/far signal problem can also occur where a nearby satellite drowns out satellites that are far away. - In these simulations, no major effect was observed Typically, the use of multi-constellation GNSS navigation improves GDOP by a factor of two or more over GPS alone center dot In addition, at the higher altitudes, four satellite solutions can be obtained much more often center dot This show the value of having commitments to provide signals in the Space Service Volume Besides a commitment to provide a minimum signal in the Space Service Volume, detailed signal gain information is useful for mission planning center dot Knowledge of group and phase delay over the pattern would also reduce the navigational uncertainty

Force, Dale A.↗
NASA NTRS2017

Electromagnetic Scattering by Spheroidal Volumes of Discrete Random Medium

We use the superposition T-matrix method to compare the far-field scattering matrices generated by spheroidal and spherical volumes of discrete random medium having the same volume and populated by identical spherical particles. Our results fully confirm the robustness of the previously identified coherent and diffuse scattering regimes and associated optical phenomena exhibited by spherical particulate volumes and support their explanation in terms of the interference phenomenon coupled with the order-of-scattering expansion of the far-field Foldy equations. We also show that increasing non-sphericity of particulate volumes causes discernible (albeit less pronounced) optical effects in forward and backscattering directions and explain them in terms of the same interference/multiple-scattering phenomenon.

Electromagnetic scattering; Multi-particle groups;↗