Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Issue Brief”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Use of Soft Computing Technologies for a Qualitative and Reliable Engine Control System for Propulsion Systems

The problem to be addressed in this paper is to explore how the use of Soft Computing Technologies (SCT) could be employed to improve overall vehicle system safety, reliability, and rocket engine performance by development of a qualitative and reliable engine control system (QRECS). Specifically, this will be addressed by enhancing rocket engine control using SCT, innovative data mining tools, and sound software engineering practices used in Marshall's Flight Software Group (FSG). The principle goals for addressing the issue of quality are to improve software management, software development time, software maintenance, processor execution, fault tolerance and mitigation, and nonlinear control in power level transitions. The intent is not to discuss any shortcomings of existing engine control methodologies, but to provide alternative design choices for control, implementation, performance, and sustaining engineering, all relative to addressing the issue of reliability. The approaches outlined in this paper will require knowledge in the fields of rocket engine propulsion (system level), software engineering for embedded flight software systems, and soft computing technologies (i.e., neural networks, fuzzy logic, data mining, and Bayesian belief networks); some of which are briefed in this paper. For this effort, the targeted demonstration rocket engine testbed is the MC-1 engine (formerly FASTRAC) which is simulated with hardware and software in the Marshall Avionics & Software Testbed (MAST) laboratory that currently resides at NASA's Marshall Space Flight Center, building 4476, and is managed by the Avionics Department. A brief plan of action for design, development, implementation, and testing a Phase One effort for QRECS is given, along with expected results. Phase One will focus on development of a Smart Start Engine Module and a Mainstage Engine Module for proper engine start and mainstage engine operations. The overall intent is to demonstrate that by employing soft computing technologies, the quality and reliability of the overall scheme to engine controller development is further improved and vehicle safety is further insured. The final product that this paper proposes is an approach to development of an alternative low cost engine controller that would be capable of performing in unique vision spacecraft vehicles requiring low cost advanced avionics architectures for autonomous operations from engine pre-start to engine shutdown.

Trevino, Luis↗
NASA NTRS2013

Large-Scale Extratropical Weather Systems in Mars' Atmosphere

During late autumn through early spring, extratropical regions on Mars exhibit profound mean zonal equator-to-pole thermal contrasts. The imposition of this strong meridional temperature variation supports intense eastward-traveling, synoptic weather systems (i.e., transient baroclinic/barotropic waves) within Mars' extratropical atmosphere. Such disturbances grow, mature and decay within the east-west varying seasonal-mean midlatitude jet stream (i.e., the polar vortex) on the planet. Near the surface, the weather disturbances indicated large-scale spiraling "comma"-shaped dust cloud structures and scimitar-shaped dust fronts, indicative of processes associated with cyclo-/fronto-genesis. The weather systems occur during specific seasons on Mars, and in both hemispheres. The northern hemisphere (NH) disturbances are significantly more intense than their counterparts in the southern hemisphere (SH). Further, the NH weather systems and accompanying frontal waves appear to have significant impacts on the transport of tracer fields (e.g., particularly dust and to some extent water species (vapor/ice) as well). And regarding dust, frontal waves appear to be key agents in the lifting, lofting, organization and transport of this particular atmospheric aerosol. In this paper, a brief background and supporting observations of Mars' extratropical weather systems is presented. This is followed by a short review of the theory and various modeling studies (i.e., ranging from highly simplified, mechanistic and full global circulation modeling investigations) which have been pursued. Finally, a discussion of outstanding issues and questions regarding the character and nature of Mars' extratropical traveling weather systems is offered.

Hollingsworth, Jeffery L.↗
NASA NTRS1998

Numerical Study of Tip Vortex Flows

This paper presents an overview and summary of the many different research work related to tip vortex flows and wake/trailing vortices as applied to practical engineering problems. As a literature survey paper, it outlines relevant analytical, theoretical, experimental and computational study found in literature. It also discusses in brief some of the fundamental aspects of the physics and its complexities. An appendix is also included. The topics included in this paper are: 1) Analytical Vortices; 2) Experimental Studies; 3) Computational Studies; 4) Wake Vortex Control and Management; 5) Wake Modeling; 6) High-Lift Systems; 7) Issues in Numerical Studies; 8) Instabilities; 9) Related Topics; 10) Visualization Tools for Vertical Flows; 11) Further Work Needed; 12) Acknowledgements; 13) References; and 14) Appendix.

Dacles-Mariani, Jennifer↗
NASA NTRS2010

Assessing the Health and Performance Risks of Carbon Dioxide Exposures

Carbon dioxide (CO2) is an anthropogenic gas that accumulates in spacecraft to much higher levels than earth-normal levels. Controlling concentrations of this gas to acceptable levels to ensure crew health and optimal performance demands major commitment of resources. NASA has many decades of experience monitoring and controlling CO2, yet we are uncertain of the levels at which subtle performance decrements develop. There is limited evidence from ground-based studies that visual disturbances can occur during brief exposures and visual changes have been noted in spaceflight crews. These changes may be due to CO2 alone or in combination with other known spaceflight factors such as increased intracranial pressure due to fluid shifts. Discerning the comparative contribution of each to performance decrements is an urgent issue if we hope to optimize astronaut performance aboard the ISS. Long-term, we must know the appropriate control levels for exploration-class missions to ensure that crewmembers can remain cooperative and productive in a highly stressful environment. Furthermore, we must know the magnitude of interindividual variability in susceptibility to the adverse effects of CO2 so that the most tolerant crewmembers can be identified. Ground-based studies have been conducted for many years to set exposure limits for submariners; however, these studies are typically limited and incompletely reported. Nonetheless, NASA, in cooperation with the National Research Council, has set exposure limits for astronauts using this limited database. These studies do not consider the interactions of spaceflight-induced fluid shifts and CO2 exposures. In an attempt to discern whether CO2 levels affect the incidence of headache and visual disturbances in astronauts we performed a retrospective study comparing average CO2 levels and the prevalence of headache and visual disturbances. Our goal is to narrow gaps in the risk profile for in-flight CO2 exposures. Such studies can provide no more than partial answers to the questions of environmental interactions, interindividual variability, and optimal control levels. Future prospective studies should involve assessment of astronaut well being using sophisticated measures during exposures to levels of CO2 in the range from 2 to 8 mmHg.

James, John T.↗
DOE OSTI2022

Demystify the 1.1 Factor for Ultimate Tensile Strength Above Room Temperature in Development of the Code Stress Tables

As the Boiler and Pressure Vessel Code increasingly gains popularity worldwide, it is not uncommon that many users are mystified by the 1.1 factor required for ultimate tensile strength above room temperature in developing the allowable design stresses of Section II Part D Stress Tables. Questions often arise about the origin and purpose of the factor, the reason for it not applied to the yield strength, its due considerations when evaluating an alloy for acceptance to construction use from the perspective of the alloy’s tested tensile strength value, and more. Not knowing reliable sources for explicit explanations, some users tend to misinterpret the factor, abuse its application, incorrectly define their alloy acceptance or qualification criteria, and mistakenly manipulate the safety margin in structural component design.To help the Code users who struggle with these frequent and confusing issues, particularly those in nuclear industry where rigorous criteria are required for component design and alloy acceptance or qualification, this paper is intended to demystify the 1.1 factor and facilitate knowledgeable interpretation and use of the Section II Part D Stress Tables as well as relevant Mandatory Appendices.A brief review is first given on the background of the 1.1 factor, followed by a summary of its application in the Stress Tables. The provenance and purpose of the factor are then discussed in detail with graphic examples. Finally, current applicability and necessity of the factor are considered through a demonstration using example alloys.

Ren, Weiju↗
NASA NTRS1995

Annual Research Briefs: 1995

This report contains the 1995 annual progress reports of the Research Fellows and students of the Center for Turbulence Research (CTR). In 1995 CTR continued its concentration on the development and application of large-eddy simulation to complex flows, development of novel modeling concepts for engineering computations in the Reynolds averaged framework, and turbulent combustion. In large-eddy simulation, a number of numerical and experimental issues have surfaced which are being addressed. The first group of reports in this volume are on large-eddy simulation. A key finding in this area was the revelation of possibly significant numerical errors that may overwhelm the effects of the subgrid-scale model. We also commissioned a new experiment to support the LES validation studies. The remaining articles in this report are concerned with Reynolds averaged modeling, studies of turbulence physics and flow generated sound, combustion, and simulation techniques. Fundamental studies of turbulent combustion using direct numerical simulations which started at CTR will continue to be emphasized. These studies and their counterparts carried out during the summer programs have had a noticeable impact on combustion research world wide.

Source record↗
DOE OSTI2020

Preparations for a European R&D roadmap for an inertial fusion demo reactor

A European consortium of 15 laboratories across nine nations have worked together under the EUROFusion Enabling Research grants for the past decade with three principle objectives. These are: (a) investigating obstacles to ignition on megaJoule-class laser facilities; (b) investigating novel alternative approaches to ignition, including basic studies for fast ignition (both electron and ion-driven), auxiliary heating, shock ignition, etc.; and (c) developing technologies that will be required in the future for a fusion reactor. This paperr presents a brief overview of these activities, along with new calculations relates the concept of auxiliary heating of inertial fusion targets, and provides possible future directions of research and development for the updated European Roadmap that is due at the end of 2020. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1980

Automation literature: A brief review and analysis

Current thought and research positions which may allow for an improved capability to understand the impact of introducing automation to an existing system are established. The orientation was toward the type of studies which may provide some general insight into automation; specifically, the impact of automation in human performance and the resulting system performance. While an extensive number of articles were reviewed, only those that addressed the issue of automation and human performance were selected to be discussed. The literature is organized along two dimensions: time, Pre-1970, Post-1970; and type of approach, Engineering or Behavioral Science. The conclusions reached are not definitive, but do provide the initial stepping stones in an attempt to begin to bridge the concept of automation in a systematic progression.

Smith, D.↗
NASA NTRS1987

Issues in space photovoltaic research and technology

Key issues and opportunities in space photovoltaic research and technology are addressed relative to future NASA mission requirements and drivers. Examples are given of future space missions and/or operational capabilities that are on NASA's planning horizon presenting major tachnology challenges to the use of photovoltaic power generation in space. A brief description of the capabilities ascribed to the competing technologies of nuclear and solar thermal power systems are given. The performance goals that space photovoltaic power systems must meet to remain competitive are described.

Flood, Dennis J.↗
NASA NTRS1987

Issues in space photovoltaic research and technology

Key issues and opportunities in space photovoltaic research and technology are addressed relative to future NASA mission requirements and drivers. Examples are given of future space missions and/or operational capabilities that are on NASA's planning horizon, presenting major technology challenges to the use of photovoltaic power generation in space. A brief description of the capabilities ascribed to the competing technologies of nuclear and solar thermal power systems are discussed. The performance goals that space photovoltaic power systems must meet to remain competitive are described.

Flood, Dennis J.↗
NASA NTRS2012

Flight Test Results on the Stability and Control of the F-15 Quiet Spike(TradeMark) Aircraft

The Quiet Spike F-15B flight research program investigated supersonic shock reduction using a 24-ft sub-scale telescoping nose boom on an F-15B airplane. The program primary flight test objective was to collect flight data for aerodynamic and structural models validation up to 1.8 Mach. Other objectives were to validate the mechanical feasibility of a morphing fuselage at the operational conditions and determine the near-field shock wave characterization. The stability and controls objectives were to assess the effect of the spike on the stability, controllability, and handling qualities of the aircraft and to ensure adequate stability margins across the entire research flight envelop. The two main stability and controls issues were the effects of the telescoping nose boom influenced aerodynamics on the F-15B aircraft flight dynamics and air data and angle of attack sensors. This paper reports on the stability and controls flight envelope clearance methods and flight test analysis of the F-15B Quiet Spike. Brief pilot commentary on typical piloting tasks, approach and landing, refueling task, and air data sensitivity to the flight control system are also discussed in this report.

Moua, Cheng M.↗
NASA NTRS1992

Biological Contamination of Mars: Issues and Recommendations

The ad hoc Task Group on Planetary Protection formed by the Space Studies Board (SSB) of the National Research Council focused on making recommendations concerning the protection of Mars from forward contamination (i.e., Earth to Mars) during upcoming missions by both the United States and the former Soviet Union. In so doing, it distinguished between missions whose goals include reconnaissance and measurement and those that specifically include experiments to detect life. The task group also discussed what additional knowledge will be needed in order to assure that future recommendations regarding contamination of Earth from Mars might be made with a higher degree of certainty than is now possible. Following a short introduction to the rationale underlying planetary exploration (Chapter 1) is a brief summary of approved and contemplated missions to Mars (Chapter 2). Chapter 3 briefly reviews the state of knowledge in several areas pertinent to the problem of planetary protection, in the limits of life on Earth and the abilities of known terrestrial organisms to withstand extreme environment conditions, as well as new approaches to detecting life forms. Chapter 5 includes a review and comments (made in light of current knowledge)- on the recommendations made in 'Recommendations on Quarantine Policy for Mars, Jupiter, Saturn, Uranus, Neptune, and Titan'. Updates to the recommendations made in 1978 are also given in Chapter 5. Chapter 6 gives additional recommendations concerning collection of essential data, spacecraft sterilization and bioburden assessment, and future research, as well as legal and social issues and NASA's overall planetary protection program.

Source record↗
NASA NTRS1994

Muscular activity and its relationship to biomechanics and human performance

The purpose of this manuscript is to address the issue of muscular activity, human motion, fitness, and exercise. Human activity is reviewed from the historical perspective as well as from the basics of muscular contraction, nervous system controls, mechanics, and biomechanical considerations. In addition, attention has been given to some of the principles involved in developing muscular adaptations through strength development. Brief descriptions and findings from a few studies are included. These experiments were conducted in order to investigate muscular adaptation to various exercise regimens. Different theories of strength development were studied and correlated to daily human movements. All measurement tools used represent state of the art exercise equipment and movement analysis. The information presented here is only a small attempt to understand the effects of exercise and conditioning on Earth with the objective of leading to greater knowledge concerning human responses during spaceflight. What makes life from nonliving objects is movement which is generated and controlled by biochemical substances. In mammals. the controlled activators are skeletal muscles and this muscular action is an integral process composed of mechanical, chemical, and neurological processes resulting in voluntary and involuntary motions. The scope of this discussion is limited to voluntary motion.

Ariel, Gideon↗
NASA NTRS2016

Status of MODIS Spatial and Spectral Characterization and Performance

Since launch, both Terra and Aqua MODIS instruments have continued to operate and make measurements of the earth's top of atmospheric (TOA) radiances and reflectance. MODIS collects data in 36 spectral bands covering wavelengths from 0.41 to 14.4 microns. These spectral bands and detectors are located on four focal plane assemblies (FPAs). MODIS on-board calibrators (OBC) include a spectro-radiometric calibration assembly (SRCA), which was designed to characterize and monitor sensor spatial and spectral performance, such as on-orbit changes in the band-to-band registration (BBR), modulation transfer function (MTF), spectral band center wavelengths (CW) and bandwidths (BW). In this paper, we provide a status update of MODIS spatial and spectral characterization and performance, following a brief description of SRCA functions and on-orbit calibration activities. Sensor spatial and spectral performance parameters derived from SRCA measurements are introduced and discussed. Results show that on-orbit spatial performance has been very stable for both Terra and Aqua MODIS instruments. The large BBR shifts in Aqua MODIS, an issue identified pre-launch, have remained the same over its entire mission. On-orbit changes in CW and BW are less than 0.5 nm and 1 nm, respectively, for most VIS/NIR spectral bands of both instruments.

Link, Daniel↗
NASA NTRS2019

Powering OSCAR

Recycling waste has been an issue on Earth for decades. The OSCAR project seeks to find ways to make sure that it does not become an issue in space. The main focus of OSCAR is the combustion of waste and reclamation of gaseous products in microgravity. The first phase of testing relies on a ground rig that operates both under normal (Earth) gravity and in drop tower tests that briefly simulate a microgravity environment. In the second phase, a test will be performed during a suborbital flight were the experiment will be carried out in microgravity. Throughout the spring term, interns have played an integral part in continuing the progress made by the project. They performed work in upgrading the electrical and mechanical systems that make up OSCAR. They made multiple improvements to the test rig's operating software to improve readability and usability. They prepared and edited documents that were vital to the engineering process. And, they were responsible for performing lab tests and refining the lab operations document and procedure. The interns were a big help in maintaining the rigorous test schedule. OSCAR, which stands for Orbital Syngas Commodity Augmentation Reactor, is to find a way to turn astronaut waste into chemical energy. The two parts of this are important: finding a way to dispose of waste generated in space, and seeing if there is a way to recycle that waste into chemical energy. The importance of the disposal aspect is that there is currently no way to dispose of, or recycle, waste that is created in space other than jettisoning it (which is what the ISS does via empty supply capsules). As manned missions go deeper into space, that method will no longer be viable, as a craft would essentially be littering the space and planets that they visit. Energy reclamation is also important because of the high monetary and spatial costs of sending supplies on space missions. Every little bit extra that can be reused out of what is sent can save room and funds for other supplies. The facet of this problem that the OSCAR project is focusing on is how to combust waste in zero gravity. Combustion in the presence of gravity is one of those things that is taken for granted. When something burns on Earth, the flames rise above the fuel as oxygen flows from underneath. In microgravity, the flames surround the object completely, which restricts the amount of oxygen that can reach the fuel, and retards the combustion. OSCAR uses a vortex reaction chamber to counter this phenomenon. The OSCAR test rig will eventually be tested on a suborbital flight to see if it is an effective solution to the issue in real-world conditions. Currently, there is a prototype test rig that is fully functional. This rig has been previously tested in a 2 second drop test at Glenn Research Center’s (GRC) Zero Gravity Facility (ZGF). (The free-fall conditions of the drop mimic microgravity, if only for a brief period of time). This session’s focus was on upgrading the test rig and software, updating the paperwork, performing additional lab tests, and readying the rig for the five second drop test, again at GRC. II. Upgrades The state of the testing rig at the start of the session was in between its configurations for the two second drop tower and the five second drop tower. The rig needed upgrades to address various insufficiencies that either were discovered during the two second campaign or were a direct result of the differences between the two drop tower setups. The main differences that had to be handled were the increase in shock loads from 30g to 65g, a difference in drop indicating signal (on the falling edge of a pulse instead of a change from high to low), and the ambient pressure of the test apparatus (the two second tower dropped the rig in atmosphere, while the five second tower drops in vacuum).

Cauvel, Thomas↗
DOE OSTI2022

La-Based Perovskite Oxide Catalysts for Alkaline Oxygen Reduction: The Importance of Electrochemical Stability

Alkaline fuel cells represent a promising energy conversion technology since they enable the use of precious metal-free electrocatalysts for the oxygen reduction reaction. Among these, La-based perovskite oxides, with great compositional and structural tunability, are especially attractive. However, we believe that the current literature lacks a thorough understanding of their inherent (in)stability issues. Here, in this study, we report on nine La-based perovskite oxide electrocatalysts for the oxygen reduction reaction, including LaMO 3 (M = Mn, Co, Ni) and LaCo x M 1–x O 3 (M = Mn, Ni; x = 0.9, 0.5, 0.1). While some exhibited initial promising activity, they all degraded significantly, even after brief electrochemical testing. Through comprehensive structural characterization of LaCo 0.9 Mn 0.1 O 3 , particularly scanning transmission electron microscopy, we found evidence to support a degradation mechanism in which the B-site cation species irreversibly leach from the perovskite under testing conditions. A sample cycled 10 000 times from +0.4 to +1.2 V vs reversible hydrogen electrode (RHE) showed an amorphous La oxide shell 1–2 nm thick. Bulk analyses showed that B-site leaching also occurs for samples soaked in 1 M KOH or pure EtOH. The mechanistic insights provided here should help inform the future design of La-based perovskite oxide electrocatalysts for alkaline fuel cells and stress the importance of stability metrics validating claims of promising electrocatalytic activity.

Seok, Jeesoo↗
NASA NTRS1990

Applications of ISES for the atmospheric sciences

The proposed Information Sciences Experiment System (ISES) will offer the opportunity for real-time access to measurements acquired aboard the Earth Observation System (Eos) satellite. These measurements can then be transmitted to remotely located ground based stations. The application of such measurements to issues related to atmospheric science which was presented to a workshop convened to review possible application of the ISES in earth sciences is summarized. The proposed protocol for Eos instruments requires that measurement results be available in a central data archive within 72 hours of acquiring data. Such a turnaround of raw satellite data to the final product will clearly enhance the timeliness of the results. Compared to the time that results from many current satellite programs, the 72 hour turnaround may be considered real time. Examples are discussed showing how real-time measurements from one or more of the proposed Eos instruments could have been applied to the study of certain issues important to global atmospheric chemistry. Each of the examples discussed is based upon a field mission conducted during the past five years. Each of these examples will emphasize how real-time data could have been used to alter the course of a field experiment, thereby enhancing the scientific output. For the examples, brief overviews of the scientific rationale and objectives, the region of operation, the measurements aboard the aircraft, and finally how one or more of the proposed Eos instruments could have provided data to enhance the productivity of the mission are discussed.

Hoell, James M., Jr.↗
NASA NTRS1992

A beginner's guide to belief revision and truth maintenance systems

This brief note is intended to familiarize the non-TMS audience with some of the basic ideas surrounding classic TMS's (truth maintenance systems), namely the justification-based TMS and the assumption-based TMS. Topics of further interest include the relation between non-monotonic logics and TMS's, efficiency and search issues, complexity concerns, as well as the variety of TMS systems that have surfaced in the past decade or so. These include probabilistic-based TMS systems, fuzzy TMS systems, tri-valued belief systems, and so on.

Mason, Cindy L.↗