Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “SHUTDOWN”

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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Propulsion Health Monitoring for Enhanced Safety

This report presents the results of the NASA contract Propulsion System Health Management for Enhanced Safety performed by General Electric Aircraft Engines (GE AE), General Electric Global Research (GE GR), and Pennsylvania State University Applied Research Laboratory (PSU ARL) under the NASA Aviation Safety Program. This activity supports the overall goal of enhanced civil aviation safety through a reduction in the occurrence of safety-significant propulsion system malfunctions. Specific objectives are to develop and demonstrate vibration diagnostics techniques for the on-line detection of turbine rotor disk cracks, and model-based fault tolerant control techniques for the prevention and mitigation of in-flight engine shutdown, surge/stall, and flameout events. The disk crack detection work was performed by GE GR which focused on a radial-mode vibration monitoring technique, and PSU ARL which focused on a torsional-mode vibration monitoring technique. GE AE performed the Model-Based Fault Tolerant Control work which focused on the development of analytical techniques for detecting, isolating, and accommodating gas-path faults.

Butz, Mark G.↗
NASA NTRS2003

Development of the Next Generation Gas Trap for the Space Station Internal Thermal Control System

The current dual-membrane gas trap is designed to remove non-condensed gases (NCG) from the Internal Thermal Control System (ITCS) coolant on board the International Space Station (ISS). To date it has successfully served its purpose of preventing depriming, overspeed, and shutdown of the ITCS pump. However, contamination in the ITCS coolant has adversely affected the gas venting rate and lifetime of the gas trap, warranting a development effort for a next-generation gas trap. Design goals are to meet or exceed the current requirements to (1) include greater operating ranges and conditions, (2) eliminate reliance on the current hydrophilic tube fabrication process, and (3) increase operational life and tolerance to particulate and microbial growth fouling. In addition, the next generation gas trap will essentially be a 'dropin" design such that no modifications to the ITCS pump package assembly (PPA) will be required, and the implementation of the new design will not affect changes to the ITCS operational conditions, interfaces, or software. This paper will present the initial membrane module design and development work which has included (1) a trade study among several conceptual designs, (2) performance modeling of a hydrophobic-only design, and (3) small-scale development test data for the hydrophobic-only design. Testing has shown that the hydrophobic-only design is capable of performing even better than the current dual-membrane design for both steady-state gas removal and gas slug removal.

Leimkuehler, Thomas O.↗
NASA NTRS2003

Subsurface Stress Fields in Single Crystal (Anisotropic) Contacts

Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and fatigue stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. Techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts are presented in this report. Figure 1 shows typical damper contact locations in a turbine blade. The subsurface stress results are used for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades.

Arakere, Nagaraj K.↗
NASA NTRS2003

Single Event Effects Testing of the Linfinity SG1525A Pulse Width Modulator Controller

Pulse Width Modulator (PWM) Controllers are the heart of switching power supply systems in development today. The PWMs considered here have the same integration advantages as many other controllers but it also includes the interface drivers for the follow-on power Field Effect Transistors (FET). Previous work on these types of devices looked into the required test methodologies [ 11 and the impact of radiation on the soft start and shutdown circuits of typically incorporated in the technology [2]. Taking advantage of this previous work this study was undertaken to determine the single event destructive and transient susceptibility of the Linfinity SG1525A Pulse Width Modulator Controller. The device was monitored for transient interruptions in the output signals and for destructive events induced by exposing it to a heavy ion beam at the Texas A&M University Cyclotron Single Event Effects Test Facility. After exposing these devices to the beam, a new upset mode has been identified that can lead to catastrophic power supply system failure if this event would occur while drive power FETs off the two device outputs. The devices and the test methods used will be described first. This will be followed by a brief description of the data collected to date (not all data can be presented with the length constraints of the summary) and a summary of the key results.

Howard, J. W., Jr.↗
NASA NTRS2003

A USA Commercial Flight Track Database for Upper Tropospheric Aircraft Emission Studies

A new air traffic database over the contiguous United States of America (USA) has been developed from a commercially available real-time product for 2001-2003 for all non-military flights above 25,000 ft. Both individual flight tracks and gridded spatially integrated flight legs are available. On average, approximately 24,000 high-altitude flights were recorded each day. The diurnal cycle of air traffic over the USA is characterized by a broad daytime maximum with a 0130-LT minimum and a mean day-night air traffic ratio of 2.4. Each week, the air traffic typically peaks on Thursday and drops to a low Saturday with a range of 18%. Flight density is greatest during late summer and least during winter. The database records the disruption of air traffic after the air traffic shutdown during September 2001. The dataset should be valuable for realistically simulating the atmospheric effects of aircraft in the upper troposphere.

Garber, Donald P.↗
NASA NTRS2002

Improved Electrohydraulic Linear Actuators

A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to similar industrial uses. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The shortcomings are the following: They perform unreliably and inconsistently as positioning devices. Their capabilities for end-of-stroke buffering (that is, deceleration to gentle stops at designated stopping positions) range from unsatisfactory to nonexistent, with consequent potential for inducing catastrophic failures. It takes long times to modify standard actuators to meet specifications, and the costs of such modifications are high. In the cases of actuators equipped with fail-safe shutdown systems, the stroking times of these systems cannot be adjusted in the field.

Hamtil, James↗
NASA NTRS2004

Subsurface Stress Fields In Single Crystal (Anisotropic) Contacts

Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is , presented, for evaluating the subsurface stresses in the elastic half-space, using a complex potential method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis. Effects of crystal orientation on stress response and fatigue life are examined.

Arakere, Nagaraj K.↗
NASA NTRS2004

Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts

Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves considerable post-processing work. For these reasons it is very advantageous to develop analytical solution schemes for subsurface stresses, whenever possible.

Arakere, Nagaraj K.↗
NASA NTRS2004

Recent Operational Experience with the Internal Thermal Control System Dual-Membrane Gas Trap

A dual-membrane gas trap is currently used to remove gas bubbles from the Internal Thermal Control System (ITCS) coolant on board the International Space Station. The gas trap consists of concentric tube membrane pairs, comprised of outer hydrophilic tubes and inner hydrophobic fibers. Liquid coolant passes through the outer hydrophilic membrane, which traps the gas bubbles. The inner hydrophobic fiber allows the trapped gas bubbles to pass through and vent to the ambient atmosphere in the cabin. The gas removal performance and operational lifetime of the gas trap have been affected by contamination in the ITCS coolant. However, the gas trap has performed flawlessly with regard to its purpose of preventing gas bubbles from causing depriming, overspeed, and shutdown of the ITCS pump. This paper discusses on-orbit events over the course of the last year related to the performance and functioning of the gas trap.

Leimkuehler, Thomas O.↗
NASA NTRS2004

Effects of Surfactant Contamination on the Next Generation Gas Trap for the ISS Internal Thermal Control System

The current dual-membrane gas trap is designed to remove non-condensed gas bubbles from the Internal Thermal Control System (ITCS) coolant on board the International Space Station (ISS). To date it has successfully served its purpose of preventing gas bubbles from causing depriming, overspeed, and shutdown of the ITCS pump. However, contamination in the ITCS coolant has adversely affected the gas venting rate and lifetime of the gas trap, warranting a development effort for a next-generation gas trap. Previous testing has shown that a hydrophobic-only design is capable of performing even better than the current dual-membrane design for both steady-state gas removal and gas slug removal in clean deionized water. This paper presents results of testing to evaluate the effects of surfactant contamination on the steady-state performance of the hydrophobic-only design.

Leimkuehler, Thomas O.↗
NASA NTRS2004

Advanced Health Management System for the Space Shuttle Main Engine

Boeing-Canoga Park (BCP) and NASA-Marshall Space Flight Center (NASA-MSFC) are developing an Advanced Health Management System (AHMS) for use on the Space Shuttle Main Engine (SSME) that will improve Shuttle safety by reducing the probability of catastrophic engine failures during the powered ascent phase of a Shuttle mission. This is a phased approach that consists of an upgrade to the current Space Shuttle Main Engine Controller (SSMEC) to add turbomachinery synchronous vibration protection and addition of a separate Health Management Computer (HMC) that will utilize advanced algorithms to detect and mitigate predefined engine anomalies. The purpose of the Shuttle AHMS is twofold; one is to increase the probability of successfully placing the Orbiter into the intended orbit, and the other is to increase the probability of being able to safely execute an abort of a Space Transportation System (STS) launch. Both objectives are achieved by increasing the useful work envelope of a Space Shuttle Main Engine after it has developed anomalous performance during launch and the ascent phase of the mission. This increase in work envelope will be the result of two new anomaly mitigation options, in addition to existing engine shutdown, that were previously unavailable. The added anomaly mitigation options include engine throttle-down and performance correction (adjustment of engine oxidizer to fuel ratio), as well as enhanced sensor disqualification capability. The HMC is intended to provide the computing power necessary to diagnose selected anomalous engine behaviors and for making recommendations to the engine controller for anomaly mitigation. Independent auditors have assessed the reduction in Shuttle ascent risk to be on the order of 40% with the combined system and a three times improvement in mission success.

Davidson, Matt↗
NASA NTRS2004

Geoscience Laser Altimeter System (GLAS) Loop Heat Pipes: An Eventual First Year On-Orbit

Goddard Space Flight Center's Geoscience Laser Altimeter System (GLAS) is the sole scientific instrument on the Ice, Cloud and land Elevation Satellite (ICESat) that was launched on January 12, 2003 from Vandenberg AFB. A thermal control architecture based on propylene Loop Heat Pipe technology was developed to provide selectable/stable temperature control for the lasers and other electronics over the widely varying mission environment. Following a nominal LHP and instrument start-up, the mission was interrupted with the failure of the first laser after only 36 days of operation. During the 5-month failure investigation, the two GLAS LHPs and the electronics operated nominally, using heaters as a substitute for the laser heat load. Just prior to resuming the mission, following a seasonal spacecraft yaw maneuver, one of the LHPs deprimed and created a thermal runaway condition that resulted in an emergency shutdown of the GLAS instrument. This paper presents details of the LHP anomaly, the resulting investigation and recovery, along with on-orbit flight data during these critical events.

Grob, E.↗
NASA NTRS1993

The role of cytokines in immune changes induced by spaceflight

It has become apparent that spaceflight alters many immune responses. Among the regulatory components of the immune response that have been shown to be affected by spaceflight is the cytokine network. Spaceflight, as well as model systems of spaceflight, have been shown to affect the production and action of various cytokines including interferons, interleukins, colony stimulating factors, and tumor necrosis factors. These changes have been shown not to involve a general shutdown of the cytokine network but, rather, to involve selective alterations of specific cytokine functions by spaceflight. The full breadth of changes in cytokines induced by spaceflight, as well as mechanisms, duration, adaptation, reversibility, and significance to resistance to infection and neoplastic diseases, remains to be established.

NASA Discipline Number 18-10↗
NASA NTRS2004

Solar Variability and the Near-Earth Environment: Mining Enhanced Low Dose Rate Sensitivity Data From the Microelectronics and Photonics Test Bed Space Experiment

This effort is a detailed analysis of existing microelectronics and photonics test bed satellite data from one experiment, the bipolar test board, looking to improve our understanding of the enhanced low dose rate sensitivity (ELDRS) phenomenon. Over the past several years, extensive total dose irradiations of bipolar devices have demonstrated that many of these devices exhibited ELDRS. In sensitive bipolar transistors, ELDRS produced enhanced degradation of base current, resulting in enhanced gain degradation at dose rates <0.1 rd(Si)/s compared to similar transistors irradiated at dose rates >1 rd(Si)/s. This Technical Publication provides updated information about the test devices, the in-flight experiment, and both flight-and ground-based observations. Flight data are presented for the past 5 yr of the mission. These data are compared to ground-based data taken on devices from the same date code lots. Information about temperature fluctuations, power shutdowns, and other variables encountered during the space flight are documented.

Turflinger, T.↗
NASA NTRS2005

Of Ashes and Atoms

This feature length DVD documentary, reviews the history of the Plum Brook Nuclear Reactor from the initial settlers of the area, through its use as a munitions facility during the second World War to the development of the nuclear facility and its use as one of the first nuclear test reactors built in the United States, and the only one built by NASA. It concludes with the beginning of the decommissioning of the facility. There is a brief review of the reactor design, and its workings. Through discussions with the NASA engineers and operators of the facility, the film reviews the work done to advance the knowledge of the effects of radiation, the properties of radiated materials, and the work to advance the state of the art in nuclear propulsion. The film shows footage of public tours, and shows actual footage of the facility in operation, and after its shutdown in 1973. The DVD was narrated by Kate Mulgrew, who leads the viewer through the history of the facility to its eventual ongoing decommissioning, and return to the state of pastoral uses.

Source record↗
NASA NTRS2005

Transient Approximation of SAFE-100 Heat Pipe Operation

Engineers at Los Alamos National Laboratory (LANL) have designed several heat pipe cooled reactor concepts, ranging in power from 15 kWt to 800 kWt, for both surface power systems and nuclear electric propulsion systems. The Safe, Affordable Fission Engine (SAFE) is now being developed in a collaborative effort between LANL and NASA Marshall Space Flight Center (NASA/MSFC). NASA is responsible for fabrication and testing of non-nuclear, electrically heated modules in the Early Flight Fission Test Facility (EFF-TF) at MSFC. In-core heat pipes must be properly thawed as the reactor power starts. Computational models have been developed to assess the expected operation of a specific heat pipe design during start-up, steady state operation, and shutdown. While computationally intensive codes provide complete, detailed analyses of heat pipe thaw, a relatively simple. concise routine can also be applied to approximate the response of a heat pipe to changes in the evaporator heat transfer rate during start-up and power transients (e.g., modification of reactor power level) with reasonably accurate results. This paper describes a simplified model of heat pipe start-up that extends previous work and compares the results to experimental measurements for a SAFE-100 type heat pipe design.

Bragg-Sitton, Shannon M.↗
NASA NTRS2005

Fatigue Behavior and Deformation Mechanisms in Inconel 718 Superalloy Investigated

The nickel-base superalloy Inconel 718 (IN 718) is used as a structural material for a variety of components in the space shuttle main engine (SSME) and accounts for more than half of the total weight of this engine. IN 718 is the bill-of-material for the pressure vessels of nickel-hydrogen batteries for the space station. In the case of the space shuttle main engine, structural components are typically subjected to startup and shutdown load transients and occasional overloads in addition to high-frequency vibratory loads from routine operation. The nickel-hydrogen battery cells are prooftested before service and are subjected to fluctuating pressure loads during operation. In both of these applications, the structural material is subjected to a monotonic load initially, which is subsequently followed by fatigue. To assess the life of these structural components, it is necessary to determine the influence of a prior monotonic load on the subsequent fatigue life of the superalloy. An insight into the underlying deformation and damage mechanisms is also required to properly account for the interaction between the prior monotonic load and the subsequent fatigue loading. An experimental investigation was conducted to establish the effect of prior monotonic straining on the subsequent fatigue behavior of wrought, double-aged, IN 718 at room temperature. First, monotonic strain tests and fully-reversed, strain-controlled fatigue tests were conducted on uniform-gage-section IN 718 specimens. Next, fully reversed fatigue tests were conducted under strain control on specimens that were monotonically strained in tension. Results from this investigation indicated that prior monotonic straining reduced the fatigue resistance of the superalloy particularly at the lowest strain range. Some of the tested specimens were sectioned and examined by transmission electron microscopy to reveal typical microstructures as well as the active deformation and damage mechanisms under each of the loading conditions. In monotonically strained specimens, deformation during the subsequent fatigue loading was mainly confined to the deformation bands initiated during the prior monotonic straining. This can cause dislocations to move more readily along the previously activated deformation bands and to pile up near grain boundaries, eventually making the grain boundaries susceptible to fatigue crack initiation. The mechanisms inferred from the microstructural investigation were extremely valuable in interpreting the influence of prior monotonic straining on the subsequent fatigue life of Inconel 718 superalloy.

Source record↗
NASA NTRS1996

Thermal and Structural Analysis Conducted on Hollow-Core Turbine Blade of the Space Shuttle Main Engine

Hot-section components of spacecraft engines are exposed to severe thermal-structural loading conditions, especially during the startup and shutdown portions of the engine cycle. For instance, the thermal transient during startup within the space shuttle main engine (SSME) can lead to a gas temperatures in excess of 3000 C, affecting the operating life of key components, such as the turbine blades. To improve the durability of these components and in particular the turbine blade, single crystal superalloys have been considered. PWA-1480, a nickel-base superalloy, has been used as the turbine blade material for the Alternate Turbopump Development (ATD) program for the SSME.

Source record↗