Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “stacked operation”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Technology development for phosphoric acid fuel cell powerplant, phase 2

The development of materials, cell components, and reformers for on site integrated energy systems is described. Progress includes: (1) heat-treatment of 25 sq cm, 350 sq cm and 1200 sq cm cell test hardware was accomplished. Performance of fuel cells is improved by using this material; (2) electrochemical and chemical corrosion rates of heat-treated and as-molded graphite/phenolic resin composites in phosphoric acid were determined; (3) three cell, 5 in. x 15 in. stacks operated for up to 10,000 hours and 12 in. x 17 in. five cell stacks were tested for 5,000 hours; (4) a three cell 5 in. x 15 in. stack with 0.12 mg Pt/sq cm anodes and 0.25 mg Pt/sq cm cathodes was operated for 4,500 hours; and (5) an ERC proprietary high bubble pressure matrix, MAT-1, was tested for up to 10,000 hours.

Christner, L.↗
NASA NTRS1988

Investigations of bonded and curved microchannel plate stacks

The technique of fusing, or bonding, individual microchannel plate (MCP) stacks together offers the possibility of improving the uniformity of MCP stack operating characteristics and provides a convenient monolithic format. Here, the effectiveness of bonded MCP stacks and stacks of MCPs with curved surfaces is investigated to determine if MCP requirements for future astrophysical detectors can be achieved. The results show that both configurations give superior MCP performance characteristics. However, some problems remain with regard to the fabrication of bonded MCP stacks resulting in poor flat field characteristics and increased background.

Siegmund, O. H. W.↗
NASA NTRS2010

Space Operations for a New Era of Exploration Launch Vehicles

NASA's Constellation Program is depending on the Ares Projects to deliver the crew and cargo launch capabilities needed to send human explorers to the Moon and beyond. Ares I and V will provide the core space launch capabilities needed to continue providing crew and cargo access to the International Space Station (ISS), and to build upon the U.S. history of human space exploration. Since 2005, Ares has made substantial progress on designing, developing, and testing the Ares I crew launch vehicle and has continued its in-depth studies of the Ares V cargo launch vehicles. The combined Ares I/Ares V architecture has been designed to reduce the complexity and labor intensity of ground operations for America's next journeys beyond low-Earth orbit (LEO). A deliberate effort is being made to ensure a high level of system operability to significantly increase safety and system availability as well as reduce recurring costs for this new launch vehicle. The Ares Projects goal is to instill operability as part of the vehicles requirements development, design, and operations. This simplicity will come from using simpler, proven engine designs, as in the case of the J-2X upper stage engine and RS-68 engine; improving existing hardware, as in the case of the Shuttle-heritage 5-segment solid rocket motor; and using common propulsion and instrument unit elements between Ares I and Ares V. Furthermore, lessons learned while developing Ares I will be applied directly to Ares V operations. In 2009, the Ares Projects plan to conduct the first flight test of Ares I, designated Ares I-X. Ares I-X preparations have already prompted changes to the vehicle stacking and launch infrastructure at Kennedy Space Center (KSC), including removing Shuttle-specific fixtures from the Vehicle Assembly Building (VAB) to accommodate Ares I-style stacking operations, new firing room computers and infrastructure in the VAB Launch Control Center, and new lightning protection system towers at Launch Complex 39B to accommodate the greater height of Ares I-X. In addition to lessons learned from the stacking of Ares I-X, the flight test itself promises to yield important data and operations lessons for assembling, launching, and flying Ares I.

Cook, Stephen A.↗
NASA NTRSDate not supplied

Transient Optimization of a Gas Turbine Engine

Gas turbine engines are the primary power plants for modern commercial aircraft. Transients prompted by significant changes in thrust or power demand are common and unavoidable. Extreme transient scenarios such as those associated with a go-around during a landing attempt are possible and must be accounted for in the design of the engine and its controller. Engine transients tend to cause a reduction in compressor operability margin, which must be addressed by the engine control system and accounted for in the engine design to prevent events such as compressor stall/surge and combustor blow out. Transient operability concerns typically lead to compromises in the engine design that sacrifice efficiency and/or limit responsiveness. Transient operability is typically managed by logic that limits the fuel flow command. If this logic is not optimized, then the potential for valuable performance could be lost. This study presents a strategy for optimizing the transient limit logic and proposes a strategy for updating the control logic over the lifespan of the engine. The results demonstrate significant improvements in transient operability. For example, of the results at sea level static conditions demonstrated a 31% reduction in the usage of the high pressure compressor operability stack during a snap acceleration transient. Furthermore, a reinforcement learning algorithm is demonstrated to modify the transient logic as the engine degrades to minimize response time while respecting a prescribed compressor operability margin limit. A simple demonstration of the reinforcement learning algorithm resulted in a thrust response time reduction of ~11.8%.

transient↗
NASA NTRSDate not supplied

Transient Optimization of a Gas Turbine Engine

Gas turbine engines are the primary power plants for modern commercial aircraft. Transients prompted by significant changes in thrust or power demand are common and unavoidable. Extreme transient scenarios such as those associated with a go-around during a landing attempt are possible and must be accounted for in the design of the engine and its controller. Engine transients tend to cause a reduction in compressor operability margin, which must be addressed by the engine control system and accounted for in the engine design to prevent events such as compressor stall/surge and combustor blow out. Transient operability concerns typically lead to compromises in the engine design that sacrifice efficiency and/or limit responsiveness. Transient operability is typically managed by logic that limits the fuel flow command. If this logic is not optimized, then the potential for valuable performance could be lost. This study presents a strategy for optimizing the transient limit logic and proposes a strategy for updating the control logic over the lifespan of the engine. The results demonstrate significant improvements in transient operability. For example, of the results at sea level static conditions demonstrated a 31% reduction in the usage of the high pressure compressor operability stack during a snap acceleration transient. Furthermore, a reinforcement learning algorithm is demonstrated to modify the transient logic as the engine degrades to minimize response time while respecting a prescribed compressor operability margin limit. A simple demonstration of the reinforcement learning algorithm resulted in a thrust response time reduction of ~11.8%.

transient↗
NASA NTRSDate not supplied

Transient Optimization of a Gas Turbine Engine

Gas turbine engines are the primary power plants for modern commercial aircraft. Transients prompted by significant changes in thrust or power demand are common and unavoidable. Extreme transient scenarios such as those associated with a go-around during a landing attempt are possible and must be accounted for in the design of the engine and its controller. Engine transients tend to cause a reduction in compressor operability margin, which must be addressed by the engine control system and accounted for in the engine design to prevent events such as compressor stall/surge and combustor blow out. Transient operability concerns typically lead to compromises in the engine design that sacrifice efficiency and/or limit responsiveness. Transient operability is typically managed by logic that limits the fuel flow command. If this logic is not optimized, then the potential for valuable performance could be lost. This study presents a strategy for optimizing the transient limit logic and proposes a strategy for updating the control logic over the lifespan of the engine. The results demonstrate significant improvements in transient operability. For example, of the results at sea level static conditions demonstrated a 31% reduction in the usage of the high pressure compressor operability stack during a snap acceleration transient. Furthermore, a reinforcement learning algorithm is demonstrated to modify the transient logic as the engine degrades to minimize response time while respecting a prescribed compressor operability margin limit. A simple demonstration of the reinforcement learning algorithm resulted in a thrust response time reduction of ~11.8%.

transient↗
NASA NTRS2021

Effect of Reactant Pressure on Proton Exchange Membrane Fuel Cell Performance

It is an objective of the National Aeronautics and Space Administration (NASA) to return to the moon and to create sustained lunar operations. Since many applicable lander and upper stage vehicles utilize cryogenic hydrogen and oxygen propellants, it is appealing to incorporate fuel cells into potential mission concepts. A fuel cell could generate electricity, heat, and water from the residual hydrogen and oxygen propellants. Such a concept depends on the capability of the fuel cell to utilize dry, propellant-grade reactants at reduced pressures compared to typical fuel cell operating conditions. This report describes a NASA evaluation of two passive water removal, non-flow-through proton exchange membrane (PEM) fuel cells: a twelve-cell 50 sq. cm active area stack and a seven-cell 150 sq. cm active area stack. Both stacks operated on research grade hydrogen and oxygen reactants supplied at pressures ranging from 20 psia up to the 45-48 psia design operating point, reliably supporting current densities of at least 450 mA/sq. cm at reduced pressures. Polarization curves, fitted with a semi-empirical equation for overpotential, show an increase in effective ohmic resistance and decrease in reversible cell potential, hydrogen crossover current, and Tafel slope when operating at lower pressures, resulting in a reduction in cell voltage at all current densities. Fitted parameters are compared to published values and rationalized with first principles explanations.

fuel cells↗
NASA NTRSDate not supplied

Space Launch System (SLS) Human Factors Engineering Modeling & Analysis

The Human Systems Integration & Engineering (HSI&E) team at NASA’s Marshall Space Flight Center (MSFC) strives to advocate for the humans in the loop of Space Launch System’s (SLS) ground operations. Using assessment methods like human simulation, virtual reality, and physical mockups, both flight hardware and ground support equipment (GSE) are evaluated for human integration. Those ranging from 5th percentile female (approximately 5’2” tall) to 95th percentile male (approximately 6’2” tall) should be able to perform all SLS stacking operations. Operations include element physical mates, element electrical mates, and testing activities. The primary human simulation software used is Process Simulate Human (PSH) made by Siemens. This software supplies highly accurate human manikins that can interact with CAD models. PSH was used to evaluate the Transportation and Integration Platform’s (TIP) side opening that was designed for access to the Payload Adapter (PLA) cables. Technicians will need to access these cables for testing purposes before element stacking at Kennedy Space Center (KSC). After performing an analysis in PSH using the TIP side opening, it was found that neither a 5th percentile female or a 95th percentile male could perform the task as the designers had intended. There is a C-beam that blocks access to the cables (both physically and visually). An alternative analysis was performed using PSH to look at another access point to the PLA cables. Although this method would disrupt already established procedures and produce more work, the designers confirmed it was an option. Instead of technicians accessing the cables through the side opening in the TIP, a human simulation was performed for going through a panel opening in the bottom of the TIP. This method requires removal of a TIP panel and a stepladder of at least 36 inches for a 5th percentile female to access the cables.

human factors↗
NASA NTRS1984

Electric utility acid fuel cell stack technology advancement

The principal effort under this program was directed at the fuel cell stack technology required to accomplish the initial feasibility demonstrations of increased cell stack operating pressures and temperatures, increased cell active area, incorporation of the ribbed substrate cell configuration at the bove conditions, and the introduction of higher performance electrocatalysts. The program results were successful with the primary accomplishments being: (1) fabrication of 10 sq ft ribbed substrate, cell components including higher performing electrocatalysts; (2) assembly of a 10 sq ft, 30-cell short stack; and (3) initial test of this stack at 120 psia and 405 F. These accomplishments demonstrate the feasibility of fabricating and handling large area cells using materials and processes that are oriented to low cost manufacture. An additional accomplishment under the program was the testing of two 3.7 sq ft short stacks at 12 psia/405 F to 5400 and 4500 hours respectively. These tests demonstrate the durability of the components and the cell stack configuration to a nominal 5000 hours at the higher pressure and temperature condition planned for the next electric utility power plant.

Congdon, J. V.↗
NASA NTRS1993

STS-51, RSRM-033, 360T033 KSC processing configuration and data report

KSC Processing Configuration and Data Report is being provided as a historical document and as an enhancement to future RSRM manufacturing and processing operations. The following sections provide information on segment receipt, aft booster build up, motor assembly, and closeout for STS-51, RSRM flight set 360T033. Section 2.0 contains a summary of RSRM-033 processing. Section 3.0 discusses any significant problems or special issues that require special attention. Sections 4.0 through 6.0 contain narrative descriptions of all key events, including any related processing problems. Appendix A provides engineering specifications and changes. A list and matrix of all problem reports (PR's) pertinent to this flight set is provided in Appendix B. The matrix was provided by the Thiokol LSS Quality Engineering office. Copies of the PR's generated during the processing of RSRM-033 will be provided upon request. Appendix C contains the motor set status matrix, which provides milestone dates for the RSRM-033 flow. Section 7.0 provides recommendations for the improvement of flight hardware processing. Section 8.0 contains data sheets that provide flight hardware parts and consumable information installed during the booster build-up and stacking operations by location, lot/serial number, expiration and cure dates/times, and installation dates.

Hillard, Robert C.↗
NASA NTRS1993

STS-56, RSRM-031, 360L031 KSC processing configuration and data report

KSC Processing Configuration and Data Report is being provided as a historical document and as an enhancement to future RSRM manufacturing and processing operations. The following sections provide information on segment receipt, aft booster build-up, booster assembly, and closeout for STS-56, RSRM flight set 36OL031. Section 2.0 contains a summary of RSRM-031 processing. Section 3.0 discusses any significant problems or special issues that require special attention. Sections 4.0 through 6.0 contain narrative descriptions of all key events, including any related processing problems. Appendix A provides engineering specifications and changes. A list and matrix of all problem reports (PR's) pertinent to this flight set is provided in Appendix B. The matrix was provided by the Thiokol LSS Quality Engineering office. Copies of the PR's generated during the processing of RSRM-031 will be provided upon request. Appendix C contains the motor set status matrix, which provides milestone dates for the RSRM-031 flow. Section 7.0 provides recommendations, if any, for the improvement of flight hardware processing. Section 8.0 contains data sheets that provide flight hardware parts and consumables information installed during the booster build-up and stacking operations by location, lot/serial number, expiration and cure dates/times, and installation dates.

Source record↗
NASA NTRS1989

Advanced space power PEM fuel cell systems

A model showing mass and heat transfer in proton exchange membrane (PEM) single cells is presented. For space applications, stack operation requiring combined water and thermal management is needed. Advanced hardware designs able to combine these two techniques are available. Test results are shown for membrane materials which can operate with sufficiently fast diffusive water transport to sustain current densities of 300 ma per square centimeter. Higher power density levels are predicted to require active water removal.

Vanderborgh, N. E.↗
NASA NTRS2018

Challenges and Opportunities in Gen3 Embedded Cooling with High-Quality Microgap Flow

Gen3, Embedded Cooling, promises to revolutionize thermal management of advanced microelectronic systems by eliminating the sequential conductive and interfacial thermal resistances which dominate the present 'remote cooling' paradigm. Single-phase interchip microfluidic flow with high thermal conductivity chips and substrates has been used successfully to cool single transistors dissipating more than 40kW/sq cm, but efficient heat removal from transistor arrays, larger chips, and chip stacks operating at these prodigious heat fluxes would require the use of high vapor fraction (quality), two-phase cooling in intra- and inter-chip microgap channels. The motivation, as well as the challenges and opportunities associated with evaporative embedded cooling in realistic form factors, is the focus of this paper. The paper will begin with a brief review of the history of thermal packaging, reflecting the 70-year 'inward migration' of cooling technology from the computer-room, to the rack, and then to the single chip and multichip module with 'remote' or attached air- and liquid-cooled coldplates. Discussion of the limitations of this approach and recent results from single-phase embedded cooling will follow. This will set the stage for discussion of the development challenges associated with application of this Gen3 thermal management paradigm to commercial semiconductor hardware, including dealing with the effects of channel length, orientation, and manifold-driven centrifugal acceleration on the governing behavior.

microchannel↗
NASA NTRSDate not supplied

NASA’s Space Launch System: High C3 Launch Capability for Science Missions

As NASA’s initial Space Launch System (SLS) Block 1 vehicle enters integration and stacking operations at Kennedy Space Center (KSC) this year in preparation for a 2021 launch, work is in progress on future more powerful variants of the vehicle. Available in the mid 2020s and 2030s, Block 1B and Block 2 will feature increased performance and unparalleled volume for payloads, providing an enabling launch option for science mission planners. The baseline SLS architecture consists of two five-segment solid rocket boosters and four RS-25 LH2/LOX engines. The evolved Block 1B and Block 2 vehicles use a four-engine LH2/LOX upper stage and can be outfitted with an 8.4 m-diameter pay-load fairing. Additional upper stages can be packaged in the 8.4 m fairing to enable high C3 (in the range of 300 km2/sec2) missions to Mercury, the Jovian system, the ice giants, the Kuiper Belt and beyond.

Stephen D Creech↗
NASA NTRS2010

Modeling and Simulation of the ARES UPPER STAGE Transportation, Lifting, Stacking and Mating Operations Within the Vehicle Assembly Building at KSC

This viewgraph presentation describes the modeling and simulation of the Ares Upper Stage Transportation, lifting, stacking, and mating operations within the Vehicle Assembly Building (VAB) at Kennedy Space Center (KSC). An aerial view of KSC Launch Shuttle Complex, two views of the Delmia process control layout, and an upper stage move subroutine and breakdown are shown. An overhead image of the VAB and the turning basin along with the Pegasus barge at the turning basin are also shown. This viewgraph presentation also shows the actual design and the removal of the mid-section spring tensioners, the removal of the AFT rear and forward tensioners tie downs, and removing the AFT hold down post and mount. US leaving the Pegasus Barge, the upper stage arriving at transfer aisle, upper stage receiving/inspection in transfer aisle, and an overhead view of upper stage receiving/inspection in transfer aisle are depicted. Five views of the actual connection of the cabling to the upper stage aft lifting hardware are shown. The upper stage transporter forward connector, two views of the rotation horizontal to vertical, the disconnection of the rear bolt ring cabling, the lowering of the upper stage to the inspection stand, disconnection of the rear bolt ring from the upper stage, the lifting of the upper stage and inspection of AFT fange, and the transfer of upper stage in an integrated stack are shown. Six views of the mating of the upper stage to the first stage are depicted. The preparation, inspection, and removal of the forward dome are shown. The upper stage mated on the integrated stack and crawler is also shown. This presentation concludes with A Rapid Upper Limb Assessment (RULA) utilizing male and female models for assessing risk factors to the upper extremities of human beings in an actual physical environment.

Kromis, Phillip A.↗
NASA NTRS1992

Effects of the cooling system parameters on heat transfer and performance of the PAFC stack during transient operation

An experimental investigation for the effects of transient operation of a phosphoric acid fuel-cell stack on heat transfer and temperature distribution in the electrodes has been conducted. The proposed work utilized the experimental setup with modifications, which was designed and constructed under NASA Contract No. NCC-3-17(5). The experimental results obtained from this investigation and the mathematical model obtained under NASA Contract No. NCC3-17(4) after modifications, were utilized to develop mathematical models for transient heat transfer coefficient and temperature distribution in the electrode and to evaluate the performance of the cooling - system under unsteady state conditions. The empirical formulas developed were then implemented to modifying the developed computer code. Two incompressible coolants were used to study experimentally the effect of the thermophysical properties of the cool-ants on the transient heat transfer coefficient and the thermal contact resistance during start-up and shut-down processes. Coolant mass flow rates were verified from 16 to 88.2 Kg/hr during the transient process when the electrical power supply was gradually increased or decreased in the range (O to 3000 W/sq m). The effect of the thermal contact resistance with a range of stack pressure from O to 3500 KPa was studied.

Ridha, Rabi M. J.↗
NASA NTRS2014

Development and Experimental Evaluation of Passive Fuel Cell Thermal Control

To provide uniform cooling for a fuel cell stack, a cooling plate concept was evaluated. This concept utilized thin cooling plates to extract heat from the interior of a fuel cell stack and move this heat to a cooling manifold where it can be transferred to an external cooling fluid. The advantages of this cooling approach include a reduced number of ancillary components and the ability to directly utilize an external cooling fluid loop for cooling the fuel cell stack. A number of different types of cooling plates and manifolds were developed. The cooling plates consisted of two main types; a plate based on thermopyrolytic graphite (TPG) and a planar (or flat plate) heat pipe. The plates, along with solid metal control samples, were tested for both thermal and electrical conductivity. To transfer heat from the cooling plates to the cooling fluid, a number of manifold designs utilizing various materials were devised, constructed, and tested. A key aspect of the manifold was that it had to be electrically nonconductive so it would not short out the fuel cell stack during operation. Different manifold and cooling plate configurations were tested in a vacuum chamber to minimize convective heat losses. Cooling plates were placed in the grooves within the manifolds and heated with surface-mounted electric pad heaters. The plate temperature and its thermal distribution were recorded for all tested combinations of manifold cooling flow rates and heater power loads. This testing simulated the performance of the cooling plates and manifold within an operational fuel cell stack. Different types of control valves and control schemes were tested and evaluated based on their ability to maintain a constant temperature of the cooling plates. The control valves regulated the cooling fluid flow through the manifold, thereby controlling the heat flow to the cooling fluid. Through this work, a cooling plate and manifold system was developed that could maintain the cooling plates within a minimal temperature band with negligible thermal gradients over power profiles that would be experienced within an operating fuel cell stack.

Fuel Cells↗