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At least 343 records · Page 19

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NASA NTRS2004

Strategy Developed for Selecting Optimal Sensors for Monitoring Engine Health

Sensor indications during rocket engine operation are the primary means of assessing engine performance and health. Effective selection and location of sensors in the operating engine environment enables accurate real-time condition monitoring and rapid engine controller response to mitigate critical fault conditions. These capabilities are crucial to ensure crew safety and mission success. Effective sensor selection also facilitates postflight condition assessment, which contributes to efficient engine maintenance and reduced operating costs. Under the Next Generation Launch Technology program, the NASA Glenn Research Center, in partnership with Rocketdyne Propulsion and Power, has developed a model-based procedure for systematically selecting an optimal sensor suite for assessing rocket engine system health. This optimization process is termed the systematic sensor selection strategy. Engine health management (EHM) systems generally employ multiple diagnostic procedures including data validation, anomaly detection, fault-isolation, and information fusion. The effectiveness of each diagnostic component is affected by the quality, availability, and compatibility of sensor data. Therefore systematic sensor selection is an enabling technology for EHM. Information in three categories is required by the systematic sensor selection strategy. The first category consists of targeted engine fault information; including the description and estimated risk-reduction factor for each identified fault. Risk-reduction factors are used to define and rank the potential merit of timely fault diagnoses. The second category is composed of candidate sensor information; including type, location, and estimated variance in normal operation. The final category includes the definition of fault scenarios characteristic of each targeted engine fault. These scenarios are defined in terms of engine model hardware parameters. Values of these parameters define engine simulations that generate expected sensor values for targeted fault scenarios. Taken together, this information provides an efficient condensation of the engineering experience and engine flow physics needed for sensor selection. The systematic sensor selection strategy is composed of three primary algorithms. The core of the selection process is a genetic algorithm that iteratively improves a defined quality measure of selected sensor suites. A merit algorithm is employed to compute the quality measure for each test sensor suite presented by the selection process. The quality measure is based on the fidelity of fault detection and the level of fault source discrimination provided by the test sensor suite. An inverse engine model, whose function is to derive hardware performance parameters from sensor data, is an integral part of the merit algorithm. The final component is a statistical evaluation algorithm that characterizes the impact of interference effects, such as control-induced sensor variation and sensor noise, on the probability of fault detection and isolation for optimal and near-optimal sensor suites.

Source record↗

NASA NTRS2002

Long-Term Creep of a Thin-Walled Inconel 718 Stirling Power-Convertor Heater Head Assessed

The Department of Energy and NASA have identified Stirling power convertors as candidate power supply systems for long-duration, deep-space science missions. A key element for qualifying the flight hardware is a long-term durability assessment for critical hot section components of the power convertor. One such critical component is the power convertor heater head. The heater head is a high-temperature pressure vessel that transfers heat to the working gas medium of the convertor, which is typically helium. An efficient heater head design is the result of balancing the divergent requirements of thin walls for increased heat transfer versus thick walls to lower the wall stresses and thus improve creep resistance and durability. In the current design, the heater head is fabricated from the Ni-base superalloy Inconel 718 (IN 718, Inco Alloys International, Inc., Huntington, WV). Although IN 718 is a mature alloy system (patented in 1962), there is little long-term (>50,000-hr) creep data available for thin-specimen geometries. Since thin-section properties tend to be inferior to thicker samples, it is necessary to generate creep data using specimens with the same geometry as the actual flight hardware. Therefore, one facet of the overall durability assessment program involves generating relatively short-term creep data using thin specimens at the design temperature of 649 C (1200 F).

Bowman, Randy R.↗

NASA NTRS2001

Fusion for Space Propulsion

There is little doubt that humans will attempt to explore and develop the solar system in this century. A large amount of energy will be required for accomplishing this. The need for fusion propulsion is discussed. For a propulsion system, there are three important thermodynamical attributes: (1) The absolute amount of energy available, (2) the propellant exhaust velocity, and (3) the jet power per unit mass of the propulsion system (specific power). For human exploration and development of the solar system, propellant exhaust velocity in excess of 100 km/s and specific power in excess of 10 kW/kg are required. Chemical combustion can produce exhaust velocity up to about 5 km/s. Nuclear fission processes typically result in producing energy in the form of heat that needs to be manipulated at temperatures limited by materials to about 2,800 K. Using the energy to heat a hydrogen propellant increases the exhaust velocity by only a factor of about two. Alternatively the energy can be converted into electricity which is then used to accelerate particles to high exhaust velocity. The necessary power conversion and conditioning equipment, however, increases the mass of the propulsion system for the same jet power by more than two orders of magnitude over chemical system, thus greatly limits the thrust-to-weight ratio attainable. The principal advantage of the fission process is that its development is relatively mature and is available right now. If fusion can be developed, fusion appears to have the best of all worlds in terms of propulsion - it can provide the absolute amount, the propellant exhaust velocity, and the high specific jet power. An intermediate step towards pure fusion propulsion is a bimodal system in which a fission reactor is used to provide some of the energy to drive a fusion propulsion unit. The technical issues related to fusion for space propulsion are discussed. The technical priorities for developing and applying fusion for propulsion are somewhat different from those for terrestrial electrical power generation. Thus fusion schemes that are initially attractive for electrical power generation might not necessarily be attractive also for propulsion and vice versa, though the underlying fusion science and engineering enjoy much overlap. Parallel efforts to develop these qualitatively differently fusion schemes for the two applications could benefit greatly from each other due to the synergy in the underlying physics and engineering. Pulsed approaches to fusion have not been explored to the same degree as steady-state or long-pulse approaches to fusion in the fusion power research program. The concerns early on were several. One was that the pulsed power components might not have the service lifetimes meeting the requirements of a practical power generating plant. Another was that, for many pulsed fusion schemes, it was not clear whether the destruction of hardware per pulse could be minimized or eliminated or recycled to such an extent as to make economical electrical power generation feasible, Significant development of the underlying pulsed power component technologies have occurred in the last two decades because of defense and other energy requirements. The state of development of the pulsed power technologies are sufficiently advanced now to make it compelling to visit or re-visit pulsed fusion approaches for application to propulsion where the cost of energy is not so demanding a factor as in the case of terrestrial power application. For propulsion application, the overall mass of the fusion system is the critical factor. Producing fusion reactions require extreme states of matter. Conceptually, these extreme states of matter are more readily realizable in the pulsed states, at least within appropriate bounds, than in the steady states. Significant saving in system mass may result in such systems. Magnetic fields are effective in confining plasma energy, whereas inertial compression is an effective way of heating and containing the plasma. Intensive research in developing magnetic energy containment and inertial plasma compression are being pursued in distinctively different fusion experiments in the terrestrial fusion power program. Fusion schemes that attempt to combine the favorable attributes of these two aspects into one single integrated fusion scheme appear to have benefits that are worth exploring for propulsion application.

Thio, Y. C. Francis↗

NASA NTRSDate not supplied

Autonomous Navigation of a Lunar Relay Using GNSS and Other Measurements

Many of the highest priority destinations at the Moon lack a continuous view of Earth, such as the lunar poles or lunar far side. Exploration of these sites will require spacecraft in cislunar space to relay communications and provide position, navigation, and timing (PNT) services. Accurate knowledge of relay position, velocity, and time is essential to these services. This paper describes a concept for a PNT Instrument being developed for the Lunar Communications Relay and Navigation Systems (LCRNS) Project. The instrument is intended as a payload that would enable autonomous, on-board, real-time navigation and timing using Global Navigation Satellite System (GNSS), optical navigation, and one-way measurements from Earth-based ground stations. Hardware-in-the-loop simulations using flight software are used to realistically characterize performance on hardware platforms with a path to flight. These results provide preliminary validation of the proposed PNT Instrument, demonstrate the benefits of augmenting GNSS with other measurements, and serve as an insightful reference for the design of future lunar missions, including those that will operate within the LunaNet framework of standards. This instrument concept relies on several technologies developed at NASA Goddard Space Flight Center (GSFC). For GNSS observables, the instrument relies on the high-altitude NavCube 3 mini (NC3m) GNSS receiver specifically designed for cislunar applications. The autoNGC system, which consists of flight software and a hardware platform, is responsible for fusing the observables using its extended Kalman filter, the Goddard Enhanced Onboard Navigation System (GEONS). Optical navigation observables are processed within autoNGC (“autonomous Navigation, Guidance, and Control”) using the Goddard Image Analysis & Navigation Tool (GIANT) which is also responsible for simulating high-fidelity images for test and analysis. In addition to describing the PNT Instrument and its components, the paper will present predicted performance based on simulation results. As a baseline, it will present GNSS-only hardware-in-the loop results using a NC3m test unit to process Spirent-simulated GPS signals in a potential lunar relay trajectory: a 12-hour elliptical frozen lunar orbit (ELFO). GEONS then processes the GPS pseudorange and time differenced carrier phase measurements to estimate and propagate the relay state (position, velocity, and time). These results extend previously published work that showed preliminary ELFO performance. Previous work has shown the importance of other measurement types, so additional simulations are performed which augment GNSS with ground station observables and several methods of optical navigation, including celestial navigation, limb-finding (e.g., observations of the lunar horizon), and terrain relative navigation (TRN). TRN involves correlating simulated predicted images of the lunar surface with actual imagery; misalignments of landmarks identified in each image are translated into relay state updates. TRN is valuable as a measurement of the relay’s state relative to the Moon, especially during GNSS outages or after maneuvers. One-way Pseudorange and Doppler measurements from Earth-based ground stations are also simulated. The full set of observables is processed using autoNGC. These simulations make use of autoNGC and NC3m test units, a lab atomic clock, and a pulse-per-second (PPS) generation and distribution system. This combination of subsystems, and the hardware platforms used in this analysis, represents a PNT Instrument that could be flown on a lunar relay. Results from the hardware-in-the-loop simulations presented in this paper provide a preliminary assessment of the achievable navigation performance of this instrument concept. PNT Instrument performance is compared to the GPS-only performance, and a discussion is provided on the apparent merits and challenges of each measurement type.

Ben Ashman↗

NASA NTRS1986

Electrochemical carbon dioxide concentrator subsystem development

The most promising concept for a regenerative CO2 removal system for long duration manned space flight is the Electrochemical CO2 Concentrator (EDC), which allows for the continuous, efficient removal of CO2 from the spacecraft cabin. This study addresses the advancement of the EDC system by generating subsystem and ancillary component reliability data through extensive endurance testing and developing related hardware components such as electrochemical module lightweight end plates, electrochemical module improved isolation valves, an improved air/liquid heat exchanger and a triple redundant relative humidity sensor. Efforts included fabrication and testing the EDC with a Sabatier CO2 Reduction Reactor and generation of data necessary for integration of the EDC into a space station air revitalization system. The results verified the high level of performance, reliability and durability of the EDC subsystem and ancillary hardware, verified the high efficiency of the Sabatier CO2 Reduction Reactor, and increased the overall EDC technology engineering data base. The study concluded that the EDC system is approaching the hardware maturity levels required for space station deployment.

Koszenski, E. P.↗

NASA NTRS1984

Computer generated animation and movie production at LARC: A case study

The process of producing computer generated 16mm movies using the MOVIE.BYU software package developed by Brigham Young University and the currently available hardware technology at the Langley Research Center is described. A general overview relates the procedures to a specific application. Details are provided which describe the data used, preparation of a storyboard, key frame generation, the actual animation, title generation, filming, and processing/developing the final product. Problems encountered in each of these areas are identified. Both hardware and software problems are discussed along with proposed solutions and recommendations.

Gates, R. L.↗

NASA NTRSDate not supplied

Comparing the Electrical Modeling and Thermal Analysis Toolbox Simulation Data to Electrified Aircraft Propulsion Test Hardware Data

The Electrical Modeling and Thermal Analysis Toolbox (EMTAT), a National Aeronautics and Space Administration (NASA)-developed Simulink™ model block library of electrical components developed with the goal of facilitating system-level control design and analysis, has two levels of fidelity depending on the test needs. The Physics Based model blocks are designed to use physical component characteristics to more accurately model real hardware, including power losses, efficiency, thermal effects, electromagnetic losses, voltage drops and current requirements. These blocks model electrical dynamics that occur at the millisecond turbomachinery time scale which allows for faster-than-real-time electrified turbomachinery simulations. A model was developed to mirror the Hybrid Propulsion Emulation Rig (HyPER) hardware, a laboratory focused on Electrified Aircraft Propulsion (EAP) hardware tests. The present hardware setup supports Turbine Electrified Energy Management (TEEM) testing. The outputs of the model were compared to the results of several tests on the HyPER laboratory motor-generator setup with the goal of matching the steady state simulation data to steady state hardware data within 5% of full scale. The objective of this paper is to present the background, setup, testing and results of this comparison. It will describe some of the adjustments that were necessary to match the system hardware, as well as next steps in verification and validation.

Hyper↗

NASA NTRS2009

Sublimator Driven Coldplate Engineering Development Unit Test Results and Development of Second Generation SDC

The Sublimator Driven Coldplate (SDC) is a unique piece of thermal control hardware that has several advantages over a traditional thermal control scheme. The principal advantage is the possible elimination of a pumped fluid loop, potentially increasing reliability and reducing complexity while saving both mass and power. Furthermore, the Integrated Sublimator Driven Coldplate (ISDC) concept couples a coolant loop with the previously described SDC hardware. This combination allows the SDC to be used as a traditional coldplate during long mission phases. The previously developed SDC technology cannot be used for long mission phases due to the fact that it requires a consumable feedwater for heat rejection. Adding a coolant loop also provides for dissimilar redundancy on the Altair Lander ascent module thermal control system, which is the target application for this technology. Tests were performed on an Engineering Development Unit at NASA s Johnson Space Center to quantify and assess the performance of the SDC. Correlated thermal math models were developed to help explain the test data. The paper also outlines the preliminary results of an ISDC concept being developed.

Stephan, Ryan A.↗

NASA NTRS2003

Simulation, Model Verification and Controls Development of Brayton Cycle PM Alternator: Testing and Simulation of 2 KW PM Generator with Diode Bridge Output

Professor Stankovic will be developing and refining Simulink based models of the PM alternator and comparing the simulation results with experimental measurements taken from the unit. Her first task is to validate the models using the experimental data. Her next task is to develop alternative control techniques for the application of the Brayton Cycle PM Alternator in a nuclear electric propulsion vehicle. The control techniques will be first simulated using the validated models then tried experimentally with hardware available at NASA. Testing and simulation of a 2KW PM synchronous generator with diode bridge output is described. The parameters of a synchronous PM generator have been measured and used in simulation. Test procedures have been developed to verify the PM generator model with diode bridge output. Experimental and simulation results are in excellent agreement.

Anna V Stankovic↗

NASA NTRS1971

Shuttle cryogenic supply system optimization study

Technical information on different cryogenic supply systems is presented for selecting representative designs. Parametric data and sensitivity studies, and an evaluation of related technology status are included. An integrated mathematical model for hardware program support was developed. The life support system, power generation, and propellant supply are considered. The major study conclusions are the following: Optimum integrated systems tend towards maximizing liquid storage. Vacuum jacketing of tanks is a major effect on integrated systems. Subcritical storage advantages over supercritical storage decrease as the quantity of propellant or reactant decreases. Shuttle duty cycles are not severe. The operational mode has a significant effect on reliability. Components are available for most subsystem applications. Subsystems and components require a minimum amount of technology development.

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NASA NTRS1980

Eight microprocessor-based instrument data systems in the Galileo Orbiter spacecraft

Instrument data systems consist of a microprocessor, 3K bytes of Read Only Memory and 3K bytes of Random Access Memory. It interfaces with the spacecraft data bus through an isolated user interface with a direct memory access bus adaptor, and/or parallel data from instrument devices such as registers, buffers, analog to digital converters, multiplexers, and solid state sensors. These data systems support the spacecraft hardware and software communication protocol, decode and process instrument commands, generate continuous instrument operating modes, control the instrument mechanisms, acquire, process, format, and output instrument science data.

Barry, R. C.↗

NASA NTRS1983

Permanent-Magnet Motors and Generators for Aircraft

Electric motors and generators that use permarotating machinery, but aspects of control and power conditioning are also considered. The discussion is structured around three basic areas: rotating machine design considerations presents various configuration and material options, generator applications provides insight into utilization areas and shows actual hardware and test results, and motor applications provides the same type of information for drive systems.

Echolds, E. F.↗

NASA NTRS1986

Development of an impulsive noise source to study the acoustic reflection characteristics of hard-walled wind tunnels

Two impulsive sound sources, one using multiple acoustic drivers and the other using a spark discharge were developed to study the acoustic reflection characteristics of hard-walled wind tunnels, and the results of laboratory tests are presented. The analysis indicates that though the intensity of the pulse generated by the spark source was higher than that obtained from the acoustic source, the number of averages needed for a particular test may require an unacceptibly long tunnel-run time due to the low spark generation repeat rate because of capacitor charging time. The additional hardware problems associated with the longevity of electrodes and electrode holders in sustaining the impact of repetitive spark discharges, show the multidriver acoustic source to be more suitable for this application.

Salikuddin, M.↗

NASA NTRS1987

Carbon deposition characteristics of LO2/HC propellants

The generation and deposition of carbon have been studied using subscale hardware with LO2/RP-1, LO2/propane, and LO2/methane at low mixture ratio conditions. The deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60, and at chamber pressures from 720 to 1650 psia. The carbon-deposition rate is a strong function of mixture ratio and a weak function of chamber pressure. There is a mixture ratio that will minimize deposition for LO2/RP-1; a threshold mixture ratio for LO2/propane; and no deposition for LO2/methane at any mixture ratio tested. The turbine drive operating limits were defined for each fuel tested.

Hernandez, Rosemary↗

NASA NTRS1988

Turnaround operations analysis for OTV. Volume 2: Detailed technical report

The objectives and accomplishments were to adapt and apply the newly created database of Shuttle/Centaur ground operations. Previously defined turnaround operations analyses were to be updated for ground-based OTVs (GBOTVs) and space-based OTVs (SBOTVs), design requirements identified for both OTV and Space Station accommodations hardware, turnaround operations costs estimated, and a technology development plan generated to develop the required capabilities. Technical and programmatic data were provided for NASA pertinent to OTV round and space operations requirements, turnaround operations, task descriptions, timelines and manpower requirements, OTV modular design and booster and Space Station interface requirements. SBOTV accommodations development schedule, cost and turnaround operations requirements, and a technology development plan for ground and space operations and space-based accommodations facilities and support equipment. Significant conclusion are discussed.

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NASA NTRS1990

Realtime multi-plot graphics system

The increased complexity of test operations and customer requirements at Langley Research Center's National Transonic Facility (NTF) surpassed the capabilities of the initial realtime graphics system. The analysis of existing hardware and software and the enhancements made to develop a new realtime graphics system are described. The result of this effort is a cost effective system, based on hardware already in place, that support high speed, high resolution, generation and display of multiple realtime plots. The enhanced graphics system (EGS) meets the current and foreseeable future realtime graphics requirements of the NTF. While this system was developed to support wind tunnel operations, the overall design and capability of the system is applicable to other realtime data acquisition systems that have realtime plot requirements.

Shipkowski, Michael S.↗

NASA NTRS1995

Performance and policy dimensions in internet routing

The Internet Routing Project, referred to in this report as the 'Highball Project', has been investigating architectures suitable for networks spanning large geographic areas and capable of very high data rates. The Highball network architecture is based on a high speed crossbar switch and an adaptive, distributed, TDMA scheduling algorithm. The scheduling algorithm controls the instantaneous configuration and swell time of the switch, one of which is attached to each node. In order to send a single burst or a multi-burst packet, a reservation request is sent to all nodes. The scheduling algorithm then configures the switches immediately prior to the arrival of each burst, so it can be relayed immediately without requiring local storage. Reservations and housekeeping information are sent using a special broadcast-spanning-tree schedule. Progress to date in the Highball Project includes the design and testing of a suite of scheduling algorithms, construction of software reservation/scheduling simulators, and construction of a strawman hardware and software implementation. A prototype switch controller and timestamp generator have been completed and are in test. Detailed documentation on the algorithms, protocols and experiments conducted are given in various reports and papers published. Abstracts of this literature are included in the bibliography at the end of this report, which serves as an extended executive summary.

Mills, David L.↗

NASA NTRS1997

2 kWe Solar Dynamic Ground Test Demonstration Project: Executive Summary - Volume 1

The Solar Dynamic Ground Test Demonstration (SDGTD) successfully demonstrated a solar-powered closed Brayton cycle system in a relevant space thermal environment. In addition to meeting technical requirements the project was completed 4 months ahead of schedule and under budget. The following conclusions can be supported: 1. The component technology for solar dynamic closed Brayton cycle technology has clearly been demonstrated. 2. The thermal, optical, control, and electrical integration aspects of systems integration have also been successfully demonstrated. Physical integration aspects were not attempted as these tend to be driven primarily by mission-specific requirements. 3. System efficiency of greater than 15 percent (all losses fully accounted for) was demonstrated using equipment and designs which were not optimized. Some preexisting hardware was used to minimize cost and schedule. 4. Power generation of 2 kWe. 5. A NASA/industry team was developed that successfully worked together to accomplish project goals. The material presented in this report will show that the technology necessary to design and fabricate solar dynamic electrical power systems for space has been successfully developed and demonstrated. The data will further show that achieved results compare well with pretest predictions. The next step in the development of solar dynamic space power will be a flight test.

Alexander, Dennis↗