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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.
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These viewgraphs present three examples of structural grid generation from MSFC analysts. The propulsion systems components include high performance requirements and multi-curved surfaces. Grid generation or finite element meshing for structural and thermal analysis models is currently accomplished using interactive graphics based software on personal workstations.
A major goal in the control of complex mechanical system such as spacecraft rocket engine's advanced aircraft, and power plants is to achieve high performance with increased reliability, component durability, and maintainability. The current practice of decision and control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the materials degradation. In view of the high performance requirements of the system and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea in this report is that a significant improvement in service life could be achieved by a small reduction in the system dynamic performance. The major task is to characterize the damage generation process, and then utilize this information in a mathematical form to synthesize a control law that would meet the system requirements and simultaneously satisfy the constraints that are imposed by the material and structural properties of the critical components. The concept of damage mitigation is introduced for control of mechanical systems to achieve high performance with a prolonged life span. A model of fatigue damage dynamics is formulated in the continuous-time setting, instead of a cycle-based representation, for direct application to control systems synthesis. An optimal control policy is then formulated via nonlinear programming under specified constraints of the damage rate and accumulated damage. The results of simulation experiments for the transient upthrust of a bipropellant rocket engine are presented to demonstrate efficacy of the damage-mitigating control concept.
The Space Shuttle Thermal Protection System (TPS) tiles and blankets are waterproofed using DimethylEthoxySilane (DMEX) in the Orbiter Processing Facilities (OPF). DMES has a Threshold Limit Value (TLV) for exposure of personnel to vapor concentration in air of 0.5 ppm. The OPF high bay cannot be opened for normal work after a waterproofing operation until the DMES concentration is verified by measurement to be below the TLV. On several occasions the high bay has been kept closed for up to 8 hours following waterproofing operations due to high DMES measurements. In addition, the Miran 203 and Miran 1 BX infrared analyzers calibrated at different wavelengths gave different readings under the same conditions. There was reason to believe that some of the high DMES concentration readings were caused by interference form water and ethanol vapors. The Toxic Vapor Detection Laboratory (TVDL) was asked to test the existing DMES instruments and identify the best qualified instrument. In addition the TVDL was requested to develop instrumentation to ensure the OPF high bay could be opened safely as soon as possible after a waterproofing operation. A Fourier Transform Infrared (FTIR) spectrophotometer instrument developed for an earlier project was reprogrammed to measure DMES vapor along with ethanol, water, and several common solvent vapors. The FTIR was then used to perform a series of laboratory and field tests to evaluate the performance of the single wavelength IR instruments in use. The results demonstrated that the single wavelength IR instruments did respond to ethanol and water vapors, more or less depending on the analytical IR wavelength selected. The FTIR was able to separate the responses to DMES, water and ethanol, and give consistent readings for the DMES vapor concentration. The FTIR was then deployed to the OPF to monitor real waterproofing operations. The FTIR was also used to measure the time for DMES to evaporate from TPS tile under a range of humidity conditions in controlled laboratory tests. The combination of laboratory and field tests with the FTIR instrument demonstrated superior sensitivity, ability to reject interference from water and ethanol vapors, ruggedness to be transported from the lab to the OPF and set up without special procedures or degradation of performance. The multiple component vapor analysis algorithm was developed at KSC and incorporates automatic baseline correction and shape fitting of the spectra. The analysis for DMES, TetraMethylDiSiloxane (TMDS), ethanol, methanol, isopropanol, and baseline parameters uses 161 points per sample at 4 cm(exp -1) resolution, and processes an eight scan sample every ten seconds. The standard deviation of the measurements is 0.013 ppm and the upper linear limit is 125 ppm DMES. Based on successful demonstration of capabilities we produced three mobile instrument carts to be used in each OPF to support future waterproofing operations. The design and building of the 'DMES Carts' were accomplished in Fiscal year 1995.
Results from several satellite observations are used to discuss the discrete emission component of galaxies, including bright binary sources, supernova and supernova remnants. Through X-ray observations, direct evidence of the chemical and dynamical interactions between galaxies and the surrounding medium can be obtained. Although the X-ray emission represents only a small fraction of the bolometric emission of a normal galaxy, it allows the study of the system's component to be performed. The results on low luminosity active galactic nuclei are also discussed.
This paper presents the results of applying two different types of neural networks in two different approaches to the sensor validation problem. The first approach uses a functional approximation neural network as part of a nonlinear observer in a model-based approach to analytical redundancy. The second approach uses an auto-associative neural network to perform nonlinear principal component analysis on a set of redundant sensors to provide an estimate for a single failed sensor. The approaches are demonstrated using a nonlinear simulation of a turbofan engine. The fault detection and sensor estimation results are presented and the training of the auto-associative neural network to provide sensor estimates is discussed.
As a key component in its ground test bed capability, NASA's Advanced Life Support Program has been developing a large-scale advanced life support test facility capable of supporting long-duration evaluations of integrated bioregenerative life support systems with human test crews. This facility-targeted for evaluation of hypogravity compatible life support systems to be developed for use on planetary surfaces such as Mars or the Moon-is called the Bioregenerative Planetary Life Support Systems Test Complex (BIO-Plex) and is currently under development at the Johnson Space Center. This test bed is comprised of a set of interconnected chambers with a sealed internal environment which are outfitted with systems capable of supporting test crews of four individuals for periods exceeding one year. The advanced technology systems to be tested will consist of both biological and physicochemical components and will perform all required crew life support functions. This presentation provides a description of the proposed test "missions" to be supported by the BIO-Plex and the planned development strategy for the facility.
The exploration of deep space presents a variety of significant control challenges. Long communication delays coupled with challenging new science objectives require high levels of system autonomy and increasingly demanding pointing and control capabilities. Historically, missions based on the use of a large single spacecraft have been successful and popular since the early days of NASA. However, these large spacecraft missions are currently being displaced by more frequent and more focused missions based on the use of smaller and less expensive spacecraft designs. This trend drives the need to design smart software and good algorithms which together with the miniaturization of control components will improve performance while replacing the heavier and more expensive hardware used in the past. NASA's future space exploration will also include mission types that have never been attempted before, posing significant challenges to the underlying control system. This includes controlled landing on small bodies (e.g., asteroids and comets), sample return missions (where samples are brought back from other planets), robotic exploration of planetary surfaces (e.g., intelligent rovers), high precision formation flying, and deep space optical interferometry, While the control of planetary spacecraft for traditional flyby and orbiter missions are based on well-understood methodologies, control approaches for many future missions will be fundamentally different. This paradigm shift will require completely new control system development approaches, system architectures, and much greater levels of system autonomy to meet expected performance in the presence of significant environmental disturbances, and plant uncertainties. This paper will trace the motivation for these changes and will layout the approach taken to meet the new challenges. Emerging missions will be used to explain and illustrate the need for these changes.
I am developing a prototype of a Linux remote disk block server whose purpose is to serve as a lower level component of a parallel file system. Parallel file systems are an important component of high performance supercomputers and clusters. Although supercomputer vendors such as SGI and IBM have their own custom solutions, there has been a void and hence a demand for such a system on Beowulf-type PC Clusters. Recently, the Parallel Virtual File System (PVFS) project at Clemson University has begun to address this need (1). Although their system provides much of the functionality of (and indeed was inspired by) the equivalent file systems in the commercial supercomputer market, their system is all in user-space. Migrating their 10 services to the kernel could provide a performance boost, by obviating the need for expensive system calls. Thanks to Pavel Machek, the Linux kernel has provided the network block device (2) with kernels 2.1.101 and later. You can configure this block device to redirect reads and writes to a remote machine's disk. This can be used as a building block for constructing a striped file system across several nodes.
Scalability analysis forms an important component of any performance debugging cycle, for massively parallel machines. However, tools that help in performing such analysis for parallel programs are non-existent. The primary reason for lack of such tools is the complexity involved in capturing program dynamics such as communication-computation overlap, communication latencies and memory hierarchy reference patterns. In this paper, we highlight some simple techniques that can be used to study scalability of explicit message-passing parallel programs that consider the above issues. We start from the high level source code and use a methodology for deducing communication characteristics and its impact on the total execution time of the program. The approach is validated with the help of a pipelined method for solving scalar tri-diagonal systems, using both simulations and symbolic cost models on the Intel hypercube.
A new Adaptable, Robust, Metallic, Operable, Reusable (ARMOR) thermal protection system (TPS) concept has been designed, analyzed, and fabricated. In addition to the inherent tailorable robustness of metallic TPS, ARMOR TPS offers improved features based on lessons learned from previous metallic TPS development efforts. A specific location on a single-stage-to-orbit reusable launch vehicle was selected to develop loads and requirements needed to design prototype ARMOR TPS panels. The design loads include ascent and entry heating rate histories, pressures, acoustics, and accelerations. Additional TPS design issues were identified and discussed. An iterative sizing procedure was used to size the ARMOR TPS panels for thermal and structural loads as part of an integrated TPS/cryogenic tank structural wall. The TPS panels were sized to maintain acceptable temperatures on the underlying structure and to operate under the design structural loading. Detailed creep analyses were also performed on critical components of the ARMOR TPS panels. A lightweight, thermally compliant TPS support system (TPSS) was designed to connect the TPS to the cryogenic tank structure. Four 18-inch-square ARMOR TPS panels were fabricated. Details of the fabrication process are presented. Details of the TPSS for connecting the ARMOR TPS panels to the externally stiffened cryogenic tank structure are also described. Test plans for the fabricated hardware are presented.
Wireless networks are being used to connect mobile computing elements in more applications as the technology matures. There are now many products (such as 802.11 and 802.11b) which ran in the ISM frequency band and comply with wireless network standards. They are being used increasingly to link mobile Intranet into Wired networks. Standard methods of analyzing and testing their performance and compatibility are needed to determine the limits of the technology. This paper presents analytical and experimental methods of determining network throughput, range and coverage, and interference sources. Both radio frequency (BE) domain and network domain analysis have been applied to determine wireless network throughput and range in the outdoor environment- Comparison of field test data taken under optimal conditions, with performance predicted from RF analysis, yielded quantitative results applicable to future designs. Layering multiple wireless network- sooners can increase performance. Wireless network components can be set to different radio frequency-hopping sequences or spreading functions, allowing more than one sooner to coexist. Therefore, we ran multiple 802.11-compliant systems concurrently in the same geographical area to determine interference effects and scalability, The results can be used to design of more robust networks which have multiple layers of wireless data communication paths and provide increased throughput overall.
The development of the International Space Station (ISS) presents extensive opportunities for the implementation of long duration space life sciences studies. Continued attention has been placed in the development of plant growth chamber facilities capable of supporting the cultivation of plants in space flight microgravity conditions. The success of these facilities is largely dependent on their capacity to support the various growth requirements of test plant species. The cultivation requirements for higher plant species are generally complex, requiring specific levels of illumination, temperature, humidity, water, nutrients, and gas composition in order to achieve normal physiological growth and development. The supply of water, nutrients, and oxygen to the plant root system is a factor, which has proven to be particularly challenging in a microgravity space flight environment. The resolution of this issue is particularly important for the more intensive crop cultivation of plants envisaged in Nasa's advanced life support initiative. BioServe Space Technologies is a NASA, Research Partnership Center (RPC) at the University of Colorado, Boulder. BioServe has designed and operated various space flight plant habitat systems, and placed specific emphasis on the development and enhanced performance of subsystem components such as water and nutrient delivery, illumination, gas exchange and atmosphere control, temperature and humidity control. The further development and application of these subsystems to next generation habitats is of significant benefit and contribution towards the development of both the Space Plant biology and the Advanced Life Support Programs. The cooperative agreement between NASA Ames Research center and BioServe was established to support the further implementation of advanced cultivation techniques and protocols to plant habitat systems being coordinated at NASA Ames Research Center. Emphasis was placed on the implementation of passive-based water and nutrient support systems and techniques, which can be used to minimize demands on power, mass, and operational complexity in space flight studies. This effort has direct application to the development of next-generation space flight plant chambers such as the Plant Research Unit (PRU). Work was also directed at the development of in-flight plant preservation techniques and protocols consistent with the interest in applying recent developments in gene chip micro array technologies. Cultivation technologies and protocols were evaluated in a 55 day space flight plant growth study, conducted on the ISS, mission 9A (10/7/02 - 12/7/02).
A study was conducted to identify and evaluate noise reduction technologies for advanced ducted prop propulsion systems that would allow increased capacity operation and result in an economically competitive commercial transport. The study investigated the aero/acoustic/structural advancements in fan and nacelle technology required to match or exceed the fuel burned and economic benefits of a constrained diameter large Advanced Ducted Propeller (ADP) compared to an unconstrained ADP propulsion system with a noise goal of 5 to 10 EPNDB reduction relative to FAR 36 Stage 3 at each of the three measuring stations namely, takeoff (cutback), approach and sideline. A second generation ADP was selected to operate within the maximum nacelle diameter constrain of 160 deg to allow installation under the wing. The impact of fan and nacelle technologies of the second generation ADP on fuel burn and direct operating costs for a typical 3000 nm mission was evaluated through use of a large, twin engine commercial airplane simulation model. The major emphasis of this study focused on fan blade aero/acoustic and structural technology evaluations and advanced nacelle designs. Results of this study have identified the testing required to verify the interactive performance of these components, along with noise characteristics, by wind tunnel testing utilizing and advanced interaction rig.
UV/optical emission lines offer some of the most detailed information obtainable about the intrinsic properties of quasars. Studies of the density, ionization and metal abundance of gas near the accreting black hole are probed through an intriguing but poorly understood complex of correlations between emission lines and overall quasar spectral energy distributions that has long suffered from a lack of large, consistently measured samples. As part of a broader effort to expand and systematize the data upon which these studies are built, we proposed to NASA to model, fit, and measure UV/optical emission line parameters in large samples of quasar spectra. As part of the project, we developed an automated measurement technique that accounts for galactic reddening, includes iron emission blends, galactic and intrinsic absorption lines, and performs multi-component fits to the emission line profiles. We present measured line parameters (equivalent width and FWHM) for a large number of (28) different UV/optical lines, including upper limits for undetected lines.
High-Speed Civil Transport (HSCT) engine combustor liners are subjected to complex thermal environments and have to endure these for thousands of hours with assured reliability. In the past, several deterministic analyses have been performed, including detailed heat transfer analyses to obtain thermal profiles and deterministic stress analyses to identify critical locations of high stresses. Actual rig tests also have been performed for segments by simulating these loading situations as closely as possible. However, it is well known that many uncertainties exist in loading (primarily thermal loads due to heat transfer), boundary conditions (end fixity unknowns), and material properties (moduli, thermal-expansion coefficients, and conductivities). The present in-house effort at the NASA Lewis Research Center is directed toward accounting for these in a formal way to assess the performance of liner components under complex and uncertain loading conditions as well as subject to other geometry- and material-related uncertainties.
Since January 1999, the chemical the International Space Station Thermal Control System (IATCS) and microbial state of (ISS) Internal Active fluid has been monitored by analysis of samples returned to Earth. Key chemical parameters have changed over time, including a drop in pH from the specified 9.5 +/- 0.5 ta = 58.4, an increase in the level of total inorganic carbon (TIC), total organic carbon (TOC) and dissolved nickel (Ni) in the fluid, and a decrease in the phosphate (PO,) level. In addition, silver (AS) ion levels in the fluid decreased rapidly as Ag deposited on internal metallic surfaces of the system. The lack of available Ag ions coupled with changes in the fluid chemistry has resulted in a favorable environment for microbial growth. Counts of heterotrophic bacteria have increased from less than 10 colony-forming units (CFUs)/l00 mL to l0(exp 6) to l0(exp 7) CFUs/100 mL. The increase of the microbial population is of concern because uncontrolled microbiological growth in the IATCS can contribute to deterioration in the performance of critical components within the system and potentially impact human health if opportunistic pathogens become established and escape into the cabin atmosphere. Micro-organisms can potentially degrade the coolant chemistry; attach to surfaces and form biofilms; lead to biofouling of filters, tubing, and pumps; decrease flow rates; reduce heat transfer; initiate and accelerate corrosion; and enhance mineral scale formation. The micro- biological data from the ISS IATCS fluid, and approaches to addressing the concerns, are summarized in this paper.
This paper will describe the system architecture, the avionics components, the key performance and reliability requirements, and the current development status of the X2000 Avionics.
A satellite communication system suitable for distribution of local oscillator reference signals for a widely spaced microwave array has been developed and tested experimentally. The system uses a round-trip correction method of the satellite This experiment was carried out using Telstar-5, a commercial Ku-band geostationary satellite. For this initial experiment, both earth stations were located at the same site to facilitate direct comparison of the received signals. The local oscillator reference frequency was chosen to be 300MHz and was sent as the difference between two Ku-band tones. The residual error after applying the round trip correction has been measured to be better than 3psec for integration times ranging from 1 to 2000 seconds. For integration times greater then 500 seconds, the system outperforms a pair of hydrogen masers with the limitation believed to be ground-based equipment phase stability. The idea of distributing local oscillators using a geostationary satellite is not new; several researchers experimented with this technique in the eighties, but the achieved accuracy was 3 to 100 times worse than the present results. Since substantially and the performance of various components has improved. An important factor is the leasing of small amounts of satellite communication bandwidth. We lease three 100kHz bands at approximately one hundredth the cost of a full 36 MHz transponder. Further tests of the system using terminal separated by large distances and comparison tests with two hydrogen masers and radio interferometry is needed.