A vacuum system for mass-spectrometric analyses of the atmosphere
Vacuum system for mass spectrometric analyses of atmosphere at pressures above critical value
ATMOSPHERIC COMPOSITION↗
SEARCH · Engineering Papers
Results for “system value”
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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Dynamic analysis of an open-cycle gas-core nuclear rocket
Reactivity and flow disturbances were used to investigate the transient response of a conceptual open cycle gas core nuclear rocket engine. The disturbances were made with the system initially operating at its steady state design point. Results of the study show that the feedbacks associated with the propellant density and propellant temperature have a dominant effect on the response of the system. Furthermore, there appears to be a rather limited range of values of these propellant feedback coefficients for which the gas core nuclear rocket has a stable response. The system was rather insensitive to a fuel flow rate disturbance, whereas a similar disturbance in the propellant flow rate caused large changes in reactor power. For a similar disturbance in the propellant flow rate caused large changes in reactor power. For most reactivity and flow rate disturbances, the response showed oscillations of various intensity.
Turney, G. E.↗
Computer program for prediction of capture maneuver probability for an on-off reaction controlled upper stage
A FORTRAN coded computer program which computes the capture transient of a launch vehicle upper stage at the ignition and/or separation event is presented. It is for a single degree-of-freedom on-off reaction jet attitude control system. The Monte Carlo method is used to determine the statistical value of key parameters at the outcome of the event. Aerodynamic and booster induced disturbances, vehicle and control system characteristics, and initial conditions are treated as random variables. By appropriate selection of input data pitch, yaw and roll axes can be analyzed. Transient response of a single deterministic case can be computed. The program is currently set up on a CDC CYBER 175 computer system but is compatible with ANSI FORTRAN computer language. This routine has been used over the past fifteen (15) years for the SCOUT Launch Vehicle and has been run on RECOMP III, IBM 7090, IBM 360/370, CDC6600 and CDC CYBER 175 computers with little modification.
Knauber, R. N.↗
The Dynamical Evolution of the Earth-Moon Progenitors: Motivation and Methodology - 1
The Giant Impact Hypothesis was introduced in the mid-1970's after consideration of results from the Apollo Moon missions. This hypothesis best explains the similarity in elemental proportions in lunar and terrestrial rocks, the depletion of lunar volatiles, the lack of lunar iron. and the large angular momentum in the Earth-Moon system. Comparison between the radiometric ages of inclusions in the most primitive meteorites and those of inclusions in the oldest lunar rocks and the differentiation age of Earth suggests that the Earth-Moon system formed about 100 Myr after the oldest meteorites. In addition, the age of the famous Martian meteorite ALH84001 and an early solidification time estimated from the Martian crust, suggest that the inner Solar System was fairly clear of large bodies about 10 Myr after the oldest meteorites formed. Thus, the 'standard model' suggests that for a period of several tens of millions of years the terrestrial planet region had few. if any, lunar-sized bodies and there were five terrestrial planets, Mercury, Venus, the two progenitors of the Earth-Moon system, and Mars. To simulate the dynamics of the Solar System before the hypothesized Moon-forming impact, we are integrating the Solar System with the Earth-Moon system replaced by two bodies in heliocentric orbits between Venus and Mars. The total (orbital) angular momentum of the Earth-Moon progenitors is that of the present Earth-Moon system, and their total mass is that of the Earth-Moon system. We are looking at ranges in mass ratio and initial values for eccentricity, inclination. and semi-major axis. We are using the SYMBA integrator to integrate these systems until a collision occurs or a time of 200 Myr elapses. Results are presented in a companion paper.
Lissuer, Jack↗
A qualitative assessment of a random process proposed as an atmospheric turbulence model
A random process is formed by the product of two Gaussian processes and the sum of that product with a third Gaussian process. The resulting total random process is interpreted as the sum of an amplitude modulated process and a slowly varying, random mean value. The properties of the process are examined, including an interpretation of the process in terms of the physical structure of atmospheric motions. The inclusion of the mean value variation gives an improved representation of the properties of atmospheric motions, since the resulting process can account for the differences in the statistical properties of atmospheric velocity components and their gradients. The application of the process to atmospheric turbulence problems, including the response of aircraft dynamic systems, is examined. The effects of the mean value variation upon aircraft loads are small in most cases, but can be important in the measurement and interpretation of atmospheric turbulence data.
Sidwell, K.↗
Effects of expected-value information and display format on recognition of aircraft subsystem abnormalities
This study identifies improved methods to present system parameter information for detecting abnormal conditions and to identify system status. Two workstation experiments were conducted. The first experiment determined if including expected-value-range information in traditional parameter display formats affected subject performance. The second experiment determined if using a nontraditional parameter display format, which presented relative deviation from expected value, was better than traditional formats with expected-value ranges included. The inclusion of expected-value-range information onto traditional parameter formats was found to have essentially no effect. However, subjective results indicated support for including this information. The nontraditional column deviation parameter display format resulted in significantly fewer errors compared with traditional formats with expected-value-ranges included. In addition, error rates for the column deviation parameter display format remained stable as the scenario complexity increased, whereas error rates for the traditional parameter display formats with expected-value ranges increased. Subjective results also indicated that the subjects preferred this new format and thought that their performance was better with it. The column deviation parameter display format is recommended for display applications that require rapid recognition of out-of-tolerance conditions, especially for a large number of parameters.
Palmer, Michael T.↗
Verification of L-band SAR calibration
Absolute calibration of a digital L-band SAR system to an accuracy of better than 3 dB has been verified. This was accomplished with a calibration signal generator that produces the phase history of a point target. This signal relates calibration values to various SAR data sets. Values of radar cross-section (RCS) of reference reflectors were obtained using a derived calibration relationship for the L-band channel on the ERIM/CCRS X-C-L SAR system. Calibrated RCS values were compared to known RCS values of each reference reflector for verification and to obtain an error estimate. The calibration was based on the radar response to 21 calibrated reference reflectors.
Larson, R. W.↗
A Simple Beamshaping Device for Cassegrainian Antennas
A simple beamshaping modification for Cassegrainian systems is described. A qualitative analysis is used to describe this device as well as to explain the poor performance observed with an unmodified Cassegrainian system. Experimental data are presented on both the modified and unmodified systems. The modification reduces spillover by a factor of 2 to a value of only 1. 3%. Simultaneously, the aperture efficiency is increased from 50% for the unmodified system to 60% for the modified system. Field measurements on an 85- ft modified Cassegrainian system are described which experimentally verify the applicability of the modified subreflector to low-noise antenna design. The measured zenith antenna temperature for this system is 9. 5° K; measured aperture efficiency is 50%.
ANTENNA↗
A multiloop, digital flutter suppression control law synthesis case study
A methodology for obtaining a digital low-order, multiloop, robust control law for aeroelastic application from a full-state Linear Quadratic Gaussian design is presented. As part of the design methodology, the multivariable system robustness at the plant input and output is evaluated using singular value properties and improved using constrained optimization procedures. To validate the methodology, a digital flutter suppression system has been designed for the full-span Active Flexible Wing (AFW) wind-tunnel model as part of a collaborative effort between the NASA Langley Research Center and Rockwell International. Preliminary results for a low-order discrete, symmetric flutter suppression system design that significantly improved the AFW model stability are provided and the experiences gained during the design process are discussed.
Mukhopadhyay, Vivek↗
The Observed State of the Water Cycle in the Early Twenty-First Century
This study quantifies mean annual and monthly fluxes of Earth's water cycle over continents and ocean basins during the first decade of the millennium. To the extent possible, the flux estimates are based on satellite measurements first and data-integrating models second. A careful accounting of uncertainty in the estimates is included. It is applied within a routine that enforces multiple water and energy budget constraints simultaneously in a variational framework in order to produce objectively determined optimized flux estimates. In the majority of cases, the observed annual surface and atmospheric water budgets over the continents and oceans close with much less than 10% residual. Observed residuals and optimized uncertainty estimates are considerably larger for monthly surface and atmospheric water budget closure, often nearing or exceeding 20% in North America, Eurasia, Australia and neighboring islands, and the Arctic and South Atlantic Oceans. The residuals in South America and Africa tend to be smaller, possibly because cold land processes are negligible. Fluxes were poorly observed over the Arctic Ocean, certain seas, Antarctica, and the Australasian and Indonesian islands, leading to reliance on atmospheric analysis estimates. Many of the satellite systems that contributed data have been or will soon be lost or replaced. Models that integrate ground-based and remote observations will be critical for ameliorating gaps and discontinuities in the data records caused by these transitions. Continued development of such models is essential for maximizing the value of the observations. Next-generation observing systems are the best hope for significantly improving global water budget accounting.
Numerical analysis/modeling↗
The cost of energy from utility-owned solar electric systems. A required revenue methodology for ERDA/EPRI evaluations
This methodology calculates the electric energy busbar cost from a utility-owned solar electric system. This approach is applicable to both publicly- and privately-owned utilities. Busbar cost represents the minimum price per unit of energy consistent with producing system-resultant revenues equal to the sum of system-resultant costs. This equality is expressed in present value terms, where the discount rate used reflects the rate of return required on invested capital. Major input variables describe the output capabilities and capital cost of the energy system, the cash flows required for system operation amd maintenance, and the financial structure and tax environment of the utility.
Source record↗
Sensory redundancy management: The development of a design methodology for determining threshold values through a statistical analysis of sensor output data
Sensor redundancy management (SRM) requires a system which will detect failures and reconstruct avionics accordingly. A probability density function to determine false alarm rates, using an algorithmic approach was generated. Microcomputer software was developed which will print out tables of values for the cummulative probability of being in the domain of failure; system reliability; and false alarm probability, given a signal is in the domain of failure. The microcomputer software was applied to the sensor output data for various AFT1 F-16 flights and sensor parameters. Practical recommendations for further research were made.
Scalzo, F.↗
More Efficient Precipitation Rate Data Acquisition with the STORM Swath-Based Analysis Tool
A multitude of locations exist for acquiring satellite-derived precipitation rate data. Because the volume of data exceeds what can reasonably be analyzed manually, online tools have been developed to help researchers make more informed data acquisition decisions. Some interfaces provide sample images generated from prioritized variables to enable efficient visual inspection, while others include the ability to subset geographically to reduce the volume of the data to the area of interest. Building upon such value-added services is the STORM (the NASA Precipitation Processing System (PPS) data product ordering system) Swath-Based Analysis Tool (https://storm.pps.eosdis.nasa.gov/storm/Analysis.jsp). With it, users can compare overflights of multiple precipitation satellites simultaneously and from this make determinations about which swaths will best serve their research. They can preview these overflights with two distinct visualization tools. Finally, they can then download geographically subset swaths that have precipitation rate characteristics matching their research needs. A user starts by making up to six selections. They then select their date range of interest going back to 1997. Finally, they select a geographical region either by inputting latitude-longitude corners of a rectangle or drawing that rectangle on an interactive map. The system processes each file, determining aggregate statistics about the precipitation rates within the selected region as observed by each instrument. These statistical values are added to a time series graph as a "time remaining" counter is continuously updated. The chart is fully interactive, with detailed values displayed upon mouseover, and numerous options available upon clicking each point. Since the user is likely to need the relevant files for their own research, they can generate an order from their request. All files are geographically subset to the region of interest, and the user can use the statistical values to limit which files are added to the order. This flexibility helps to ensure researchers are only downloading the files they need for their work, making for a more efficient process both from a time-consumption and a storage perspective. This paper will introduce the Swath-Based Analysis Tool and explore its numerous features. It will discuss several use cases for precipitation scientists.
remote sensing↗
The Efficacy of Seasonal Terrestrial Water Storage Forecasts for Predicting Vegetation Activity Over Africa
Terrestrial water storage (TWS) provides important information on terrestrial hydroclimate and may have value for seasonal forecasting because of its strong persistence. We use the NASA Hydrological Forecast and Analysis System (NHyFAS) to investigate TWS forecast skill over Africa and assess its value for predicting vegetation activity from satellite estimates of leaf area index (LAI). Forecast skill is high over East and Southern Africa, extending up to 3–6 months in some cases, with more modest skill over West Africa. Highest skill generally occurs during the dry season or beginning of the wet season when TWS anomalies from the previous wet season are most likely to carry forward in time. In East Africa, this occurs prior to and during the transition into the spring “Long Rains” from January–March, while in Southern Africa this period of highest skill starts at the beginning of the dry season in April and extends through to the start of the wet season in October. TWS is highly and positively correlated with LAI, and a logistic regression model shows high cross-validation skill in predicting above or below normal LAI using TWS. Combining the LAI regression model with the NHyFAS forecasts, 1-month lead LAI predictions have high accuracy over East and Southern Africa, with reduced but significant skill at 3-month leads over smaller sub-regions. This highlights the potential value of TWS as an additional source of information for seasonal forecasts over Africa, with direct applications to some of the most vulnerable agricultural regions on the continent.
Terrestrial water shortage↗
The MATHEMATICA economic analysis of the Space Shuttle System
Detailed economic analysis shows the Thrust Assisted Orbiter Space Shuttle System (TAOS) to be the most economic Space Shuttle configuration among the systems studied. The development of a TAOS Shuttle system is economically justified within a level of space activities between 300 and 360 Shuttle flights in the 1979-1990 period, or about 25 to 30 flights per year, well within the U.S. Space Program including NASA and DoD missions. If the NASA and DoD models are taken at face value (624 flights), the benefits of the Shuttle system are estimated to be $13.9 billion with a standard deviation of plus or minus $1.45 billion in 1970 dollars (at a 10% social rate of discount). If the expected program is modified to 514 flights (in the 1979-1990 period), the estimated benefits of the Shuttle system are $10.2 billion, with a standard deviation of $940 million (at a 10% social rate of discount).
Heiss, K. P.↗
ICR study of nonreactive ion-molecule collision rate constants for Cl/-/ and Cr/CO/5/-/
Determination of experimental momentum transfer rate constants for systems of Cl(-) and Cr(CO)5(-) ions by means of an ion cyclotron resonance (ICR) line-broadening technique. It is found that in the pure polarization limit of small ion/large neutral collisions the Langevin ion mobility theory gives good agreement with experimental results. A comparison of isotropic and anisotropic neutral systems suggests that a correction for the anisotropic systems is necessary. Beyond the pure polarization limit the Langevin theory gives poor predictions for ion mobilities. The adjustable parameter, gamma, of the Mason-Schamp (12-6-4) potential function permits unique solution of the ion mobility for Cr(CO)5(-) in a wide range of neutral gases. The large values of gamma obtained for most of these systems imply, in terms of the Mason-Schamp theory, that the r to the minus 6th power contribution to the potential function is significant.
Dymerski, P. P.↗
Calculation of long range forces and their applications in determining gaseous properties
A discussion of various theoretical and experimental techniques for the calculation of long range interaction between two atomic systems at moderate separation is presented. Some applications of these techniques for obtaining gaseous properties are described. The forces between neutral molecules and metallic surfaces are also discussed and numerical values of heats of adsorption for a number of systems are calculated.
Singh, J. J.↗
Detailed Chemical Kinetic Modeling of Hydrazine Decomposition
The purpose of this research project is to develop and validate a detailed chemical kinetic mechanism for gas-phase hydrazine decomposition. Hydrazine is used extensively in aerospace propulsion, and although liquid hydrazine is not considered detonable, many fuel handling systems create multiphase mixtures of fuels and fuel vapors during their operation. Therefore, a thorough knowledge of the decomposition chemistry of hydrazine under a variety of conditions can be of value in assessing potential operational hazards in hydrazine fuel systems. To gain such knowledge, a reasonable starting point is the development and validation of a detailed chemical kinetic mechanism for gas-phase hydrazine decomposition. A reasonably complete mechanism was published in 1996, however, many of the elementary steps included had outdated rate expressions and a thorough investigation of the behavior of the mechanism under a variety of conditions was not presented. The current work has included substantial revision of the previously published mechanism, along with a more extensive examination of the decomposition behavior of hydrazine. An attempt to validate the mechanism against the limited experimental data available has been made and was moderately successful. Further computational and experimental research into the chemistry of this fuel needs to be completed.
Meagher, Nancy E.↗