SEARCH · Engineering Papers
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.
A series of viewgraphs on computer networks at the Johnson Space Center (JSC) are given. Topics covered include information resource management (IRM) at JSC, the IRM budget by NASA center, networks evolution, networking as a strategic tool, the Information Services Directorate charter, and SSC network requirements, challenges, and status.
A proof of concept system is described for analyzing high energy physics (HEP) data using data base computing. The system is designed to scale up to the size required for HEP experiments at the Superconducting SuperCollider (SSC) lab. These experiments will require collecting and analyzing approximately 10 to 100 million 'events' per year during proton colliding beam collisions. Each 'event' consists of a set of vectors with a total length of approx. one megabyte. This represents an increase of approx. 2 to 3 orders of magnitude in the amount of data accumulated by present HEP experiments. The system is called the HEPDBC System (High Energy Physics Database Computing System). At present, the Mark 0 HEPDBC System is completed, and can produce analysis of HEP experimental data approx. an order of magnitude faster than current production software on data sets of approx. 1 GB. The Mark 1 HEPDBC System is currently undergoing testing and is designed to analyze data sets 10 to 100 times larger.
Given here is the annual report of the John C. Stennis Space Center (SSC), a NASA center responsible for testing NASA's large propulsion systems, developing supporting test technologies, conducting research in a variety of earth science disciplines, and facilitating the commercial uses of NASA-developed technologies. Described here are activities of the Earth Sciences Research Program, the Technology Development Program, commercial programs, the Technology Utilization Program, and the Information Systems Program. Work is described in such areas as forest ecosystems, land-sea interface, wetland biochemical flux, thermal imaging of crops, gas detectors, plume analysis, synthetic aperture radar, forest resource management, applications engineering, and the Earth Observations Commercial Applications Program.
The Naval Space Surveillance Center (NAVSPASUR) is an operational naval command that has the mission of determining the location of all manmade objects in space and transmitting information on objects of interest to the fleet. NAVSPASUR operates a 217 MHz radar fence that has 9 transmitting and receiving stations deployed in a line across southern Continental United States (CONUS). This surveillance fence provides unalerted detection of satellites overflying CONUS. NAVSPASUR also maintains a space catalog of all orbiting space objects. NAVSPASUR plays an important role as operational alternate to the primary national Space Surveillance Center (SSC) and Space Defence Operations Center (SPADOC). In executing these responsibilities, NAVSPASUR needs precise and/or standardized time and frequency in a number of applications. These include maintenance of the radar fence references to specification, and coordination with other commands and agencies for data receipt and dissemination. Precise time and frequency must be maintained within each site to enable proper operation of the interferometry phasing technique used. Precise time-of-day clocking must exist between sites for proper intersite coordination. After 'time tags' are attached to the data at the receiver sites, proper referencing and standardization are necessary at the Dahlgren, Va. operations center to ensure proper data synchronization and communications with the fleet and other agencies.
Simultaneous multiwavelength observations of BL Lacertae were performed on two occasions separated by 1 month in 1988 June and July, covering the radio, submillimeter, infrared, optical, ultraviolet, and X-ray wave bands. In the wide-band photon spectra, the X-ray flux lies clearly above the extension of radio-ultraviolet continuum as expected. The slope of the X-ray spectra is significantly flatter than that at optical-ultraviolet regimes, and its spectral index 0.7-1.0 corresponds to the slope at submillimeter band. Comparison with earlier observations, in fact, indicates that the X-ray flux is correlated with the submillimeter band, and not with the others, and supports the SSC model.
The Diagnostics Test Facility (DTF) at NASA's Stennis Space Center (SSC) was designed and built to provide a standard rocket engine exhaust plume for use in the research and development of engine health monitoring instrumentation. A 1000 lb thrust class liquid oxygen (LOX)-gaseous hydrogen (GH2) fueled rocket engine is used as the subscale plume source to simulate the SSME during experimentation and instrument development. The ability of the DTF to provide efficient, and low cost test operations makes it uniquely suited for plume diagnostic experimentation. The most unique feature of the DTF is the Multiple Dopant Injection System (MDIS) that is used to seed the exhaust plume with the desired element or metal alloy. The dopant injection takes place at the fuel injector, yielding a very uniform and homogeneous distribution of the seeding material in the exhaust plume. The MDIS allows during a single test firing of the DTF, the seeding of the exhaust plume with up to three different dopants and also provides distilled water base lines between the dopants. A number of plume diagnostic-related experiments have already utilized the unique capabilities of the DTF.
Quantitative analysis of exhaust plume spectral data has long been a goal of developers of advanced engine health monitoring systems which incorporate optical measurements of rocket exhaust constituents. Discussed herein is the status of present efforts to model and predict atomic radiation spectra and infer free-atom densities from emission/absorption measurements as part of the Optical Plume Anomaly Detection (OPAD) program at Marshall Space Flight Center (MSFC). A brief examination of the mathematical formalism is provided in the context of predicting radiation from the Mach disk region of the SSME exhaust flow at nominal conditions during ground level testing at MSFC. Computational results are provided for Chromium and Copper at selected transitions which indicate a strong dependence upon broadening parameter values determining the absorption-emission line shape. Representative plots of recent spectral data from the Stennis Space Center (SSC) Diagnostic Test Facility (DTF) rocket engine are presented and compared to numerical results from the present self-absorbing model; a comprehensive quantitative analysis will be reported at a later date.
The major SSC experiments are expected to produce up to 1 Petabyte of data per year each. Once the primary reconstruction is completed by farms of inexpensive processors, I/O becomes a major factor in further analysis of the data. We believe that the application of database techniques can significantly reduce the I/O performed in these analyses. We present examples of such I/O reductions in prototypes based on relational and object-oriented databases of CDF data samples.
We report the detection and spectrum of the distant (z = 1.839), highly polarized quasar PKS 1502+106 in the X-ray band based on data collected over the period 1990-1994 using ROSAT and ASCA. We find the source to exhibit intensity variations of a factor approximately greater than 2 at 1 keV on timescales of years, small compared to the variability observed historically in the radio, millimeter, and optical bands. The (energy) spectral index is found in the range 0.4 approximately less than alpha(sub x) approximately less than 0.8 (at 90% confidence). Its multiwaveband spectral index is broadly consistent with other highly polarized quasars (HPQs). From the application of an inhomogeneous synchrotron self-Compton (SSC) jet we find that a model similar to that proposed for 3C 279 is consistent with the multiwaveband spectrum. We suggest that a change in the energy injection and/or transport mechanisms within such a jet could easily result in PKS 1502+106 being detectable at gamma-ray energies.
Four different arraying schemes applicable to deep space communications are discussed and analyzed. These include symbol stream combining (SSC), baseband combining (BC), carrier arraying (CA) and full spectrum combining (FSC). Complexity versus performance is traded off throughout the paper and benefits to the reception of existing spacecraft signals are discussed.
Ground testing of rocket engines and rocket engine components has played an essential role in the development of flight-rated propulsion systems. The government has built many unique facilities to perform this function. Outlined in this paper are the ground testing capabilities of the National Aeronautics and Space Administration (NASA) John C. Stennis Space Center (SSC), ranging from the component level to fully-integrated, multi-engine stage testing.
A Space Shuttle Main Engine (SSME) test program was conducted between August 1995 and May 1996 using the Technology Test Bed (TTB) Engine. SSTO vehicle studies have indicated that increases in the propulsion system operating range can save significant weight and cost at the vehicle level. This test program demonstrated the ability of the SSME to accommodate a wide variation in safe operating ranges and therefore its applicability to the SSTO mission. A total of eight tests were completed with four at Marshall Space Flight Center's Advanced Engine Test Facility and four at the Stennis Space Center (SSC) A-2 attitude test stand. Key demonstration objectives were: 1) Mainstage operation at 5.4 to 6.9 mixture ratio; 2) Nominal engine start with significantly reduced engine inlet pressures of 50 psia LOX and 38 psia fuel; and 3) Low power level operation at 17%, 22%, 27%, 40%, 45%, and 50% of Rated Power Level. Use of the highly instrumented TTB engine for this test series has afforded the opportunity to study in great detail engine system operation not possible with a standard SSME and has significantly contributed to a greater understanding of the capabilities of the SSME and liquid rocket engines in general.
The present report concerns the following projects 'High energy emission from hot accretion disks from active galactic nuclei'; 'OSSE spectral timing and monitoring observations of Cygnus X- 1'; 'OSSE observations of blazars'; and 'Search for correlated time variations of bright EGRET blazars'. The most favored model for the central engine inAGNs is the supermassive black hole hypothesis (Rees 1978). The observed luminosities range from approx. 10 logical and 44-45 erg /s for objects such as Mk 421 and Seyferts to as much as approx. 10logical and 47 for powerful QSOs such as 3C 273 and 3C 279, a large fraction of the observed bolometric luminosity being, in all likelihood, beamed. As such, these objects are strong X-ray emitters (cf. Makino et al. 1987) and often undergo gamma-ray flaring detected at the EGRET range (Hartman et al. 1992) and in the case of one of two known nearby BL Lacs, Mk 421, at TeV energies as well (Punch et al. 1992, Macomb et al. 1995). Previous campaigns emphasizing radio through X-ray and even gamma-ray observations have generally found that the multiwavelength spectrum is adequately fit by a standard synchrotron self-Compton (SSC-cf. Jones et al. 1974) model of a relativistic jet (e.g. Makino et al. 1987 and Macomb et al. 1995 for the BL Lac object Mk 421) or inhomogeneous relativistic jet (Mufson et al 1990). It also was examined the gamma-gamma transperency constraints inblazars.
To determine the readiness of a rocket engine, and facilitate decisions on continued use of the engine before servicing is required, high-resolution optical spectrometers are used to acquire spectra from the exhaust plume. Such instruments are in place at the Technology Test Bed (TTB) stand at Marshall Space Flight Center (MSFC) and the A1 stand at Stennis Space Center (SSC). The optical spectrometers in place have a wide wavelength range covering the visible and near-infrared regions, taking approximately 8000 measurements at about one Angstrom spacing every half second. In the early stages of this work, data analysis was done manually. A simple spectral model produced a theoretical spectrum for given amount of elements and an operator visually matched the theoretical and real spectra. Currently, extensive software is being developed to receive data from the spectrometer and automatically generate an estimate of element amounts in the plume. It will result in fast and reliable analysis, with the capability of real-time performance. This software is the result of efforts of several groups but mainly it has been developed and used by scientists and combustion engineers, in their effort of understanding the underlying physical processes and phenomena and creating visualization and report generation facilities. Most of the software has been developed using the IDL language and programming environment which allows for extensive data visualization. Although this environment has been very beneficial, the resulting programs execute very slowly and are not easily portable to more popular, real-time environments. The need for portability and high speed of execution is becoming more apparent as the software matures moving out of the experimentation stage and into the production stage where ease of use and short response time are the most desirable features. The purpose of the work described here is to assist the scientists who developed the original IDL-based version in the conversion of the software into the real-time, production version. Specifically, a section of the software devoted to the preprocessing of the spectra has been converted into the C language. In addition, parts of this software which may be improved have been identified, and recommendations are given to improve the functionality and ease of use of the new version.
The blazar 3C 279, one of the brightest identified extragalactic objects in the gamma-ray sky, underwent a large (factor of approximately 10 in amplitude) flare in gamma-rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The flare peak represents the highest gamma-ray intensity ever recorded for this object. During the high state, extremely rapid gamma-ray variability was seen, including an increase of a factor of 2.6 in approximately 8 hr, which strengthens the case for relativistic beaming. Coordinated multifrequency observations were carried out with Rossi X-Ray Timing Explorer (RXTE), Advanced Satellite for Cosmology and Astrophysics (ASCA; or, Astro-D), Roentgen Satellite (ROSAT), and International Ultraviolet Explorer (IUE) and from many ground-based observatories, covering most accessible wavelengths. The well-sampled, simultaneous RXTE light curve shows an outburst of lower amplitude (factor of approximately = 3) well correlated with the gamma-ray flare without any lag larger than the temporal resolution of approximately 1 day. The optical-UV light curves, which are not well sampled during the high-energy flare, exhibit more modest variations (factor of approximately 2) and a lower degree of correlation. The flux at millimetric wavelengths was near a historical maximum during the gamma-ray flare peak, and there is a suggestion of a correlated decay. We present simultaneous spectral energy distributions of 3C 279 prior to and near to the flare peak. The gamma-rays vary by more than the square of the observed IR-optical flux change, which poses some problems for specific blazar emission models. The synchrotron self-Compton (SSC) model would require that the largest synchrotron variability occurred in the mostly unobserved submillimeter/far-infrared region. Alternatively, a large variation in the external photon field could occur over a time-scale of a few days. This occurs naturally in the "mirror" model wherein the flaring region in the jet photoionizes nearby broad emission line clouds, which, in turn, provide soft external photons that are Comptonized to gamma-ray energies.
The blazar 3C 279, one of the brightest identified extragalactic objects in the gamma-ray sky, underwent a large (factor of approx. 10 in amplitude) flare in gamma-rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The flare peak represents the highest gamma-ray intensity ever recorded for this object. During the high state, extremely rapid gamma-ray variability was seen, including an increase of a factor of 2.6 in approx. 8 hrs., which strengthens the case for relativistic beaming. Coordinated multifrequency observations were carried out with Rossi X-Ray Timing Explorer (RXTE), Advanced Satellite for Cosmology and Astrophysics (ASCA; or, Astro-D), Roentgen Satellite (ROSAT), and International Ultraviolet Explorer (IUE) and from many ground-based observatories, covering most accessible wavelengths. The well-sampled, simultaneous RXTE light curve shows an outburst of lower amplitude (factor of approx. or equal to 3) well correlated with the gamma-ray flare without any lag larger than the temporal resolution of approx. 1 day. The optical-UV light curves, which are not well sampled during the high-energy flare, exhibit more modest variations (factor of approx. 2) and a lower degree of correlation. The flux at millimetric wavelengths was near a historical maximum during the gamma-ray flare peak, and there is a suggestion of a correlated decay. We present simultaneous spectral energy distributions of 3C 279 prior to and near to the flare peak. The gamma-rays vary by more than the square of the observed IR-optical flux change, which poses some problems for specific blazar emission models. The synchrotron self-Compton (SSC) model would require that the largest synchrotron variability occurred in the mostly unobserved submillimeter/far-infrared region. Alternatively, a large variation in the external photon field could occur over a time scale of a few days. This occurs naturally in the "mirror" model wherein the flaring region in the jet photoionizes nearby broad emission line clouds, which, in turn, provide soft external photons that are Comptonized to gamma-ray energies.
As the new millennium approaches, a long anticipated reckoning for the education system of the United States is forthcoming, Years of school reform initiatives have not yielded the anticipated results. A particularly perplexing problem involves the lack of significant improvement of student achievement in math and science. Three "Partnership" projects represent collaborative efforts between Xavier University (XU) of Louisiana, Southern University of New Orleans (SUNO), Mississippi Valley State University (MVSU), and the National Aeronautics and Space Administration (NASA), Stennis Space Center (SSC), to enhance student achievement in math and science. These "Partnerships" are focused on students and teachers in federally designated rural and urban empowerment zones and enterprise communities. The major goals of the "Partnerships" include: (1) The identification and dissemination of key indices of success that account for high performance in math and science; (2) The education of pre-service and in-service secondary teachers in knowledge, skills, and competencies that enhance the instruction of high school math and science; (3) The development of faculty to enhance the quality of math and science courses in institutions of higher education; and (4) The incorporation of technology-based instruction in institutions of higher education. These goals will be achieved by the accomplishment of the following objectives: (1) Delineate significant ?best practices? that are responsible for enhancing student outcomes in math and science; (2) Recruit and retain pre-service teachers with undergraduate degrees in Biology, Math, Chemistry, or Physics in a graduate program, culminating with a Master of Arts in Curriculum and Instruction; (3) Provide faculty workshops and opportunities for travel to professional meetings for dissemination of NASA resources information; (4) Implement methodologies and assessment procedures utilizing performance-based applications of higher order thinking via the incorporation of Global Learning Observations To Benefit the Environment (GLOBE), Mission to Planet Earth and the use of Geographic Imaging Systems into the K-12th grade curriculum.
Recent activities at the Remote Sensing Program at Stennis Space Center have identified the need to properly verify and validate data provided by the remote sensing community. One important variable, which effects remote sensing data is bi-directional reflectance distribution (BRDF). In order to quantify the effects of BRDF on man-made and natural ground targets, the Stennis Verification & Validation (V&V) team commissioned the Systems Engineering Division at NASA Ames Research Center to develop a Field Goniometer for use at the V&V Large Target Range and for various ground truthing missions. The Swiss Field Goniometer (FIGOS) was used as a benchmark instrument to design the new state of the art Sandmeier Field Goniometer (SGF), named after Stefan Sandmeier, developer of FIGOS. After establishing requirements for the SFG, design efforts began in early May 1998. The design of the SFG was completed in September 1998. Manufacturing, construction, and testing was completed in May 1999. The SFG was shipped to NASA SSC and fully operational by June 1999.