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This viewgraph presentation gives an overview of the investigation of a fire at NASA Stennis Space Center (SSC) on February 21, 2004. The fire occurred during structural welding to accomodate a new propellant tank. The presentation includes images of the fire damage, as well as findings/recommendations from the investigators.
A research area of high activity in connection with aerospace engineering has been the development of polymer thermosetting resins that can resist temperature as high as 300 C while maintaining adequate toughness, and providing ease of processing to enable low temperature and low cost composite fabrication methods. In order to meet such requirements, sequential interpenetrating polymer networks (IPNs) based on bismaleimide (BMI) and cyanate ester (CE) monomers were investigated. In these systems, a polycyanurate network is first formed in the presence of BMI and appropriate reactive diluent monomers and in a second step, a network based on the BMI is created in the presence of a fully formed polycyanurate network. The materials developed can be processed at relatively low temperature (less than 150 C) and with the aid of electron beam (EB) curing. Of major importance to the success of this work was the identification of a reactive diluent that improves ease of processing and has tailored reactivity to allow for the controlled synthesis of CE-BMI sequential IPNs. Based on solubility and reactivity of a number of reactive diluents, N-acryloylmorpholine (AMP) was selected as a comonomer for BMI copolymerization. A donor-acceptoreaction mechanism was suggested to explain the relative reactivity of a variety of reactive diluents towards maleimide functionality. The optimum processing parameters for the formation of the first network were determined through the study of metal catalyzed cure and hydrolysis of cyanate esters, whereas the reaction behavior for second network formation in terms of the influence of EB dose rate and temperature was elucidated through an in-situ kinetics study of maleimide and AMP copolymerization. Structure-property relationships were developed which allowed for the design of improved resin systems. In particular, appropriate network coupler possessing cyanate ester and maleimide functionality was synthesized to link the polycyanurate first network to the BMI/AMP second network and thus form linked sequential IPNs (LIPNs). Consequently, Tg as high as 370 C was achieved and a fracture toughness of 120 Joules per square meters was obtained for resin systems that possess adequately low viscosity for processing using liquid molding techniques at low temperature.
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This paper describes a new process of performing online documentation for large complex projects.
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For January-March 2003, we use 12.5-km resolution Advanced Microwave Scanning Radiometer (AMSR) data for the first time in a comparison with Synthetic Aperture Radar (SAR) and Special Sensor Microwave/Imager (SSM/I) data to study two Chukchi coast polynyas, one consisting of many, the other of only a few 25-km SSM/I pixels. Within these polynyas, the ice thicknesses are derived separately from the SMM/I 37-GHz and AMSR 36-GHz channels; the heat fluxes are derived by combining thicknesses with meteorological data. Comparison with ScanSAR data shows that for the large polynya, because AMSR provides better resolution of the surrounding coastline and first-year ice, the AMSR heat losses are greater than the SSM/I; for the small polynya, AMSR measures its variability even when its area is order of a single SSM/I pixel. This means that AMSR permits more accurate calculation of polynya heat losses, yielding the potential of improved estimates of Arctic polynya productivity.
For January-March 2003, we use 12.5-km resolution Advanced Microwave Scanning Radiometer (AMSR) data for the first time in a comparison with Synthetic Aperture Radar (SAR) and Special Sensor Microwave/Imager (SSM/I) data to study two Chukchi coast polynyas, one consisting of many, the other of only a few 25-km SSM/I pixels. Within these polynyas, the ice thicknesses are derived separately from the SMM/I 37-GHz and AMSR 36-GHz channels; the heat fluxes are derived by combining thicknesses with meteorological data. Comparison with ScanSAR data shows that for the large polynya, because AMSR provides better resolution of the surrounding coastline and first-year ice, the AMSR heat losses are greater than the SSM/I; for the small polynya, AMSR measures its variability even when its area is order of a single SSM/I pixel. This means that AMSR permits more accurate calculation of polynya heat losses, yielding the potential of improved estimates of Arctic polynya productivity.
For January-March 2003, we use 12.5-km resolution Advanced Microwave Scanning Radiometer (AMSR) data for the first time in a comparison with Synthetic Aperture Radar (SAR) and Special Sensor Microwave/Imager (SSM/I) data to study two Chukchi coast polynyas, one consisting of many, the other of only a few 25-km SSM/I pixels. Within these polynyas, the ice thicknesses are derived separately from the SMM/I 37-GHz and AMSR 36-GHz channels; the heat fluxes are derived by combining thicknesses with meteorological data. Comparison with ScanSAR data shows that for the large polynya, because AMSR provides better resolution of the surrounding coastline and first-year ice, the AMSR heat losses are greater than the SSM/I; for the small polynya, AMSR measures its variability even when its area is order of a single SSM/I pixel. This means that AMSR permits more accurate calculation of polynya heat losses, yielding the potential of improved estimates of Arctic polynya productivity.
This paper describes an operations concept for electronic scheduling and software interface for organizations to extract required views of the schedule. Advantages include widespread accessibility to a common schedule document, virtually instantaneous distribution of new schedule releases, and the ability of missions to perfom conflict resolution off-line without time-consuming meetings.
Aerosol from aircraft can affect the environment in three ways: First, soot aerosol has been implicated to cause Icing-tern ozone depletion at mid-latitudes in the lower stratosphere at a rate of approx. 5% per decade. This effect is in addition and unrelated to the polar ozone holes which are strongly influenced by heterogeneous chemistry on polar stratospheric clouds. Second, the most obvious effect of jet aircraft is the formation of visible contrails in the upper troposphere. The Salt Lake City region experienced an 8% increase in cirrus cloud cover over a 15-year period which covariates with an increase in regional commercial air traffic. If soot particles act as freezing nuclei to cause contrail formation heterogeneously, they would be linked to a secondary effect to cloud modification that very likely is climatologically important. Third, a buildup of soot aerosol could reduce the single scatter albedo of stratospheric aerosol from 0.993+0.004 to 0.98, a critical value that has been postulated to separate stratospheric cooling from warming. Thus arises an important question: Do aircraft emit sufficient amounts of soot to have detrimental effects and warrant emission controls? During the 1996 SUCCESS field campaign, we sampled aerosols in the exhaust wake of a Boeing 757 aircraft and determined emission indices for sulfuric acid (EI(sub H2SO4) = 9.0E-2 and 5.0E-1 g/kg (sub FUEL) for 75 and 675 ppm fuel-sulfur, respectively) and soot aerosol (2.2E-3 less than EI(sub SOOT) = l.lE-2 g/kg (sub FUEL)). The soot particle analysis accounted for their fractal nature, determined electron-microscopically, which enhanced the surface area by a factor of 26 and the volume 11-fold over equivalent-volume spheres. The corresponding fuel-sulfur to H2SO4 conversion efficiency was 10% (for 675 ppmm fuel-S) and 37% (for 75 ppmm fuel-S). Applying the H2SO4 emission index to the 1990 fuel use by the worlds commercial fleets of 1.3E11 kg, a conversion efficiency of 30% of 500 ppmm fuel-S would have led to an annual contribution to the atmospheric sulfur budget by aircraft of 2.E7 kg H2SO4. This is about one part in 1.E4 of anthropogenic sulfate from other sources. The soot emission index given above yielded a 1990 injection of soot aerosol by aircraft of 1.E6 kg. Thus, soot amounts to only five percent of the aerosol generated by aircraft. Its reactivity with ozone would have to be 20 times that of sulfuric acid particles to make it chemically significant. Nevertheless, the findings, of stratospheric soot loadings commensurate with aircraft fuel consumption, based on the emission index given above and the assumption of stratospheric residence times of the order of one year implicate aircraft as stratospheric polluters. A trend similar to soot of H2SO4 aerosol loading could not be deciphered, neither from in situ measurements nor SAGE II satellite extinction, against the "noise" due to volcanic eruptions. Observation of soot particles at 20 km altitude which, if emitted by aircraft were generated at 10-12 km altitude, suggests a displacement of those particles against gravity. Because eddy mixing is virtually absent in the lower stratosphere and isentropic mixing explains lofting to only about 15 km, radiometric forces acting on morphologically and chemically asymmetric soot particles must be considered a possibility. The consequence could be an extended residence time of soot against that of sulfuric acid aerosol that would lower the single scatter albedo with time.
A team directed by the NASA Engineering and Safety Center (NESC) collected methodologies for how best to develop safe and reliable human rated systems and how to identify the drivers that provide the basis for assessing safety and reliability. The team also identified techniques, methodologies, and best practices to assure that NASA can develop safe and reliable human rated systems. The results are drawn from a wide variety of resources, from experts involved with the space program since its inception to the best-practices espoused in contemporary engineering doctrine. This report focuses on safety and reliability considerations and does not duplicate or update any existing references. Neither does it intend to replace existing standards and policy.
A team directed by the NASA Engineering and Safety Center (NESC) collected methodologies for how best to develop safe and reliable human rated systems and how to identify the drivers that provide the basis for assessing safety and reliability. The team also identified techniques, methodologies, and best practices to assure that NASA can develop safe and reliable human rated systems. The results are drawn from a wide variety of resources, from experts involved with the space program since its inception to the best-practices espoused in contemporary engineering doctrine. This report focuses on safety and reliability considerations and does not duplicate or update any existing references. Neither does it intend to replace existing standards and policy.
Two calculations in the area of positron collisions are presented. The first is the calculation of the photodetachment cross section of the positronium negative ion (Ps-) using accurate variational wave functions for both the initial bound-state and the final P continuum state. The second is the calculation of partial wave cross sections for Ps(1s)-formation in ef -H(ls) collisions using the hyperspherical hidden crossing method. Since the S-wave Stiickelberg phase is close to pi, the very small S-wave Ps(1s) formation cross section can be understood in terms of destructive interference. Other examples in positron collisions are given where it is either known or expected that destructive interference is the cause of the small S-wave Ps(1s) formation cross section. In addition, examples are presented of processes in atomic physics where the Stiickelberg phase is a multiple of pi/2.
For test and evaluation of airplanes, it is desirable to telemeter large volumes of data to the ground. This telemetry has generally utilized W communication systems, which have relatively low data rates, and, due to limited spectrum availability, imposes limitations on the number of simultaneous communications in a given region. Appropriate application of optical communication technology is expected to provide higher data rate capability without the spectrum limitations of W systems, facilitating simultaneous telemetry of more data from a greater number of aircraft. This paper reviews our recent brief study to assess the insertion of free space lasercom to DOD Test and Evaluation applications.
This slide presentation begins with a listing of the papers that were submitted to the Journal of Geophysical Research -- Special Section on AIRS Validation, and those whose submission were still in progress. Included in the presentation are graphs showing differences by total water and cloud amount.
As a step towards development of Stirling power conversion for potential use in Fission Surface Power (FSP) systems, a pair of commercially available 1 kW class free-piston Stirling convertors was modified to operate with a NaK liquid metal pumped loop for thermal energy input. This was the first-ever attempt at powering a free-piston Stirling engine with a pumped liquid metal heat source and is a major FSP project milestone towards demonstrating technical feasibility. The tests included performance mapping the convertors over various hot and cold-end temperatures, piston amplitudes and NaK flow rates; and transient test conditions to simulate various start-up and fault scenarios. Performance maps of the convertors generated using the pumped NaK loop for thermal input show increases in power output over those measured during baseline testing using electric heating. Transient testing showed that the Stirling convertors can be successfully started in a variety of different scenarios and that the convertors can recover from a variety of fault scenarios.
We have developed a software library (KVTP-lib) for VLBI data transmission over the network with the VDIF (VLBI Data Interchange Format), which is the newly proposed standard VLBI data format designed for electronic data transfer over the network. The software package keeps the application layer (VDIF frame) and the transmission layer separate, so that each layer can be developed efficiently. The real-time VLBI data transmission tool sudp-send is an application tool based on the KVTP-lib library. sudp-send captures the VLBI data stream from the VSI-H interface with the K5/VSI PC-board and writes the data to file in standard Linux file format or transmits it to the network using the simple- UDP (SUDP) protocol. Another tool, sudp-recv , receives the data stream from the network and writes the data to file in a specific VLBI format (K5/VSSP, VDIF, or Mark 5B). This software system has been implemented on the Wettzell Tsukuba baseline; evaluation before operational employment is under way.
Automating and remotely controlling observations are important for future operations in a Global Geodetic Observing System (GGOS). At the Geodetic Observatory Wettzell, in cooperation with the Max-Planck-Institute for Radio Astronomy in Bonn, a software extension to the existing NASA Field System has been developed for remote control. It uses the principle of a remotely accessible, autonomous process cell as a server extension for the Field System. The communication is realized for low transfer rates using Remote Procedure Calls (RPC). It uses generative programming with the interface software generator idl2rpc.pl developed at Wettzell. The user interacts with this system over a modern graphical user interface created with wxWidgets. For security reasons the communication is automatically tunneled through a Secure Shell (SSH) session to the telescope. There are already successful test observations with the telescopes at O Higgins, Concepcion, and Wettzell. At Wettzell the software is already used routinely for weekend observations. Therefore the first public release of the software is now available, which will also be useful for other telescopes.