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The status of the technologies for phased-array-fed dual reflector systems is reviewed. The different aspects of these technologies, including optical performances, phased array systems, problems encountered in phased array design, beamforming networks, MMIC design and its incorporation into waveguide systems, reflector antenna structures, and reflector deployment mechanisms are addressed.
The current phase of the Space Station Operating System study is based on the analysis, evaluation, and comparison of the operating systems implemented on the computer systems and workstations in the software development laboratory. Primary emphasis has been placed on the DEC MicroVMS operating system as implemented on the MicroVax II computer, with comparative analysis of the SUN UNIX system on the SUN 3/260 workstation computer, and to a limited extent, the IBM PC/AT microcomputer running PC-DOS. Some benchmark development and testing was also done for the Motorola MC68010 (VM03 system) before the system was taken from the laboratory. These systems were studied with the objective of determining their capability to support Space Station software development requirements, specifically for multi-tasking and real-time applications. The methodology utilized consisted of development, execution, and analysis of benchmark programs and test software, and the experimentation and analysis of specific features of the system or compilers in the study.
Results are reported from an experimental study of phase stability in a plasma-sprayed Ti3Al+Nb alloy using TEM and electron diffraction techniques. The alloys was produced from Ti3Al+Nb powder via an inductively coupled plasma deposition process. Evidence was found for the ordering of the B2 phase to a structure similar to the DO3-type phase, but with a tetragonal distortion. An ordered tetragonal phase (T) is proposed to account for these observations, and the existence of the B2 - T ordering transformation in the Ti3Al+Nb system is suggested. The T phase can be regarded as a DO3-like phase with a tetragonal distortion. The tegragonality c0/a0 is approximately equal to 1.02, and a0 equals 0.65 +/-0.01 nm.
We present a description and preliminary results of the proof-of-principle studies on betatron-oscillation phase tracking of a single electron in the Fermilab IOTA storage ring during Run 3 (2021). We describe the general principles of the experiment, the optical diagnostics setup, the configuration of the ring, a chronology of the studies, the structure of the measured data, and results of the preliminary analysis of the collected data. It was observed that the coherence time of betatron oscillations exceeds 60,000 turns. The betatron tune of the single electron was accurately measured and compared with that of electron bunches. In addition, chromaticity was extracted from the combined analysis of synchrotron oscillations and betatron phase tracking.
The U.S. Department of Energy’s Co-Optima initiative has focused on improving fuel economy and vehicle performance while reducing emissions through the simultaneous development of emerging sustainable fuels with beneficial properties and advanced combustion strategies. A major thrust has been the development of advanced compression ignition (ACI) combustion strategies of gasoline range fuels in combination with spark-ignited (SI) combustion in a single engine capable of multi-mode operation to achieve high power density with enhanced part load efficiency. The aim of this study was to further the understanding of how emissions from both ACI and SI strategies operating on the same fuels in the same engine are impacted by different fuel properties. This investigation focused on particulate matter (PM) and gaseous hydrocarbon emissions from 6 different fuels across 3 different combustion modes on the same single-cylinder engine designed for multi-mode operation: SI combustion, partial fuel stratification (PFS), and spark-assisted compression ignition (SACI). In each of these modes, 3 different CA50 phasings were studied such that all 6 fuels could be studied at the same phasings. Three of the six different fuels used were specially formulated in a previous investigation to study the impact of fuel distillation and aromatic content while maintaining the research octane number (RON) and octane sensitivity. Additionally, neat isooctane and two ethanol containing fuels (RD5-87 and Co-Optima E30) were studied. Different fuel and phasing impacts on emissions were observed across the three combustion modes. Fuel properties were found to impact soot PM and particle number more than the CA50 phasing, while the phasing had more impact on NOx emissions. The NOx emissions were reduced in the PFS mode for all fuels compared to SI combustion, but the SACI combustion mode did not reduce NOx emissions. Although PFS produced low soot PM emissions like SI, total PM mass emissions were significantly higher due to large organic carbon (OC) PM mass contribution. Both PFS and SACI had greater particle number emission than SI operation with small nuclei mode particles dominating in PFS compared to large agglomeration particles in SACI.
This study provides a preliminary assessment of the potential benefits of applying unsteady separation control to transport aircraft. Estimates are given for some of the costs associated with a specific application to high-lift systems. High-leverage areas for future research were identified during the course of the study. The study was conducted in three phases. Phase 1 consisted of a coarse screening of potential applications within the aerodynamics discipline. Potential benefits were identified and in some cases quantified in a preliminary way. Phase 2 concentrated on the application to the wing high-lift system, deemed to have the greatest potential benefit for commercial transports. A team of experts, including other disciplines (i.e. hydraulic, mechanical, and electrical systems, structures, configurations, manufacturing, and finance), assessed the feasibility, benefits, and costs to arrive at estimates of net benefits. In both phases of the study, areas of concern and areas for future research were identified. In phase 3 of this study, the high-leverage areas for future research were prioritized as a guide for future efforts aimed at the application of active flow control to commercial transport aircraft.
The development of low-cost, high-performance anode materials for Li-ion batteries (LIBs) is imperative to meet the ever-increasing demands for advanced power sources. In this paper we report our findings on the design, synthesis, and characterization of a new cation-disordered ZnSiP 2 anode. When tested in LIBs, the disordered phase of ZnSiP 2 demonstrates faster reaction kinetics and higher energy efficiency than the cation-ordered phase of ZnSiP 2 . The superior performance is attributed to the greater electronic and ionic conductivity and better tolerance against volume variation during cycling, as confirmed by theoretical calculations and experimental measurements. Moreover, the cation-disordered ZnSiP 2 /C composite exhibits excellent cycle stability and superior rate capability. The performance surpasses all reported multi-phase anodes studied. Further, a number of the cation-disordered phases in the Zn(Cu)–Si–P family with a wide range of cation ratios show similar performance, achieving large specific capacities and high first-cycle coulombic efficiency while maintaining desirable working potentials for enhanced safety.
Pressure gradients, i.e. pressure head, and buoyancy driven convection can be greatly decreased in experimental systems by acceleration of the laboratory reference frame at a rate consistent with the acceleration due to gravity. This may be done in a number of ways, the best known of which is the use of orbiting spacecraft. Other techniques include the use of aircraft following an appropriate parabolic trajectory or drop towers. The result is an experimental condition in which fluids experience virtually no outside forces relative to the laboratory reference frame. Such conditions are appropriate for the study of processes with diffusion dominated heat and/or mass Under, the study of phase transitions in the absence of pressure gradients, the study of solutal or thermal capillary convection, or containerless processes. Ways of achieving these conditions and complexities that arise in performing experiments in this environment are discussed.
The Five Segment Booster (FSB) concept has been evolving for a number of years as a means to enhance the overall safety and reliability of the Space Shuttle system by minimizing the need to fly the more challenging Return to Launch Site (RTLS) and Transoceanic Abort Landing (TAL) abort profiles. The initial evaluation of the FSB concept was conducted in 1996 to determine the feasibility of the FSB in achieving transatlantic abort leading TAL from the pad, thus eliminating the return to launch site (RTLS) abort mode. The initial study was conducted by ATK Thiokol and did show the potential for the FSB to eliminate the RTLS abort mode. Later Rockwell (now Boeing) conducted a similar study utilizing FSB performance characteristics and verified that the FSB could indeed achieve TAL from the pad, thereby eliminating the necessity for the RTLS abort. The purpose of this paper is to discuss the details of the enhancements achieved through the internally funded study conducted by Boeing and ATK Thiokol. To better understand the enhancements that were addressed as part of this follow-on study, some background on what was achieved in the Phase A study is appropriate.
A major cause of project failure can be attributed to an emphasized focus on end products and inadequate attention to resolving development risks during the initial phases of a project. The initial phases of a project, which we will call the "study period", are critical to determining project scope and costs, and can make or break most projects. If the requirements are not defined adequately, how can the scope be adequately determined, also how can the costs of the entire project be effectively estimated, and how can the risk of project success be accurately assessed? Using the proper material specifications and standards and incorporating these specifications and standards in the design process should be considered inherently crucial to the technical success of a project as just as importantly, crucial to the cost and schedule success. This paper will intertwine several important aspects or considerations for project success: 1) Characteristics of a "Good Material Requirement"; 2) Linking material requirements to the implementation of "Design for Manufacturing"; techniques and 3) The importance of decomposing materials requirements during the study phase/development phase to mitigate project risk for the maturation of technologies before the building of hardware.
Atmospheric confetti. Inchworm crawlers. Blankets of ground penetrating radar. These are some of the unique mission concepts which could be enabled by a printable spacecraft. Printed electronics technology offers enormous potential to transform the way NASA builds spacecraft. A printed spacecraft's low mass, volume and cost offer dramatic potential impacts to many missions. Network missions could increase from a few discrete measurements to tens of thousands of platforms improving areal density and system reliability. Printed platforms could be added to any prime mission as a low-cost, minimum resource secondary payload to augment the science return. For a small fraction of the mass and cost of a traditional lander, a Europa flagship mission might carry experimental printed surface platforms. An Enceladus Explorer could carry feather-light printed platforms to release into volcanic plumes to measure composition and impact energies. The ability to print circuits directly onto a variety of surfaces, opens the possibility of multi-functional structures and membranes such as "smart" solar sails and balloons. The inherent flexibility of a printed platform allows for in-situ re-configurability for aerodynamic control or mobility. Engineering telemetry of wheel/soil interactions are possible with a conformal printed sensor tape fit around a rover wheel. Environmental time history within a sample return canister could be recorded with a printed sensor array that fits flush to the interior of the canister. Phase One of the NIAC task entitled "Printable Spacecraft" investigated the viability of printed electronics technologies for creating multi-functional spacecraft platforms. Mission concepts and architectures that could be enhanced or enabled with this technology were explored. This final report captures the results and conclusions of the Phase One study. First, the report presents the approach taken in conducting the study and a mapping of results against the proposed Phase One objectives. Then an overview of the general field of printed electronics is provided, including manufacturing approaches, commercial drivers, and the current state of integrated systems. The bulk of the report contains the results and findings of Phase One organized into four sections: a survey of components required for a printable spacecraft, technology roadmaps considerations, science mission and engineering applications, and potential risks and challenges of the technology.
Recently, we studied the phase behavior of ionic fluids under confinement using the classical density functional theory within the framework of the restricted primitive model. Additionally, the theoretical results indicate that narrowing the pore size may lead to a drastic reduction in the electric double layer capacitance, while increasing the surface electrical potential would improve the ionic accessibility of micropores. In this work, we extend the theoretical investigation to systems containing size-asymmetric electrolytes that may exhibit a vapor-liquid like phase transition in the bulk phase. The effects of pore size and surface electric potential on the phase diagram and microscopic structures of the confined electrolytes were studied over a broad range of parameters. We found that decreasing the pore size or increasing the surface potential could destabilize the liquid phase in micropores, and capillary evaporation could occur regardless of the size asymmetry between cations and anions. Compared to that in a symmetric ionic system, the vapor-liquid phase separation is more likely to take place as the size asymmetry becomes more pronounced. The phase transition would alter the “accessibility” of ions to micropores and lead to coexisting micropores with different surface charge densities as identified by Monte Carlo simulation.
The X-ray observations from the Yohkoh SXT provided the greatest step forward in our understanding of the solar corona in nearly two decades. Expanding on the accomplishments of Yohkoh, we believe that the scientific objectives of the Solar-B mission are achieved with a significantly improved X-ray telescope (XRT) similar to the SXT. The Solar-B XRT will have twice the spatial resolution and a broader temperature response, while building on the knowledge gained from the successful Yohkoh mission. We present the scientific justification for this view, discuss the instrumental requirements that flow from the scientific objectives, and describe the instrumentation to meet these requirements. We then provide a detailed discussion of the design activities carried out during Phase A, noting the conclusions that were reached in terms of their implications for the detailed design activities which are now commencing. Details of the instrument that have changed as a result of the Phase A studied are specifically noted, and areas of concern going into Phase B are highlighted. XRT is a grazing-incidence (GI) modified Wolter I X-ray telescope, of 35cm inner diameter and 2.7m focal length. The 2048x2048 back-illuminated CCD (now an ISAS responsibility) has 13.5 micron pixels, corresponding to 1.0 arcsec and giving full Sun field of view. This will be the highest resolution GI X-ray telescope ever flown for Solar coronal studies, and it has been designed specifically to observe both the high and low temperature coronal plasma. A small optical telescope provides visible light images for co-alignment with the Solar-B optical and EUV instruments. The XRT science team is working in close cooperation with our Japanese colleagues in the design and construction of this instrument. All of the expertise and resources of the High Energy and Solar/Stellar Divisions of the Center for Astrophysics are being made available to this program, and our team will carry its full share of responsibility for mission operations, data reduction and education and public outreach. All aspects of the XRT design were reviewed during Phase A. The study focussed particularly on those aspects that have the greatest affect on instrument performance and extended lifetime, on the image quality error budget, and on the camera (mechanical and electrical) interface and the instrument mounting interfaces. The present instrument design differs in some details from that originally proposed. Selection of the XRT for Phase A study was contingent upon the removal of the camera and its associated electronics, and the acceptance of a stringent cost cap. The removal of the electronics left the XRT without control electronics for the instrument mechanisms. A mechanism controller was therefore added. The removal of the camera resulted in major complications to the integration and test plan. After many discussions, it was decided that the system would be less expensive, and the risk of unacceptable performance lower, if we include a focus mechanism. The remainder of the XRT design baseline matches the proposed configuration. Data requirements for the XRT are driven by the science plans, which are based on the physical processes in the solar outer atmosphere. Discussions to date of the XRT observing plan, both alone and in conjunction with the other Solar-B instruments, shows that the XRT needs 2 Gbits of on-board storage, at least one circulating buffer of 640 Mbits, and twelve 10- minute downlinks per day in order to carry out its required programs.
Abstract We present a synthetic phase contrast imaging (PCI) diagnostic for studying turbulence at the Wendelstein 7-X (W7-X) stellarator. We first describe the implemented instrument response model, which captures diffraction effects, detector noise, and the long-wavelength cutoff due to the phase plate of the PCI system. To verify the instrument response model, we show that it is capable of reproducing the PCI signal generated by the sound wave speaker used for calibration at W7-X. Next, we discuss the calculation of synthetic PCI signals based on the global, nonlinear gyrokinetic codes GENE-3D and EUTERPE, including results from some of the first stellarator simulations of this type with kinetic electrons (KEs) in GENE-3D. While the simulations used in this work lack a neoclassical radial electric field, which is crucial for reproducing experimental PCI signals, they do indicate that the dominant rotation direction and velocities of the turbulent fluctuations can be inferred from the wave number-frequency spectra of the PCI signals, as expected. The synthetic PCI wave number spectra are further shown to be similar to those of the line-integrated fluctuating electron density, with distinct differences between adiabatic and KE simulations, explainable by previously published turbulence models. For example, the wave number spectra of all adiabatic electron simulations analyzed here follow a power law with an exponent close to −5 for sufficiently large wave numbers. This indicates that universal features of electron density turbulence at W7-X may be studied using the PCI system.
We will discuss the results of a planned observation campaign of Near Earth Asteroids (NEAs), 1999 CU3, 2002 GM2, 2002 FG7, and 3691 Bede with instruments on the United Kingdom Infrared Telescope (UKIRT) from 15-Mar-2015 to 28-April 2015 UT. We will study the phase-angle dependence of the reflectance and thermal emission spectra. Recent publications reveal that the assignment of the asteroid class from visible and near-IR spectroscopy can change with phase angle for NEAs with silicate-bearing minerals on their surfaces (S-class asteroids) (Thomas et al. 2014, Icarus 228, 217; Sanchez et al. 2012 Icarus 220, 36). Only three of the larger NEAs have been measured at a dozen phase angles and the trends are not all the same, so there is not yet enough information to create a phase-angle correction. Also, the phase angle effect is not characterized well for the thermal emission including determination of the albedo and the thermal emission. The few NEAs were selected for our study amongst many possible targets based on being able to observe them through a wide range of phase angles, ranging from less than about 10 degrees to greater than 45 degrees over the constrained date range. The orbits of NEAs often generate short observing windows at phase angles higher than 45 deg (i.e., whizzing by Earth and/or close to dawn or dusk). Ultimately, lowering the uncertainty of the translation of asteroid class to meteorite analog and of albedo and size determinations are amongst our science goals. On a few specific nights, we plan to observe the 0.75-2.5 micron spectra with IRTF+SpeX for comparison with UKIRT data including 5-20 micron with UKIRT+UIST/Michelle to determine as best as possible the albedos. To ensure correct phasing of spectroscopic data, we augment with TRAPPIST-telescope light curves and R-band guider image data. Our observations will contribute to understanding single epoch mid-IR and near-IR measurements to obtain albedo, size and IR beaming parameters (the outcomes of thermal models) and asteroid spectral class.
This paper presents the preliminary results of an architecture study that provides continuous telemetry coverage for NASA missions for immediate post-separation phase. This study is a collaboration effort between Jet Propulsion Laboratory (JPL), Goddard Space Flight Center (GSFC), and Applied Physics Laboratory (APL). After launch when the spacecraft separated from the upper stage, the spacecraft typically executes a number of mission-critical operations prior to the deployment of solar panels and the activation of the primary communication subsystem. JPL, GSFC, and APL have similar design principle statements that require continuous coverage of mission-critical telemetry during the immediate post-separation phase. To conform to these design principles, an architecture that consists of a separate spacecraft transmitter and a robust communication network capable of tracking the spacecraft signals is needed.This paper presents the preliminary results of an architecture study that provides continuous telemetry coverage for NASA missions for immediate post-separation phase. This study is a collaboration effort between Jet Propulsion Laboratory (JPL), Goddard Space Flight Center (GSFC), and Applied Physics Laboratory (APL). After launch when the spacecraft separated from the upper stage, the spacecraft typically executes a number of mission-critical operations prior to the deployment of solar panels and the activation of the primary communication subsystem. JPL, GSFC, and APL have similar design principle statements that require continuous coverage of mission-critical telemetry during the immediate post-separation phase. To conform to these design principles, an architecture that consists of a separate spacecraft transmitter and a robust communication network capable of tracking the spacecraft signals is needed. The main results of this study are as follows: 1) At low altitude (< 10000 km) when most post-separation critical operations are executed, Earth-based network (e.g. Deep Space Network (DSN)) can only provide limited coverage, whereas space-based network (e.g. Space Network (SN)) can provide continuous coverage. 2) Commercial-off-the-shelf SN compatible transmitters are available for small satellite applications. In this paper we present the detailed coverage analysis of Earth-based and Space-based networks. We identify the key functional and performance requirements of the architecture, and describe the proposed selection criteria of the spacecraft transmitter. We conclude the paper with a proposed forward plan.
A multi-phase, experimental study in the Basic Aerodynamics Research Tunnel at the NASA Langley Research Center has provided new insight into the unsteady flow interaction around cylinders in tandem arrangement. Phase 1 of the study characterized the mean and unsteady near-field flow around two cylinders of equal diameter using 2-D Particle Image Velocimetry (PIV) and hot-wire anemometry. These measurements were performed at a Reynolds number of 1.66 x 10(exp 5), based on cylinder diameter, and spacing-to-diameter ratios, L/D, of 1.435 and 3.7. The current phase, Phase 2, augments this dataset by characterizing the surface flow on the same configurations using steady and unsteady pressure measurements and surface flow visualization. Transition strips were applied to the front cylinder during both phases to produce a turbulent boundary layer upstream of the flow separation. For these flow conditions and L/D ratios, surface pressures on both the front and rear cylinders show the effects of L/D on flow symmetry, pressure recovery, and the location of flow separation and attachment. Mean streamlines and instantaneous vorticity obtained from the PIV data are used to explain the flow structure in the gap and near-wake regions and its relationship to the unsteady surface pressures. The combination of off-body and surface measurements provides a comprehensive dataset to develop and validate computational techniques for predicting the unsteady flow field at higher Reynolds numbers.
Several observations in space plasmas have reported the presence of coherent structures at different plasma scales. Structure formation is believed to be a direct consequence of nonlinear interactions between the plasma modes, which depend strongly on phase synchronization of those modes. Despite this important role of the phases in turbulence, very limited work has been however devoted to study the phases as a potential tracers of nonlinearities in comparison with the wealth of literature on power spectra of turbulence where phases are totally missed. We present a method based on surrogate data to systematically detect coherent structures in turbulent signals. The new method has been applied successfully to magnetosheath turbulence (Sahraoui, Phys. Rev. E, 2008, in press), where the relationship between the identified phase coherence and intermittency (classically identified as non Gaussian tails of the PDFs) as well as the energy cascade has been studied. Here we review the main results obtained in that study and show further applications to small scale solar wind turbulence. Implications of the results on theoretical modelling of space turbulence (applicability of weak/wave turbulence, its validity limits and its connection to intermittency) will be discussed.