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The Small Explorer Data System was developed by NASA Goddard Space Flight Center using a 'standard interfaces' approach. Standard interfaces make it adaptable to a wide variety of missions. The paper describes the Small Explorer Data System with particular emphasis on the standard interfaces incorporated in both the hardware and software.
Based on relatively high spatial and temporal resolution satelite data collected at 0700 CST and at each hour from 1000 CST to 1700 CST during the summer of 1986, cloud and convection variations over the area from Mississippi east to Georgia and from the Gulf of Mexico north to Tennessee are discussed. The data analyses show an average maximum cloud frequency over the land areas at 1400 local time and a maximum of deep convection one hour later. Both cloudiness and deep convection are found to be at a maximum during the nocturnal hours over the Gulf of Mexico. Cloud frequency shows a strong relationship to small terrain features. Small fresh water bodies have cloud minima relative to the surroundings in the afternoon hours. Higher, steep terrain shows cloud maxima and the adjacent lower terrain exhibits afternoon cloud minima due to a divergence of mountain breeze caused by the valley.
A series of tests has been completed in which suckdown and fountain forces and pressures were measured on circular plates and twin-tandem-jet generic STOVL (short takeoff and vertical landing) configurations. The tests were conducted using a small-scale hover rig, for jet pressure ratios up to 6 and jet temperatures up to 700 F. The measured suckdown force on a circular plate with a central jet was greater than that found with a commonly used empirical prediction method. The present data showed better agreement with other sets of data. The tests of the generic STOVL configurations were conducted to provide force and pressure data with a parametric variation of parameters so that an empirical prediction method cold be developed. The effects of jet pressure ratio and temperature were found to be small. Lift improvement devices were shown to substantially reduce the net suckdown forces.
A stability analysis based on Arnol'd-Liapunov arguments in a gauge-variable formalism is applied to a generalized form of propagating modons. The method was previously applied to the special case of Stern's modon in a quiescent background flow. The analysis presented here shows that propagating-modon solutions in the shallow-water equations are stable to small-amplitude perturbations, regardless of the sign of their translational speed, as long as this is much smaller in magnitude than the solid-rotation speed of the earth. Sufficient conditions for stability are that the given flow be quasigeostrophic, i.e., that the Rossby number be small, and that the associated Froude number be one order of magnitude smaller than the Rossby number.
Fluctuations of the diffuse X-ray background are investigated using the Einstein Observatory Deep Survey data. Small angular-scale variations of the numbers of counts in the energy range 0.8-3.5 keV in the central 32 x 32 sq arcmin of the IPC are analyzed by means of the two-point correlation function. It is shown that detector modulation contributes substantially to the observed fluctuations. Instrumental effects are estimated and subtracted from the raw observations. The residual fluctuations are used to estimate the log N-log S relation of the X-ray sources below the Einstein sensitivity limit. Taking into account numerous uncertainties involved in this analysis, it is shown that the amplitude of fluctuations observed in the Deep Survey data is consistent with a relatively small number of sources producing the X-ray background.
Two results on the small-scale clustering properties of dwarf galaxies are reported, which were identified in the vicinity of early-type Shapley-Ames galaxies on high-resolution photographic plates. The first result indicates that dwarf galaxies display the same trend of stronger clustering toward earlier morphological type on small scales as their giant counterparts on larger scales. It is suggested that early-type dwarfs can be used as dynamical probes of dark halos around early-type giant galaxies and as tracers of the dynamical evolution of such halos in dense environments. The second result pertains to the trend of increasing early-type dwarf frequency per early-type giant with environment richness previously established for rich groups. It is found that a minimum value of isolated early-type galaxies is approximately 0.25, as compared to a maximum of approximately 8 in rich environments like the Virgo Cluster.
Design of electrically controlled valve exploits force-multiplying principle to overcome large back-pressure force resisting initial opening. Design makes possible to open valve by use of relatively small motor adequate for rest of valve motion, but otherwise not large enough to open valve. In simple linear lifting, small horizontal forces applied to pair of taut cables to lift large weight through short distance. In rotary lifting, similar effect achieved by rotating, about an axis, disk to which initially axial cables attached.
The power system electronics for the NASA Goddard Space Flight Center Small Explorer Satellites are intended to satisfy various planned missions. The selected topology is a direct energy transfer (DET) system with the battery connected directly to the bus. The shunt control technique is a linear sequential full shunt which provides a simple solar array interface and can support both 3 axis stabilized and spinner satellites. In addition, it can meet stringent electromagnetic interference requirements which are expected on some Small Explorer Missions. The Power Systems Electronics (PSE) performs battery charge control using both temperature compensated charge/discharge ratio ampere hour integration and voltage-temperature control. The PSE includes all the circuits needed to perform telemetry and command functions using an optical MIL-STD-1773 interface.
A significant percentage of the carbon inventory of the circumstellar and interstellar media may be in the form of large refractory molecules (or small grains) referred to as carbon clusters. At the small end, uneven numbers of carbon atoms seem to be preferred, whereas above 12 atoms, clusters containing an even number of carbon atoms appear to be preferred in laboratory chemistry. In the lab, the cluster C-60 appears to be a particularly stable form and has been nicknamed Bucky Balls because of its resemblance to a soccer ball and to geodesic domes designed by Buckminster Fuller. In order to investigate the prevalence of these clusters, and their relationship to the polycyclic aromatic hydrocarbons (PAHs) that have become the newest focus of IR astronomy, it is necessary to determine the spectroscopic characteristics of these clusters at near and far infrared wavelengths. Described here is the construction of a near to far IR laser magnetic resonance spectrometer that has been built at the University of California Berkeley in order to detect and characterize these spectra. The equipment produces carbon clusters by laser evaporation of a graphitic target. The clusters are then cooled in a supersonic expansion beam in order to simulate conditions in the interstellar medium (ISM). The expansion beam feeds into the spectrometer chamber and permits concentrations of clusters sufficiently high as to permit ultra-high resolution spectroscopy at near and far IR wavelengths. The first successful demonstration of this apparatus occurred last year when the laboratory studies permitted the observational detection of C-5 in the stellar outflow surrounding IRC+10216 in the near-IR. Current efforts focus on reducing the temperature of the supersonic expansion beam that transport the C clusters evaporated from a graphite target into the spectrometer down to temperatures as low as 1 K.
Described here is the small engine technology program being sponsored at the Lewis Research Center. Small gas turbine research is aimed at general aviation, commuter aircraft, rotorcraft, and cruise missile applications. The Rotary Engine program is aimed at supplying fuel flexible, fuel efficient technology to the general aviation industry, but also has applications to other missions. The Automotive Gas Turbine (AGT) and Heavy-Duty Diesel Transport Technology (HDTT) programs are sponsored by DOE. The Compound Cycle Engine program is sponsored by the Army. All of the programs are aimed towards highly efficient engine cycles, very efficient components, and the use of high temperature structural ceramics. This research tends to be generic in nature and has broad applications. The HDTT, rotary technology, and the compound cycle programs are all examining approaches to minimum heat rejection, or 'adiabatic' systems employing advanced materials. The AGT program is also directed towards ceramics application to gas turbine hot section components. Turbomachinery advances in the gas turbine programs will benefit advanced turbochargers and turbocompounders for the intermittent combustion systems, and the fundamental understandings and analytical codes developed in the research and technology programs will be directly applicable to the system projects.
The MIL-STD-1773 Fiber Optic Data Bus as implemented in the GSFC Small Explorer Data System (SEDS) for the Small Explorer Program is described. It provides an overview of the SEDS MIL-STD-1773 bus components system design considerations, reliability figures, acceptance and qualification testing requirements, radiation requirements and tests, error handling considerations, and component heritage. The first mission using the bus will be launched in June of 1992.
The National Aeronautics and Space Administration (NASA) invites small businesses to submit Phase 1 proposals in response to its Small Business Innovation Research (SBIR) Program Solicitation 92-1. Firms with research or research and development capabilities (R/R&D) in science or engineering in any of the areas listed are encouraged to participate. This, the tenth annual SBIR solicitation by NASA, describes the program, identifies eligibility requirements, describes the proposal evaluation and award selection process, and provides other information to assist those interested in participating in NASA's SBIR program. It also identifies, in Section 8.0, the technical topics and subtopics in which SBIR Phase 1 proposals are solicited in 1992. These topics and subtopics cover a broad range of current NASA interests but do not necessarily include all areas in which NASA plans or currently conducts research. The NASA SBIR program seeks innovative approaches that respond to the needs, technical requirements, and new opportunities described in the subtopics. The focus is on innovation through the use of emerging technologies, novel applications of existing technologies, exploitation of scientific breakthroughs, or new capabilities or major improvements to existing technologies. NASA plans to select about 320 high-quality research or research and development proposals for Phase 1 contract awards on the basis of this Solicitation. Phase 1 contracts are normally six months in duration and funded up to $50,000, including profit. Selections will be based on the competitive merits of the offers and on NASA needs and priorities.
An experimental study was conducted concerning the influence of small changes in initial conditions on the near- and far-field evolution of the three-dimensional structure of a plan mixing layer. A two-stream mixing layer with a velocity ratio of 0.6 was generated with the initial boundary layers on the splitter plate laminar and was nominally two-dimensional. The initial conditions were changed slightly by interchanging the high- and low-speed sides of the wind tunnel, while maintaining the same velocities, and hence velocity ratio. This resulted in small changes in the initial boundary layer properties, and the perturbations present in the boundary layers were interchanged between the high- and low-speed sides for the two cases. The results indicate that, even with this relatively minor change in initial conditions, the near-field regions of the two cases differ significantly. The peak Reynolds stress levels in the near-field differ by up to 100 percent, and this is attributed to a difference in the location of the initial spanwise vortex roll-up. In addition, the positions and shapes of the individual streamwise vortical structures differ for the two cases, although the overall structures differ for the two cases, although the overall qualitative description of these structures is comparable. The subsequent reorganization and decay of the streamwise vortical structures is very similar for the two cases. As a result, in the far field, both mixing layers achieve similar structure, yielding comparable growth rates, Reynolds stress, distribution, and spectral content.
The present study investigates the evolution of streamwise vortices in a plane mixing layer and their role in the generation of small-scale 3D motion in a closed-return water facility. Spanwise-periodic streamwise vortices are excited by a time-harmonic wavetrain with spanwise-periodic amplitude variations synthesized by a mosaic of 32 surface film heaters flush-mounted on the low partition. The onset of streamwise vortices is accompanied by significant distortion in the transverse distribution of the streamwise velocity component. The presence of inflexion points, absent in corresponding velocity distributions of the unforced flow, suggests the formation of locally unstable regions of large shear in which broadband perturbations already present in the base flow undergo rapid amplification, followed by breakdown to small-scale motion. The cores of the primary vortices are significantly altered as a result of spanwise nonuniform excitation. The 3D features of the streamwise vortices and their interaction with the base flow are inferred from surfaces or rms velocity fluctuations and an approximation to cross-stream vorticity using 3D single component velocity data.
The effects of nonspherical small ice crystals on the IR radiative properties of cirrus clouds are investigated utilizing light scattering properties of spheroidal particles. Employing the anomalous diffraction theory for spheres and results from the exact spheroid scattering program, efficient parameterization equations are developed for calculations of the absorption and scattering properties for small ice crystals. Parameterization formulas are developed for large ice crystals employing results computed from the geometric ray-tracing method and the Fraunhofer diffraction theory for hexagonal crystals and spheroids.
Redshifts and K magnitudes have been obtained for a small but complete sample of 22 galaxies with B magnitudes down to 24. In the luminosity range B = 23-24, the B-band galaxy counts are dominated by a population of small blue galaxies at z roughly 0.25, which may collectively contain as much baryonic matter as the normal galaxies. It is possible either that these earlier galaxies have undergone merging to create the present galaxy population, or that they represent a quite different galactic population which has now faded or disappeared. Either possibility has considerable implications for understanding of galaxy formation.
The growth of naturally-initiated small cracks under a variety of constant amplitude and variable amplitude load sequences is examined for several airframe materials: the conventional aluminum alloys, 2024-T3 and 7075-T6, the aluminum-lithium alloy, 2090-T8E41 and 4340 steel. Loading conditions investigated include constant amplitude loading at R = 0.5, 0, -1 and -2 and the variable amplitude sequences FALSTAFF, Mini-TWIST, and FELIX/28. Crack growth was measured at the root of semicircular edge notches using acetate replicas. Crack growth rates are compared on a stress intensity factor basis, to those for large cracks to evaluate the extent of the small crack effect in each alloy. In addition, the various alloys are compared on a crack initiation and crack growth morphology basis.
An examination is conducted of the influence of partial ionization on the electrophoresis of small particles and fluid globules, with a view to the nature of conditions under which dissociation-association (D-A) alters electrokinetics. It is found that, since D-A processes are important in cases where double-layer polarization and relaxation would otherwise prevail, the predicted effect on electrophoretic mobility is greatest for the drops and bubbles whose surfaces are fluid and convection within the interface is significant. While the computation scheme used applies only to situations where forcing-field magnitude is small, the results obtained indicate that D-A processes involving ionogenic solutes may be significant in apolar liquids where electrokinetic phenomena are driven by strong forcing fields.