Optimum parameters of a gravitational satellite-stabilizer system

Dynamics of a satellite-stabilizer system is studied. It is supposed that there is a viscous friction in a hinge connecting two bodies, but there is no elasticity. The attitude motion in a plane of circular orbit is considered, and parameters are determined, at which natural oscillations near a stable equilibrium position in the orbital coordinate system are damped out most rapidly. The rate of transient processes is estimated by a value of the degree of stability of linearized equations of motion. The optimization of the degree of stability is sequentially performed in dimensionless damping coefficient (the first stage) and in inertial system parameters (the second stage). The result of the first stage is the partition of system parameter space into the regions, in each of which the maximum of the degree of stability is reached on a particular configuration of roots of the characteristic equation. It is shown at the second stage that the global maximum is reached at two points of parameter space, where one of system bodies degenerates into a plate, and the characteristic equation has four equal real roots.     

Advanced materials for next generation NiMH portable, HEV and EVbatteries

While Ovonic NiMH batteries are already in high volume commercial production for portable applications, advances in materials technology have enabled performance improvements in specific energy (100 Wh/kg), specific power (600-1000 W/kg), high temperature operation, charge retention, and voltage stability. Concurrent with technology advances, Ovonic NiMH batteries have established performance and commercial milestones in electric vehicles, hybrid electric vehicles, as well as scooter, motorcycle and bicycle applications. As important as these advances, significant manufacturing cost reductions have also occurred which allow continued growth of NiMH technology. In this paper, advances in performance, applications and cost reduction are discussed with particular emphasis on the improved proprietary metal hydride and nickel hydroxide materials that make such advances possible     

Modeling Piecewise-Linear Systems by Topological Techniques

Flowgraph techniques are extended to systems with piecewise-linear characteristics by developing criteria for construction of an optimum model from related subregions in which linearity holds. This requires the synthesis of several known techniques and results in a wide range of useful applications including: 1) devices with nonlinear characteristics which may be considered as linear over certain subregions; 2) networks whose response to changes in applied signal frequency or magnitude may be approximated by piecewise-linear asymptotes; 3) systems processing two or more signals simultaneously with different transfer or immitance characteristics for each signal; 4) circuits approximated by different equivalent circuits depending on the numerical values of critical parameters. Representative examples will illustrate these and similar applications. Procedures are presented to provide a logical, orderly, and effective approach to construct a model, to determine figures of merit, and to optimize the model for a prescribed region of operation or for a desired range of parameters.     

Statistical study of interplanetary condition effect on geomagnetic storms: 2. Variations of parameters

We investigate the behavior of mean values of the solar wind’s and interplanetary magnetic field’s (IMF) parameters and their absolute and relative variations during the magnetic storms generated by various types of the solar wind. In this paper, which is a continuation of paper [1], we, on the basis of the OMNI data archive for the period of 1976–2000, have analyzed 798 geomagnetic storms with D _st ≤ −50 nT and their interplanetary sources: corotating interaction regions CIR, compression regions Sheath before the interplanetary CMEs; magnetic clouds MC; “Pistons” Ejecta, and an uncertain type of a source. For the analysis the double superposed epoch analysis method was used, in which the instants of the magnetic storm onset and the minimum of the D _st index were taken as reference times. It is shown that the set of interplanetary sources of magnetic storms can be sub-divided into two basic groups according to their slowly and fast varying characteristics: (1) ICME (MC and Ejecta) and (2) CIR and Sheath. The mean values, the absolute and relative variations in MC and Ejecta for all parameters appeared to be either mean or lower than the mean value (the mean values of the electric field E _y and of the B _z component of IMF are higher in absolute value), while in CIR and Sheath they are higher than the mean value. High values of the relative density variation sN/〈N〉 are observed in MC. At the same time, the high values for relative variations of the velocity, B _z component, and IMF magnitude are observed in Sheath and CIR. No noticeable distinctions in the relationships between considered parameters for moderate and strong magnetic storms were observed.     

Probing the first stars and black holes in the early Universe with the Dark Ages Radio Explorer (DARE)

A concept for a new space-based cosmology mission called the Dark Ages Radio Explorer (DARE) is presented in this paper. DARE’s science objectives include: (1) When did the first stars form? (2) When did the first accreting black holes form? (3) When did Reionization begin? (4) What surprises does the end of the Dark Ages hold (e.g., Dark Matter decay)? DARE will use the highly-redshifted hyperfine 21-cm transition from neutral hydrogen to track the formation of the first luminous objects by their impact on the intergalactic medium during the end of the Dark Ages and during Cosmic Dawn (redshifts z = 11–35). It will measure the sky-averaged spin temperature of neutral hydrogen at the unexplored epoch 80–420 million years after the Big Bang, providing the first evidence of the earliest stars and galaxies to illuminate the cosmos and testing our models of galaxy formation. DARE’s approach is to measure the expected spectral features in the sky-averaged, redshifted 21-cm signal over a radio bandpass of 40–120 MHz. DARE orbits the Moon for a mission lifetime of 3 years and takes data above the lunar farside, the only location in the inner solar system proven to be free of human-generated radio frequency interference and any significant ionosphere. The science instrument is composed of a low frequency radiometer, including electrically-short, tapered, bi-conical dipole antennas, a receiver, and a digital spectrometer. The smooth frequency response of the antennas and the differential spectral calibration approach using a Markov Chain Monte Carlo technique will be applied to detect the weak cosmic 21-cm signal in the presence of the intense solar system and Galactic foreground emissions.     

Structural health management technologies for inflatable/deployable structures: Integrating sensing and self-healing

Inflatable/deployable structures are under consideration as habitats for future Lunar surface science operations. The use of non-traditional structural materials combined with the need to maintain a safe working environment for extended periods in a harsh environment has led to the consideration of an integrated structural health management system for future habitats, to ensure their integrity. This article describes recent efforts to develop prototype sensing technologies and new self-healing materials that address the unique requirements of habitats comprised mainly of soft goods. A new approach to detecting impact damage is discussed, using addressable flexible capacitive sensing elements and thin film electronics in a matrixed array. Also, the use of passive wireless sensor tags for distributed sensing is discussed, wherein the need for on-board power through batteries or hardwired interconnects is eliminated. Finally, the development of a novel, microencapuslated self-healing elastomer with applications for inflatable/deployable habitats is reviewed.     

Survival of dormant organisms after long-term exposure to the space environment

The RF SRC—Institute of Biomedical Problems, Russian Academy of Sciences, developed Biorisk hardware to study the effects of long-term exposure of dormant forms of various organisms to outer space and used it to complete a series of experiments on the Russian Module (RM) of the International Space Station (ISS).The experiments were performed using prokaryotes (Bacillus bacteria) and eukaryotes (Penicillium, Aspergillus, and Cladosporium fungi), as well as spores, dormant forms of higher plants, insects, lower crustaceans, and vertebrates. The biological samples were housed in two containers that were exposed to outer space for 13 or 18 months. The results of the 18-month experiment showed that, in spite of harsher temperature than in the first study, most specimens remained viable.These experiments provided evidence that not only bacterial and fungal spores but also dormant forms of organisms that reached higher levels of evolutionary development had the capability to survive a long-term exposure to outer space. This observation suggests that they can be transferred on outer walls of space platforms during interplanetary missions.     

Thermodynamic properties of mixed fuel combustion products

In this paper, the results of calculating the processes of two fuel mixture combustion in different proportions are presented. The values of temperature, thermal capacity, specific gas constant and isentropic expansion ratio of combustion products are given. Also shown is the distinction of thermodynamic properties from the additivity law.