Optimal design of composite lattice shell structures for aerospace applications

An optimization method for composite lattice shell structures under axially compressive loads is proposed aiming at the preliminary design. The method implements and improves some previous results of the fully analytical approach which is currently adopted at the state-of-the-art. The fully analytical approach provides the minimum mass solution under buckling and strength constraints, irrespective of other possible design limitations, such as, shell stiffness constraints. As a consequence, the minimum mass solution turns out to be satisfactory whereas other requirements are absent or automatically achieved but, on the contrary, it can drive the final preliminary configuration far from the real optimum.The proposed method implements numerical minimization allowing the designer to easily handle suboptimal configurations which are located in the vicinity of the minimum mass solution. When stiffness requirement is present (as in most cases) the benefit of this approach – in terms of weight saving with respect to the analytical design – is finally shown with a practical example.     

Study of the 28 October 2003 and 20 January 2005 solar flares by means of 2.223 MeV gamma-emission line

By the data on intensity-time profiles of the neutron capture line of 2.223 MeV we have studied some characteristics of two solar flares, 28 October 2003 and 20 January 2005 (INTEGRAL and CORONAS-F observations, respectively). The SINP code was applied making allowance for the main processes of neutron interactions and deceleration in the solar plasma, character of neutron source, losses of neutrons and density model of the solar atmosphere. Comparison of the computed time profiles of 2.223 MeV line with observed ones for the flare of 28 October 2003 confirms the results obtained earlier for three other flares. Namely, the effect of density enhancement (EDE) in the sub-flare region, as well as the variations (hardening) of accelerated particle spectrum in the course of the event have been confirmed. The usual modeling procedure by the SINP code, however, seems to be inapplicable to the event of 20 January 2005. Possible causes of density enhancements during some flares and peculiarities of the 20 January 2005 flare are discussed.     

The brief history of experimental research of cosmic ray variations in Yakutia

Some unknown historical facts of cosmic ray studies in the north-east of the former Soviet Union related to the Yakutsk scientific group are reported for the benefit of the international scientific community. It focuses on the founders of Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of Siberian Branch of Russian Academy of Sciences. A chronology of measurements of cosmic ray intensity variations since 1949 in Yakutia (Sakha Republic; NE Siberia) is given. In particular, for the first time the data of the first solar cosmic ray event registered at Yakutsk (GLE04), with a small ionization chamber S-2 (volume: 20 L) are presented. Moreover, the data of the large ionization chamber ASK-1 (volume: 950 L) for the 1953–2003 period useful for specialists in the field of cosmic ray variations are also shown.     

Mid-latitude amplitude scintillation of GPS signals and GPS performance slips

Degradation of transionospheric radio signals and operation failures during ionospheric disturbances constitute a crucial factor of space weather influence on radio engineering satellite systems performance. We found that during the main phase of strong magnetic storms in 2000–2003 when the auroral oval expands into mid-latitudes, its southern boundary develops a region with intense small-scale electron density irregularities. Such irregularities may cause strong amplitude scintillations of GPS signals at both GPS operating frequencies. The another consequence of it was significant random GPS signal phase fluctuations, breaking-down of signal tracking, and sharp increasing of GPS positioning errors as a result.     

Concentration of ions in the topside ionosphere as measured onboard the <Emphasis Type="Italic">DEMETER</Emphasis> satellite: Morphology and dependence on solar and geomagnetic activity

Variations in concentration of ions H⁺, He⁺, and O⁺ are studied at a height of about 700 km using the data of continuous observations onboard the DEMETER satellite at the decline and in the minimum of solar activity from 2004 to 2008. Latitudinal distributions, seasonal behavior, and irregular variations in ion concentrations and their dependence on solar and geomagnetic activity are considered. Within this altitude range, for the first time an analysis is performed of the dataset of many-year continuous observations in both hemispheres from the equatorial to subauroral latitudes. This made it possible to describe the seasonal and irregular variations of the concentrations of main ion species with better time and spatial resolution than in the available empirical models. The dependence of concentrations of three types of ions on solar and geomagnetic activity is studied at time scales from several days to several years, and it is shown that the anti-phase change in concentrations of O⁺ and light ions known from publications is partly a result of mutual dependence of solar and geomagnetic activity and is observed only at time scales beginning from several months. At time scales from several days to several weeks, variations in the concentration of O⁺ and light ions are governed mainly by solar and geomagnetic activity, respectively.     

A technique for calculating large deflections of nonshallow elastoplastic shells of revolution under nonaxisymmetric loading

A technique for calculating the geometrically and physically nonlinear stress strain state of nonshallow shells of revolution under the nonaxisymmetric wind-like loading is proposed. The calculation results for a semispherical shell with the central hole and rigidly fixed edges depending on the loading nonaxisymmetry, material characteristics and thickness are presented. We demonstrate not only quantitative but also qualitative influence of taking into account the factor of joint nonlinearity on the process of shell deformation.     

Fractal assessment of microaccelerations at weak damping of natural oscillation in spacecraft elastic elements. II

Making use of the Weierstrass-Mandelbrot fractal function, some problems connected with the adequate assessment of microaccelerations aboard a spacecraft are considered. The ranges of values for the function parameters that make it possible to simulate the quasi-static component of microaccelerations are also determined.     

Spatial structure of Pc5 waves in the outer magnetosphere according to observations onboard the THEMIS satellites

We have analyzed oscillations in the Pc5 range recorded in the outer region of the evening magnetosphere onboard 5 THEMIS satellites when all vehicles were moving with a small distance along one and the same orbit. Gradients of the spatial structure of oscillations and fluxes of energetic protons are determined. The observed phase shifts of the oscillation field between the satellites are presumably caused by their sunward (westward) propagation with azimuthal wave numbers m ～ 30–60. According the data of particle detectors, non-equilibrium character of the distribution of protons is found: their non-monotonous distribution in energy and sharp spatial heterogeneity. The calculated parameters of plasma and oscillations are not consistent with the assumption on drift-mirror instability as a source of the oscillations. A complete theory of these waves should include effects of the finite Larmor radius and simultaneous existence of two types of nonequilibrium plasma.     

Spacecraft “Foton-M” in-flight thermal conditions

The problem of thermal conditions aboard the “Foton-M” spacecraft during its orbital flight is under consideration in this paper. The problem is very acute for performing microgravity experiments onboard of the orbital platform, because on one hand, many experiments need a definite temperature range to be performed, and on the other hand all electrical devices aboard radiate heat. To avoid uncontrolled heating of the environment special heat exchangers are used. To transport heat from different places of the capsule to heat exchanger special fans are installed given definite orientation. All the heat exchange facilities should be designed in advance being adjusted to current capsule loading and heat radiation by equipment. Thus special tools are needed predicting the capsule thermal conditions being function of equipment placement.The present paper introduces a new developed prognostic mathematical model able to forecast temperature distribution inside the capsule with account of fan induced air flows, thermal irradiation by scientific equipment and heat losses due to cooling system.