Variation of aircraft GTE turbine disks cyclic life depending on operational factors

Influence of the free air temperature during aircraft takeoff and engine operating time upon the cyclic life of an aircraft GTE turbine disk made from the heat-resistance deformable nickel-base alloy is analyzed and the variation of engine operating parameters in the process of service is taken into account.     

Analysis and parametric synthesis of the air ion counter measurement channel with impulse signal pickup from the aspiration chamber

The measurement channel of the air ion counter with impulse signal pickup from the aspiration chamber is considered. Peculiarities of its functional parts operation are analyzed and restrictions imposed on their parameters are stated. A technique is proposed and a set of equations that allows determining design parameters of the functional counter parts is presented.     

Fatigue life of a plate with an arbitrary-shaped concentrator under low-cycle plane loading

A technique and an algorithm for calculating fatigue life of a plate with a concentrator under complex loading in the low-cycle fatigue region are presented and the life of the plate with different shape concentrators is considered. The local stress strain state is investigated in the framework of plane loading using the finite element method with the aid of the MSC NASTRAN software and the life is evaluated with the use of an integral criterion of the concentrator contour loaded-up condition.     

Choice of optimal parameters of a gasodynamic temperature stratification process in the supersonic gas flow

The results of design analysis of the different factor influence on the gasodynamic temperature flow stratification efficiency in the Leont’ev tube are presented. It is justified that the temperature stratification efficiency can be increased at the expense of using longitudinal ribs on the heat exchange surface in the subsonic flow path, and the parameters determining the process can be optimized.     

Scaling Effects in the Impact Resistance of Flat and Cylindrical Samples from Composite Materials

The scaling factors in the problems of assessing the resistance to high-speed impact of plates and shells are analytically determined. Numerical experimentation shows the possibility of applying certain scaling factors in assessing the impact resistance of laminated plates and shells from materials with orthotropic properties.     

Multi-beam sounding ionograms in the polar cap region: Absorption induced by proton precipitations

The simulation of the multi-beam ionograms in the polar cap region, assessing absorption effect is performed. It is reasonable to distinguish among four different mechanisms responsible for absorption: regular absorption due to solar UV illumination, absorption associated with energetic particles precipitation, absorption connected with X-rays flare and additional absorption in Auroral oval area. In this paper the absorption attributed to proton precipitations is envisaged. The computational model of the high-latitude ionosphere with irregularities oriented to application for the high frequency wave propagation problem was elaborated (Zaalov et al., 2005). A number of the quasi-vertical ionograms in the polar cap region were simulated on the basis of this model. A well-known algorithm (Sauer and Wilkinson, 2008) is applied for the absorption effects calculation. The simulated high-latitude ionograms with the absorption effect and the measured ionograms exhibit quite a good resemblance. This paper illustrates the importance of the understanding and taking into account the absorption effect in the presence of the various structural features in the polar ionosphere (in particular, patches of enhanced electron density) in interpreting ionosonde data.     

On mid-term periodicities of high-latitude solar activity

The mid-term periodicities of polar faculae are studied separately for the total disk, northern and southern hemispheres of the Sun for a time interval from 1951 August to 1998 December. Apart from the 11-year Schwabe cycle which is the fundamental period and is found in all of the three time series, the following prominent results are found: (1) the rotational periodicity of solar activity at high latitudes is approximately from 28 to 32 days; (2) a large number of quasi-periods appearing in low-latitude solar activity (annual variation, 1.3–1.7 years, quasi-biennial oscillation, and 4–5 years) also exist in polar faculae; (3) the periodicities on both hemispheres are not identical.     

A method for calculating the laser rocket engine thermal state based on the optical discharge with numerous plasma formations

A method is presented for calculating the thermal state of the laser rocket engine (LRE) structure with numerous plasma formations in the absorption chamber. The results of evaluating radiant heat fluxes and the temperature of the LRE structure walls with regard for convective and conductive heat exchange are given; the actions of a heat flux with the specified distribution density on the structure surface are considered as functions of time and thermal radiation, that is due to the temperature and optical properties of a radiating body. It is shown that working process organization in the absorption chamber on the basis of numerous plasma formations makes it possible to produce a uniform profile of the heat flux distribution along the absorption chamber axis and thus reduce a possibility of separate structure sections overheating.     

Estimation of the Combustion Chamber Shell Working Capacity for the Reusable Liquid-Propellant Rocket Engine

On the base of the simplified analytical model for the bimetallic shell of the combustion chamber of the reusable liquid-propellant rocket engine, the analysis of the loading of connectors between the shell walls and the accumulation of inelastic deformations in the inner wall material was carried out. The results obtained can be used for evaluation of the maximal number of engine operation cycles.     

NeQuick 2 and IRI Plas VTEC predictions for low latitude and South American sector

Using vertical total electron content (VTEC) measurements obtained from GPS satellite signals the capability of the NeQuick 2 and IRI Plas models to predict VTEC over the low latitude and South American sector is analyzed. In the present work both models were used to calculate VTEC up to the height of GPS satellites. Also, comparisons between the performance of IRI Plas and IRI 2007 have been done. The data correspond to June solstice and September equinox 1999 (high solar activity) and they were obtained at nine stations. The considered latitude range extends from 18.4°N to ?64.7°N and the longitude ranges from 281.3°E to 295.9°E in the South American sector. The greatest discrepancies among model predictions and the measured VTEC are obtained at low latitudes stations placed in the equatorial anomaly region. Underestimations as strong as 40?TECU [1?TECU?=?10¹⁶?m^?2] can be observed at BOGT station for September equinox, when NeQuick2 model is used. The obtained results also show that: (a) for June solstice, in general the performance of IRI Plas for low latitude stations is better than that of NeQuick2 and, vice versa, for highest latitudes the performance of NeQuick2 is better than that of IRI Plas. For the stations TUCU and SANT both models have good performance; (b) for September equinox the performances of the models do not follow a clearly defined pattern as in the other season. However, it can be seen that for the region placed between the Northern peak and the valley of the equatorial anomaly, in general, the performance of IRI Plas is better than that of NeQuick2 for hours of maximum ionization. From TUCU to the South, the best TEC predictions are given by NeQuick2.The source of the observed deviations of the models has been explored in terms of CCIR foF2 determination in the available ionosonde stations in the region. Discrepancies can be also related to an unrealistic shape of the vertical electron density profile and or an erroneous prediction of the plasmaspheric contribution to the vertical total electron content. Moreover, the results of this study could be suggesting that in the case of NeQuick, the underestimation trend could be due to the lack of a proper plasmaspheric model in its topside representation. In contrast, the plasmaspheric model included in IRI, leads to clear overestimations of GPS derived TEC.