2000. № 1

Aerospace propulsion engineering

Sergienko A. A., Semenov V. V.

Theoretical analysis and experimental research of a supersonic flow of gas nozzle and head part of the flying device with rhombic, row-like and chess relief surfaces is carried out in the work. For small displacement of a surface the theoretical description of the problem in linear approximation with flat waves is presented. In experience with model nozzle inserts it is revealed a new phenomenon - critical modes of a flow over the relief surface, which happen each time, when the corner of an inclination of a wave of displacement coincides with the Mach corner, and in the case of =0 of this corner the flow passes in the Prandtle - Meyer form of the flow.


Semenov V. V.

The way of essential increase of an overall performance of a high-altitude nozzle in terrestrial conditions is offered by variation of its expansion ratio at the expense of a ring slot on a supersonic part. The results of slot-hole tests at a differential installation on overexpansion modes are resulted. It is shown, that the results of fire tests of a slot-hole nozzle coincide well with the experimental data received at its cold purges by compressed air. The optimum sizes of a ring slot and its site on a supersonic part of the round nozzle are determined. It is established, that at organization of several ring slots in a supersonic part of the high-altitude nozzle the range of change of external pressure, at which the positive effect is kept, considerably extends.


Kudrin O. I., Finogenov S. L.

The possibility of significant simplification of solar thermal propulsion (STP) with thermal energy storage (TES) of impulse working mode is provided by means of usage of lithium hydride LiH, having high melting enthalpy and lower melting temperature, is considered. In comparison with STP containing thermal energy storage medium with high melting temperature, the lower working temperature at the LiH usage makes it possible to decrease the mass of TES up to 50% and it also allows to reduce the required dimensions and accuracy of concentrator reflecting surface. Non-high required accuracy of the concentrator allows significant decreasing of the permissible angle of the "concentrator-absorber" system orientation accuracy. In dynamic orientation mode the permitted desorientation angle can approach to solar arrays orientation conditions. The possibility of the improvement of the characteristics of the STP with LiH is considered also in reference to the engine with post-burning of heated hydrogen in combustion chamber with cold oxygen addition. At the optimal oxidizer-to-fuel mass ratio value corresponing to the maximum of the payload mass, the required TES mass and concentrator square significantly decreases. The mass efficiency of the considered STP usage can be larger up to 10-15% in comparison with the LH2-LOX LRE.


Mathematics. Physics. Mechanics

Kozoriz V. I.

The problem of movement of electron with spin in constant and homogeneous magnetic and electric fields. The explicit analytical solution for spatial and spin coordinates is obtained, the analysis of results is made.


Uldanov S. V.

Close model for dynamics of charged particles is obtained. It is proved that the correlation of concentrations pulsations and gradient of potential pulsations do not contribution into transport. Model for calculations in boundary layer is suggested.


Aviation technics and technology

Tryamkin A. V., Emelyanov U. N.

The subject of this article is the mathematical model of deceleration process of landing object by a parachute-jet system. The obtained model allows to determine motion characteristics of the object during its deceleration, to analyze the effect of unstability of parameters parachute-jet system and meteorological conditions on motion characteristics of touching down object.


Space technics and technology

Burgasov M. P., Nadiradze A. B.

In the article the problem of principally possible to measure parameters of space debris using information about spacecraft (SC) solar batteries (SB) power decrease at the moment of solid particles impact is discussed. It is represented the numerical data about SB reaction onto particles impacts which have different velocities, sizes and mass density. Basing on these data, particles flow parameters, which can be measured with the help of SB are determined. The problem deals with restore of function of distribution for space debris particle on the SC orbit is formulated.


Novikov L. S., Nadiradze A. B., Bedniakov S. A., Gavrushin A. V.

The results of laboratory experiments showing that under high velocity impact over the solar battery cells surface, thier shunting is happened, are represented in the paper. So for one of the examined samples it was recorded that loss power was about 90%. Impact destroys not only the one cell, but group of several parallel connected ones. The model of solar cell damaged is presented. According to this model shunting is appeared as a result of structural changed in the p-n junction due to semi-conductor smelting in the area of the impact. Critical velocity of the impact under which solar cell shunting is happened by 7-12 km/s.


Technical cybernetics. Information technology. Computer facilities

Syrin V. V.

The problems of identification are solving with the using of digital certificates into global and corporate computer networks. This article explains some algorithms of generating and issuing the digital certificates, structures of Certificate Authority (CA). There is some classification of the digital certificates according to their using and security. There are also examples of the using of the digital certificates into different network services. As a result the analysis of existent certificate systems is made with the purpose to detect the weak sides of the certificate algorithms.


mai.ru — informational site MAI

Copyright © 2000-2021 by MAI