Experimental studies indicate that separation formations exist in a diversity of forms [1]. Even in the case of a flow past bodies of uncomplicated configuration the structure of the separation formation has not yet been studied sufficiently and so a priori systems of separating flow must be used in numerical calculations. The experimental study of this problem, therefore, is applied as well as cognitive importance.In a water tunnel with a throat measuring 150 • 150 mm we studied the flow past a model consisting of two plates, connected so that the plane passing through the trailing edge of the fhst plate and the leading edge of the second was perpendicular to plane of the fast (Fig. 1). The plates were separated by a gap. The fast plate, set up along the flow, was flat and the second was curved along a circular arc. The leading edge of the second plate was profiled to eliminate breakaways. Drainage tubes with a dye to visualize the flow were connected to the trailing edge of the fh-st plate and the leading edge of the second. The second plate was 85 mm long and its radius of curvature was 55 mm.Our aim here is to study the interaction of the boundary layers formed on the two plates. A typical pattern of this interaction is shown in Fig. 2. This interaction evidently should model the flow in the vicinity of the gap between a wing and a flap. The flow past such a configuration in a particular range of Reynolds numbers Re leads to an isolated separation [2].The flow has two characteristic scales: l is the length of the first plate, which was 100 mm in the given case, and h ,~ 1 is the distance between the plates. The entire region of flow can thus be divided into two subregions: an external subregion associated with the total flow past the model and an internal subregion associated with the flow around the gap.The flow in the external region has a characteristic Reynolds number of the order of 103. A Blasius boundary layer forms on the front plate and its thickness 5 varies with the distance from the leading edge x by the law [3]

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The mathematical model for calculation of the ion density in the gas-discharge chamber of a radio-frequency ion thruster is developed. The model is based on the assumption of higher potential of the central plasma volume comparing to the chamber walls due to higher mobility of electrons. Firstly, the initial approximation for the plasma potential is set and parameters of the ion trajectories in quasistationary electric field are computed. Then, from the assumption of keeping the total ion flow for each trajectory, the ion density is computed as well as the next approximation for plasma potential. The computation is performed iteratively until the change in the ion density is less than the predefined small value. The model was verified by comparing the results of numerical simulation with the analytical solution for spherical volume. The high accuracy of the numerical model is shown. Also, the ion density in the discharge chamber of a radio-frequency ion thruster was calculated with the uniform distribution of neutral atom density and coefficient of ionization rate. It was shown that at such conditions the ion density has a maximum in central part of the discharge chamber and it decreases towards the walls.

Research Institute of Applied Mechanics and Electrodynamics of the Moscow Aviation Institute (RIAME MAI) develops ablative pulsed plasma thrusters with low power consumption for small spacecraft. The paper considers the development of power processing unit (PPU) for such thrusters. PPU under discussion should meet the following requirements: design simplicity, small overall dimensions, ensuring the required power and frequency of thruster operation and high energy efficiency.