Estimation of the Rejection Boundaries of the Spacecraft Schematic Layout by Thermal and Erosive Effects Level of the Electric Rocket Engines Plasma Jets

Abstract

The paper proposes an engineering method to account for thermal and erosive effects of the electric rocket engine plasma jet on the spacecraft structural elements with the electric rocket engines installed on a spacecraft. The method is based on introducing the rejection boundaries that define the region of space, where installation of the spacecraft structural elements is unacceptable from the point of view of certain impact type. The rejection boundary is a surface, where the impact indicators are equal to the allowable value, inside the boundaries they exceed the allowable values (critical impact area), and outside the boundaries they stay below the allowable values (admissible impact area). If the spacecraft elements appear in the critical impact area, position of the electric rocket engines on the spacecraft should be corrected. Equilibrium surface temperature is the thermal effect indicator, which should not exceed the given allowable value; an erosion depth is the erosive effect indicator. Allowable level of erosive action depends on material and characteristics of the sprayed structural element. The considered indicators were determined by the ion current density at the given point in space for the worst case without accounting for the jet ions angle of incidence on the surface. Rejection boundaries were found for the plasma jet thermal and erosive effects of the SPT-100 stationary engine on various materials. It is shown that, incontrast to the traditionally used limitation on the jet divergence angle, the rejection boundary method makes it possible to significantly improve the accuracy of estimates and reduce the probability of errors in the layout of a modern spacecraft