Evaluation of plasma shock layer electrophysical properties near critical point of lander

A continual radiocommunication with landers in upper atmosphere is of great importance in some applications. The problem consists in sufficient attenuation of radio waves propagating through a high-heated plasma shock layer that arises in nose part of a lander due to its motion with high supersonic velocity in upper atmosphere. Radio wave energy losses are partly caused by its reflection of “plasma/free space” boundary and partly by its absorption in plasma. Plasma losses can be evaluated using plasma indexes of refraction and absorption. The purpose of this paper consists in evaluating of these indexes near critical point of a lander for different heights of its flight and up-stream velocities. To fulfill this, the following assumptions were made: plasma is uniform and isotropic, classical theory can be applied to describe the motion of charged particles, external magnetic field is absent, electron gas is nondegenerate, plasma is in the state of thermodynamic equilibrium, lander heat-resistant coating does not contain components with low ionization potential, thus, there is no additional ionization in plasma shock layer. Utilizing notorious equations, the following plasma shock layer parameters near critical point of a lander for range of heights from 80 to 20 km and up-stream velocities 4,6; 6 and 7,4 km/s were calculated: electron and molecular densities, temperature, effective number of electron/ion and electron/molecule collisions. Involving this parameters, plasma permittivity, conductivity and indexes of refraction and absorption were obtained. While plasma conductivity is nonzero, in spite of negative values of permittivity, index of refraction is always real for considered conditions. Hence, traveling wave exists in plasma shock layer. Plasma indexes of refraction and absorption are functions of height, up-stream velocity and radio wave frequency. These indexes always grow with lowering of lander flight height. This regularity is caused by plasma conductivity and permittivity absolute value growth. Obtained results are parameters for lander electrodynamic model. From now on, to choose an optimal design and parameters for on-board communication equipment, a number of numerical experiments will be carried out using the model.