Determination of plume impingement disturbance characteristics for the ROCSAT-1 satellite

Abstract

The impingement disturbance characteristics of the hydrazine thruster plumes have been examined comprehensively for the ROCSAT-1 satellite. In this study, the velocity and temperature distributions at the nozzle exit are obtained from the nozzle flowfield analysis. The axial velocity, transverse velocity and temperature profiles are further correlated with the curve-fitting procedure for resolving inflow properties of molecules ejected into a vacuum. The free-molecular direct simulation Monte Carlo technique is used to describe the particle nature of the distant plume flow behaviour near the impingement surface. The inflow molecular motions as well as the collision interactions between the molecules and the solid surface are treated on a probabilistic basis. On the other hand, the inter-collisions among molecules are considered to be relatively unimportant in the far-field plume region. A reasonable number of simulated molecules is also employed to reproduce the fluid behaviour in the macroscopic level. The predicted disturbance torques and thrust loss are found to be much less than the design control torques and the nominal thrust force for ROCSAT-1 satellite, indicating that the plume impingement effect will not cause any performance deterioration of the propulsive function.