In-Flight Plume Control and Thrust Tuning in Magnetic Nozzle Using Tapered-Coils System Under the Effect of Density Gradient

A three-thick tapered-coils system is developed and the role of spacing and relative size of the coils along with their tapering in controlling the plume geometry through a magnetic nozzle in-flight is revealed under the effect of the density gradient. Empirical relations for the plume radius as a function of the axial distance are obtained for a deeper understanding of the plume geometry after establishing a concept of plasma detachment. For the same current, the translation of the middle coil has a weaker impact on the plume geometry (size and slope profile) compared to the middle-to-outer coil diameter ratio. The combined effect of the tailorable plume geometry and the gradient of the plasma density, occurring because of the varying magnetic field, on the axial thrust is numerically evaluated. As the middle coil is shifted toward the rightmost or the leftmost coil in the system, a significant enhancement in the thrust is noticed, which rises further on tapering the coils and more than 3 mN thrust is achieved for the taper angle of 22°. The results indicate that the plume structure can be changed and optimized in-flight for tuning the thrust without varying the input power.