Energy and Mass Utilization During Drag-Modulated Plasma Aerocapture

An analytical model is presented to assess the utilization of atmospheric energy and mass by a magnetoshell plasma during aerocapture. An appropriate control volume describing the plasma is defined using single ion trajectory analysis in the dipole magnetic field. Equations of continuity and state are developed to describe the plasma interaction with the atmospheric flow. The populations and temperatures of ions, electrons, and magnetoshell neutrals are tracked and steady state results are obtained. A strong correlation is demonstrated between applied magnetic field strength and absorbed mass, confirming initial notions that the magnetoshell drag can be modulated by the magnet. The plasma is found to self-sustain with no input power from the spacecraft, though propellant injection is required on the order of 1 mg/s during the maneuver. The mass absorbed from the flow is observed to decrease with increasing velocity due to shrinking of the control volume and reduced charge exchange interaction. The percentage of incident atmospheric mass and energy absorbed by the plasma is determined to be between 1% and 33% across a spacecraft velocity range of 2-20 km/s and atmospheric density range of 10(16)-10(18) m(-3). That this percentage is not 100% indicates that some flow passes through the plasma without interaction, contrary to previous studies which assumed the plasma to be fully opaque.