Plasma MagnetoShells (PMS) for Orbit Insertion on Deep-Space Planetary Missions

For deep-space planetary missions, the challenge of orbit insertion at the target planetary body is as critical and potentially as fuel consumptive as launch. The total required velocity change can be on the order of 10s of km/s, resulting in fuel being a large fraction of the spacecraft mass thus limiting valuable payload. Virtually all the planetary bodies in the solar system have an atmosphere of sufficient depth and mass density to provide for rapid vehicle deceleration from aerodrag. Even braking in the Earth's atmosphere would be highly advantageous for a Martian sample return mission. Employing a solid deflector for orbit insertion has been successful in the past, but due to frictional heating, as well as unknown and changing atmospheric conditions, the braking must be distributed over many elliptical orbital passes into the atmosphere to achieve the required braking. The concept to be elucidated in this paper is one possible solution to the limitations of aerobraking with a solid shield. The method entails the deployment of an arrangement of dipolar magnetic field coils that is populated with plasma and sustained in a manner that provides the necessary impediment to atmospheric flow and thereby creates the desired drag. This braking technique is referred to as a Plasma MagnetoShell (PMS). The requisite drag-inducing interactions are between the incoming neutral's directed momentum and the magnetically confined ions in the form of charge exchange and elastic scattering. During the interaction, the neutral's momentum is imparted to the magnetized ion which is then reacted onto the magnetic coils tethered to the spacecraft through field line bending and stretching. It will be shown that there are several unique advantages to PMS braking and aerocapture. Frictional heating is no longer a concern. The aeroshell is now composed of massless magnetic field and plasma. The scale of the magnetic barrier can be as large as needed (∼10-100 m) while requiring less than a gram of plasma. While the dipole coil system will be the dominant mass, it is negligible compared to the spacecraft mass. With the ability to control the drag by changing field strength and/or plasma density on a sub-second timescale, the larger drag force and precision trajectory required for aerocapture is now feasible. Since the PMS provides for dynamic control under rapidly changing conditions, it should be suitable for human missions. A laboratory scale PMS was designed, built, and tested in a large vacuum chamber at MSNW. A supersonic flowing neutral jet was aimed a subscale PMS that was mounted on a boom attached to a thrust stand. The tests results validated the concept with the drag force increasing by a factor of 1000X when the PMS was activated. Mission analyses and system designs two missions were also conducted: a Cassini-class Neptune orbiter and a HEOMD-scale Mars orbital insertion. The design included the Plasma MagnetoShell magnet, tether, power processing, and battery mass. The orbital code Copernicus was used to determine optimal trajectories. The results from these studies will also be presented.