We propose a new mission concept, called MAGNETOUR, that enables a spacecraft to orbit and travel between multiple moons of an outer planet, using very little or even no propellant. To achieve this free-lunch 'Grand Tour', we exploit the unexplored combination of magnetic and multi-body gravitational fields of planetary systems. This concept involves combining two main innovations:
- Design of a very low delta-v tour of planetary moons by considering the intrinsic multi-body gravitational dynamics of planetary systems. The low-energy paths between the moons are based on using unstable resonant periodic orbits and their associated manifolds in order to efficiently navigate between the moons rather than 'fighting' the dynamics with thrusting. This innovative space travel technique is called the Intermoon Superhighway, and can be seen as an extension to intermoon transfers of the well-established Interplanetary Superhighway concept. In this framework, the cost of inserting and orbiting the moons is also reduced via loosely captured orbits, such as Halo orbits and high altitude eccentric orbits, that act as destination science orbits and waypoints to the next moon.
- Use of the electromagnetic Lorentz force as a revolutionary means for performing the required low delta-v maneuvers of our low-energy tour. This force originates from the magnetic field of the planet, and acts on moving spacecraft carrying an electrical charge, such as an electrodynamic tether. As they travel through the planetary surrounding plasma, interaction between the magnetosphere and spacecraft can be used to change the orbital pro#le by means of propellantless maneuvers. The electromagnetic system could also serve as its own power source by plugging in an electric load where convenient. By switching on and off the electromagnetic system in specifically designed sequences, the orbit could be made to evolve without recourse to propellant and on-board power sources. A full planetary tour, involving navigation through the moon system and gravitational capture, would therefore offer a perfect opportunity to exploit this idea.
Revolutionary Value (Significance):
The prospect of a quasi-propellantless mission to explore planetary systems is extremely appealing. Without the burden of propellant, scientific payload could be larger and the lifetime of the spacecraft would be only limited by the failure of its primary components and its ability to sustain the harmful radiation environment. This very long tour mission has therefore a strong potential for improved (possibly unforeseen currently) scientific return at planetary moons In addition, combining multi-body gravitational and electromagnetic dynamics is totally new and would open up path planning options mission designers are currently unaware of. If successful, this concept will therefore represent a dramatic departure from conventional mission design for planetary moon systems and could lead to the next generation of high science value, low cost robotic solar system exploration. In the future, we envision future NASA missions directly utilizing the results of this study to orbit multiple planetary moons (e.g. a mini-JIMO class mission) in a single, quasi-propellantless mission, thus obtaining flagship class science using possibly sub-flagship programs (e.g. New Frontiers).