MAGNETIC SAILS AND INTERPLANETARY TRAVEL

A new concept, the magnetic sail, or "magsail," which propels spacecraft by using the magnetic field generated by a loop of superconducting cable to deflect interplanetary or interstellar plasma winds, is proposed. The performance of such a device is evaluated using both a plasma particle model and a fluid model, and the results of a series of investigations are presented. It is found that a magsail sailing on the solar wind at a radius of one astronautical unit can attain accelerations on the order of 0.01 m/s2, much greater than that available from a conventional solar lightsail, and also greater than the acceleration due to the sun's gravitational attraction. A net tangential force, or "lift," can also be generated. Lift-to-drag ratios of about 0.3 appear attainable. Equations are derived whereby orbital transfers using magsail propulsion can be calculated analytically. It is found that a magsail can transfer payloads to and from any two circular orbits in the solar system in a flight time slightly larger than the Hohmann ballistic transfer time. The magsail can accomplish these missions at any time, unrestricted by the usual ballistic transfer launch window. The necessary magsail/payload mass ratios are less than 0.15.