A magnetic sail is a proposed method of spacecraft propulsion that uses a static magnetic field to deflect a plasma wind of charged particles radiated by the Sun or a Star thereby transferring momentum to accelerate or decelerate a spacecraft. Most approaches require little to no propellant and thus are a form of Field propulsion. A magnetic sail could also thrust against a planetary ionosphere or magnetosphere. Important use cases are: a modest force from the solar wind sustainable for a long period of time; deceleration in the interstellar medium and the plasma wind of a destination Star following interstellar travel at relativistic speeds achieved by some other means; and efficient deceleration in a planetary ionosphere. Plasma characteristics for the Solar wind, a planetary ionosphere and the interstellar medium and the specifics of the magnetic sail design determine achievable performance; such as, thrust, required power and mass. History of concept Dana Andrews and Robert Zubrin first proposed the magnetic sail concept in 1988. Andrews was working on use of a magnetic scoop to gather interstellar material as propellant for a nuclear electric ion drive spacecraft, allowing the craft to operate in a similar manner to a Bussard ramjet. Andrews asked Zubrin to help compute the magnetic scoop drag against the interplanetary medium, which turned out to be much greater than the ion drive thrust. The ion drive component of the system was dropped, and use of the concept of using the magnetic scoop as a magnetic sail or Magsail (MS) was born. Published magsail analysis was done for interstellar in 1988, interplanetary in 1989, planetary orbital propulsion in 1991 and a detailed design in 2000. Freeland did further analysis in 2015 for Project Icarus that used a more accurate model of the magnetic field and showed that the Andrews and Zubrin results for drag (thrust) were optimistic by a factor of 3.1 In 2016 Gros published results for magsail use for deceleration in the Interstellar medium. In 2017, Crowl documented an analysis for a mission starting near the Sun and destined for Planet nine. Another mission profile for the magsail is heliocentric transfers, as described in 2013 by Quarta, in 2019 by Bassetto, and in 2020 by Perakis. A drawback of the magsail design was that a large (50–100 km radius) superconducting loop weighing on the order of was required. In 2000, Winglee proposed a Mini-Magnetospheric Plasma Propulsion (M2P2) design