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.
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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.
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Drawback of the magMagnetic sail design was that a large superconducting loop weighing on the order of 100 tonnes was required.
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Radio emissions of cyclotron radiation due to interaction of charged particles in the interstellar medium as they spiral around the magnetic field lines of a magnetic sail would have a frequency of approximately kHz, where is the spacecraft velocity and the speed of light.
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Thrust that a magnetic sail delivers within a magnetosphere decreases with the fourth power of its distance from the planet's internal magnetic field.
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When close to a planet with a strong magnetosphere such as Earth or a gas giant, the magnetic sail could generate more thrust by interacting with the magnetosphere instead of the solar wind.
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An electric Magnetic sail uses an electric field that under certain conditions interact with charged particles to create thrust.
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Magnetic sail designs operating in a plasma wind share a theoretical foundation based upon a magnetohydrodynamic model, sometimes called a fluid model, from plasma physics for an artificially generated magnetosphere.
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Under certain conditions, the plasma wind and the magnetic sail are separated by a magnetopause that blocks the charged particles, which creates a drag force that transfers momentum to the magnetic sail, which then applies thrust to the attached spacecraft.
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All magnetic sail designs assume a standoff between plasma wind pressure and magnetic pressure of the same form with parameters specific to a plasma environment, differing only in a constant coefficient as follows:.
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In 2004, Fujita published numerical analysis using a hybrid PIC simulation using a magnetic dipole model that treated electrons as a fluid and a kinematic model for ions to estimate the coefficient of drag for a magnetic sail operating in the radial orientation resulting in the following approximate formula:.
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Important measures that determine the relative performance of different magnetic sail systems include: mass of the field source generator and its power and energy requirements; thrust achieved; thrust to weight ratio, any limitations and constraints, and propellant system exhausted, if any.
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Mass of the field source in the MagMagnetic sail design was relatively large and subsequent designs strove to reduce this measure.
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Andrews and Zubrin derived equation for the drag force of the Magnetic sail that determined the characteristic length for a tilt angle but according to Section 6.
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Comparison purposes, the effective Magnetic sail area determined for the magMagnetic sail by Zubrin from equation MS.
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Figure shows the normalized effective Magnetic sail area normalized by the coil area for the MKM case from Gros of equation MKM.
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In 2003, Khazanov published MagnetoHydroDynamic and kinetic studies that confirmed some aspects of M2P2 but raised issues that the sail size was too small, and that very small thrust would result and concluded that the hypothesized magnetic field falloff rate was closer to.
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Detailed analysis by Toivanen and others in 2004 compared a theoretical model of MagMagnetic sail, dubbed Plasma-free Magnetospheric Propulsion versus M2P2 and concluded that the thrust force predicted by Winglee and others was over ten orders of magnitude optimistic since the majority of the solar wind momentum was delivered to the magnetotail and current leakages through the magnetopause and not to the spacecraft.
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Many MPS papers have been published on the magnetic sail contributing to the understanding of general physical principles of an artificial magnetosphere, its magnetohydrodynamic model, and the design approach for computing the magnetopause distance for a given magnetic field source are documented in the linked sections of this article.
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Plasma magnet sail design introduced a different approach to generate a static magnetic dipole as illustrated in the figure.
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The classic MagMagnetic sail design generates the most thrust force and has considerable mass but still has relatively good time performance.
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