Sail Propulsion Using the Solar Wind

Abstract

A magnetic sail (MagSail) is a unique interplanetary propulsion system. To propel a spacecraft in the direction leaving the Sun, the MagSail produces a large-scale magnetic field to block the hypersonic solar wind plasma flow. Since thrust of the MagSail is proportional to the blocking area, a very large-scale interaction between the artificial magnetic field and the solar wind is required as in the case of the geomagnetic field to capture the energy of very low density solar wind flow. For example, the original MagSail by Zubrin requires an unrealistic spacecraft design with a large hoop coil of 100 km in radius to form 1000-km-radius blocking area (which corresponds to 10-N-class thrust). Due to this large structural requirement the idea of the MagSail did not draw attention so far. In 2001, however, the idea of the MagSail received a renewed interest when Winglee proposed Mini-Magnetospheric Plasma Propulsion (M2P2) concept, which inflates a weak original magnetic field made by a small coil of about 0.1 m in diameter with an assistance of a high-density plasma jet. Although the feasibility of this compact M2P2 design is denied by several researchers, we revised the M2P2 design by changing the coil to moderate sizes of 10 to 100 m in diameter to efficiently enlarge the blocking area. Such revised systems, which we call Magnetoplasma Sail (MPS), still has some both technical and physical issues to be clarified; most of them are reviewed in this article with the comprehensive list of the solar wind sail propulsion systems