A plasma magnet is a proposed

spacecraft propulsion Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric e ...

device that uses a dipole magnetic field to capture energy from the

solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...

. The field acts as a sail, using the captured energy to propel the spacecraft analogously to how the wind propels a sailing vessel. It could accelerate a vessel moving away from the sun and decelerate it when approaching a distant star at the end of an interstellar journey. Thrust vectoring and steering could be achieved by manipulating the dipole tilt for any type of magnetic sail.

Solar wind

The solar wind is a stream of energetic

charged particle In physics, a charged particle is a particle with an electric charge. It may be an ion, such as a molecule or atom with a surplus or deficit of electrons relative to protons. It can also be an electron or a proton, or another elementary particle, ...

s released from the upper atmosphere of a star, such as the Sun, called the

corona Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...

. This

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

mostly consists of

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

s and

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...

s with

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...

between 0.5 and 10

keV Kev can refer to: Given name * Kev Adams, French comedian, actor, screenwriter and film producer born Kevin Smadja in 1991 * Kevin Kev Carmody (born 1946), Indigenous Australian singer-songwriter * Kev Coghlan (born 1988), Scottish Grand Prix motor ...

. The solar wind travels at velocities greater than 10⁵ m/s. Its dynamic pressure is roughly 2x10⁻⁹ N/m2 at 1 AU. A properly designed system allows the spacecraft to accelerate to near the speed of the solar wind. The thrust provided from the solar wind remains constant, regardless of the distance from the Sun, because the plasma magnet expands in size as the distance from the Sun increases.

Design

The basic principle is that a rotating magnetic field, driven by

alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...

in a crossed pair of coils, creates a circulating current, and that current then expands in radius until it creates a dipolar

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

much larger than the coils' radius. To achieve sufficient thrust for a spacecraft (0.1-1 N), the "sail" must be at least 4 km in radius. The magnetic field strength must be 50n T. To create such a field using an

electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the ...

requires large-scale engineering. A circular electromagnet would reach 300m in radius, carrying 10⁵ amp-turns. Such an electromagnet would likely be so massive that the captured thrust would barely move it. Use of superconducting electromagnets may make a "wind rider" technically feasible. A travel-relevant balance requires a vessel mass of a few 100 kg and power of at least a few kW. Phased antennas operating in the

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upp ...

range produce a rapidly rotating magnetic field. This field preferentially accelerates electrons within a

to produce a

direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even ...

that can generate a steady state magnetic field that is much larger than can be sustained by practical electromagnets.

Drag device

A drag device is one that is pushed by an external energy source. The classic drag device is a sailing vessel. By contrast, an

airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spe ...

or a

rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...

use a fuel source to supply their own energy.

References

External links

* {{Spacecraft propulsion Plasma physics Space plasmas Propulsion Magnetic propulsion devices Spacecraft propulsion

Solar wind

Design

Drag device

See also

References

External links