Plasma Magnet Sails to get manned missions to Mars in 1 week

The plasma magnet sail engine is little more than 2 pairs of charged rotating coils and is therefore extremely simple and inexpensive. A fully powered plasma magnet sail using a small nuclear power source could accelerate at 0.5G and reach 400-700 km/sec (0.2% of lightspeed) in half a day.

(H/T Centauri Dreams)

* Carrying a 10 Kilowatt power source enables very cheap missions to the Gravitational lens with trips taking 5 years. Multiple gravitational lens missions are needed since you can only observe what is on the exact opposite side of the sun from the gravitational lens mission
* 10kW power supply could propel a 2500 kg craft with an acceleration of 0.5g, reaching 400-700 km/s in just half a day. Greason suggested that with this acceleration, the FOCAL mission for gravitational lens telescopes requiring many craft should be achievable.
* A stream of charged particles could be generated from Phobos or Demos to slow the Plasma magnet sail to Mars. If you were slowing a 100-ton manned spacecraft, then you would need to produce 100,000 tons of particles. There would need to be multi-megawatt plant on the moons of Mars. It is possible to scale up for manned missions and to stop the craft.
* Neptune has a large enough magnetosphere where a plasma magnet sail could stop by decelerating at 5Gs. It would be a 4-month mission to Neptune
* a 10 KW system could slow an interstellar spacecraft from 20% of lightspeed over 2 years. Interstellar missions could then explore the target solar system.

Plasma sail propulsion based on the plasma magnet is a unique system that taps the ambient energy of the solar wind with minimal energy and mass requirements. The coupling to the solar wind is made through the generation of a large-scale over 30 km) dipolar magnetic field. Unlike the original magnetic sail concept, the coil currents are conducted in a plasma rather than a superconducting coil. In this way the mass of the sail is reduced by orders of magnitude for the same thrust power. The plasma magnet consists of a pair of polyphase coils that produce a rotating magnetic field (RMF) that drives the necessary currents in the plasma to inflate and maintain the large-scale magnetic structure. The plasma magnet is deployed by the Lorentz self-force on the plasma currents, expanding outward in a disk-like shape until the expansion is halted by the solar wind pressure. It is virtually propellantless as the intercepted solar wind replenishes the small amount of plasma required to carry the magnet currents. Unlike a solid magnet or sail, the plasma magnet expands with falling solar wind pressure to provide constant thrust.

The plasma magnet has the advantages of the MagSail by directly maintaining a large scale magnetic structure, but by having the dipole currents carried not in a coil, but in a plasma, the large superconducting mass and shielding problems are avoided.

The ultimate spacecraft speed powered by the plasma magnet is that of the solar wind (350 to 800 km/s) which is orders of magnitude higher than the Isp limitations of existing plasma thrusters. As opposed to the solar sails and the MagSail, the dynamic nature of the plasma magnet assures a constant thrust regardless of distance from the sun. The plasma magnet acts similar to a balloon (or magnetosphere) in that it will expand as the solar wind dynamic pressure decreases with distance from the sun. As such, it will provide a constant force surface and thereby provide almost constant acceleration to the spacecraft as it moves out into the solar
system. The solar wind experiences essentially no deceleration until the termination shock at approximately 80 +/- 10 AU. The plasma magnet could thus be used for missions all the way to the Kuiper belt.


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