Spacecraft May Surf Magnetic Fields

Maggie McKee writes "Future spacecraft may surf the magnetic fields of Earth and other planets, taking previously unfeasible routes around the solar system, according to a proposal funded by NASA's Institute for Advanced Concepts. The electrically charged craft would not need rockets or propellant of any kind. To get charged up, the spacecraft could either fire a beam of charged particles into space or simply allow a radioactive isotope to emit charged particles. Because long, thin filaments have large surface areas for holding charge, the spacecraft might look like Einstein's head — with wiry filaments sticking out at all angles — or a weird space 'stocking.'"

not spacecraft.

[YenTheFirst]

with the power involved here, it wouldn't be propelling any manned missions.

After reaching orbit, his present design would be off to a slow start, taking about a year to escape the Earth's gravity.

this seems like it would only be useful for satellites and probes and such.

Remember Force=Velocity x B (magnetic field)

[viking80]

Anyone who remember physics 101 will recall the following:
A magnetic field will create a force normal to the velocity of a charged object. So
1. The force on any charge will be normal to the velocity, so it will move around in circles. This includes the charged spacecraft. (The field here is not homogeneous, but still, no gain in energy)
2. A current loop(i.e. a moving charge) can change the energy or be accelerated in a magnetic field.

(2) is and has been used since the first satellites were orbited to do orbital corrections, and are well understood and used. It can allow the life of the satellite to be expanded by many years.

Why would this craft not just use a long current carrying wire instead.