Rotor Dip Windings
The velocity transformer track couples windings inserted into a magnet sled on the vehicle with windings inserted about a centimeter into the rotor. The windings are stationary; the rotor moves at 14 km/s [1].
Note [1] I considered a 12.5 km/s rotor in 2018, to reduce errant particle energies and the chance of a hypervelocity particle cascade compared to 14 km/s. Dip windings reduce the chances more.