Capture Dynamics of Coaxial Magnetic Brakes

In a coaxial magnetic brake, the changing field produced by movement of a solenoidal magnet induces a current in the wall of a conductive tube. The interaction of the field and current leads to a repulsive force that slows the motion of the magnet. We have tested the performance of this type of brake by firing a projectile carrying a permanent magnet into an aluminum tube. The results were compared to a model based on published theoretical results. The model was then used to predict braking distance for speeds and masses of interest in hypervelocity research, and it was found that brakes incorporating presently available superconducting materials are capable of stopping projectiles in practical distances. In addition, a new means of centering the projectile in the catch tube is presented, accompanied by a calculation of the centering force on the projectile, and high-speed photographs showing the alignment of a projectile with the brake tube.