Q: IS THIS A RAIL GUN?

STMR uses a coil-gun approach, employing electromagnets in both the launcher and projectile to impart projectile acceleration.

STMR differs from other electromagnetic launchers, which typically use a railgun configuration: Railguns employ a large magnetic field oriented at right angles to the direction of projectile motion. In railguns, a very high current passes through a 'sled' which carries the projectile. The interaction of this current with a static magnetic field in the launcher results in a force that causes the sled and projectile to move. A key issue for railguns is that all of this current must pass through a sliding contact, resulting in both frictional losses and a contact resistance losses, both of which diminish the overall effectiveness of the device.

By contrast, STMR employs an axial magnetic field, colinear with the direction of motion. Fields produced by electromagnets in the projectile interact with switched fields produced by coils situated in the launch tube. With precise timing control and high-current drive circuitry, the projectile can be successively pulled-towards and then pushed-away-from each launcher coil, as it accelerates along the length of the launch tube passing through numerous launcher coils. There are no sliding electrical contacts because the projectile’s magnetic fields are energized via inductive ‘charging’ and may be re-energized multiple times as the projectile traverses the launcher. Frictional losses are minimized by magnetically levitating the projectile via an active servo control mechanism.

The STMR design has similarities with superconductor coil-guns that have been explored by various groups, which also employ axial magnetic fields together with a superconductive 'slug' magnet in the projectile/sled. A key difference is that STMR focusses on the active-drive control electronics used to dynamically adjust coil-drive timings to optimally control and switch the fields used to accelerate the projectile along the tube as well as to levitate the projectile within the launcher.