Hypersonic Electromagnetic Launch by Constant-Flux Synchronous Motor

A novel concept for electromagnetic launching is presented. The propulsion system consists of a pulsed synchronous motor that generates a constant magnetic flux zone that moves with the projectile in a traveling wave. The cylindrical projectile is equipped with high-temperature superconducting coils in persistent mode, charged prior to launch. The current pulses supplied to the track coils are adjusted in time (leading and trailing edge, pulse duration, pulse frequency) so that no magnetic flux change is seen by the superconducting coils as the projectile moves during launch. Constant flux translates to no voltage or additional currents being induced, which prevents the projectile coils from quenching or overheating. The projectile coils, built in a cable-in-conduit assembly as in pulsed fusion magnets, can carry persistent currents of up to 50 kA under severe operating conditions in pulsed magnetic fields with no need for induction or external power supply. The proposed constant flux synchronous motor (CFSM) is self-centering and avoids mechanical contact between the track and the projectile - the electromagnetic forces and torques are sufficient to compensate for the aerodynamic disturbance forces and moments during launch. A low pressure helium atmosphere inside of the launch tube is also proposed, which nearly eliminates both aerodynamic and heat transfer effects (forces, torques and heating) due to high speed gas flow around the projectile, with large safety margins. The proposed technology removes several of the technical problems that made hypersonic electromagnetic launch unfeasible, in particular the inductive heating of the projectile when a contact-free armature is desired