Electromagnetic properties of a modular MHD thruster

The magnetic field of an annular MHD thruster made of independent supercond ucting modules has been studied with analytical and numerical methods. This configuration allows to obtain large magnetized volumes and high induction levels with rapidly decreasing stray fields. When some inductors are out o f order, the thruster remains still operational, but the stray fields incre ase in the vicinity of the failure. For given structural materials and supe rconductors, it is possible to determine the size of the conductor in order to reduce the electromagnetic forces and the peak field supported by the c onductors. For an active field of 10 T in a 6 m ray annular active channel of a thruster with 24 modules, the peak field is exactly 15.6 T in the Nb3S n conductors and the structure has to sustain 10(8) N/m forces. The necessi ty to place some magnetic or superconducting shield is discussed, particula rly when the thruster is in a degraded regime.