investigation of application of magnetohydrodynamic (MHD) acceleration process for advanced propulsion system has significantly increased. The diagonal MHD accelerator is possible for this acceleration technique because of its minimum weight, size and complexity. In this paper, the fundamental performance of a diagonal type MHD accelerator under chemical and thermal equilibrium conditions is described. A one dimensional numerical simulation is performed to characterize the acceleration along the specified channel designed and developed at the NASA Marshall Space Flight Center. In order to solve the set of differential equations with MHD approximations, the MacCormack scheme is employed. In the present calculation, a working gas of air-plasma composed of diatomic molecules of nitrogen and oxygen seeded with potassium is considered in order to actualize application of the MHD accelerator propulsion system. Numerical results show the gas-dynamic characteristics (flow velocity, gas pressure and gas temperature), electrical properties (electrical conductivity, Hall parameter and Faraday current density) and electrical efficiency of the MHD accelerator. (c) 2005 Elsevier Ltd. All rights reserved.