The invention relates to a plasma accelerator that produces and controls a plasma stream exhaust, in particular for space propulsion. The ions are produced inside the discharge chamber by working gas collisional ionization by electrons from a single electron source placed outside, also employed for ion beam neutralization. The ion motion is directed outwards through the exit side by the electric field between a cathode grid and the walls of the plasma chamber. The acceleration voltage imparts energy to the ion flux and an electrically biased control grid modulates the ion outflow from the discharge chamber and the electron inflow from the electron source. This allows electrical control of throttle and/or modulation of thrust delivered along the longitudinal direction of the thruster axis. Several plasma accelerators could be clustered together to provide controlled non-axial thrust using the individual control of throttle.