A simple model of low-thrust catalytic monopropellant hydrazine thrusters is presented for attitude control simulation purposes. It is derived from test results and represents thrust histories much better than a first-order lag over a wide range of pulse widths, for the thrusters used on the Hermes spacecraft. The structure of the model should be applicable to other cases as well. © American Institute of Aeronautics and Astronautics, Inc., 1979, All rights reserved.