The effect of catalyst support on the performance of monopropellant thrusters was investigated. In the present study, two support materials (monolith honeycombs and alumina pellets) were tested and their relative performances were compared. A reference catalyst (Na(0.2)MnO(2)) was coated on both catalyst supports, and 90 wt% hydrogen peroxide was used as the monopropellant. Two test thrusters of different sizes were fabricated, and the performance of each thruster when using monolith honeycomb and alumina pellets as the catalyst bed was evaluated by measuring the product-gas temperature at the rear end of the catalyst bed and the pressure of the gas at the front and rear ends of the catalyst bed; during these measurements, the feed pressure of the propellant was fixed. Under the given test conditions, the performance of the thrusters was better when using alumina pellets as the catalyst support than when using monolith honeycomb. Since the monolith support was less reactive than the pellets, pressure buildup in the former case was relatively small; consequently, the chamber pressure and temperature were lower when using the monolith support than when using the pellet support. The pressure drop across the catalyst bed was moderate in both cases (0.02-0.1 bar in the case of a monolith and 0.3-0.7 bar in the case of a pellet catalyst).