This paper presents a silicon-micromachined fluidic thruster device, capable of a large output force. The output force is controlled by a vortex generated inside the device chamber. The vortex-controlled microthrusters are fabricated on a 500 m thick silicon wafer. This is the first time such a device has been micromachined in silicon. The vortex chamber and inlet ports are deep reactive ion etched to a depth of 300 m from the topside, and the output nozzle is deep reactive ion etched from the backside to a depth of 200 m. The topside is sealed by anodically bonding with a glass wafer. For a vortex chamber radius of 500 m and control port width of 50 m, the effects of varying supply port and output nozzle sizes are experimentally evaluated. A microthruster with a 500 m supply port width and 120 m output nozzle radius is capable of a 66.4 mN net thrust force with a pressure of 600 kPa. This represents a very large force, considering the fact that the thruster volume is less than 1 .