Microthrusters, measuring one-quarter the size of a penny, are gearing up for use in micro, nano, and picosatellites. Individual micromechanical system (MEMS) thrusters from TRW Space and Electronics, Redondo Beach, Calif., are based on silicon-chip fabrication technology. The microthrusters have no moving parts, use a variety of propellants, are scaleable, and don't require tanks, fuel lines, and valves.

The microthruster arrays are fabricated as three-layer silicon and glass sandwiches. The middle layer consists of multiple small propellant cells sealed with a rupturable diaphragm on one side and an ignitor on the other. Each cell is a separate thruster, and when ignited, delivers one impulse bit.

The microthrusters are being developed by TRW, Caltech, and the Aerospace Corp. under contract from Darpa.