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    Tiny Propulsion System Aimed At Micro-Sats

    By AviationNow.com Staff

    16-May-2001 3:05 PM U.S. EDT

    A tiny thruster designed for use on micro-satellites of the future has been successfully tested aboard a sub-orbital sounding rocket at the White Sands Missile Range in New Mexico.

    TRW of Redondo Beach, Calif., which built the thruster, said each of the micro-electromechanical system (MEMS) thruster "cells" were fired more than 20 times at 1-second intervals during a March 9 flight of a Scorpius sounding rocket from White Sands.

    Each thruster cell -- smaller than a poppy seed -- delivered .0001 Newton seconds of impulse.

    Together, the cells can fit on a thruster platform that is less than one-fourth the size of a penny (pictured).

    "The test proves the technology behind this micro-thruster is well along in its development," David Lewis, Jr., TRW's MEMS Digital Micro-Propulsion project manager, said in a statement.

    "We're very pleased with its performance at White Sands. We believe micro-thrusters have the potential to provide on-orbit propulsion for station keeping, orbital correction and attitude control for future, very small satellites weighing from less than a pound to as much as 50 pounds," Lewis said.

    The micro-thruster, which uses lead styphnate propellant, is being developed by TRW, the California Institute of Technology and The Aerospace Corporation for the U.S Defense Advanced Research Projects Agency (DARPA).

    The MEMS design, which is based on silicon chip technology, offers several advantages over conventional thrusters, according to TRW.

    It has no moving parts and uses a variety of propellants. It also is scalable and eliminates the need for tanks, fuel lines or valves. It also fully integrates the structure of the satellite with the propulsion to power it.

    The micro-thruster platform is made as a three-layer silicon and glass "sandwich," with the middle layer consisting of multiple small propellant "cells."

    These cells are sealed with a silicon nitride rupture diaphragm on one side and a polysilicon resistor that initiates combustion of the fuel on the other.

    Each cell is a separate thruster that, when ignited, delivers one impulse bit.

    Because the propulsion is delivered in discrete increments by the ignition of the thrusters in controlled sequences, the technology has come to be known as "digital propulsion."

    See Also:

    Defense Advanced Research Projects Agency