micro-thruster array measuring one-quarter the size of a penny,
designed by a TRW-led team for use on micro-, nano- and
pico-satellites, has successfully demonstrated its functionality in a
live fire test aboard a Scorpius sub-orbital sounding rocket.

Individual micro-electromechanical system (MEMS) thrusters, each a
poppy seed-sized cell fueled with lead styphnate propellant, fired
more than 20 times at 1-second intervals during the test staged at the
White Sands Missile Range. Each thruster delivered 10(-4) Newton
seconds of impulse.

“The test proves the technology behind this micro-thruster is well
along in its development,” said David H. Lewis Jr., TRW’s MEMS Digital
Micro-Propulsion project manager. “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.”

The MEMS design, based on silicon chip fabrication technology,
offers several advantages over conventional thrusters: It has no
moving parts, utilizes a variety of propellants, is scalable,
eliminates the need for tanks, fuel lines and valves, and fully
integrates the structure of the satellite with the propulsion to power
it. The micro-thruster is being developed by TRW and teammates Caltech
and the Aerospace Corp. under a contract from the Defense Advanced
Research Projects Agency.

The MEMS micro-thruster arrays are fabricated as a three-layer
silicon and glass sandwich, with the middle layer consisting 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. Delivering
propulsion in discrete increments by igniting thrusters in controlled
sequences has lent the technology the name “digital propulsion.”

TRW Space & Electronics builds communications, scientific and
defense spacecraft for military, civil and commercial customers;
produces, integrates and tests payloads; develops advanced space
instruments; and integrates experiments into spacecraft. It is an
operating unit of TRW Inc., which provides advanced technology
products and services for global automotive, aerospace,
telecommunications and information systems markets. TRW’s Web site is
at http://www.trw.com.