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
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
"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."