chips to propel small satellites
Kimberly Patch and Eric Smalley,
Technology Research News
The miniaturization trend that has produced
computers, televisions and telephones that fit in shirt pockets is coming
to satellites. A smaller satellite is, after all, easier and cheaper to
get into orbit.
Building little satellites requires more than just compact electronics,
however. Satellites also need propulsion systems that periodically provide
the boosts and course corrections needed to keep them into orbit. One
challenge to making smaller satellites is making proportional rocket thrusters.
Researchers at the National Center for Scientific Research (CNRS) in France
have done so by mating rockets with integrated circuits. The researchers
have built arrays of tiny rocket thrusters on a chip. The chips contain
reservoirs filled with solid rocket fuel, which is ignited electronically
through circuitry in the chip.
The basic idea of the microthruster research is to use the large amount
of chemical energy contained in explosive materials to propel small satellites,
said Carole Rossi, a researcher at the National Center for Scientific
Research. "The best way is to transform the chemical energy into mechanical
work because this is a direct conversion [of the energy] and the yield
is very high," she said.
The researchers' microthrusters are made from three layers of silicon:
the bottom layer contains reservoirs to hold the rocket fuel, the middle
layer contains electronic igniters to start the fuel burning, and the
top layer forms nozzles that channel the gas that is produced when the
The fuel combustion produces a large amount of hot gas that expands rapidly,
and when the gas is channeled through a nozzle it creates thrust, said
The individual thrusters measure 1 cubic millimeter. The researchers made
a prototype array that contained 36 microthrusters. Their plans call for
28- by 28- millimeter arrays that contain 256 thrusters. Each thruster
can be used only once because all of the fuel is burned when a thruster
is ignited. "The array is made to compensate [for] the fact that each
thruster is one shot," said Rossi.
The researchers' microthrusters are designed for nanosatellites, which
weigh from one to ten kilograms, or 2.2 to 22 pounds. "Micro propulsion...
is required to compensate [for] the forces acting on the satellite, for
orbital maneuvering and for satellite attitude control," said Rossi.
Small satellites weighing about ten kilograms could require between one
tenth and 10 millinewtons of thrust for typical orbit maintenance and
attitude control, said Rossi. A millinewton is the force required to give
an object with a mass of 1 gram an acceleration of one meter per second
every second. This level of thrust is hundreds of times smaller than the
thrust provided by the smallest model rocket engines.
The researchers' next step is demonstrating a solid-propellant device
that produces electricity for powering MEMS devices, said Rossi. The solid
propellant, silicon-based microthrusters could be used in practical applications
within three years, said Rossi.
Rossi's research colleagues were Thierry Do Conto, Daniel Estève and Benoit
Larangot of the National Center for Scientific Research. They published
their research in the December, 2001 issue of the journal Smart Materials
and Structures. The research was funded by the European Commission and
the National Center for Space Study (CNES) in France.
Timeline: <3 years
TRN Categories: MEMS
Story Type: News
Related Elements: Technical paper, "Design, fabrication
and modeling of MEMS-based microthrusters for space application," Smart
Materials and Structures, December, 2001
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