Rocket chips to propel small satellites

By 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 fuel burns.

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 Rossi.

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
Funding:   Government
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


January 30, 2002

Page One

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Rocket chips to propel small satellites

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Quantum network withstands noise

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