Tiny rockets may advance minisatellites

Each of the 1,000 or more kilograms of material in an average communications satellite can cost $10,000 in launch costs alone.

NEW THRUST. Test firing of the new compact plasma accelerator. The stream of ions emerging from the minirocket can be used to steer and maneuver tiny spacecraft. NASA Glenn Research Center

To reduce costs, engineers have been developing what they call microspacecraft that perform many functions of their larger counterparts while packing only 10 percent or less of the mass.

Although development of microscale electronic and mechanical components has proceeded rapidly, designs of miniature propulsion devices have proven so far to be too inefficient to be practical. Tiny thrusters are needed to propel and steer spacecraft and to synchronize craft in formation.

John Foster of NASA’s Glenn Research Center in Cleveland has developed a new type of tiny rocket that is far more efficient than earlier designs. Foster’s device generates thrust by producing plasma–a soup of ions and electrons–in millimeter-wide cavities and using an electric field to accelerate the ions out a nozzle. The design is detailed in the May Review of Scientific Instruments.

The prototype thruster is extremely fuel efficient, turning 88 percent of its xenon-gas fuel into thrust-generating ions, says Foster. This level of fuel efficiency is considerably higher than that of other, comparable plasma-driven minithrusters, he adds.

The device is certainly “novel and compact,” says Siegfried Janson who works on micropropulsion devices at the Aerospace Corporation in Los Angeles. However, he notes, the prototype may be less efficient than it appears to be. Generating plasma and accelerating ions requires drawing electricity from a microspacecraft’s limited power source, notes Janson. In accelerating the plasma, the rocket currently eats a lot of power for the amount of thrust it produces, he says. However, he adds, “more experimentation and design modifications should improve the performance.”

John Pickrell is a freelance writer based in Sydney and the author of Flames of Extinction: The Race to Save Australia’s Threatened Wildlife.

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