ANU plasma thruster gets research boost

Hopefully to Europe, and beyond

Plasma drives are much-beloved of both science fiction and real -world space research, for good reason: they have a good thrust-to-fuel ratio. Now, more than ten years' work by Australian National University physicists will get a research boost on its way to space via a European satellite.

The $3.1 million grant from the federal government will be used by researchers at the ANU's Plasma Research Laboratory to help build its Helicon Double Layer Thruster (HDLT). If its work is successful, the HDLT driver could be in space as early as 2013 via a collaboration between the ANU, Surrey University's space centre, and aerospace firm EADS-Astrium.

In the hierarchy of propulsion, conventional chemical rockets sit at the bottom of the heap, because they need huge amounts of fuel to produce thrust. Ion and plasma-based drives get more bang for the buck, because they deliver high exhaust velocities from smaller amounts of fuel. That leaves more space - or rather mass - available for payloads.

The ANU HDLT, invented by professor Christine Charles, isn't ready to lift payloads from Earth yet. As project leader professor Rod Boswell explains, the engine is less powerful than a chemical rocket, but should have a longer life-span.

Because of the high temperatures generated in plasma drives, the trick is confining the hot gas without it destroying the chamber. The HDLT uses a magnetic field, uniform in the "source tube" (where a gas like Krypton or Xenon is heated by a radio antenna) and expanding away from the source. The plasma creates its own electrical layer near the exit of the source tube, which accelerates the source plasma to high exhaust velocities.

The system requires external power only to maintain the plasma and the magnetic field: the electrical gradient that directs the plasma is the result of plasma density and the geometry of the magnetic field, which means it doesn’t need to power accelerating grids. In space, the researchers hope that less than one gram of propellant would power a five-hour burn.

In the current project, the ANU is working to deliver a device suitable for keeping a satellite on-station. This would demonstrate whether, as expected, the HDLT's long theoretical life would consequently help extend satellites' life. ®

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