CERAM Web Site (Ceram is now called Lucideon)

[September 2003]

Alumina Ceramic Aids Evolution of Ion Propulsion Systems for Deep Space Exploration

Morgan Advanced Ceramic's materials experts at Erlangen, Germany are working closely with EADS Space Transportation - Europe's No 1 satellite company - to improve the efficiency of ion propulsion systems. Morgan's role is to optimise the design and the material properties for the ceramic thruster chambers in which the propellant is ionised. This will include the development of suitable production methods to achieve the fine tolerances required.

Ion propulsion technology does not burn fuel as chemical rockets do. Instead, it uses electricity to charge heavy gas atoms, which accelerate from the spacecraft at high velocity and push it forwards. The gas of choice is Xenon, the same substance that is commonly used in photo flashlights and in some modern car headlights.

There are three main categories of ion engines, classified according to their basic physical method of operation: electrothermal; electrostatic; or electromagnetic. The design on which Morgan is engaged is a gridded ion engine, which falls into the second category.

The ceramic chamber is central to the ionisation process. It is used to contain the propellant while it is subjected to an electrical current that charges the gas atoms to create ions. There are a number of ways in which the electrical charge can be applied. In a gridded ion engine - or Radio-frequency Ion Thruster (RIT) - a metallic coil around the outside of the vessel is used to induce a radio frequency (RF) field inside the chamber. This field is sufficiently powerful to accelerate electrons which then collide with the Xenon gas, creating positively charged ions. These ions are then accelerated through a grid system carrying a negative charge and neutralised directly after leaving the vessel at high speed. It is this stream of Xenon plasma, with its characteristic blue colour, that creates the thrust to push the spacecraft forwards.

Ion propulsion is said to offer enormous potential benefits for deep space travel. For example, an ion engine can run on a few hundred grammes of propellant per day, which makes it favourably lightweight. Less weight means less cost to launch. This is an extremely important factor for any space programme's budget: it currently costs around €10,000 per kilo of weight to launch a craft. It could also mean we arrive our destination more quickly, or go farther than before with the same payload: ion propulsion can push a spacecraft about 10 times as fast as chemical propulsion per kilo of fuel.



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