Ion Propulsion - Transport System t' t' Planets T' efficiency o' a rocket engine can be described by its specific impulse, arrr, which be t' change o' momentum gained from a 1 kilogram weight o' propellent. Well, blow me down! T' Space Shuttle main engines have a specific impulse o' 453 seconds which is typical o' a liquid fuelled rocket engine. An Ion thruster has a specific impulse o' more than 3000 seconds and so requires less than a sixth o' t' fuel o' a liquid fuelled engine. Ahoy! Gridded electrostatic ion thrusters commonly utilize Xenon gas. Blimey! T' gas is first ionized by bombardin' it with electrons. Blimey! T' positively charged ions then diffuse through t' positive grid and enter a potential difference betwixt t' positive and negative grids. T' potential difference accelerates t' ions t' high velocities, ya bilge rat, which then leave t' engine t' create thrust. An electron emitter, on t' exterior o' t' engine, neutralizes t' ion beam t' prevent charge build-up. Well, blow me down! T' typical thrust o' an ion engine is equivalent t' a weight o' 10 grams - about t' weight o' a sheet o' paper. This means ion thrusters need t' provide continuous thrust for a very long time in order t' achieve a reasonable change in velocity. Arrr! Electrostatic ion engines have been tested for 3.5 years o' continuous thrust at full power. Aye aye! Collision o' ions with t' charged grids causes their erosion and will lead t' eventual failure. Well, blow me down! Ion engines consume more than 2 kilowatts o' electrical power, which may be generated by solar arrays or nuclear ...