>by the way, is it possible to create thrust
>only by electricity? If so, how?

Not quite.

One of my colleagues has an instrument on a satellite called Smart-1 which
is currently on its way to the moon. The satellite is propelled by an ion
motor, which is about as near as you can get to propelling by electricity.

How it works is as follows - an atom that can be easily ionised by
electricity is injected between a set of electrodes which are arranged in a
manner similar to a CRT tube. The cathode is a ring, and the electric field
between the anode and cathode cause the gas to ionise. The nucleus is
accelerated up to a suitable speed before disappearing out through the hole
in the cathode, and this movement of mass is what propels the spacecraft.
The spacecraft can only be propelled while there is gas to feed the motor.

This particular spacecraft is being done as a demonstrator for Smart-2 which
is yet to be built for a planned mission to Mars.

Bear in mind that the propulsion force is quite small, this very small
spacecraft is going in ever larger orbits around the earth until eventually
it gets close enough to the moon to be captured by its gravity. This is
taking a number of months. Now compare that to the 3 days or so that the
Apollo astronauts spent going each way between earth and moon.

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