Help:Automatic Extending and Retracting Tubes

To explain the meaning of this further I will provide an example. Picture one of those toy light sabers that elongate/extend when you whip them/pull them out. Or an even easier example would be a tv antenna. What kind of mechanism would I need to create that would be able to automatically/electronically extend and retract aluminum type cylinders starting at a diameter of about 12in a height of 6in and a thickness of about 2cm. In the end I would like it to be a height of about 4.5ft. PLEASE ANY IDEAS?