Changing the length of thruster

I am trying to design a thruster like Battle Star Galatica has on there game. I have the model of a cone shape behind my ship but what would be the best way to make the length of the flame change. Normally I use a partical effect for mine but I want to try something different and see if I can pull better performance.

The same way you would modify the Translate or Rotate, modify the Scale.
Scale the length dimension without scaling the height and width of your flame, and it will stretch out.
You could combine this with an effect that changed the color/brightness of the material on the flame, for some pretty decent effects.
Or have two or three layers of them stacked inside each other, with partially transparent materials so you can see into the cone a bit.
Could be pretty cool.