I just saw a line that said Co2 powered planes. How is that?

CO2 motors are quite old and have been around for a long time. The CO2 cyclinder is connected to the place glo head would normally go. When the piston reachs TDC, a pin taps a ball check valve, and CO2 enters the cyclinder and pushes it down. The prop creates a flywheel that swings the piston around and back to TDC where the cycle starts over again. This continues until the CO2 cylinder is empty.

These motors can be very small or rather large, depending on the application. There are even multi-cylinder motors, in-line, V-8s, radials and rotary engines. Here's a ******* link to Sam's Models in the UK. Click on 'Gasparin CO2 motors' for a page showing some of the available CO2 motors: http://*******.com/4ywr

Thats pretty neat. Do you use small CO2 cartridges like those used in paintball guns? What kind of "gas mileage" do you get from CO2?

The tanks in the plane are lighter and smaller, but you refill them the same way you refill a lighter. They can run for a long time, and you can even throttle them. How long they run depends on how much fuel you can lift or want to carry. They are very simple of incredibly intricate. There are v-8s, radials, rotaries, in-line, opposed motors. See the Gasparin site for more info: http://gasparin.cz/?show=main&lng=en and Sam's Models' web site 'Gasparin CO2' page for pictures of some of the motors they make.