What you're seeing below isn't the Coca-Cola Company's latest marketing gimmick but may very well be the next generation of spacecraft propulsion. This contraption, made from a glass bottle surrounded by an aluminum can demonstrates how easy a plasma propulsion system could be made.
The rocket engine works when nitrogen is pumped through a quartz tube (a glass coke bottle stands in here) and magnets surrounding a metal antenna (the coke can). Inside the tube the magnets and antenna emit radio frequency energies, charging the gas into plasma and the magnetic fields guide it out the back of the engine for thrust. This is called the VASIMR effect. The kicker is the engine is 10 times more efficient than normal rocket engines, because they generate 10 times as much propulsion per weight of fuel. In addition, the nitrogen used here is much cheaper and easier to handle than normal rocket fuel.
Already some space probes have used similar processes. NASA's Deep Space One used an earlier type of this ion drive. There's still a lot of development and refinement to be done before this type of drive can be outfitted for a manned space craft. Not to mention, it still needs a tremendous amount of safety investigation before a VASIMR engine can be strapped to the back of a space shuttle.