Plasma Propulsion

Standard rocket propulsion is gradually becoming a major limitation in our ability to travel within the solar system. For example the ~8 month trip to Mars, or 3 year trip to Pluto, is something that NASA and the general population is becoming less patient with and it greatly limits the amount of science we can do as the length of a mission means more money.
That's why plasma is currently being studied as a new form of propulsion. Technically called Variable Specific Magnetoplasma Rocket (VASIMR), it uses hydrogen heated to extremely hot temperatures by radio waves, which burns more efficiently than regular rocket fuel. A trip to Mars could last 3 months instead of 7 or 8, and the cost and efficiency would be greatly improved.
Plasma is electrically charged gas made up of atoms which have been stripped of their electrons. It is called the 4th state of matter, and it is only found in conditions of extremely high pressure and temperature (like a star). It can be created in the lab and plans for testing this method in space are already underway.
One major problem of working with plasma is that no known solid can contain it. It must be contained (except for where it leaves the rocket) by a strong magnetic field generated by superconductors - thus a completely new design for a rocket. Take a look at http://www.space.com/businesstechnology/technology/plasma_propulsion_000616.html