Ion propulsion is a phrase I first heard while watching the original Star Trek series in reruns. The USS Enterprise of the series had encountered some old fashioned satellite and Scotty marveled at the ancient and simple propulsion system used by the craft.

Of course, Star Trek, taking place in the 23rd century despite the antiquated computers of the era had mastered things like warp drives and their impulse power used a different method to propel the ship, but ion propulsion was at least not entirely technobabble made up for the show.

In fact, ion propulsion is being used today to propel satellites on their deep space voyages.

The idea has been around since the dawn of the 20th century. Early American rocketry pioneer, Robert Goddard talked about the idea of using an electric propulsion systems that allowed ships to be moved through space by accelerating electrically charged particles. The idea that would later develop into ion propulsion, was further expanded upon in a book published in 1939 by Dr. Hermann Oberth.

Oberth worked with another rocket scientist who would become famous after World War II and would work in the United States after the war. The name of his pupil, Werner von Braun is well known today, although von Braun began his career working on chemical propulsion systems. The first electrical propulsion contract would be awarded by the army in 1959.

Studies of ion propulsion continued from that time onward until NASA’s first space probe that uses ion propulsion, Deep Space One was launched in 2007. The Electrical propulsion systems used in the space craft require much less volume and weight than the chemical propulsion systems used by shuttles, rockets and many types of missiles in use today.

The first tests in 1959 developed a working ion propulsion engine, but the the scientists and engineers working on the project had trouble making the engines last. Once this hurdle had been overcome it was a cheaper, lighter and easier way to maneuver space vehicles rather than the conventional chemicals used in normal rocketry.

Once the problem of the short engine life had been overcome, the problem of how to navigate an ion propulsion spacecraft was the next hurdle. While it had taken at almost 40 years for a long living ion propulsion engine to become a reality, the problem of how to navigate the craft proved somewhat easier to solve, although Deep Space 1 will be the first craft that will show the practical results of NASA’s researchers.

The principle which ion propulsion engines operate on is similar to that of a clothes drier. A fluid is run through the engine and the particles are charged. Like particles repel each other and opposites attract. (Anyone who has encountered static cling nows the second fact as socks in a dryer are the most common metaphor used to explain the idea.) When the engine is running, positively charged particles shoot at the back providing thrust.

While the amount of thrust produced by ion propulsion systems is less than that used by conventional rockets, the engines are far more efficient and as they can be in operation longer, they can build up greater speeds. We can only hope that the actor who played Scotty on Star Trek is smiling now that ion propulsion engines on space craft are a reality.