And, more amazingly, the technology behind the craft is as easy to understand as the zap you get when you walk across a carpeted floor and touch a doorknob. The risky idea in this case is a means to propel a spacecraft over long distances and at great speeds without using heavy solid or liquid fuels. The heavier a spacecraft, the more expensive it is to lift it into space, and conventional rocket fuels in the quantities needed for long missions are undeniably heavy. The idea of ion propulsion has been kicked around by science fiction writers for years, but making the idea a reality had to wait until technology caught up. The first working ion drive was tested by NASA in 1970 and fired its engine for approximately 161 days.
New ideas are slow to catch on, however, and researchers kept plugging away at the ion drive engine.
The launch of Deep Space 1 in October 1998 was the result. The heart of the idea of ion propulsion is electric charge. We all did the experiments in elementary school, the one where we rubbed a comb to produce a charge and then picked up strands of hair or tiny bits of paper. Whether we knew it or not, we were practicing induction, the soul of ion propulsion. They're normally neutral.