Solar electric ion propulsion, first developed by NASA visionary Harold Kaufman in the 1960s, has now proven itself capable of propelling a probe through the solar system, promising an era of faster and more economical space exploration. Though Deep Space 1 is primarily a technology test bed for future missions, it will gather data as it goes. Ion propulsion will be a big help. The ion engine is compact, just under a foot in diameter. It gently pushes the spacecraft forward by firing ions, or electrically charged atoms, out into space.
Cathodes spew electrons into a chamber filled with xenon gas.
The electrons smash into the xenon atoms, knocking away an electron and turning the atoms into positively charged ions. A pair of charged metal grids pulls the xenon ions out the back of the engine at more than 60,000 miles per hour, which drives the spacecraft forward. What the ion engine lacks in immediate gratification, however, it more than makes up for in persistence. Gradually, the spacecraft reaches high speeds, with remarkably little wasted energy. It's part of the normal arsenal of things we have with which to execute deep- space missions.