Xenon Ion Engine

Ion Propulsion Technology


NASA Ion Engine Ready To Make Sci-Fi Reality
By Joe Feese

Source: ABCNEWS.com

Solar Electric Propulsion Ready for Deep Space Ion Engine Making Sci-Fi Reality

For space science, we can take advantage of the lower cost and the advanced technology to get the same information [that NASA's getting now].

Jack Stocky, NASA

DS1 spacecraft marks the first time ion propulsion, rather than chemical propulsion, will be used. (NASA)

In an early episode of Star Trek called "Spock's Brain," evil aliens take First Officer Spock's brain and speed off in an ion-powered spacecraft. The Enterprise crew is devastated - how can they possibly catch an ion-propelled spaceship?

Fret no more, Captain Kirk and fellow shipmates: Space technology has nearly caught up to science fiction.

A futuristic form of spacecraft propulsion called ion engine propulsion is one step closer to becoming a reality.

The ionic thruster (NASA) Deep Space 1 (DS1), the first launch of NASA's New Millennium program, will use ion propulsion (also known as solar electric propulsion) to power the craft on a deep-space mission next summer. This will mark the first time in the history of space exploration that ion propulsion, rather than chemical propulsion, is being used as the primary means of propelling a spacecraft.

On Sept. 25, Jet Propulsion Laboratory in Pasadena, Calif., completed the most extensive test of an ion engine ever performed. Begun on June 17, 1996, the 8,000-hour endurance test of a prototype xenon ion engine verified that the engine has what it takes for long missions. DS1 is now set to launch on July 1, 1998. During its two-year test mission, the spacecraft will fly by Mars, an asteroid, and a comet, serving as a spaceborne test bed to validate new technologies.

Little Engine That Could

DS1's xenon ion engine, which fires electrically charged atoms from its thrusters, is just 11.8 inches in diameter and is powered by more than 2,000 watts from large solar arrays, which focus, collect and store solar energy. Using xenon, a heavy inert gas, for fuel, the engine ionizes (gives an electrical charge to) the gas and electrically accelerates it to a speed of about 18.6 miles per second (about 70,000 miles per hour). When the xenon ions are emitted at such a high speed, they then push the spacecraft in the opposite direction. The converted xenon appears as a ghostly blue haze that trails from the back of the spacecraft as it catapults through space.

Perhaps the strangest thing about ion propulsion is that it provides about the same amount of thrust as the pressure of a single sheet of paper held in the palm of the hand. So how does that power a spacecraft? As more and more ions are emitted, this low thrust gradually changes the craft's velocity from low to high speed.

Since the cumulative mass of the positively charged ions fired out of the thruster doesn't weigh much, the spacecraft moves only millimeters per second in its early stages of flight. But as the energy produced accumulates, the speed can eventually build up to 70,200 miles per hour, compared to just 10,400 miles per hour for the fastest chemical propulsion engines with the same vehicle launcher and amount of propellant.

Staying Power

In addition, the ion propulsion engine is so efficient that it can operate on a small amount of propellant for months - considerably smaller, and thus lighter, than the amount of propellant on board a chemically propelled spacecraft. This makes ion propulsion ideal for long missions. And since the ion-propelled spacecraft are lighter, they can launch from smaller, cheaper launch vehicles.

"For space science, we can take advantage of the lower cost and the advanced technology to get the same information [that NASA's getting now]," explains Jack Stocky, manager of the NASA Solar Electric Propulsion Technology Application Readiness program. "That allows us to do more missions and makes the program more exciting and more interesting to the public." These factors contribute not only to tremendous savings for NASA but also greater public support for space exploration, making ion propulsion the likely choice for tomorrow's most distant missions.

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