Astounding Ion Propulsion Nearly Has Dawn to Ceres

NASA's unique Dawn spacecraft has already traveled more than three billion miles since its 2007 launch, and has made some serious changes in course after visiting a mysterious protoplanet, known as Vesta. And yet, it's still far from being out of fuel. How can this be? In a new video from NASA, experts at the Jet Propulsion Laboratory explain the wonders of ion propulsion.

As we reported just last month, NASA's unique Dawn spacecraft has nearly reached its target destination, Ceres - a titanic asteroid that's often called a "dwarf planet" or protoplanet. Even in its wide orbit around the Sun, the asteroid is usually about 257 million miles from Earth, as the crow flies. Its sister asteroid, Vesta, can be similarly found in the asteroid belt that separates Mars and Jupiter at an average of 156 million miles from Earth. That's without considering that you would have to actually circumnavigate a good portion of the Sun's massive girth to reach either of this pair.

And yet, even with those daunting distances in mind, NASA engineers were able to craft a space probe that could not only visit one of these protoplanets, but both, in the same mission, and have fuel to spare.

Space agencies have gotten pretty good at pushing the envelope on the potential for jet propulsion. As displayed in stunning missions that harness the pull of planets, moons, and even pulses of solar wind, you don't always need to expend fuel to keep a spacecraft moving in the frictionless abyss of space. However, to slow down, change course, and keep a good view, fuel MUST be spent, making the idea of visiting not one, but two massive and incredibly far asteroids in a virtual mine field of their lesser cousins seem near-impossible.

So how is Dawn pulling it off? According to NASA, it's all about the craft's unique engines - three incredible ion propulsion systems that make no use of conventional explosive force. (Scroll to read on...)

[Credit: NASA/JPL]

In an ion propulsion engine, an electrical charge is applied to xenon gas, and charged metal grids accelerate the xenon particles out of the thruster. In your classic action and reaction, the expulsion of these particles pushes the craft slightly forward. And as there are countless particles in a single engine, it can thrust for an exceptionally long time with little trouble.

However, it's important to note that the force of this thrust is lighter than a soft breeze. In a zero-gravity vacuum, it would take a whopping four days for the 65-foot-wide craft to go 0 to 60 mph. Amazingly, that small force builds up fast, as Dawn is currently 400,000 miles from Ceres, approaching it at around 450 mph. It is expected to fall into orbit in a mere three months' time.

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