Thinking Tech

NASA's Dawn heads to the Asteroid Belt

NASA's Dawn heads to the Asteroid Belt

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With a little over 400 days to go, the spacecraft sets a record.

Dawn has been moving toward the asteroid Vesta since September 27, 2007, and is due to arrive in July of next year.

This week it broke NASA's record for how fast a rocket can change its path through space using only the power of its engines.

NASA sounds very excited about Dawn's fuel system, which it calls "the most exciting new rocket propulsion system since the Chinese invented the rocket about a thousand years ago."

Since Dawn's trip would be impossible using conventional engines, the rocket is powered by two large solar panels that ionize Dawn's fuel (which is Xenon) by creating an electric field. The charged Xenon ions then propel Dawn, and very efficiently too. In the course of a year, NASA says, Dawn's speed can increase by 5,500 miles per hour using the equivalent of 16 gallons of fuel.

Although this fuel system was tested in Dawn's predecessor, Deep Space 1, this is the first time NASA has relied on it for a scientific mission.

From NASA:

To get to where it is in both the record books and the asteroid belt, the Dawn spacecraft had to fire its three engines – one at a time-- for a cumulative total of 620 days. In that time, it has used less than 165 kilograms (363 pounds) of xenon propellant. Over the course of its eight-plus-year mission, Dawn's three ion engines are expected to accumulate 2,000 days of operation -- 5.5 years of thrusting -- for a total change in velocity of more than 38,620 kilometers per hour (24,000 miles per hour).

After visiting Vesta, Dawn will move on to Ceres -- the two asteroids are very different, and NASA hopes to get some clues on the origin of the solar system. Dawn will orbit and map both asteroids and study numerous other features of these rocks.

Here are a couple of Web pages with voluminous information on ion-propelled rockets and the Dawn mission. Here, for instance, you can read journal entries from Dawn's chief engineer, Marc Rayman. When you get a grasp of the science behind the rocket, you can try designing your own.

Whatever Dawn learns should prove useful when we start sending astronauts to the asteroids, which really is supposed to happen.

We've been sending robots to the Asteroid Belt for over a decade. A Japanese mission, Hayabusa, is due to land next week -- on June 13 -- in the Australian Outback and is expected to create quite a fireball.

It will be, says Peter Jenniskens, a SETI Institute scientist at NASA Ames, "the second highest velocity re-entry of a capsule" into the Earth's atmosphere ever.

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Deborah Gage

Contributing Editor

Contributing Editor Deborah Gage has written for the San Francisco Chronicle, Minnesota Public Radio, Baseline and various magazines and newspapers. She is based in San Francisco. Follow her on Twitter. Disclosure