Launch Control: 3, 2, main engine start, 1, zero, and liftoff of the Delta 2 rocket with Dawn -- using ion propulsion to reach the catalysts of our solar system. [:14]
A year and a half after it left Earth, the Dawn mission will get its first good test this week -- along with a good kick. The spacecraft will fly past Mars. Its instruments will study the planet, giving scientists and engineers a chance to see how well they work. Most important, though, Mars will give Dawn a gravitational "kick" toward the asteroid belt.
That's because Dawn's main targets are the asteroids Vesta and Ceres. These giant chunks of rock and metal are left over from the formation of the solar system, so they can provide important details about how the planets were born. Dawn will spend several months orbiting each asteroid.
To travel from one to the other, it'll use its ion-powered engine.
Conventional rocket engines produce a lot of thrust in a short period of time. But they also need a lot of fuel. Dawn's ion engine produces thrust by giving its xenon fuel an electric charge, then firing the atoms out the back. It produces little thrust, but it can fire for months on end. And it doesn't need much fuel to get the job done. Dawn has already changed its speed by about 4,000 miles an hour -- and it needed just 150 pounds of fuel to do so.
Using the ion engine -- and the helping kick from Mars -- Dawn will reach Vesta in August of 2011.
Script by Damond Benningfield, Copyright 2008
For more skywatching tips, astronomy news, and much more, read StarDate magazine.