Ionpropulsion - Blog Posts

Solar System: Things to Know This Week

Our Dawn mission to the asteroid belt is no ordinary deep space expedition. 

Instead of traditional chemical rockets, the spacecraft uses sophisticated ion engines for propulsion. This enabled Dawn to become the first mission to orbit not one, but two different worlds — first the giant asteroid Vesta and now the dwarf planet Ceres. Vesta and Ceres formed early in the solar system's history, and by studying them, the mission is helping scientists go back in time to the dawn of the planets. To mark a decade since Dawn was launched on Sept. 27, 2007, here are 10 things to know about this trailblazing mission.

1. Ion Engines: Not Just for Sci-Fi Anymore

Most rocket engines use chemical reactions for propulsion, which tend to be powerful but short-lived. Dawn's futuristic, hyper-efficient ion propulsion system works by using electricity to accelerate ions (charged particles) from xenon fuel to a speed seven to 10 times that of chemical engines. Ion engines accelerate the spacecraft slowly, but they're very thrifty with fuel, using just milligrams of xenon per second (about 10 ounces over 24 hours) at maximum thrust. Without its ion engines, Dawn could not have carried enough fuel to go into orbit around two different solar system bodies. Try your hand at an interactive ion engine simulation.

2. Time Capsules 

Scientists have long wanted to study Vesta and Ceres up close. Vesta is a large, complex and intriguing asteroid. Ceres is the largest object in the entire asteroid belt, and was once considered a planet in its own right after it was discovered in 1801. Vesta and Ceres have significant differences, but both are thought to have formed very early in the history of the solar system, harboring clues about how planets are constructed. Learn more about Ceres and Vesta—including why we have pieces of Vesta here on Earth.

3. Portrait of a Dwarf Planet

This view of Ceres built from Dawn photos is centered on Occator Crater, home of the famous "bright spots." The image resolution is about 460 feet (140 meters) per pixel.

Take a closer look.

4. What's in a Name? 

Craters on Ceres are named for agricultural deities from all over the world, and other features carry the names of agricultural festivals. Ceres itself was named after the Roman goddess of corn and harvests (that's also where the word "cereal" comes from). The International Astronomical Union recently approved 25 new Ceres feature names tied to the theme of agricultural deities. Jumi, for example, is the Latvian god of fertility of the field. Study the full-size map.

5. Landslides or Ice Slides? 

Thanks to Dawn, evidence is mounting that Ceres hides a significant amount of water ice. A recent study adds to this picture, showing how ice may have shaped the variety of landslides seen on Ceres today.

6. The Lonely Mountain 

Ahuna Mons, a 3-mile-high (5-kilometer-high) mountain, puzzled Ceres explorers when they first found it. It rises all alone above the surrounding plains. Now scientists think it is likely a cryovolcano — one that erupts a liquid made of volatiles such as water, instead of rock. "This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and that formed in the geologically recent past," one researcher said. Learn more.

7. Shining a Light on the Bright Spots 

The brightest area on Ceres, located in the mysterious Occator Crater, has the highest concentration of carbonate minerals ever seen outside Earth, according to studies from Dawn scientists. Occator is 57 miles (92 kilometers) wide, with a central pit about 6 miles (10 kilometers) wide. The dominant mineral of this bright area is sodium carbonate, a kind of salt found on Earth in hydrothermal environments. This material appears to have come from inside Ceres, and this upwelling suggests that temperatures inside Ceres are warmer than previously believed. Even more intriguingly, the results suggest that liquid water may have existed beneath the surface of Ceres in recent geological time. The salts could be remnants of an ocean, or localized bodies of water, that reached the surface and then froze millions of years ago. See more details.

8. Captain's Log 

Dawn's chief engineer and mission director, Marc Rayman, provides regular dispatches about Dawn's work in the asteroid belt. Catch the latest updates here.

9. Eyes on Dawn 

Another cool way to retrace Dawn's decade-long flight is to download NASA's free Eyes on the Solar System app, which uses real data to let you go to any point in the solar system, or ride along with any spacecraft, at any point in time—all in 3-D.

10. No Stamp Required

Send a postcard from one of these three sets of images that tell the story of dwarf planet Ceres, protoplanet Vesta, and the Dawn mission overall.

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Ion Propulsion…What Is It?

Ion thrusters are being designed for a wide variety of missions – from keeping communications satellites in the proper position to propelling spacecraft throughout our solar system. But, what exactly is ion propulsion and how does an ion thruster work? Great question! Let’s take a look:

Regular rocket engines: You take a gas and you heat it up, or put it under pressure, and you push it out of the rocket nozzle, and the action of the gas going out of the nozzle causes a reaction that pushes the spacecraft in the other direction.

Ion engines: Instead of heating the gas up or putting it under pressure, we give the gas xenon a little electric charge, then they’re called ions, and we use a big voltage to accelerate the xenon ions through this metal grid and we shoot them out of the engine at up to 90,000 miles per hour.

Something interesting about ion engines is that it pushes on the spacecraft as hard as a single piece of paper pushes on your hand while holding it. In the zero gravity, frictionless, environment of space, gradually the effect of this thrust builds up. Our Dawn spacecraft uses ion engines, and is the first spacecraft to orbit two objects in the asteroid belt between Mars and Jupiter.

To give you a better idea, at full throttle, it would take our Dawn spacecraft four days to accelerate from zero to sixty miles per hour. That may sounds VERY slow, but instead of thrusting for four days, if we thrust for a week or a year as Dawn already has for almost five years, you can build up fantastically high velocity.

Why use ion engines? This type of propulsion give us the maneuverability to go into orbit and after we’ve been there for awhile, we can leave orbit and go on to another destination and do the same thing.

As the commercial applications for electric propulsion grow because of its ability to extend the operational life of satellites and to reduce launch and operation costs, we are involved in work on two different ion thrusters of the future: the NASA Evolutionary Xenon Thruster (NEXT) and the Annular Engine. These new engines will help reduce mission cost and trip time, while also traveling at higher power levels.

Learn more about ion propulsion HERE.

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