Editing Newsletter/Winter 2007 (section)

== Ion Drive Works Well for Dawn Explorer  ==
[[Image:Deep Space 1 Ion Drive.jpg|275px|right|thumb|Artistic rendering of a working Ion Drive]]
by [[herbalsheila]]

Talked about in theory for many years in science fiction by writers such as Isaac Asimov, the ion drive is now a practical reality. An ion drive engine was first constructed by Glenn Research Laboratory back in 1960 and has been in development by various agencies and laboratories for over 50 years.
 
The exploratory remote robotic vessel Dawn was launched on September 27, 2007 and its ion drive was tested successfully the following October 4-7. The tests included assessment of idle, slow speed, faster speed and full throttle. As of December 18, 2007, the Dawn spacecraft has successfully completed the initial checkout phase of the mission.  It has begun its 8 year interplanetary cruise phase, which is highlighted by nearly continuous thrusting of its ion propulsion system. It’s mission is to explore the dwarf planet Ceres and the asteroid Vesta, two of the largest asteroidal bodies in our own solar system. 

To cruise from Earth to its targets, it will use three Deep Space 1 Heritage Xenon Ion Thrusters built by NASA's Jet Propulsion [[Image:Dawn Asteroids.jpg|325px|left|thumb|Artistic rendering of Dawn with Ceres and Vesta]]Laboratory, by firing one at a time to take it on its course in a long outward spiral. An extended mission in which Dawn explores other asteroids after Ceres is also possible, depending on available fuel and mission objective. Dawn's ion drive is capable of accelerating from 0 to 60 mph in 4 days.

That may sound like a slow speed to us, but the drive itself is highly cost effective. The testing over the weekend in October 2007 used only 10 oz or .28 kg of fuel in 27 hours. Though the power consumption and cost is low, the acceleration curve is not as immediate and takes time to build up with continuous thrusting. 

Dawn’s fuel tank carries 425 kilograms or 937 pounds of xenon propellant and will power it for 50,000 hours of thrust during its 3 billion mile journey.
[[Image:Ion drive.jpg|200px|right|thumb|Ion Drive lab test]]
Basically an ion drive, also called an electrostatic engine, works by using ionized gas to propel a craft. Instead of a spacecraft being propelled with standard chemicals, the generally inert gas xenon, like neon or helium but heavier, is given an electrical charge, or ionized. Electrical current is shot through the gas to accelerate it to a speed of about 30 km/second. When xenon ions are emitted at a high speed as exhaust from a spacecraft under low or no gravity, they push the spacecraft in the opposite direction.

When compared to standard chemical propulsion used in the Mercury and Apollo missions as well as the shuttle flights, the ion drive is actually faster, though the speed needs time to accumulate. Since the thrust is more gentle, it does not work well against Earth’s gravity and is more appropriate for space outside of celestial gravity wells. Technologically at this time, the ion drive cannot be used as a way to escape Earth’s gravity. Until advances have been made, chemical propulsion will still be a standard part of space exploration.

'''Fun fact:''' The word "cereal" comes from Ceres, the Roman goddess of grain (or agriculture).