Humankind’s first true interplanetary spacecraft, Dawn, entered orbit around the asteroid Vesta on Saturday (July 16th, 2011) and will begin mapping operations soon. Dawn is a very cool robotic probe that NASA sent to examine two of the largest rocks in the asteroid belt, Vesta and Ceres.
It uses ion engines which have very weak thrust but can apply that thrust continuously for months. During its trip to Mars to get a gravity boost from that planet, it operated its ion engines for a combination of 270 days.
Current theory holds that the asteroid belt exists in that orbit instead of a planet because Jupiter’s gravity acts like a huge spatula, stirring the area and preventing planets from forming. Both Ceres and Vesta are a lot smaller than Earth’s moon. They represent two contrasts of asteroid formation and scientists hope to learn quite a lot from them about the formation of the other planets in our solar system. The title image of this article is by far the best ever taken of it. The image Ceres here is from the Hubble Space Telescope.
Next year about this time Dawn will leave Vesta orbit and proceed to Ceres. Other probes, including the two Voyager spacecraft, now examining the extreme outer shell of our solar system, did rapid flybys of various scientific interests on their way out to wherever they were headed. However, Dawn is the first probe ever built that can enter stable orbit around one body, stay over and study it for a while, then leave and fly to a different body and study it also. This because of its three very fuel-efficient ion engines. With ion engines, the energy used for thrust is not derived from a chemical process, but electrically, using energy collected by the spacecraft’s huge solar panels. The stored “fuel” is xenon gas, which the engines ionize and then expel out the engine nozzle electrically. The effect is very weak, but sustained over time has a much larger effect on a spacecraft’s speed than an equal weight of fuel consumed by much more powerful chemical rocket engines. Ion thrust can’t send a spacecraft from Earth-to-orbit, but future variants of this technology may be the future of interplanetary propulsion. NASA first used Ion thrust in flight on the experimental Deep Space 1 comet-chasing probe, which used its less-advanced, solar powered, ion engines for 678 days. BTW…the Starwars TIE fighter also uses solar panels and Ion engines, so maybe the video below would have been more appropriately narrated by James Earl Jones (Darth Vader of Starwars) instead of Leanard Nimoy (Spock of Star Trek). 😉
Heres to Dawn. I suggest you follow her Twitter feed and website at JPL over this year to learn about Vesta along with the rest of us. Vesta or Ceres might be a target for human space flight sometime in the next decade or two and I’m sure some of what they learn through Dawn‘s surveys will be used to plan those missions.