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"Dawn" launched: ion drive to Ceres & Vesta

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  • "Dawn" launched: ion drive to Ceres & Vesta



    Dawn homepage....

    "Dawn will be history's first mission to go out into the solar system, orbit and explore a distant body, and then go on to a totally different celestial body and explore that one," said Dawn project manager Keyur Patel of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "To do all that you need a spacecraft with a lot under the hood."
    >
    "In the end it is about the science," added Patel. "What we find when Dawn gets to Vesta and Ceres will re-write the history books on the beginning of our solar system. But how we get there is almost as remarkable, 1.8 billion miles to Vesta, months flying around it performing science adjusting our orbits as we go. Then we travel another billion miles to Ceres where we do it all over again. That is a lot to ask of a beam of blue light."
    The Dawn spacecraft is powered by 3 (for redundancy) steerable 30 cm (12 inch) advanced ION drives; basically solar-electric rockets capable of running continuously for 2,100 days instead of just a few minutes while using just 425 kg (937 lb) of Xenon as fuel. The span of Dawns 10.3 kW solar arrays is 19.7 m (65 ft).

    Their thrust is low, but over the course of the mission the total change in velocity from the ION drives will be similar to that delivered by all the chemical rockets used for the launch; 9 SRB's + the Delta II's first, second and third stages.

    For all of this each ION drive is about the size of a basketball and weighs about 9 kg (20 lbs).

    [NOTE: VASIMR, a variable power plasma electric rocket ultimately capable of thousands to millions of times the thrust of any ION drive while maintaining ION's efficiency, is due to fly its first checkout mission by 2011 if not sooner. Ad Astra just built one of the largest vacuum chambers in the world for testing the prototype for that flight, but smaller ones have already been fired for several hours continuously.]



    The 8 year mission's goal is to investigate in detail two of the largest protoplanets remaining intact; Ceres and Vesta. Dawn will use its ION drives to speed its trip and to maneuver into orbit around each object for extended examinations.

    Ceres is a minor planet with a mass about 4% that of the Moon but containing ~200 million cu/km of water, more than the amount of fresh water on Earth, frozen over its rocky core. This could make Ceres an important way-station for extended manned missions around the solar system as it could provide both water and rocket fuel (water split into H2 and O2).

    Vesta is the 2nd largest object in the asteroid belt after Ceres and thought to be a metallic iron-nickel core, an olivine mantle with a surface crust of basalts and other types. A few meteorites are thought to be fragments of Vesta blown off in collisions, and they raised many interesting questions.



    More launch pics....
    Last edited by Dr Mordrid; 28 September 2007, 03:57.
    Dr. Mordrid
    ----------------------------
    An elephant is a mouse built to government specifications.

    I carry a gun because I can't throw a rock 1,250 fps

  • #2
    Things are getting interesting again

    Now we just need some "BIG ASS" versions of these engines, a radiation shield, and we can exploring our neighborhood in style
    Last edited by Technoid; 28 September 2007, 13:17. Reason: spelling
    If there's artificial intelligence, there's bound to be some artificial stupidity.

    Jeremy Clarkson "806 brake horsepower..and that on that limp wrist faerie liquid the Americans call petrol, if you run it on the more explosive jungle juice we have in Europe you'd be getting 850 brake horsepower..."

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    • #3
      That's VASIMR - VAriable Specific Impulse Magnetoplasma Rocket.

      The best way to use them is to hook up a nuclear reactor, and they can be used in clusters. A megawatt setup could cut the trip to Mars down to 2-3 months instead of a year or more, and the VASIMR going into testing is a 200 kW unit.

      Exhaust velocities

      VASIMR: 10,000 - 300,000 m/s (or more)
      ION thruster: 29,000 m/s
      Nuclear thermal rocket: 8,340 m/s
      SSME (Space Shuttle main engine): 4,500 m/s)
      Liquid rocket: 4,400 m/s
      Solid rocket: 2,500 m/s

      Provide enough input power and the proper fuel and VASIMR becomes a fusion rocket, and yes a lot of physicists think that's possible down the road. In fact VASIMR is an outgrowth of fusion research.

      Last edited by Dr Mordrid; 28 September 2007, 16:55.
      Dr. Mordrid
      ----------------------------
      An elephant is a mouse built to government specifications.

      I carry a gun because I can't throw a rock 1,250 fps

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