1. Joined
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    09 Oct '13 09:48
    If i could ever get my spelling down i'ld be fine. An ion prop sattelite was shot off into space a few years ago. On the Discovery channel there was a two hour show on its making and where it was at the time of the show. Its travel was past Saturn in a mere 8 months. Anyone hear of it since then?
  2. Subscribersonhouse
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    09 Oct '13 10:281 edit
    Originally posted by Pudgenik
    If i could ever get my spelling down i'ld be fine. An ion prop sattelite was shot off into space a few years ago. On the Discovery channel there was a two hour show on its making and where it was at the time of the show. Its travel was past Saturn in a mere 8 months. Anyone hear of it since then?
    Are you talking about 'Dawn'? Here is an update:

    http://www.jpl.nasa.gov/news/news.php?release=2010-192

    It ran one accel run for 630 days using only about 350 pounds of propellant. Think about how much the old shuttle used just getting off the ground๐Ÿ™‚
  3. Cape Town
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    09 Oct '13 10:30
    Originally posted by Pudgenik
    If i could ever get my spelling down i'ld be fine. An ion prop sattelite was shot off into space a few years ago. On the Discovery channel there was a two hour show on its making and where it was at the time of the show. Its travel was past Saturn in a mere 8 months. Anyone hear of it since then?
    Possibly the Dawn mission?
    http://dawn.jpl.nasa.gov/mission/live_shots.asp

    If so, you won't hear much from it till its rendezvous with dwarf planet Ceres in 2015.

    This might also interest you:
    http://www.space.com/22916-nasa-ion-thruster-world-record-test.html
  4. Joined
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    09 Oct '13 10:35
    Originally posted by Pudgenik
    If i could ever get my spelling down i'ld be fine. An ion prop sattelite was shot off into space a few years ago. On the Discovery channel there was a two hour show on its making and where it was at the time of the show. Its travel was past Saturn in a mere 8 months. Anyone hear of it since then?
    I thought it sounded interesting. Googled for 5 min and this is what I found. I did not read them proberly (not the time for doing so). If only someone, could explain what it is about...?? Thay would make me a happy person! I am a quite curious person. ๐Ÿ™‚

    http://en.wikipedia.org/wiki/Artemis_(satellite)
    http://space.skyrocket.de/doc_sdat/artemis.htm
    http://telecom.esa.int/telecom/www/area/index.cfm?fareaid=26
    http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=32194
  5. Subscribersonhouse
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    09 Oct '13 11:01
    Originally posted by bikingviking
    I thought it sounded interesting. Googled for 5 min and this is what I found. I did not read them proberly (not the time for doing so). If only someone, could explain what it is about...?? Thay would make me a happy person! I am a quite curious person. ๐Ÿ™‚

    http://en.wikipedia.org/wiki/Artemis_(satellite)
    http://space.skyrocket.de/doc_sdat/artemis.htm ...[text shortened]... w/area/index.cfm?fareaid=26
    http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=32194
    The interesting thing about ion propulsion is the propellant usage doesn't change much as compared to a chemical rocket, where if you want more thrust and you are already using the best chemicals, like H2 and O2, the only way you get more thrust is to burn more H2 and O2 per unit time, so more flow and shorter operating times.

    With ion rockets, you get more thrust with basically the same amount of propellant flow by using more energy to boost the exhaust velocity of the propellant.

    That works even at relativistic velocities, because as you get closer to c the propellant gains mass and therefore kinetic energy. Of course today's technology isn't anywhere close to c as far as exhaust velocity goes but that is the potential.

    There is a more advanced version called Vasimir that would get folks to Mars in about 1 month but requires the use of nuclear power, that craft wants 200 megawatts to do the job.

    I calculated for 100% perfect power in vs acceleration v mass that 32 horsepower can accelerate 550 pounds at 1 G.

    Call it 25 Kw for 550 Lbs @ 1 g, so round it off to 100 Kw for one ton at 1 g.

    So 100 mw used 100% could accelerate 1000 tons at 1 g, so 200 mw could accelerate 2000 tons to 1 g.

    Even with Vasimir, it is not anywhere like those kind of numbers because the Vasimir plus living quarters are being accel'd at 0.05 g which is enough to get you to Mars in a month. That would be about 2 weeks of acceleration and 2 weeks of deceleration so you reach Mars being at the same relative velocity so you can go into orbit or land 'easily'. Not sure how many tons the whole Vasimir design weighs so can't figure a good efficiency rating of power in vs acceleration out. 200 megawatts is about 280,000 hp which on a boat is more than enough to make an aircraft carrier go 60 Kph and carriers are something like 100,000 tons so trucks on land and boats in the water are much more efficient in terms of how efficiently they convert electrical or chemical energy into kinetic energy but in space you don't get the benefit of a large body of water to thrust against or flat land for a truck. You waste an extreme amount of energy just heating or accelerating a propellant to get thrust.
  6. Cape Town
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    09 Oct '13 18:08
    Originally posted by sonhouse
    The interesting thing about ion propulsion is the propellant usage doesn't change much as compared to a chemical rocket, where if you want more thrust and you are already using the best chemicals, like H2 and O2, the only way you get more thrust is to burn more H2 and O2 per unit time, so more flow and shorter operating times.
    Its not just about the increased acceleration of propellant (which leads to greater thrust per unit mass of propellant), its also where the power is coming from. With chemical fuel rockets, the power is stored as chemical potential energy. The ion drive gets its power from electricity which can be collected from solar power en-route.
  7. Subscribersonhouse
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    09 Oct '13 18:19
    Originally posted by twhitehead
    Its not just about the increased acceleration of propellant (which leads to greater thrust per unit mass of propellant), its also where the power is coming from. With chemical fuel rockets, the power is stored as chemical potential energy. The ion drive gets its power from electricity which can be collected from solar power en-route.
    Sure, you CAN get power from solar but there are two problems with that:

    One is the amount of raw power you need for something serious like the Vasimir where you are trying to get to Mars in a month instead of six, 0.2 GIGAGWATT. In space near the Earth you get about 1300 watts per square meter so it takes about 160,000 square meters to get that much power and that is if it is 100% efficient. Try it at 30% and you are up to 600,000 square meters of PV cells. 3/4 X 3/4 KILOMETER. Them are a lot of cells to shlep out into space.

    The second problem which is not such a big deal going to Mars but will certainly effect trips to Jupiter: Just an estimate but you probably get only about 1/25th the amount of power there so now instead of 600,000 square meters you need about 4X4 Kilometers area of PV cells. Impossible.

    So you are left with one power source: Nuclear, which has its own set of problems.
  8. Cape Town
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    09 Oct '13 20:03
    Originally posted by sonhouse
    Sure, you CAN get power from solar ....
    Well I believe the Dawn mission does.
    And according to this site:
    http://www.adastrarocket.com/aarc/missions
    There are plenty of other types of missions where solar is suitable.

    But my point was that the power source is electric rather than chemical which wasn't clear in your earlier post so I thought it was worth adding.
  9. Joined
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    10 Oct '13 05:35
    Originally posted by sonhouse
    The interesting thing about ion propulsion is the propellant usage doesn't change much as compared to a chemical rocket, where if you want more thrust and you are already using the best chemicals, like H2 and O2, the only way you get more thrust is to burn more H2 and O2 per unit time, so more flow and shorter operating times.

    With ion rockets, you get m ...[text shortened]... . You waste an extreme amount of energy just heating or accelerating a propellant to get thrust.
    Thankyou, that was interesting reading.
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