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Thread: Ion Drive

  1. #1 Ion Drive 
    Forum Junior Kolt's Avatar
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    How much closer have we come to achieving ion propelled space flight?

    I've read that NASA has not yet been willing to implement the technology to its fullest potential for fears that it simply will not work. Yet I've had trouble learning the specifics as to why. I do know that in outer space ion thrusters, though fast over long distances, still have trouble gaining proper acceleration and that propulsion via electrically charged gases within Earths atmosphere results in a less than adequate performance all around. But what exactly are the limitations that cause this? And what other problems have we not solved at this point?

    Any information on this would be much appreciated.

    I have always been fascinated by the idea that we could be going to mars using ion drive. I hope that I will be able to see it within my life time.


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    Universal Mind John Galt's Avatar
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    ESA is certainly not inhibited by doubts. The SMART probe to the moon, launched in 2003 used an ion engine, powered by solar panels, to carry the craft from Earth orbit to lunar orbit. The BepiColombo ESA/JAXA jpint mission to Mercury will also, I think, be powered by ion drive.

    Indeed NASA has already successfully tested an ion drive on Deep Space 1, in 1999.

    what exactly are the limitations that cause this?
    Ion drives deliver very low thrust levels and therefore small accelerations. These are too low to efficiently reach orbit starting from the Earth's surface. Their advantage is that they can operate for very long time periods, so that high speeds can be achieved.

    As always, wikipedia contains much useful information and relevant references.
    http://en.wikipedia.org/wiki/Ion_drive


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  4. #3 Re: Ion Drive 
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    Quote Originally Posted by Kolt
    I have always been fascinated by the idea that we could be going to mars using ion drive. I hope that I will be able to see it within my life time.
    It would probably be a looooong trip. Like ophiolite said, the acceleration with ion engines is very slow. You can reach a much higher top speed with a given amount of fuel, but since you burn through the fuel very slowly it takes a long time to get up to speed.

    Consider the performance of a VASIMR type ion engine (which have actually been built and tested by NASA - so we know they work) vs the space shuttle's main engine. Suppose your spaceship is 80% fuel by mass (meaning you start with 4 kg of fuel for every 1kg of spaceship. With the space shuttle's main engine, you could reach a top speed of about 7 km/sec. With the VASIMR ion engine, on the other hand, you could reach a top speed of 634 km/sec - over 90 times faster than with the shuttle engine! But it will take you about 15 years to get up to speed because your acceleration will only be around 0.0013 m/s max. The shuttle engine, on the other hand, can burn through all its fuel in a few minutes, after which you will be going your 7 km/sec. So the ion engine has a mugh higher top speed, but it takes much longer to get up to speed.

    Nuclear engines are really the way to go for fast travel around the solar system, in my opinion.
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