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Mars Science

VASIMR Ion Engine Could Cut Mars Trip To 39 Days 356

An anonymous reader writes "It would take about 39 days to reach Mars, compared to six months by conventional rocket power. 'This engine is in fact going to be tested on the International Space Station, launched about 2013,' astronaut Chris Hadfield said. The Variable Specific Impulse Magnetoplasma Rocket (VASIMR®) system encompasses three linked magnetic cells. The 'Plasma Source' cell involves the main injection of neutral gas (typically hydrogen, or other light gases) to be turned into plasma and the ionization subsystem. The 'RF Booster' cell acts as an amplifier to further energize the plasma to the desired temperature using electromagnetic waves. The 'Magnetic Nozzle' cell converts the energy of the plasma into directed motion and ultimately useful thrust."
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VASIMR Ion Engine Could Cut Mars Trip To 39 Days

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  • Re:No quite yet. (Score:5, Insightful)

    by doug ( 926 ) on Monday October 19, 2009 @10:34AM (#29793971)

    No stated in this article.

    But I'm pretty sure the engine discussed will need to be roughly 100x more powerful to make that 39 day trip a reality.

    No, not really. Hauling the fuel for chemical rockets into orbit is expensive, so mostly they do hard burns to get the right speed and direction, then they coast most of the trip. VASIMR doesn't need the heavy fuel, as it is solar powered, so it provides constant thrust. Apparently days of constant acceleration makes a difference.

    - doug

  • by Guysmiley777 ( 880063 ) on Monday October 19, 2009 @10:53AM (#29794269)
    These types of ion engines are only useful once you're in orbit, they're of no use in a deep gravity well or in an atmosphere. They are useful for things such as station keeping thrusters in satellites where you don't want to have to carry a lot of fuel with you.

    Sure, they'd be nice for a Mars mission as well, the problem is that they require external power. Not a big deal when you're talking about a couple hundred watts of electric power for less than a Newton of thrust. When you're talking about hundreds of kilowatts it gets a lot more impractical.
  • Re:I'm dizzy. (Score:1, Insightful)

    by Anonymous Coward on Monday October 19, 2009 @11:05AM (#29794429)

    except in 78 days, the earth will have completed 21.% of its orbit of the sun...

  • by slack_justyb ( 862874 ) on Monday October 19, 2009 @11:10AM (#29794495)
    I have to agree with the grandparent. VASMIR is old news as far as cutting edge technology. Really, why not put out an article about how awesome Blu-Ray is (rolls eyes)? So let's look pass the whole VASMIR thing and start looking at the applications themselves, "to be used on ISS in 2013" strikes me as the most useful piece of information in the summary. VASMIR technology is getting better and better every day, but so is diesel and bio-diesel technology.

    At some point, continuing to beat the gong on something starts to make it look like those "Wow" commercials from the Windows Vista days, or all those promises of action during the campaigning days here in the United States.
  • Re:No quite yet. (Score:5, Insightful)

    by TheRaven64 ( 641858 ) on Monday October 19, 2009 @11:18AM (#29794609) Journal

    VASIMR doesn't need the heavy fuel, as it is solar powered, so it provides constant thrust

    Ummm, no. Or, rather, technically yes, but not really. In a chemical rocket, fuel and reaction mass are the same thing. The fuel burns, expands, and flies out of the back. With an ion engine, they are separate. The fuel is anything that can produce electricity (e.g. solar or nuclear plants) and the reaction mass is something that you've ionised. This still has mass, and still has to be carried with you until you throw it out of the back, irrespective of where the power comes from.

    The important thing to remember is that all of these are reaction drives. They work according to the principle of conservation of momentum. When you throw some mass out of the back of your space ship, the space ship gains the same amount of momentum as the thing you throw out of the back. You can double the momentum that you gain from your engine by either doubling the speed of the ejected reaction mass, or by doubling the amount you throw out. With conventional rockets, the speed is limited by the rate of reaction, which is fairly fixed. With an ion drive, the speed is limited by the amount of power you put in.

    You still need to carry the propellant, but if you can throw it out at ten times the speed then you need a tenth of the amount. If you need a tenth of the amount, then your space ship will mass a little over a tenth as much, and so the speed that it gains from this change in momentum will be almost ten times as much.

    In theory, you could use a small glass of water, accelerated to a significant fraction of the speed of light, as your propellant for an entire trip to Mars and back. In practice, there is a limit to the speed to which an ion thruster can accelerate the ions it's throwing out and so you still need quite a large amount of propellant.

  • Newsflash (Score:3, Insightful)

    by Dunbal ( 464142 ) on Monday October 19, 2009 @11:38AM (#29794855)

    Engine that hasn't really been invented yet might rhubarb rhubarb rhubarb rhubarb....

          Of course as a nationalized Costa Rican citizen, perhaps I should celebrate the fact that Franklin Chang Diaz is the creator of this engine, however let's wait and see until it has actually been tested before we make specific claims, yes? []

  • by pixelpusher220 ( 529617 ) on Monday October 19, 2009 @11:55AM (#29795063)
    I believe the 'safer' idea is that instead of a 2 year round trip, we might be talking a few months. Lots easier to get help when it's only 45 days away rather than 6-12 months.

    And yes, 'easy' in this case is still ridiculously hard...but still it's a good bit better than 2 years.
  • Re:No quite yet. (Score:4, Insightful)

    by GigsVT ( 208848 ) on Monday October 19, 2009 @11:58AM (#29795093) Journal

    Imagine if we could do a close flyby on another solar system!

    A close flyby at 0.5C might not be as exciting as you'd think.

  • by Anonymous Coward on Monday October 19, 2009 @11:59AM (#29795109)
    Well, to be fair, the planet does spin faster the closer you get to the poles.
  • Re:I'm dizzy. (Score:3, Insightful)

    by CrimsonAvenger ( 580665 ) on Monday October 19, 2009 @12:20PM (#29795473)

    Depends on how much he weighs. The drive provides a force of 0.5N. A typical car plus passengers masses around 1000kg. F=ma, so, 0.5 / 1000 gives him an acceleration of 0.0005 m/s/s (ignoring friction and air resistance). 800 miles is a little under 1,300 km, or 1,300,000m. Assuming a stationary start, and accelerating for the whole time, we get sqrt(2s/a), which is around 51,000 seconds, or around 14 hours. Of course, after that time he'd be going quite quickly, so he'd probably want to be slowing down for the second half of the journey which increases the total travel time to about 20 hours.

    "quite quickly"? He'd be going (using your approximations) about 25.5 m/s. Which is only about 92 km/hour (57 miles per hour for those who don't do metric). He should be able to stop just fine with normal brakes in just a hundred feet or so.

  • by prisoner-of-enigma ( 535770 ) on Monday October 19, 2009 @12:30PM (#29795625) Homepage

    I for one am tired of hearing about all these wonderful propulsion ideas that inevitably fade into the background. What is it going to take to get one of these damned things built and tested?

    Yes, I know the trite answer is "money," but that's merely a means. What we lack is desire. I have a funny feeling that all the billions we've wasted on the ISS and keeping the nigh-useless Shuttle flying these past decades could've easily funded an unmanned test vehicle that could've used VASIMIR to fly to Mars and back as a technology demonstrator.

    Let's quit talking about what this technology "could" do and actual do it for a change. If it's feasible then we should be screaming at our Congress-critters to get behind it.

  • Re:I'm dizzy. (Score:3, Insightful)

    by TheRaven64 ( 641858 ) on Monday October 19, 2009 @12:39PM (#29795783) Journal
    Yup, I wrote that before calculating exactly how fast. Of course, in a hypothetical world where friction is low enough that you could use a 0.5N ion engine on the ground, your brakes probably wouldn't work so well...

The road to ruin is always in good repair, and the travellers pay the expense of it. -- Josh Billings