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Relativistic Navigation Needed For Solar Sails

Posted by Soulskill on from the i'd-rather-be-sailing dept.

KentuckyFC writes "Last year, physicists calculated that a solar sail about a kilometer across with a mass of 300 kg (including 150 kg of payload) would have a peak acceleration of roughly 0.6g if released about 0.1AU from the Sun, where the radiation pressure is highest. That kind of acceleration could take it to the heliopause — the boundary between the Solar System and interstellar space — in only 2.5 years; a distance of 200 AU. In 30 years, it could travel 2500AU, far enough to explore the Oort Cloud. But the team has discovered a problem. Ordinary Newtonian physics just doesn't cut it for the kind of navigational calculations needed for this journey. Because the sail has to be released so close to the Sun, it becomes subject to the effects of general relativity. And although the errors these introduce are small, they become magnified over the course of a long journey, sending the sail roughly 1 million kilometers off course by the time it reaches the Oort Cloud. What these guys are saying is that if ever such a sail is launched (and the earliest estimate is 2040), the navigators will have to be proficient in a new discipline of relativistic navigation."

10 of 185 comments (clear)

  1. Computers? by Extremus · · Score: 4, Insightful

    the navigators will have to be proficient in a new discipline of relativistic navigation.

    Probably you are trying to say that the computers will have to be proficient in this new discipline.

    1. Re:Computers? by FooAtWFU · · Score: 4, Insightful

      Probably you are trying to say that the computers will have to be proficient in this new discipline.

      It's not that hard, either. Just math. We have the equations. They're well-understood. Some physics grad students could probably write the basic engine for such an endeavour. I'd worry more about $UNKNOWN_EXOTIC_EFFECT pushing something off-course.

      --
      The World Wide Web is dying. Soon, we shall have only the Internet.
    2. Re:Computers? by TooMuchToDo · · Score: 4, Insightful

      Even if you get pushed off course, you get to discover $UNKNOWN_EXOTIC_EFFECT =)

  2. One part in 37 million... by argent · · Score: 5, Insightful

    One million kilometers sounds like a big number, until you realize that 2,500 AU is 3.7 * 10^11 kilometers. So that error is one part in thirty seven million. I suspect that accumulated errors from variations in light intensity due to sunspots and flares will be a bigger problem.

    1. Re:One part in 37 million... by R2.0 · · Score: 4, Funny

      I would think that the Oort cloud itself would be the destination. Theoretically, the distribution of rocks is pretty even, so we should be able to get data no matter where in the cloud the probe goes. If it gets to that random point and finds either nothing, or a whole lot, we need to change the theory, don't we?

      Remember, Columbus set out to sail to the Indies, not land in Mumbai harbor. Of course, if we follow that example the probe will crash into Neptune and we'll declare it a new comet, but the general principle is the same.

      --
      "As God is my witness, I thought turkeys could fly." A. Carlson
  3. What else is new? by jarocho · · Score: 5, Interesting

    Pioneer 10 has been off-course for a while now. Maybe the trick for reaching the Oort Cloud is to aim for 1 million kilometers to the left.

  4. Is this that important? by MiniMike · · Score: 5, Insightful

    sending the sail roughly 1 million kilometers off course by the time it reaches the Oort Cloud.

    Is there a specific part of the Oort Cloud they want to go to?
    If this ability is needed to travel to other planets accurately, then it seems important. For the Oort cloud, not as much.

    .

    Will this solar sail be going at a speed that will allow it to do any useful observations, or are we just going to watch for the flash when it 'finds' something at that speed?

  5. Mid-course corrections? by vrmlguy · · Score: 4, Insightful

    No space craft has ever been aimed accurately. At various times during the mission, you look at where you are and where you're supposed to be, and make a correction to your trajectory. Is there some reason why this won't work with a solar sail?

    --
    Nothing for 6-digit uids?
  6. Just how big is the Oort Cloud? by Eevee · · Score: 4, Funny

    From Wikipedia, "The Oort cloud is a hypothetical spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun." So...um...how do you miss it? You go straight out in any direction. When you see a lot of icy chunks floating around, you're there.

  7. Need to think relatively by Lev13than · · Score: 5, Funny

    Course correcting a small ship is easy - I'm more worried about everything else. In a relativistic navigation model, the ship is going to be in exactly the right place. However, the energy required to course correct the entire universe by one million km will be prohibitive.

    --
    When you have nothing left to burn you must set yourself on fire