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Thread: Will a starship be destroyed by dust?

  1. #1 Will a starship be destroyed by dust? 
    Forum Radioactive Isotope skeptic's Avatar
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    I got into an argument on another forum about this. Scientific American featured, a long while ago (10 to 15 years?)an article by a couple of NASA rocket scientists on the future of interstellar travel. They said that a suitably advanced craft, with ion drive engines, could get to one tenth light speed (0.1c). I suggested that such a craft, if it took ten years for acceleration and ten for deceleration, would get to Alpha Centauri in 55 years.

    My debate opponent scoffed at this, and claimed it would be destroyed by the first speck of dust it ran into at those speeds. I checked a NASA web site, and found that such specks, while reasonably abundant, were a maximum of 1 micrometre in diameter. I would also point out that the trip to Alpha Centauri is a course almost at right angles to the ecliptic, meaning it goes nowhere near the asteroid belt or the Kuiper Belt, though (of course) it has to pass through the Oort Cloud.

    So my question is whether a starship at 0.1c would be destroyed by dust?


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  3. #2  
    Moderator Moderator Janus's Avatar
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    Assuming the density of said dust speck was ~3.2 g/cc (About that of a grain of sand), and the speck was cube shaped (Spherical cows and all that), it would have a mass in the order of 3.2e-15 kg. At 0.1c, this gives it a kinetic energy of ~ 1.44 joules ( not likely to vaporize a ship)

    Now the interstellar density is about 50 atoms/cc. which works out to ~8.35e-20 kg/m^3. At 0.1c, the ship will be moving at 3e7 m/sec. Which means that a 1 meter square cross section will collide with ~ 2.5e-12 kg of interstellar medium per second. This amounts to ~1125 joules/sec = 1125 watts of energy per meter. This is in the order of how much solar energy strikes the surface of the Earth when the Sun is at Zenith. Again, hardly ship vaporizing. ( though there will be some amount of erosion after years of this.)


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  4. #3  
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    in the book, Songs of Distant Earth, by Arthur C. Clarke in 1986, he postulated that a starship would need some protection from interstellar matter. he proposed a large water-ice shield.

    The Songs of Distant Earth - Wikipedia, the free encyclopedia

    Two hundred and fifty years after the end of Earth the Magellan arrives at Thalassa, the midpoint of a 550-year voyage to colonise the distant ice planet Sagan 2. Though primarily the objective is to replenish the ship's mammoth ice shield that had prevented micrometeors from damaging it during its interstellar journey, it soon becomes apparent that the human colony is still present and flourishing. Thalassa is the obvious choice for this operation, as 95% of the planet's surface is covered by water. Aboard are several crew members, awakened by the ship to undertake the mission, and 900,000 sleeping passengers. Among the crew is Loren Lorenson, a young engineer, and Moses Kaldor, an eminent and wise counsellor.
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  5. #4  
    Forum Radioactive Isotope skeptic's Avatar
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    Nice reply, Janus

    Thank you for that.
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  6. #5  
    Forum Professor astromark's Avatar
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    So the answer is NO.. shielding and methods of shielding can be employed to assert safety at interstellar velocities..
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  7. #6  
    Forum Bachelors Degree GoldenRatio's Avatar
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    No. However once you get up to about the size of a small pebble, you might need to worry. Not really a ship "vaporizer" but certainly enough to punch a hole through most matter & cause hull breeches, assuming we do not have some sort of shielding.
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  8. #7  
    Forum Radioactive Isotope skeptic's Avatar
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    To GR

    How dense is the material of that size? What are the odds of our starship actually hitting one?
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  9. #8  
    Forum Bachelors Degree GoldenRatio's Avatar
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    Quote Originally Posted by skeptic View Post
    To GR

    How dense is the material of that size? What are the odds of our starship actually hitting one?
    on a trip to alpha centauri, the density will vary much like all meteoroid's floating around out there. If its just a bunch of dust that has clumped together its not going to be very dense & will likely just splash around the spaceship upon impact like it was a large droplet of water. If however say two asteroids crashed together and particles broke off I would say its very dense & would behave more like a bullet whizzing through the cockpit. Odds are probably the same on which you will find, both exist in more or less equal quantity.

    As far as the odds of your starship colliding into one, well consider that earth is bombarded by millions of meteor's daily on a fixed orbit ranging in size normally from a grain of sand to the size of a quarter (sometimes bigger but bigger it gets, the more rare it is). Now of course, earth is much larger than a spaceship & does have some gravitational influence over nearby meteoroid so acts like a cosmic vacuum cleaner, still. It does help illustrate how much clutter is.

    I would personally say odds are low you are going to run into anything, even when passing through the oort cloud given mostly to the size of the spaceship. However, a 4 LY trek is a long one with many opportunity's for bad fortune to rear its ugly head & given that you are traveling at 0.1C you dont want to strike anything big. Plus, that adds to the question "is this a one time trip, or are we going to be traveling it on a regular basis?"

    Odds are low we are going to be struck by a planet killer tomorrow, but it has happened in the past & will happen in the future. Its just a matter of time
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  10. #9  
    Forum Radioactive Isotope skeptic's Avatar
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    To GR

    For your info.

    Most of the material striking the Earth has an origin within the ecliptic of our solar system. The density drops off very, very dramatically when you leave the ecliptic. Both asteroid belt and Kuiper Belt are pretty much confined to the ecliptic.

    Now if you were sending a starship to Alpha Centauri, you need to remember that the direct course is almost at right angles to the ecliptic. In other words, our vessel will leave the zone of maximum density quite rapidly. Within a few million klms, it will be travelling well away from the 'high' density region of dust and gas. The only real risk zone would be the Oort Cloud, and it is probable that even there, the density of dust and gas would be very, very low.

    As far as striking a pebble or something larger, I would guess that the odds against it are enormous, but I would appreciate comments on that risk.
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  11. #10  
    Forum Bachelors Degree GoldenRatio's Avatar
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    of course. I agree density would be low. Density would be low even in the astroid or kuiper belt (i know we are traveling at right angles, but the density is still low) If you can slow your ship down when traveling through high density area's your chances of success increases. There is also the question of what you are going to find when you reach alpha centauri, What is there inner solar system like. Are you going to be going through a rich area of high density objects? How far in are you intending to travel? I agree completly, the chances of striking anything above the size of a popcorn kernel is small but the risk is there.
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  12. #11  
    Forum Radioactive Isotope skeptic's Avatar
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    Of course, no such journey will be possible for hundreds of years from now. I tend to suspect that, by then, humanity will have incredible spectroscopic telescopes, and we will have a pretty damn good idea what we will find at Alpha Centauri. My guess is a bunch of planets, plus comets, asteroids etc. I also guess there will be no Earth like planets. These are only guesses, and I could well be wrong, but by then our descendants will know.

    I would also suspect that, by that time, it will be possible to build habitats on Mars like planets, or even Ganymede like moons. A full life would be possible for our colonists on whatever bodies exist in the Alpha Centauri triple star system.
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  13. #12  
    Forum Bachelors Degree GoldenRatio's Avatar
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    I rather go to wolf 359. Maybe I will see some borg
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