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Thread: Detection of submarines via gravity detecting satellite?

  1. #1 Detection of submarines via gravity detecting satellite? 
    New Member
    Join Date
    Mar 2009
    I have a question for you, and would appreciate your feedback….

    Would a large military submarine, whilst travelling below the sea surface, affect the Earth's geoid, enabling an extremely sensitive satellite based gradiometer, to detect the anomaly caused by a submarine, in comparison to a high-resolution reference map of the geoid?

    The submarine would most probably be at neutral buoyancy, with depth adjusted via its control surfaces.

    Rune Floberghagen, Esa's GOCE (Gravity field and steady-state Ocean Circulation Explorer satellite) mission manager explained the sensitivity of GOCE as follows: "Imagine a snowflake, which has a fraction of a gram, slowly falling down on to the deck of a super tanker. The acceleration that the super tanker experiences from that snowflake is comparable to the sensitivity of our instrument"

    Whilst the overall structure of the submarine would be neutral in buoyancy, there would be a large internal volume where the water will be 100% displaced by air, and thus have almost nil mass in comparison to the water surrounding it.

    What do you think?

    We still do not know one thousandth of one percent of what nature has revealed to us.
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  3. #2  
    Join Date
    Jan 2008
    How does a snowflake falling vertically onto a supertanker cause an acceleration of the vessel? -- It does not, I think Planck might be violated here,,,

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  4. #3  
    Forum Sophomore
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    Jan 2009
    USA, VA
    actually it might, but you wouldnt notice it because of earth's gravity and reletivity. there are just so many greater forces acting on the ship that the snowflake just doesnt even factor in.

    as for detecting gravitational anomalies from space. boy, were to start.
    1. the meter could be thrown off by even the tinyest bits of space debris
    2. there are other things in the ocean. not just submarines
    3. it could even be thrown off by larger than normal waves

    it might work, i really dont know much about it, but there are just so many different factors that would affect gravity in any particular spot. hell, i'd venture a guess and say that perhaps even higher/lower air pressures could throw it off...
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  5. #4  
    Forum Masters Degree Numsgil's Avatar
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    Jan 2009
    I'm not totally convinced that gradiometry can tell the difference between an object the size of a submarine with the same mass and volume as water(same mass and volume is why it's neutrally bouyant), and water. Doesn't it work by taking essentially a vertical sampling? It can't (as far as I know) differentiate between anything in that vertical sample. Like it can't tell the difference between the water at the top of the sample and the mantle for the other 99% of the sample. It just knows that that vertical sample has mass X.

    A better method might be to look for something with a changing and moving gradiometric signature. Like suddenly the sea has a spot that's less massive than reference scans and that spot is moving (submarine is moving and rising in the water), or more dense that water.

    Also you'd need a fair amount of processing power to do it in real time, I think. And obviously the sensitivity of the equipment needed is staggering. But the tech might also have non military purposes, like tracking schools of fish or whales or such.
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