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Thought problem: torpedo with a drill

  1. Mar 14, 2015 #1
    Earlier today I was reading Battle for the Abyss (one of the Warhammer 40,000 novels) and a battle was described between two spaceships where the villains used torpedoes described as "Unguided and slow, but still dangerous because they were tipped with drill heads" so that they could bore through the target's hull.

    Now, neglecting the parts of the story that are obviously outside of the realm of reality (ie spaceship battles), would such a weapon actually be of any use?

    I assume that how it works is that the torpedo reaches the surface of the target and then drills in. But that causes a problem: wouldn't the torpedo's body just start spinning around with the drill bit stuck in the target? In order for it to drill in, it doesn't just need force behind it, but also needs force holding the body in place so that the torque of the drill's motor spins the drill bit rather than the torpedo's body. But this is in space, so it doesn't have that, and it would just harmlessly spin itself around while sticking to its target's armor because equal and opposite reaction would mean that the torque of the armor on the drill bit is equal to the drill's motor's torque.

    Or, am I just thinking about this the wrong way, and enough force behind the drill bit while it spins (from the torpedo's motor) will still make it able to bore into the target?

    Alternatively, the designers of this exotic weapon could make it so that the missile penetrates the target by way of its kinetic energy (neglecting the point that if you're able to do that you likely don't need the drill bit) and then starts drilling. But wouldn't you then run into the same problem? Instead of spinning around harmlessly outside the target, it now just starts spinning inside the hole it made.

    tl;dr: Would putting a drill bit at the tip of a missile confer any benefit to its ability to penetrate its target?
  2. jcsd
  3. Mar 14, 2015 #2


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    It confers no benefit if the missile is able to penetrate the armor via other means. If not, then maybe. But that's all sci-fi mumbo jumbo anyways. In the far future who knows what kinds of technology they'll have. Besides, I could imagine some means of keeping the missile from simply spinning in space. Perhaps it has some kind of mechanism that grabs onto the hull and keeps the missile from spinning.
  4. Mar 14, 2015 #3


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    It could work if you had some sharp tips away from the drill axis that penetrate the wall, and then prevent the torpedo from rotating.
  5. Mar 14, 2015 #4


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    Warhammer 40k is more fantasy than sci-fi. It's less about futuristic prediction and more about style, which has a steampunk component to it.
  6. Mar 14, 2015 #5
    One could have a bunch of these, well similar, on the torpedo head, with the spindles revolving in alternate directions to bore a hole right into the ship.
  7. Mar 14, 2015 #6


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    I use sci-fi in the most general way. I realize it's about as sci-fi as star wars is.
  8. Mar 14, 2015 #7


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    I would be more concerned about how slow, vulnerable and impractical such a weapon is in general.

    How much must it slow down so as not to disintegrate its own mechanical parts upon contact with the hull?
    How long does it take to drill through a hull? How hard can it be to simply sweep away (or blow away) torps that are sitting on the hull like bugs on a windshield?
    What makes the hull so strong that all that initial velocity is not enough to have it penetrate with a pointy torp?

    I know these sound like nitpicks, but I think it's really more a matter of just how impractical such a device would be compared with the elegance of kinetic energy combined with explosives.

    But that's not in the spirit of the genre.
  9. Mar 17, 2015 #8


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    It would try to but there is no reason why the torpedo can't attach itself to the target before starting to drill.

    PS: This is exactly how the Philae probe was going to do it.
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