Question about bows/ballista for a fantasy story?

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Lord Revan
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Question about bows/ballista for a fantasy story?

Post by Lord Revan »

First off I aplogize if this seems more like something that's suited for fanfics forum. However there was something I was thinking about for an orginal universe story I'm writing. What would happen if someone used a heavy siege crossbow or a ballista on a large(ish) (about 190cm or so) human sized target wearing plate armor, assuming the plate doesn't get penetrated, dented or thrown thru the body of the person wearing it due to magic. Yes I'm being quite vague but I don't quite have the exact scene in my mind yet and I'm doing fact check atm.
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Re: Question about bows/ballista for a fantasy story?

Post by Batman »

Unless the armour's magic includes inertial compensation, we have one dead wearer. It's Stormtrooper armour against KE/momentum attacks writ large.
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Re: Question about bows/ballista for a fantasy story?

Post by Zixinus »

My first guess would be Newton's laws take effect: you just thrown a large chunk of wood at someone at high speed. Momentum transfers. Momentum transfers, the energy of the bolt sinking into the target, throwing them forward while providing tearing forces. At the minimum, fall over and get some bruises (any real, decent armor has padding underneath the metal). Comparable to a horse-kick. At most, lots of bones get broken all at once, joints are torn all over the place and the person is either out of the fight or just dies from massive collective trauma.
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Re: Question about bows/ballista for a fantasy story?

Post by SpottedKitty »

One of the late Sir Terry Pratchett's characters in Discworld is a troll who used a siege crossbow as a hand-held weapon. He modified it to fire bundles of ordinary wooden crossbow bolts. He called it the "Piecemaker", which should answer your question nicely.

Actually, I don't think the damage would reach the "chunky salsa" level, but I'd be very surprised if a direct hit didn't have a pretty good chance of an instant kill.
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Re: Question about bows/ballista for a fantasy story?

Post by Napoleon the Clown »

Lord Revan wrote:First off I aplogize if this seems more like something that's suited for fanfics forum. However there was something I was thinking about for an orginal universe story I'm writing. What would happen if someone used a heavy siege crossbow or a ballista on a large(ish) (about 190cm or so) human sized target wearing plate armor, assuming the plate doesn't get penetrated, dented or thrown thru the body of the person wearing it due to magic. Yes I'm being quite vague but I don't quite have the exact scene in my mind yet and I'm doing fact check atm.
Is the magic able to do something about the momentum? If not, see Batman's response. Look at clay tests for when body armor is rated against various weapons. Even if the bullet is stopped, the clay can undergo only so much deformation before the armor is rated as failing to deal with that particular round. Just because the projectile's motion ceases doesn't mean the energy it contained goes away. That energy still ends up all going into the target, it's just a question of if you can spread it out enough to not still royally fuck up the target. Getting hit by a fairly typical handgun while wearing body armor has been compared to taking a 90 mph fastball to the ribs. It's still gonna hurt like a motherfucker, and it can still break bones. And it will almost definitely cause significant bruising.

Remember, a ballista is a goddamn siege weapon. A crossbow is more easily reduced to non-lethal status, though. Still could ruin the hell out of your day, though.

Newton's laws are pretty unforgiving.
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Re: Question about bows/ballista for a fantasy story?

Post by LadyTevar »



As you see, that is with a hollow plastic tube, a tennis ball, and ducttape, and it knocked the fighter on his ass when it hit him in the head.
Make the bolt a solid shaft of wood or iron, add a metal head that won't deform and absorb some of the momentum, and you're gonna give a warrior a Bad Day.
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Re: Question about bows/ballista for a fantasy story?

Post by Sea Skimmer »

If magic prevents the armor from being affected in any logical manner, even so much as entire plates moving, then logically the user should be totally unaffected too. Certainly that would not require more magic then you're already employing, and magic is magic. Otherwise skin and bone are going to crush before the plate armor can compress the user enough to launch them backwards to death.
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Re: Question about bows/ballista for a fantasy story?

Post by Lord Revan »

The target isn't a human but a super naturally durable creature, though he's only though not able to ignore the laws of physics.
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Re: Question about bows/ballista for a fantasy story?

Post by Elheru Aran »

*Tough.

And just treat it as a heavy impact, then. But if there's any kind of decent tip (perhaps magic-alloy?) on there, that could conceivably hole it. How much is the question, depends on how tough its skin/natural armour/plot-armour is.
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Re: Question about bows/ballista for a fantasy story?

Post by Lord Revan »

true enough but that's a worry for another time as I'm nowhere close to getting into that part yet (at least if I plan to use it where my orginal intention is)
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Re: Question about bows/ballista for a fantasy story?

Post by Elheru Aran »

Basically just compare it to hunting a large animal like an elephant or rhino, and that should give you a decent parallel. Rhinos in particular can be very tough.
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Re: Question about bows/ballista for a fantasy story?

Post by Khaat »

Well, in Who's Afraid of Beowulf [Tom Holt], the magic armor negated the (modern) weapons' effects entirely (the vikings were picking bullets out of their beards like fleas.)
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Re: Question about bows/ballista for a fantasy story?

Post by Sea Skimmer »

Lord Revan wrote:The target isn't a human but a super naturally durable creature, though he's only though not able to ignore the laws of physics.
Then how big a bolt do you really mean?

Also one way to deal with high momentum attacks is to have an energy shield that actually deflects the hit instead of stopping it. Then your threshold to be badly hurt could rise considerably without negating the forces out of existence. But that requires some kind of active sensing on the part of the shield to form the required barrier shape, or else magic 'infinite' type armor slope effect. That's how my fiction works in general, but it's not very typical of sci fi.
Elheru Aran wrote:Basically just compare it to hunting a large animal like an elephant or rhino, and that should give you a decent parallel. Rhinos in particular can be very tough.
Cape Buffalo too. But both are also just physically very big compared to typical hunting cartridges, or thrown spears, which means a narrow damage path weapon can just fail to hit anything vital hard enough. A massive shock effect, from say armor displaced by a bolt hitting it, is a bit difference, since it's going to affect a wide area out of hand. So a less then fatal wound can stun or cripple easier.
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