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So if you remember my dragons:

  1. They aren't that big (roughly a shire horse in size, but a longer neck and a tail)
  2. They use graphene in their bodies, which might or might not explain how they fly
  3. They have additional player classes and levels, but that's against vehicles and the Terminator.

So, dragons use their breath attacks as a ranged weapon,

  1. They can shoot far (~50 meters)
  2. The liquid, they shoot, remains a thin stream and doesn't lose cohesion until connecting with the target.
  3. They should be able to aim precisely.

How could they propel their breath attacks, given these criteria?

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    $\begingroup$ I have one word for you... just one word... Llamas. $\endgroup$ – JBH May 12 at 1:18
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They just need for the liquid to have a very high surface tension or even be slightly gelatinous (like napalm, which was developed for the same needs you have).

Then they can employ a relatively simple two-chamber mechanism, with a larger reservoir chamber where the liquid accumulates, and a smaller chamber with muscle walls and a sphincter to shoot the liquid.

Having the liquid catch fire at a small distance from the mouth protects the dragon from the fire (they simply need to shoot the liquid faster than its flame speed, and stop the jet at once without slowing it down; hence the two-chamber mechanism). The dragons might do that through electric discharges from the teeth, for example, or by quickly sparking together their fangs (they'd need to be made of, or covered with, some suitable substance, like flintstone).

To attack, the dragon opens the sphincter between the fuel reservoir and the shooting chamber, enlarging the latter. The depression pumps the fuel out of the reservoir. Then the sphincter serrates and the muscles begin to tighten, greatly increasing the pressure in the shooting chamber. The release sphincter at the opposite end opens, and a short cartilagineous duct drives the liquid outside, past the larynx and the mouth. The teeth smash together giving off sparks that ignite the jet, exactly like a flamethrower.

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  • $\begingroup$ The operating pressure of the air tank on an M2 Flamethrower, {PDF}, is about 2000 psi, effective range: 20–40 meters. That's the question imo: How are dragons capable of producing 2k psi or more? $\endgroup$ – Mazura May 12 at 4:57
  • $\begingroup$ @Mazura, the obvious answer is "muscles", possibly with a skeletal structure to give a mechanical advantage. But you could be creative and inject water and something that reacts exothermically with the napalm to create pressure, sort of like what bombardier beetles do. $\endgroup$ – Mark May 12 at 21:23
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You want napalm.

enter image description here

The substance which gives it its name - it's made of aluminum naphthenate and aluminium palmitate - serves as a thickening agent. This allows it to stick to surfaces, part of what made it so successful, but also means that it maintains a fairly cohesive spray.

As you can see in the picture, napalm can do all the things you specify. It can be sprayed dozens of metres, with decent precision, and doesn't dissipate into droplets but remains in a steady jet.

See the top answer here - Napalm-Breathing Dragon - for how to make that work biologically.

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    $\begingroup$ Noice, +1. How do I shoot it fast enough to hit targets 50 meters away? $\endgroup$ – Mephistopheles May 11 at 22:02
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    $\begingroup$ That boat is shooting 50m, easily. $\endgroup$ – Harper May 12 at 0:41
  • $\begingroup$ @Harper Yeah, I typed this on my phone so I couldn't see the picture while I was writing. I said "dozens" rather than 50 just in case. $\endgroup$ – SealBoi May 12 at 11:30
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    $\begingroup$ @Mephistopheles You could look at archerfish and spitting cobras - they can spray fluid for large distances relative to their body size. I'll look into it some more and get back to you. $\endgroup$ – SealBoi May 12 at 11:31
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Add long polymers.

slippery water https://www.fireengineering.com/articles/print/volume-122/issue-9/features/slippery-water-cuts-friction-loss.html

The long polymers reduce friction of the water and also make it more cohesive. A fire hose can shoot farther starting with the same water pressure. When I learned about this I learned that it enabled NY firefighters on the ground to shoot water into higher windows than had previously been possible.

Tests of “slippery water” by the New York Fire Department indicate that friction losses need not continue to limit flows through 1 1/2-inch hose to the extent that they now do. Slippery water is made either by educting an additive into a hose line or by putting the additive into a booster tank.

At a public demonstration in May, two NYFD pumpers each supplied a 1 1/2-inch line with the same engine pressure. The line with the slippery water had a flow rate 50 percent higher than the plain water line and a reach that was 40 to 50 percent better, according to the department report. Also, the nozzle pressure on the slippery water line was double that of the plain water line.

Slippery water consists of an extremely dilute solution of high molecular weight, straight-chain polymer in water. The polymer is polyethylene oxide which Union Carbide, the sole producer, has trademarked as Polyox. Only 30 pounds of Polyox are enough to make “slippery” one million pounds of water (about 120,000 gallons).

Your long polymers would be something soluble in whatever the dragon breath was. Biology makes lots of long polymers - bacteria make dextran and we make mucopolysaccharides. For a good dragon breathy hydrophobic liquid like turpentine, I wonder if a long alkane could serve in this role. I wonder if you could test it with a syringe? I am pretty sure I have seen the hose distance effect of polyox demonstrated with a syringe.

For those wanting to get into the weeds with the physics behind how this works: https://www.nytimes.com/1988/01/12/science/slippery-water-mystery-seems-finally-solved.html

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    $\begingroup$ There's now an entire class of chemicals called friction reducers for this task. A common prank in oil & gas work is to convince the new guy that washing his hands with it will help degrease. $\endgroup$ – chrylis -on strike- May 12 at 5:55
  • $\begingroup$ @chrylis - okay, I have to ask. What happens? $\endgroup$ – Stilez May 12 at 7:38
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    $\begingroup$ @Stilez They can't hold on to anything for about 6 hours. $\endgroup$ – chrylis -on strike- May 12 at 7:44
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    $\begingroup$ That's evil. Do you have a video, or known a link to one? $\endgroup$ – Stilez May 12 at 14:46
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    $\begingroup$ @Stilez I'm afraid not. Among other things, playing with your phone in O&G work environments is a good way to get a new phone. $\endgroup$ – chrylis -on strike- May 13 at 16:59

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