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Post by ♫Moonbane♫ on Mar 16, 2011 0:28:46 GMT -5
Lol. Sry 'bout that. I think I need a newer version of Hypercam or something. I used that to actually get smoother video to get it paused there easier. Y'know?
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Post by HellstormOP on Mar 16, 2011 0:31:08 GMT -5
Hmm... One datail is interesting, though. For what do Night Furies need retractable teeth? Toothless didn't retract his teeth in this pic while shooting a fireball, maybe they don't need to be retracted, except for better aiming at long range shots? Or make they the fireball explode after a few meters, like in the movie (when not retracted)?
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Post by ♫Moonbane♫ on Mar 16, 2011 0:33:23 GMT -5
Why do I have the feeling it's like the moray eel's second set of jaws. Help eating, or something?
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Post by HellstormOP on Mar 16, 2011 18:03:25 GMT -5
Well, it also could just be a useless feature, so that the designers could name the dragon Toothless. Giving the powerful Night Fury no teeth at all, would be ridiculous, so I think they decided to at least make the teeth retractable, to give Hiccup a reason naming it Toothless.
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Post by Sunny on Mar 17, 2011 6:18:26 GMT -5
Yeah, but maybe they retract from different types of fire. Like when he shoots a fire ball the dont go in because its precise but when he breathes continous fire like when he warms up the ground they do retract.
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Post by HellstormOP on Mar 17, 2011 11:52:37 GMT -5
Or reverse: Not retracting the teeth makes the fireball explode shortly afer being released, because the teeth change its shape and allow it to expand/fragment/better burn with the surrounding air/whatever. Maybe also retracting them protect them from LONG jets of fire, like you said. But for really big, powerful and accurate blasts, they need to be retracted, to protect the teeth and to ensure an accurate hit. Spontaneous blasts are small enough to not affect the teeth.
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Post by HellstormOP on Mar 17, 2011 16:41:46 GMT -5
Another step to the solution: I took a screenshot where you can clearly see that the fire is a ball of something which seems at least semi-solid, but definitely not made of gas or even plasma. I'll upload it soon. I also noticed that you get that very bright white-blue light only when Toothless shoots it, and then again on explosion. Which again leads me to the thought, that only the surface really burns with an acetylene-oxygen flame (especially at launching, because it gets heated up with a such flame), while the actual ball is a semi-solid. ALso this could explain a major part of the destructive power - Night Furies really pick up some speed while dive-bombing, and a such big ball of a semi-solid will definitely cause some destruction on impact, when it hits its targets at that velocity. The way how the command tower collapses confirms this - the stones get pushed away to one side, like at the impact of a cannon ball. A really powerful explosion would send them flying in all directions.
One of the few questions not answered yet is why the ball explodes at all - and where all the oxygen comes from in the moment of the explosion. Air contains not enough of it, and an acetylene-air fire is usually yellow and sooty. Anyone got ideas?
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Post by toothless11 on Mar 26, 2011 12:55:34 GMT -5
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Post by HellstormOP on Mar 27, 2011 6:07:24 GMT -5
THX for the pics!
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Post by Serimon on Apr 26, 2011 10:09:11 GMT -5
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Post by HellstormOP on Apr 30, 2011 11:55:06 GMT -5
Thank you very much for that pics, that is exactly what I looked for!
BTW: That purple color looks like a potassium flame, maybe Night Furies use some type of acetylene-based mixture similar to black powder? And that explains the explosive effect?
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Post by HellstormOP on Aug 11, 2011 14:16:19 GMT -5
OK, since nobody has an idea how that Night Fury fire might work, I will sum up my thoughts:
The official site describes the fire as "unconventional", "a semi-solid mass", "alight with an acetylene-oxygen flame", "explodes its target on impact".
Unconventional? Of course, no other dragon in the movie has a flame which produces a such powerful explosion (Well, the Zippleback can also make very strong explosions by mixing flammable gas with air, but that is limited in range, of course. A Night Fury can blast its target from longer ranges, like with a grenade, while the Zippleback has to move close to its victim, like planting a bomb.). Although it may also mean that the other dragons use well-known or at least relatively simple principes to breathe fire, while Night Furies use a concept which most of us don't understand - maybe not even the movie designers. The fact that the mass has to be semi-solid is clear once you thik about that the Night Fury has to be able to form it into a ball which it then fires - and at the same time, the ball has to fly all the way to the target without dispersing in the air, which excludes liquids, gases and powdered substances.
Next point: the acetylene-oxygen flame. Well, that may have several meanings. The fireball itself could burn with a such flame during the flight to the target, in this case it would have to consist of something which can hold (dissolve) acetylene and release it again under the right conditions. Acetone, for example. Also, there needs to be an oxidizer in the mass, because otherwise it would burn with a sooty, yellow flame, and won't keep burning during flight. (Since I have a quite scientific and a bit nerdy mind, somewhat similar to Hiccup from the movie, I've made a few experiments. The conclusion is, that a semi-solid mass, consisting of acetone, jellied with silicon dioxide and containing about 2-2,5% acetylene dissolved in it (That's the maximum concentration under normal pressure and temperature. Sounds quite low, but that are 27 liters of acetylene gas in 1 liter of acetone), will firstly burn with a yellow acetylene flame, until all the acetylene is gone. Then, the acetone will catch fire and burn with a blue flame (yellow at the top), which is hardly visible at day. When I threw the burning mass on the ground, it stopped to burn during flight and also didn't explode, not even close to that.) Potassium nitrate is a good candidate for this, since it would also explain the flame color. (I didn't try that out yet, but that may come as soon as I can get some.) The biggest problem is that the mass has to be shock-sensitive, at least when it's on fire, and at the same time shouldn't explode just from setting it alight.
On the other hand, "alight" could also mean "set alight". This may explain why Night Furies can also use a steady acetylene-oxygen flame, and the gas gathering in the scene where Toothless defeats Stoick. In that case, the mass could comprise something completely different, and we still had to find out how the mass can explode.
However, the screenshots leave only one conclusion possible: the mass contains a lot of a flammable liquid which will burn/explode with a BLUE flame when vaporized or dispersed in air or mixed with oxygen (which may also be released from oxidizers like potassium nitrate). Acetone burns with a such flame (it has a yellow tip, but vaporized acetone will burn or deflagrate completely blue). Additionally, you can see in the movie that the indigo blue part of the blast is only visible at night or under poor lighting. Blue flames from alcohol or acetone behave exactly that way.
You can see in the movie, that when Toothless fires a blast at day when the sun shines, only a smaller ring of fire is visible which is rather violet. This may result from an acetylene combustion with enough or too much oxygen, as well as be the flame color of potassium nitrate. Most likely, both effects occur, as potassium nitrate provides additional oxygen for a complete combustion of the acetylene, preventing it from burning with a yellow flame. Also it has a flame color which fits very well to what you see in the movie.
OK, after analyzing the flame color, we can get close to the most difficult part: the question why the Night Fury's blast is actually explosive. There are a few effects which are possibly responsible for the explosivity of Night Fury fire. The first effect is the inherent instability and explosivity of acetylene gas, even without oxygen. It tends to decompose when exposed to heating, shock and (sometimes) overpressure. When the gas is stored below 1.5 bar relative to atmospheric pressure (IDK how to convert it in psi) with no presence of oxygen, the decomposition won't propagate far away from the point where it was triggered. That means that there won't be an explosion. However, if it's stored ABOVE this critical pressure, the decomposition can occur in the whole flask, causing an explosion. Dissolving the acetylene in acetone stabilizes it, making save storage possible even at higher pressures. My theory is: the semi-solid mass contains dissolved acetylene under high pressure, as well as potassium nitrate or something like this. It gets lit with an acetylene-air flame. During the flight of the fireball, the semi-solid properties of the mass prevent the gas from escaping explosively and the solvent from dispersing in a large fireball. On impact, the mass is splashed around and becomes more of a liquid (like ketchup: as long it's in the bottle, it's semi-solid and you hardly can get it out there. You hit the bottom of the bottle with your hand, and the ketchup becomes really liquid and you have half of the bottle on your plate) and allows the acetylene to escape. The acetylene now disperses the highly flammable solvent in the air, and also burns with the air and the oxygen from the potassium nitrate. Part of it decomposes explosively, forming soot and hydrogen gas. All this reactions cause a kind of a thermobaric explosion, and burning vaporized acetone splashes away from its center in the form of a burning ring of blue mist.
However, I have big concerns that it still won't work in reality, as the lack of oxygen (and acetylene needs very much oxygen) as well as the formed soot will rather cause a yellow flame from the beginning.
COMING SOON: Reports from more conducted experiments.
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Post by HellstormOP on Aug 11, 2011 16:19:17 GMT -5
Up... UP..... UPDATE!
I've found out that silica is not a good jellying agent for our purposes. It rather yields a dry mash than a semi-solid mass. Also, when you mix approx. 7 - 11 grams of acetone (can't tell it exactly, it evaporated so fast I had to refill it one time without measuring it out) with 0.6 grams silica (as a jellying agent) and 2.6 grams of finely ground potassium nitrate (I left the acetylene out this time as I didn't have the gear to produce & add it), the flame will be still yellow with only low flame coloration or fast oxygen delivery from the nitrate (even if the nitrate releases oxygen, the combustion apparently will speed up so much that the flame will still be yellow). I blame the jellying agent for the failure ( I expected a cleaner blue flame due to the added nitrate as an additional oxygen source).
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Post by HellstormOP on Aug 12, 2011 15:31:05 GMT -5
UPDATE:
Afer all, silica may be a good jellying agent for the project. But I've found another problem: The burning acetone does not heat up the potassium nitrate enough to release its oxygen and boost the combustion. As the spoon which I've used to put the mass on the ground accidentally caught fire, I noticed that the stuff was burning much more rapidly and cleanly (I held the spoon vertically, so the flame heated up the mass above it). I guess I will need to grind the nitrate finer to achieve better results. Also, the silica holds the mass in shape while it is burning, so that a solid, slow burning ball is formed. I guess I will need a polymer-based thickener which will burn off or melt during combustion, to avoid this effect. (Nitrocellulose would be fine for this, but firstly I dont want to make it too complicated and expensive and secondly it combusts with a yellow flame, which could be changed by the added nitrate.)
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Post by HellstormOP on Aug 12, 2011 15:31:56 GMT -5
BTW: Feel free to post your ideas on how that fire might work! I highly appreciate any contribution.
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