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HellstormOP
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"How to train your dragon" - Fire of a Night Fury in reality?
Hi,
as you can see from the title, this thread is about an effect from the animation movie "How to train your dragon". A few of you surely already know
that movie, the others should watch it - it's awesome^^. The question I want to ask now is whether the fire of a particular dragon there - the "Night
Fury" - might actually work in reality (without looking at the biological side of the matter) and if yes, in which way. I've already asked this
question in several other boards - an English fan board for this movie, a German board about explosives and pyrotechnics, and another German board
about chemical experiments (versuchschemie.de). The first two boards could not help me, the users in the third one flamed in my thread until it was
closed.
I hope I will find both competence and acceptance for my project in this board.
My goal is firstly to find out the working mechanism of that fire (not the way the movie designers animated it, but the way how they intended it to
work if it was real - all the other ways how the dragons breathe fire in this movie are simple and well-known concepts, only this one isn't), secondly
to adapt it to reality (this include conducting experiments) and finally to fully recreate it - all that without deviating from the official
information about the movie! I've already worked a lot on this project, including some experiments. Here is the link to the thread in the movie's fan
board where you can find my thoughts about it until now:
http://howtotrainyourdragon.proboards.com/index.cgi?action=d...
I will write a new summary of both the analysis of the movie and the experiments I did soon. For now, feel free to post your own ideas.
[Edited on 13-8-2011 by HellstormOP]
[Edited on 13-8-2011 by HellstormOP]
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Nicodem
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Thread Moved
13-8-2011 at 11:57 |
HellstormOP
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OK, let's start with the details from the movie and the official website:
- The official website describes it as an "unconventional fire, a semi-solid mass, alight with an acetylene-oxygen flame, explodes its target on
impact".
- As you can see in the movie, the fire of this dragon has a decent range, without forming a fireball until impact. Therefore, it absolutely makes
sense that the fire consists of a semi-solid - liquids, gases and powdered substances would quickly disperse and burn off in a fireball before
reaching the target. On the other hand, a dragon like the Night Fury would be unable to fire a solid projectile (i. e. a grenade), as at least a
barrel would be needed for it (not to mention the internal "magazine" and "loading mechanism"...) At one point in the movie, one can see a Night Fury
"regurgitate" something before firing a small blast. This confirms the official semi-solid-mass theory and proves the movie designers actually thought
about a possible principle for the fire, instead of playing around with "ball lightning" or "energy ball" effects and throwing some science in.
- "Alight with an acetylene-oxygen flame" could have two meanings: either that acetylene is only used to set the mass alight - or that actually the
mass burns with a such flame during the flight to the target. I believe in latter, as firstly acetylene is a powerful explosive under the right
conditions, secondly that would explain why the fire doesn't go out at that high velocities, and thirdly the way like it explodes (a blue-white burst
and then a big, yellow, sooty fireball with blue-violet rings splashing away from it) fits to acetylene dissolved in something, I think.
- The explosion seems to be pretty powerful, so powerful that one blast (I guess they fire about 0,5 - 1 liter of flaming mass per blast) can crush a
catapult tower made of stone. Also, the Vikings in the movie always get in cover when they notice that dragon, so I think they fear the shockwave. But
I also think, that since the Night Fury is a kind of a dive bomber, the kinetic energy of the semi-solid contributes to its destructive potential.
- As a conclusion, I think Night Furies fire a mass which consists of acetone (burns with a blue flame with a small yellow tip and can hold a lot of
acetylene) , which holds dissolved acetylene under increased pressure. The acetone is thickened with some kind of a shear-thinning or thixotropic
thickener (would explain the semi-solid properties) and maybe also contains very fine potassium nitrate crystals (they provide additional oxygen,
which makes the fire more likely to stay burning during flight, also the explosive power gets boosted, the potassium contributes to the violet flame
color, and to the thixotropic properties). As you can see in the movie, they can also use a steady acetylene flame. I guess, in reality there would be
a kind of "second stomach", which holds the mass and acetylene gas under pressure. This would explain the "regurgitation", as well as the ability to
breathe a steady flame.
Some other details will follow soon, when I've watched the movie and gone through the screenshots another time.
Anyone has other ideas?
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HellstormOP
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Does nobody have got ideas yet?
[Edited on 14-8-2011 by HellstormOP]
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hissingnoise
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I'm sure there are several dragon-trainers mulling over 'whatever you're on about' as we squeak . . .
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HellstormOP
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What?
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Norrys
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| Quote: |
On the other hand, a dragon like the Night Fury would be unable to fire a solid projectile (i. e. a grenade), as at least a barrel would be needed for
it (not to mention the internal "magazine" and "loading mechanism"...) |
I think there is no reason to assume, that a hard body could be spewn worse than a fluid projectile (for example you can spew your spittle not
farther, than a cherry stone or something like that). Also a magazine-like mechanism and organic shells are nothing unusual, think about eggs. So
maybe the fireball could turn out to be in fact a solid shell coated in some blue burning goo.
| Quote: |
This confirms the official semi-solid-mass theory and proves the movie designers actually thought about a possible principle for the fire, instead of
playing around with "ball lightning" or "energy ball" effects and throwing some science in. |
No, it confirms nothing, maybe those who made the visual effects didn't even write the explanation. Maybe the author even intended the dragon to be a
magical creature. Even if they thought about a mechanism to explain the semi solid acetylene-thing i doubt they used their ressources to do some
physical and chemical simulations or even practical experiments, which prove their theories.
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HellstormOP
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Hmm, I noticed that the whole concept of a semi-solid, explosive mass based on acetylene is quite a bit strange. Just imagine: You have a mass, most
likely consisting of acetone, thickened to a semi-solid consistence. This mass holds acetylene, most likely under (slight) overpressure (therefore, I
don't think that there are more than 5% acetylene in it). Then, a ball of the mass is fired by compressed air and ignited at the muzzle. It does
neither lose its shape nor the (blue burning) fire goes out, although flying with a velocity of up to 125 mph (200 kmh). As soon as it strikes a solid
surface, it explodes in a very powerful blast, and rings of blue-violet mist splash away from the impact spot. The explosion appears blue-white in the
first few milliseconds, but then a large, smoky, red-orange glowing fireball is formed.
Now the question is: Is that possible at all? When yes, which mechanisms and reactions are responsible for it?
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HellstormOP
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OK, I've calculated, that when a Night Fury fires a blast of 0,5 liters of flaming mass, and it maintains 29 psi overpressure in its organ (seems
biologically impossible, but almost all the dragons in the movie have biologically impossible attacks, including magnesium powder or eating rocks and
melting them to lava and firing them within a few minutes) , there would be 25 g of acetylene gas in this blast. This is almost equivalent to 1 mol.
Assuming it almost won't burn off during the flight, and it would all decompose at once as soon as it impacts, then we would have 227,4 kJ of thermal
energy released, as well as about 2 g of hydrogen gas - which would have a HUGE volume at this temperature! For a comparison: The same weight of RDX
(32 grams of an RDX-based plastic explosive are contained in a 40 mm grenade, so it's not a big difference) releases only around 140 kJ of thermal
energy at the explosion. So, maybe an explosive decomposition of acetylene packs enough punch to have such devastating power? But if yes, what the
heck causes the acetylene to not decompose at all when the fireball flies towards the target, and decompose all at once when it impacts?
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froot
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Here's a brain fart..
Determine the solubility of acetylene in various solvents. Alcohols, ketones and low melting waxes.
Pick one that can dissolve an appreciable amount of C2H2 under low enough pressure, has a low vapour pressure, higher boiling point and neutral pH.
Not even sure how close you can get to the ideal.
Mix in an oxygen source - 50% v/v H2O2 solution? *ducks*
Hopefully this won't affect C2H2 solutbility too badly.
You may need to add something to help catalyse O2 production.
Just don't store it.
We salute the improvement of the human genome by honoring those who remove themselves from it.
Of necessity, this honor is generally bestowed posthumously. - www.darwinawards.com |
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Bot0nist
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Don't go winning any Darwin awards, ok...
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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HellstormOP
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@frood: I rather thought about using extremely finely ground KNO3 (adding about 25%) as an oxygen source. Mixing H2O2 solution with acetone would
extremely decrease the solubility of acetylene in it. I will also add a thickening/thixotropy agent (currently silica, but I search for alternatives),
so that the KNO3 remains dispersed. For the first experiments, I thought to use a blowpipe with an attached ignitor (paper piece soaked in kerosene,
fixed on a long thick wire) to simulate a semi-solid blast being fired (with very low acetyleen contained), for latter experiments building a special
cannon (I will draw a plan of the cannon, scan and upload it here) for acetylene under overpressure.
@Bot0nist: I'm gonna wear a flame resistant Nomex version of the US Army ACU (already bought, was only 18€, which is about 25 bucks), don't worry!
Nomex will withstand 3500°F or 1900°C (temperature of acetylene burning in air) for 3 seconds without burns to the skin under it.
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froot
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The problem with using KNO3 is that the flashpoint of C2H2 is much too low and won't create the thermal impulse required instantly release the O2 from
the KNO3 regardless of how finely divided it is, and, the KNO3 now has the benign emulsifying agent to hide behind further slowing the progression of
the combustion. This is why a miscible O2 source would bring you closer to the ideal creating a homogenous mixture.
You want the mass to burn during flight while instantly consume itself apon impact - and maybe stuff around it.
Nitrocellulose dissolved in acetone with a ratio to achieve optimum viscosity comes to mind. Not blue but it might have a decent result. Maybe
nitromethane? I wonder if NC is at all soluble in NM, short of doing a search.
We salute the improvement of the human genome by honoring those who remove themselves from it.
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HellstormOP
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Hmm, on a weight basis the energy of decomposing C2H2 (likely to occur in the whole mass at impact when combined with the fact that it already burns,
I think) is higher than of exploding RDX - maybe THAT could bring the KNO3 to release O2?
I've already tried to use ping pong balls as a thickener, but unfortunately I've got some which aren't made of NC...
I will get some of them from another brand, maybe its gonna boost the combustion a bit.
As soon as I can get my hands on H2SO4 conc., I will also make my own NC, which may work best.
Unfortunately, I don't know which liquid or soluble oxygen source could be mixed with the acetone without decreasing the solubility of acetylene. I
guess I don't need to do much experiments which alcohol, ketone, etc... dissolves acetylene best - the industry seems to use acetone for a good
reason. And maybe, when the KNO3 is really damn finely powdered, the locally created energy by the decomposition of C2H2 is gonna make the KNO3 to
release its oxygen. Also it would add to thixotropy.
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gregxy
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You should probably forget about the C2H2. All you need is
something that burns and trying to keep a gas inside of a blob of anything is difficult. The blue/white glow looks "electric" and is more similar to
the energy weapons in other movies or "ball lightning".
There are lots of things that could form a burning blob, try checking out napalm literature. A blob that burns blue/white is difficult since it
implies a much higher temperature. To get that requires that a hydrocarbon be well mixed with oxygen. Or the use of something that burns hotter than
hydrocarbons like metals.
A blob that burns and detonates upon striking would be too unstable unless it contained some separate impact sensitive triggering device.
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HellstormOP
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Well, I actually neither want to deviate from the movie nor from the official information about it - and acetylene is mentioned in the official
information. I know that the ball is looking like ball lightning, but the theory of the "semi-solid mass" is logical and especially the yellow, sooty
fireball after the explosion looks like a typical product from acetylene burning/decomposition. I don't believe that the designers just played around
with energy effects, because the fire is very well made. You can even see small burning drops at some of the screenshots, as well as the fireball
leaving trails of blue-violet burning gas. Also the blue part of the mist is visible only at night and under poor lighting - that's exactly how blue
alcohol/acetone flames behave! The much smaller, violet part is also seen at sunny days, but at night it is dominated by the blue-white part. For me
that looks like if quite little acetylene (and maybe also a bit potassium nitrate) were mixed in quite a lot of acetone.
As a conclusion, I think that the movie designers have an at least partially profound concept for that type of dragon fire.
[Edited on 15-8-2011 by HellstormOP]
[Edited on 15-8-2011 by HellstormOP]
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Wizzard
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How about paintballs filled with /x/ and is violently flammable when in contact with air/nitrogen/oxygen/water?
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HellstormOP
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Well, the problem is, that I want the stuff to work without a case and with burning during flight. The idea with the paintball is more like a grenade,
which of course would be possible with far simpler methods.
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HellstormOP
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OK, here are some new results from the experiments I made:
Firstly, I prepared some sort of NC lacquer by dissolving 3 ping pong balls in 100 ml of acetone. Then, as soon as it was ready, I mixed 8.2 grams of
this lacquer with 2.4 grams of finely ground potassium nitrate (actually, I desired a 3:1 mix by weight, but since acetone evaporates very quickly,
this small excess of acetone is OK). The mix showed no thixotropic properties, I guess because the KNO3 was quite clumpy, probably from air moisture.
I poured some of the mixture on an ashtray and set it on fire. The mix burnt off with an orange flame without visible blue or violet parts (you hardly
see blue or violet flames at a bright sunny day anyway), but the orange part of the flame was substantially smaller than I expected from a NC/acetone
mix. It also burnt off much faster and with a less orange flame than a similar mixture jellied with silica. I made a video of it and I'm gonna
probably upload it today or tomorrow. Also, I'm gonna repeat the experiment with the remaining substance this evening, probably some blue or violet
flames will be visible then as the acetone will "wash" out the water from the now still clumpy KNO3, so I can mix it up very well.
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HellstormOP
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UPDATE:
Now I burnt the rest of the mixture at night. It was very thick now, since the glass jar where I stored it in is not air tight. As I mixed that stuff,
it was liquid, but now it turned into some sort of a sticky goo paste. I didn't even get it off the spoon.
Apparently there wasn't much acetone left in it, since it was relatively hard to ignite and burnt off with a yellow flame. Despite the added nitrate,
it didn't burn off very quickly. I guess this is because I used ping pong balls as the NC source. The NC they are made from is not fully nitrated and
contains camphor. The mixture made fizzling noises while burning off. That noises were a bit similar to the noises I sometimes heard in the movie.
What I'm going to do next:
- Using dry and even finer ground potassium nitrate. I already dried and ground it with a 300W coffee grinder, and I'm gonna use it in the next
experiments.
- Dissolving acetylene in the flaming mass. I've finally got the calcium carbide today, so I'm gonna crush it a bit (it was delivered as big rocks)
and then use a makeshift gas generator (I will place the ready flaming mass in a beaker into a bigger glass jar, and then pour water into that
surrounding jar. Then, I will wrap a few grams of my calcium carbide into some paper (to delay the reaction), throw that into the water, quickly close
the jar and run away, and then wait until the reaction has stopped) to "charge" my mass with acetylene.
- Using a makeshift "blow gun" to simulate fire breathing. Since in the experiments I made the mass was simply burning on the ground, it did neither
simulate that ball in movement nor an impact on a hard surface. As soon as I can get my hands on a sufficiently long metal tube, I will fix an
ignition mechanism (a thick wire with a paper towel soaked in kerosene, fixed at one end of the tube) on it, then load it with some mass (from the
"muzzle", not from the "breech" where I'm gonna blow into the tube), and then finally "fire" it. This will practically be the first experiment which
says anything about the explosivity of a such mass at all. Or at least about the ability to keep burning in flight.
[Edited on 18-8-2011 by HellstormOP]
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HellstormOP
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UPDATE²:
I've took a look at the movie again. What I've noticed, is that the yellow fireball which occurs at the explosion, releases hardly any soot.
Decomposing acetylene would yield a lot of soot, so probably the acetylene here is rather burning than decomposing. What I could think of, is that an
initial decomposition (triggered by the impact, due to the acetylene "bubbling out" from the mass, which means it's no longer stabilized) triggers an
oxidation (and the deflagration of the NC) in the whole mass. This could make the acetone evaporate in an explosion-like way, and also the KNO3
release its oxygen. Thermobaric bomb the dragonish way^^
EDIT:
Sorry for the misinformation, there is quite a bit of soot or smoke formed at the explosion. But not nearby the quantity which will form out of fully
decomposing acetylene! Also, the sound for the explosion in the movie is not a sharp bang, but rather like a combined sound of an impact and of,
maybe, deflagrating hydrocarbon vapors? The fire also apparently has VERY serious thermal effects, even if it explodes without residue. Hmm, and when
its really like 0,5 liters /1 pound of flaming mass each blast, the kinetic effect (dive-bombing dragon at maybe 160 mph + blast launched at min. 15 -
20 mph) also should play a big role.
[Edited on 18-8-2011 by HellstormOP]
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HellstormOP
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UPDATE:
Alright, I did some investigations if at least the flame color could be explained with chemistry in reality. It does.
Uploaded with ImageShack.us
That's the steady acetylene flame you see in the movie. I guess it's combined with air, not oxygen, but since the air seems to be well mixed with the
C2H2 (contrary to acetylene flames in air where the oxygen only comes to the surface of the flame) that could work. Here is a typical acetylene-oxygen
flame from a welding torch:
[img]http://image.carcraft.com/f/25255432+w750+st0/ccrp_0901_07_z+versatile_mig_welding+mig_weld.jpg[/img]
Note that when pure oxygen is used, the flame is only blue at the tip of the torch. I guess that when air was used and premixed with the C2H2, it
would look like in that movie.
What I also would like to point out: That blue mist when a blast explodes at night looks perfectly like burning vapors of either short hydrocarbons
(propane, butane etc.) or ethanol, acetone etc. It is visible at night very well, also visible at poor lighting conditions, but invisible at day. The
only thing you see at day, is a ring of glowing violet mist. No clue how this could be realized.
OK, now since it's clear the movie designers did not simply use energy blast effects or something like this, but really used some kind of a profound
concept of fire-breathing, that concept should be transferable to reality, or at least the major part of it should be. Now, please post your ideas how
that might work!
[Edited on 22-8-2011 by HellstormOP]
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Norrys
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Man, your' freaking obsessed!
| Quote: |
I guess that when air was used and premixed with the C2H2, it would look like in that movie. |
I guess this depends on the ratio of fuel and oxygen and on camera settings. Note, that infrared light is bright purple or pink for many cam-chips.
| Quote: |
OK, now since it's clear the movie designers did not simply use energy blast effects or something like this, but really used some kind of a profound
concept of fire-breathing, that concept should be transferable to reality, or at least the major part of it should be. Now, please post your ideas how
that might work! |
Its not clear, why this schould be clear now. You may even post that 20 times and its still nothing clear except of the fact, that this an animation
an no freaking scientific simulation and it was made by grafic experts and not by combustion chemists.
The strange ring effect and many other things arent even close to reality and there had never been any need to construct a real working concept, that
is even simple enough to be reconstructed by some random guys without any expensive equipment.
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HellstormOP
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Well, I guess I'm just fascinated. And impatient, since I've practically got all the gear and materials I need (acetone, KNO3, silica, ping pong
balls, nitrocellulose, carbide, ...) but many experiments already failed. But what also is clear to me, is that of course a such effect wouldn't be
perfectly reconstructable in reality. Especially because the movie itself contains some inconsistencies about it. Exaggeration is a part of movie
business and always will be. But: A lot of signs in the movie indicate that the designers really thought about a pseudo-scientific concept for the
fire of this dragon. The few chunks of "background data" provided on the official homepage match the effects in the movie. Or have you ever seen a
semi-solid (hell, there are even small drops dispersing from the main fireball), blue burning energy ball which creates a yellow-orange, smoky cloud
on explosion?
Of course, nobody simulated a such fire in reality (yet...). But: The movie designers developed some kind of a concept how this MIGHT work, and they
took at least a little bit of care of real fire/explosion processes (e. g: the blue ring could be a burning short-chain hydrocarbon, splashed away by
the impact/explosion). Now, I want to prove that concept and find a possible way how this would at least partially work in reality.
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Bot0nist
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Don't let us get you down HellstormOP. Keep experimenting and learn as much as you can on the way. Just play it safe.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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gregxy
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Perhaps the movie artists watched earlier movies showing burning projectiles
being fired from catapults. (Usually balls of cloth soaked in oil or flaming jugs of oil).
And modeled the "look" after that. I know that I have seen sequences like that in movies.
They then adjusted the graphics to get a unique and interesting visual effect,
most likely by increasing the blue to make it look more electric.
The stuff about C2H2 was just made up afterwards to keep the fans interested.
If you give up on the blue-white color it should not be hard to do what you want.
Or fill a glass sphere with gasoline, cover it with blue-star pyro powder ignite
and fire from a catapult.
You can probably get some of the effects but not all of them.
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