# ottd death battle

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## Re: ottd death battle

oaky wrote:
Flamcastro wrote:it'd be a fairly small explosion too they'd still be recognizable
explain how your dragons are large enough to fly with 'jets of gaseous hydrogen'

lets estimate

$\bg_white \textrm{Density of H}_2: \rho = 8.99 \times 10^{-5} \textrm{ kg/L}$

you said your dragons cant be 'unrealistically massive' so we can say they weigh 750kg

using the rocket equation

let's make some more assumptions because we dont know anything about fd's fantasy monsters - it needs to reach at least 10m/s (<25 MPH) to make any sense and even still that is outstandingly slow

$\bg_white \Delta v = 10 \textrm{ m/s} = v_e\times ln(\frac{750\textrm{kg}}{m_f})$

how fast can a dragon eject hydrogen (ve)? no idea but looking at shit with squids and scaling up for size lets say a dragon can eject the gas at 50m/s which means that youll need the dragon to have almost 20% of its weight be in hydrogen or around 130-140kg

what's the volume of that? using our density relationship, 140kg of hydrogen at STP is over 1600 cubic meters of uncompressed H2 gas (and even more 'realistically' because the air will probably be warmer than STP)

how the fuck does your dragon fit 1600 cubic meters of gas inside of it? does it compress it using magic? i dont even know how long that H2 would last but you have chosen the least effective propellant gas possible
there seems to be a misunderstanding, by "quite large" i didn't mean giraffe-size i meant "on the larger end of other intelligent life forms in QB" and like 200kg at most. plust it's mostly for liftoff and they start from a high place or with a running start. if they actually just blimped around on pure gas (maybe that's not the best word since they're ejecting it) they'd float sure but they wouldn't really be going anywhere. also really at 200kg-ish they're already prevented from putting too much strain on their bones and to be fighting animals that don't have to prance around and hope that they don't step on a rock like larger ungulates they can't really be any heavier. the other major rebel planet that isn't earth in QB, ankra, is a toroid with wide gravity variance and on its outer equator has gravity that's like a third of earth's so you could have a yuge dragon there and i've considered having a smaug ripoff live in that area

nice job doing the math though
oaky wrote:i realize now that you meant the hydrogen would get burned like a rocket so the speed is probably much higher but even if you decrease the volume by two orders of magnitude its impossible
that's actually a great idea i was actually just going to eject it under their wings but they could have another set of bladders on their flanks that make them EXTRA HARD CORE because we wouldn't want their wings to burn to a crisp

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## Re: ottd death battle

no sorry lad even if you somehow cram a full 1000 L or a full cubic meter of H2 inside that tiny ass dragon you get a whopping 90 grams of hydrogen gas to work with

it makes no sense your fantasy dragons all starve to death because they cant fly

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## Re: ottd death battle

i was already going to strap a jetpack to eltnas in like book 4 so it'd probably just be a glorified bulletproof hydrogen tank

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## Re: ottd death battle

oaky wrote:no sorry lad even if you somehow cram a full 1000 L or a full cubic meter of H2 inside that tiny ass dragon you get a whopping 90 grams of hydrogen gas to work with

it makes no sense your fantasy dragons all starve to death because they cant fly
at stp, it's higher pressure. and hydrogen has a lot of energy anyway, definitely enough for liftoff

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## Re: ottd death battle

Flamcastro wrote:
oaky wrote:no sorry lad even if you somehow cram a full 1000 L or a full cubic meter of H2 inside that tiny ass dragon you get a whopping 90 grams of hydrogen gas to work with

it makes no sense your fantasy dragons all starve to death because they cant fly
at stp, it's higher pressure. and hydrogen has a lot of energy anyway, definitely enough for liftoff
all my calculations are done at STP and if its inside a living thing it will require an even greater volume unless your dragons' bodies are ice cold

and you cant fit anything close to 1000 liters inside a 200kg creature - if you give a reasonable density of 1200kg/m3 (humans are 985) then you only have 167 liters of total body volume - if you can even fit 25 liters of hydrogen inside you only have 2.25 grams of hydrogen which is barely more than a mole of gas

you mention burning the wing but shit aint happening to that dragon at all - the heat capacity of human skin is 3.4 kJ/kg/kelvin and the enthalpy of combustion of H2 is 286kJ per mole so the ~322kJ of heat produced by the entire supply of gas applied to 1kg of wing tissue will only raise the temperature by a toasty 9.5 degrees celsius - what power your dragons have

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## Re: ottd death battle

i don't get it, why can't the bladders be higher density than the body?

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## Re: ottd death battle

bc they are attafhed to the body

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## Re: ottd death battle

i mean when your urinary bladder isn't full of piss isn't it a lower density than your body?

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## Re: ottd death battle

Flamcastro wrote:i don't get it, why can't the bladders be higher density than the body?
if you have a 200kg object and it has an average density of 1200kg/m3 (which is very high for something organic) then you only have a finite volume as calculated for the ENTIRE creature

the only way to cram in more volume into your bladder is to compress the hydrogen - how do you do that? compressed gaseous hydrogen is kept at 5-10 ksi in a container made of metal or high strength composites (woven aramid/carbon fiber or a metal matrix composite made of steel and these materials)

lets say your dragon can pressurize its bladder somehow to an impressive 30 PSI (equivalent to a car tire - plenty of pressure) - this is equivalent to 2 bar of pressure which makes effectively zero difference to the density of hydrogen gas

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## Re: ottd death battle

so FD i also have a dragon race they fart xenon gas out at supersonic speeds to propel themselves into the sun

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## Re: ottd death battle

oaky wrote:
Flamcastro wrote:i don't get it, why can't the bladders be higher density than the body?
if you have a 200kg object and it has an average density of 1200kg/m3 (which is very high for something organic) then you only have a finite volume as calculated for the ENTIRE creature

the only way to cram in more volume into your bladder is to compress the hydrogen - how do you do that? compressed gaseous hydrogen is kept at 5-10 ksi in a container made of metal or high strength composites (woven aramid/carbon fiber or a metal matrix composite made of steel and these materials)

lets say your dragon can pressurize its bladder somehow to an impressive 30 PSI (equivalent to a car tire - plenty of pressure) - this is equivalent to 2 bar of pressure which makes effectively zero difference to the density of hydrogen gas
hm... to me it seems like the gas itself doesn't actually have to be lighter than air if it's jetstreams pushing up anyway, so what about natural gas?
george lucas wrote:so FD i also have a dragon race they fart xenon gas out at supersonic speeds to propel themselves into the sun

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## Re: ottd death battle

btw gas propulsion isn't completely stupid i don't remember exactly where but i know something has a dragon that flies using methane (which of course flying on just methane is retarded)

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## Re: ottd death battle

Flamcastro wrote:btw gas propulsion isn't completely stupid i don't remember exactly where but i know something has a dragon that flies using methane (which of course flying on just methane is retarded)
do you think that anything involving a dragon is gonna be scientifically accurate

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## Re: ottd death battle

Flamcastro wrote:
WOW FD NICE MEME GOTTA SMASH THAT FUKKEN LIKE BUTTON XDD

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## Re: ottd death battle

oaky wrote:
Flamcastro wrote:btw gas propulsion isn't completely stupid i don't remember exactly where but i know something has a dragon that flies using methane (which of course flying on just methane is retarded)
do you think that anything involving a dragon is gonna be scientifically accurate
ANSWER MY QUESTION DAMN YOU REEEEEEEEEEEEEEEEEEEEE

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## Re: ottd death battle

also that's what i'm aiming for with QB i researched all the quantum crap in it and just avoided going into detail on things that humanity has no fucking clue on

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## Re: ottd death battle

Flamcastro wrote:also that's what i'm aiming for with QB i researched all the quantum crap in it and just avoided going into detail on things that humanity has no fucking clue on
lol

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## Re: ottd death battle

if this is the sort of quality research you put into something as important as how your dragons actually move i have absolutely no faith in your ability to figure out quantum anything

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## Re: ottd death battle

the gas was a footnote on all the research i did on bone structures wingspans etc besides i think i can still use natural gas

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## Re: ottd death battle

FUDGIEFIGHTERIA wrote:if this is the sort of quality research you put into something as important as how your dragons actually move i have absolutely no faith in your ability to figure out quantum anything
yep there is no way your dragons are propelling themselves with hydrogen sorry

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## Re: ottd death battle

easy to talk shit when your setting is deliberately not based on physics

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## Re: ottd death battle

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## Re: ottd death battle

Flamcastro wrote:easy to talk shit when your setting is deliberately not based on physics
maybe you shouldn't base your entire book's premise off of a field that you don't have a full understanding of

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## Re: ottd death battle

natural gas is 95% methane which has a density of 0.656 g/L - 25L of CH4 is 16.4 grams which is still not nearly enough to propel a 200kg dragon

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## Re: ottd death battle

why would you write a story based on concepts that you don't understand when you could just write a story

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