Semi-realistic dragon (based on ASOIAF)

Discussion in 'General Fantasy' started by MyUsername, Sep 12, 2016.

  1. MyUsername

    MyUsername New Member

    Sep 8, 2016
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    As the title states I want to discuss what would be the “parameters” of dragon that would resemble the Balerion but could semi-realistically function in world with similar physics to our own.

    I will now present the best I was able to come out with.

    So lets begin. I will assume it has 60m (200ft)wingspan. Which brings me to 1st. Thing where the semi-realistic will come to use since anything with wingspan of 60m (200ft) that is made of same tissues as we are won't be able to fly (or support its own body for that matter). There are 3 ways how to go about it.

    1, make it really light of course this will mean it will be really easily affected by wind
    2, assume its tissues are stronger than ours
    3, it can manipulate gravity (or something similar)

    We are going to go with number 2 and compare it to largest flying animal and then scale its tissues strength accordingly. The newer estimates state the wingspan to be 10m (33ft) to 11m (36ft) lets go with the 11 and work from there. Assuming the body dimensions stayed the same the strength of muscles wold increase with power of 2 and the weight with power of 3 which means the required strengthening of tissues would be the size difference to power of 1(so just the size difference :) ). 60/11=5.4545 of course The problem with this number is that they probably wouldn't be able to hover in place like you usually see so lets say their tissues are 6 times stronger than ours and for simplicity sake lets say that it applies to all tissues. So let me list the tensile strengths of the most relevant tissues and then some materials for comparison.

    Wing membrane 120MPa
    bones 800MPa
    scales 700MPa? (didn't manage to find the tensile strength of crocodilian scales but I assume it would be similiarish to bone)

    Steel 400MPa to 2700MPa (I know its big difference but there are a lots of steels and I'm no expert so I can't say what is the most common one)
    tungsten 1510MPa
    diamond 2800MPa
    graphene 130000MPa (WOW)

    (of course there are a lot more properties contributing to material strength than tensile strength but this is the easiest to find and also the most relevant to flight but for example the compresive strenght of bone would be 900 MPa and the hardness of teeth would be 5 for dentin and 8.5 for tooth enamel.)

    Now for the weight since the largest flying animal weights between 200kg (440lb) and 250kg (550lb) the dragon with wingspan of 60m (200ft) should weight between 32t (35tons) and 54t (60tons). So lets say that it will weight 30t (33tons) (I know its below the lower limit but I feel 6 times stronger tissues would struggle too much otherwise and it is still heavy enough for the dragon to not fly like paper plane.)

    For comparison african elephant is 3m (10ft) to 4m (13ft) tall and weight 4t (4.4tons) to 7t (7.7tons)

    and T-rex is around 12m (40ft) long and weights between 4.5t (5tons) and 18t (20tons) (probably around 6t (6.6tons)

    This should conclude the properties of the body now lets discuss the flame.

    Lets assume that the dragon breath is hot enough to melt stone in realistic scenario. This is a very large problem. Getting the flame hot enough to melt stone is fairly easy 2000K (3100°F) (I'm not going to list the °C here since the conversion is trivial x°C = xK – 300 so 2000K = 1700°C I know it's not precise but I'm rounding the numbers here anyway) and wast majority of materials will melt. The problem is it would take forever and half and since the dragon usually can't breath fire continuously for several minutes I'm not sure it would even be possible. Now considering it takes significant amount of time even for oxy-acetylene torch I think the minimal temperature would be at least 4000K (6700°F). but if you wanted to melt large stone structures while you fly around them I'm afraid you wold need temperature approaching that of plasma torch but since that is way too high and I'm sure it would produce a lot of problems (for example I assume the air would expand really rapidly and and most of the radiation would be in UV spectrum and around 8% of radiation would be in X-ray spectrum.) lets go with the temperature of hottest chemical flame. That would give us 6000K (10000°F). (36% of radiation is visible light, 50% is infrared and 14% is UV)

    Of course the temperature isn't the only important thing about the flame the next important thing is size. Lets say that the flame is roughly the same length as the dragon wingspan so 60m (200ft) and that it has roughly the shape of truncated cone with lower radius (near the mouth) of 0.6m (2ft) and upper radius of 6m (20ft) this is how it would look (more or less) expect 5 times larger and bright blue (assuming the color matched the temperature) the volume of the flame would be 630m3 (22000ft3) and it's surface area would be 620 m2 (6700 ft2)

    Few more important facts about the dragon fire breathing capability. Lets say it can breath the fire for 4s and the needs 2s pause (for the 60m flame if he breaths only smaller one he should be able to breath longer)

    Now how long can he actually breath the flame before he runs out of whatever he's using to create the flame. I will assume its 8min (that is around 16 times longer than M2 flamethrower can) which means if he breaths as fast as possible he should have around 12min of flame. (Albeit I assume in realistic scenario he should have around 30mins (25% off battle spend breathing flame) even in quite intense battles and more than 1hour in usual battles (around 10% of time spend breathing flame)). And lets say it takes 12 hours for the flame to completely refill.

    Now how fast would he be. This is one of the things where I have no idea how the aerodynamics would work I assume that bigger thing should find it easier to push trough air but on the other hand so would the wings. So I will just took a look how fast birds fly and go from there. Lets first divide the speed into cruise, chase, dive. The cruise speed would be 60km/h (37mi/h) the chase speed would be 100km/h (50mi/h) and dive speed would be 200 km/h (125mi/h) (I wonder if this is too low on the one hand I would think bigger things (given the same density) would tend to fall faster on the other hand I find it hard to imagine dragon of this size that can breath fire would attack by diving at his prey especially since he would probable hunt something like elephants or at least rhinos or other 1t(1.1tons) or heavier animals.)

    I also thing it may be important to know how much The dragon could carry and given that most birds can carry at least their body weight lets say he can lift for 30t (33tons) for very short distance (read uselessly short) 20t (22tons) for semi medium ones (few km (mi) at low altitude) and 10t (11tons) for long distances or steepish climb (100 or 200km (around 100mi) or picking a rock and dropping it from 1 or 2 km (around 1mi) on someones head (or castle).

    Now for some not so good things how much would dragon eat. Lets do a rough estimate. Assuming it was more like bird which should give us roughly 0.07kJ/g per day or 2000000kJ (2GJ) for the whole dragon. Which means he would need to eat roughly 300kg (660lb) of meet per day. (3 or 4 cattle per week.) Not as terrible as i expected.

    Dragon “parameters”:

    60m wingspan

    Tissues roughly 6 times stronger than ours (tensile strength 120Mpa for wing membrane 800Mpa for bones 700Mpa for scales).

    Flame temperature 6000K (10000°F)

    Flame size and 60m (200ft) long 0.6m (2ft) wide near head 6m (20ft) wide near end.

    Flame misc. can breath for 4s the needs to stop for 2s the time before he runs out of flame following this pattern is 12mins then 12hours to refill.

    The flight speed would be 60km/h (37mi/h) for normal flight 100km/h (62mi/h) for fast flight and 250km/h (155mi/h) for dive.

    Carry capacity (how far he can carry it) 30t (33tons) (few meters 20t(22tons) (few km (mi) at low altitude) 10t(11tons) (100 or 200km (around 100mi) or climb with it to 1 or 2km (around 1mi) altitude and drop it.

    Needs to eat roughly 300kg (660lb) of meet per day (3 or 4 cattle per week).

    So do you thing these “parameters” (given the assumptions that his wingspan is 60m and that his flame can relatively easily melt stone) are semi-realistic?

    I'm mostly concerned about flight speeds and carry capacity since I feel like I was unable to do any meaningful calculations (if what I was doing here can be called that) so these numbers are the ones closest to guess.

    I hope you enjoyed reading this even if you don't want to discuss it and that you perhaps learned something while reading this.

    p.s. I was originally writing this mostly to discuss if it is feasible to kill dragon like this in medieval settings with no/weak magic and how you would go about it but this post is ridiculously long as is. So I will write different one for that once I have some time (probably in few days).

    p.s.s. English isn't my 1st. Language so I'm sorry for any grammatical errors and weird sentences.