Pacific Rim Science Review

Pacific rim was exactly what I wanted to see, a movie about giant robots punching giant monsters in the face. On that front it is possibly the best movie ever made. The monster fights are fantastic. Unfortunately, they also tried to make it sci-fi. From that angle, it was a disaster. I’m pretty sure that every single sciency thing they tried to do was utterly and painfully wrong. Edit: enough people have gotten grumpy at me for not using the published values for the jaeger and kaiju height that I’ve added a section at the end to address it.

I’m going to start with making some guesses at scale. They never explicitly say how tall any of the robots or monsters are, but they did put them beside some things that I could get measurements for. They laid out a Kaiju (one of the monsters) on an aircraft carrier (~300m), one of the Jaegers (giant robots) picks up a large container ship and uses it as a bat (~300m) and they are shorter than the taller skyscrapers but taller than the shorter ones (200-400m) and finally one of the smaller kaiju was tall enough to smash up the Golden Gate bridge (~200m). While I suspect careful review will find inconsistencies in the depiction of their size, I’m going to peg them at around the 300m (1000ft) mark. That’s really big.

They make the mistake, though, of stating the weight of a kaiju at 2500 tons (Assuming short tons as everything else in the movie is stated in imperial). Given that most of the Kaiju can swim, I’m going to guess that they’re close to neutrally buoyant in seawater which means they have a density of roughly 1025 kg/m^3. That makes them about 2200 m^3 which means they could fit in an Olympic-sized swimming pool. That’s pretty big, but not nearly big enough. As a point of comparison, if we were to scale a human up to 300m tall, they would have a mass of 393 kilo-tonnes (336000 tons).

How about the Jaegers? Well they’re substantially more dense than water because they sink and can keep their feet without doing funny moon-walking stuff. That means they’re vastly in excess of the 393 kilo-tonnes we worked out above. Take notes, class, that might be important later

WTF Moments
Before I hammer out any more calculations or go on any lengthy tirades, I’m going to go over a few standout moments where they really could have used someone with a technical eye watching the production.

1: Windproof Umbrellas
There is a scene when the female lead, Mako, walks up to a Helicopter as it’s landing carrying an umbrella. The umbrella is immune the the rather substantial downdraft, which the effects people were clever enough to animate.

2: Pointless Angle Grinding
There is a scene where construction workers are building a massive wall to keep the monsters out and several of them are randomly grinding girders. My assumption is that angle grinders are a cheap tool that throws off shiny sparks, but they were just pointlessly polishing the middle of I-beams in a place that clearly didn’t need it.

3: Indestructable Container Ship
In an epic and awesome sequence, one of the Jaegers beats a Kaiju over the head using a container ship as a bat. That’s awesome, except that container ships are only structurally stable when supported by water. Just picking one up would snap it in half. It would shatter like a fluorescent light bulb if used like a bat.

4: The Jaeger Pilots are Bad Medics
In a dramatic moment of tension, one Jaeger pilot is searching for the vital signs of another. Great, but she’s wearing armored gloves, and her patient is wearing armor that covers his whole body up to the jawline. Shockingly, she says she can’t find a pulse.

5:The Chalkboard
The mathematician might have been a caricature, but not a wholly unfair one. I’ve met mathematicians rather a lot like him. His chalkboards, though, looked like gibberish to me. Unfortunately I didn’t have time to go over the math on them, but it looked like boards full of disjoint formulas without meaning and certainly no logical flow. I can’t be sure without spending hours going over what I only had a few seconds to glimpse.

(late addition) One of the Kaiju released a massive EM pulse knocking out pretty much everything in Hong Kong. Except Gypsy Danger, the jaeger of the heroes… cause it’s “analog”. That is massive BS. first, just being analog does not mean that it does not have any circuits susceptible to an EM pulse, but moreover, there are digital displays all over, a fancy neural interface and a nuclear reactor. I’d like them to explain how that could be done without a computer?

Material Science
My background is mechanical engineering, so this was just painful. I’m fine with giant robots fighting giant monsters, but the writers did something very silly, they told us what they were made of.

On a tour of the jaegers, we met the Crimson Typhoon with a full titanium core, “no alloys.” That line confused me a bit. Why wouldn’t they use alloys? Alloys aren’t lousy knock-off versions of the pure material, they’re combinations of materials that are used to improve the performance of a raw metal. With alloying elements you can change the strength, toughness, corrosion resistance and a host of other properties.

For example, pure iron is pretty much useless crap. It rusts easily, cracks, dents, and is generally junk. Wrought iron is the closest you’ll ever find to pure iron and it was abandoned ages ago for better alloys. With careful addition of carbon, nickel, chromium, silicon, manganese and other metals, you can make turn iron into stainless steel, spring steel, tool steel and a host of less sexy sounding but very useful materials. Pure iron is crap, steel is awesome.

The hero’s jaeger’s hull is made of pure iron… “no alloys.” I couldn’t believe that they said that. I thought that I just misheard it the first time about the titanium. But no, clear as day “solid iron hull, no alloys.”

What in the world were they thinking?

Also, iron feet would be crushed in combat. Remember that 393 kilo-tonne low-ball estimate of the weight of a jaeger? Well I ran some numbers. Just standing there, if it was able to evenly distribute it’s weight over both feet, the iron would be under about 3MPa of pressure. Based on the compressive yield strength of wrought iron being 234-372MPa, that’s manageable. However the jaegers take some pretty hard hits. It’s difficult to calculate how hard, but gravity is our friend in this instance. At one point the jaeger jumped up to at least half of its own height, leaping off of one foot. It took less than a second to extend its leg and leave the ground. With that and a bit of help from Newton, we can figure out the force exerted on the toe off of which the robot launched.

Equations in use:

I based on my estimates of the foot size and the height of the jump being half the jaeger’s height, that puts about 130MPA on the toe. That’s still about half of the yeild strength, but it is also assuming a perfectly even distribution across the surface of the toe. Also, that leap is by no means the hardest hit that the jaeger takes and the flat of the foot is by no means the weakest part of the machine. During some of the harder landings, the iron in the foot would literally splatter.

Dramatic Timing
All of the fights in the jaegers look like they’re in slow motion and that’s good. The things are big and even when moving very fast in an absolute sense, they look slow to us because we’re comparing them to human motion. We can extend our arm in a fraction of a second, but our arms are less than a meter long and weigh only a few kilos. Based on how fast I can punch, If a 100m long arm weighing several kilo-tonnes were to extend in the same amount of time, it would have to be moving at an average of 2600 km/h (1600mph). So the slowness of the fights was good. It represented the scope of the creatures and robots well.

Not slow enough, though. It would seem that they sacrificed some degree of physics here for dramatic purpose.

Again, gravity is our friend when doing calculations of this sort. Remember that jump the jaeger made, where it hopped up to around 150m? Well to do that, it was in the air for a full four seconds. That’s a long jump. I can’t jump that high.

Again a little high school physics can tell us how high that would be. Four seconds in the air, half up, half down, means two seconds to the peak of the arc. using h=1/2gt^2, the jaeger jumped… 20m.

Now that’s really high. That’s easily clear over a house, but compared to its height, it’s trivial. To actually reach the height of 150m, the full jump, take-off to landing, would have taken 11 seconds. I think it’s probably for the best that they fudged that number. The fights would have been painfully slow and boring otherwise.

Lift to Weight Ratio
I don’t think anyone on staff was an aeronautical engineer. First, the each of the massive jaegers were hauled around by a team of eight helicopters. Based on most powerful transport helicopter currently in existence, the most the bots could weigh is 160 tonnes. Given that we low-balled their mass at 393 kilo-tonnes, I’m gonna say that they messed that one up. I don’t care how much better they make helicopters, they aren’t going to improve their lift capacity by 2000 times.

Also, one of the Kaiju took flight. I’m fine with the fact that no known material would be able to provide the strength to make up the bones and muscles that allow it to do so, it’s a magic alien. But it is very clearly flapping its wings. It’s flapping its wings up to 50 000 feet while carrying a jaeger. What they fail to consider is that there isn’t enough air up there to keep the thing aloft. The jaeger pilots even say that they’re running out of oxygen (which seems an odd problem given that they’re submersible robots). The kaiju would have to have been flapping like a hummingbird to get anything like enough lift up there.

And then the jaeger gets dropped and they start to burn up on re-entry. I don’t even know where to begin with that one. No. Just no.

Questionable Biology
As is typical for hollywood, the word “evolving” is quite misused in this movie. It is said that the kaiju are evolving, that they are becoming bigger and stronger in each successive attack, adapting to earth’s defenses. That sounds like evolution, except of course, that each one is killed shortly upon arriving on earth.

Evolution by selection operates on the offspring of those that survive to breed. It requires a breeding population on which to do the selecting, and it requires that some members of the population breed less successfully than others. Of course there might be a breeding population of monsters, but not on earth. A population cannot adapt to an environment in which they do not live, and they do not live on earth. One at a time comes through and gets blown up. This would not affect the population on the other side of the wormhole unless they were systematically sending their smallest and weakest through. Even then, we would have to believe that the life cycle the these giant monsters is only a matter of weeks, if the next generation is ready to go on the time scale of the movie.

Also, apparently, the dinosaurs were alien kaiju, but out planet wasn’t quite suitable for full invasion in the Jurassic era. Why? because our atmosphere wasn’t right. But now, due to us filling it with pollutants and carbon dioxide, it’s perfect.

Of course, there was way more carbon dioxide in the atmosphere during the Jurassic period than there is now and the dinosaurs have a clear fossil record of evolutionary stages and relationships with creatures that existed long before and after them on earth, but whatever. Dinosaurs were a failed alien invasion.

Finally, the monsters are all clones of one-another. They all have the same DNA. This, I think, will ping most people’s skeptical mind. It doesn’t make sense at all, or does it?
DNA gives instructions for individual cells on how to behave and grow and multiply. We have the notion that any two things with the same DNA must be identical. However, environmental factors can radically change how something develops. For example, a cat was cloned. The two are genetically identical, but they are different colors.

It eventually comes to light through the course of Pacific Rim, that the kaiju are being engineered. If that is the case, the creators could have found it easier to manipulate the development of the creatures, rather than their base genetic code. So them all having the same DNA might not actually be bad science.

What is more astonishing, though, is that giant, physically impossible creatures from another planet have DNA at all. DNA is probably not the only molecule that could be used as the base instructions for life. Deoxyribonuceic Acid is a very specific chemical structure, infinitely variable in the details, but very specific in its basic composition. There is no reason to think that it is the only form of genetic instruction that could exist. It would be shocking if alien life had DNA. It would be strong evidence for panspermia

Size: The published values
Above I described how I inferred the size and weight of the jaegers and kaiju. It is very possible that my calculations based on watching the movie are artifacts of paralax and false assumptions. So let’s take a run with the published values.

Let’s start with the kaiju. For this purpose, I will use Leatherback as an example because of its similarity to a gorilla. It’s easier to scale up a known animal than to try to calculate volume from first principles. Leatherback is stated to be 267ft(81m) tall and 2900 tons (2630 tonnes). If we scale up a 1.8m, 180kg gorilla to that height it would weigh 18080 tons (16400 tonnes). The stated weight of Leatherback would make it roughly 1/6 the density of a gorilla, somewhere close to balsa wood.

What about the jaegers. Let’s talk gypsy danger. The hero’s jaeger is stated to be (260 feet) 79m and weighs 1,980 tons (1796 tonnes). What can we pull from that. Well first, we know that its hull is made of iron. How thick could that be? Well if we assume that the jaeger is roughly the proportions of a human, we can calculate its surface area and we know the density of iron, we can calculate how thick the plating could be. It’s 2.4″ (6cm). That is based on the whole weight of the machine being used up to make the outer armor. 2″ of iron would crumple. Also, it’s substantially less than a modern tank.

How about the density of the jaeger. Again, based on scaled up human proportions, it would average 250 kg/m^3, about half as dense as pine. However, we have to assume that there is a fair amount of empty space within the frame. How much? Well, it would have to be more than 75% empty space that could be filled with water in order to sink. That’s not so bad, we determined above that it would have to be 100% hollow to get a 2.4″ of iron plating to use as armor. As a comparison, if we scaled up ASIMO to the size of a jaeger, it would weigh 100 times as much as gypsy danger.

Some of the items listed in the above sections wouldn’t be as big of an issue. The hull, however thin, wouldn’t necessarily yield under the pressure because there would be a lot less. My little thing about how fast a jaeger fist would have to go to execute a punch in the same amount of time as a human would be quartered. The speed of the battles would be much closer to correct, possibly even spot on, at least close enough that I couldn’t say it wasn’t without having a DVD to scrutinize, and that’s close enough for me.

Also, while we’re splitting hairs, the wiki states that the kaiju are silicon based. Color me confused why a silicon based creature would have a carbon based genetic structure (DNA).

Also, in defense of my height assumptions, I’m going to post this official promotional shot of Striker Eureka(76m) standing beside Sydney Harbor Bridge(134m).

Copyright Warner Brothers Pictures
Copyright Warner Brothers Pictures

Finally, for those of you that don’t read the comments, Kyle Hill has done a pretty cool analysis of the underwater nuke over at Scientific American


Ryan is a professional nerd, teaching engineering in the frozen north. Somewhat less professionally, he is a costumer, author, blacksmith, juggler, gamer, serial enthusiast, and supporter of the Oxford comma. He can be found on twitter and instagram @studentofwhim. If you like what I do here, feel free to leave a tip in my tipjar.

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  1. I think the umbrella thing bugged me the most. Giant robots and monsters, sure, but a wind-proof umbrella? That’s going too far.

    The other thing that bothered me was the fact that 6-limbed insectoid aliens would create genetically-engineered tetrapods. You’d think they’d stick to a familiar body plan.

    Also, if you can make giant robots to fight monsters, why can’t you retool them to build the wall?

  2. I assumed that all available resources were being poured into wall building and that Alaska just wasn’t all that important. They didn’t get the best of the construction machines.

  3. Two things about dinosaurs:

    1) My interpretation of that dialog was that the aliens had wiped out the dinosaurs but then decided they didn’t like the planet yet.

    2) The biologist actually said that some dinosaurs had secondary brains. That broke my suspension of disbelief. Maybe it’s a generational thing but I never even heard of butt-brains until a teacher made an obscure joke about it in high school. It was disproved long before I went nuts for dinosaurs in the second grade.

  4. Pretty sure you should double check your calculations of the Jaeger and Kaiju sizes. A Jeager is about 90m, not 300m. Actually, 260ft according to the Pacific Rim wiki (or any number of other sources in a google search). That’s 79m, not 300m. This also means that the Jaeger’s arm can’t possibly be 100m long in your calculations about speed. That would make its arms longer than its body. I was going to assume you mixed up metric and imperial but you stated ~300m/1000ft. Way off.

  5. Hey Ryan,

    Interesting review, but for the sake of nerdiness, I have a few problems.

    First, your discussion of scale is off. Both the height and weight of all the Jaegers has been established before and after the movie has come out (http://pacificrim.wikia.com/wiki/Gipsy_Danger). A scale and weight chart is the first returned Google result. Neither the robots or the monsters are anywhere near 1000 feet tall. Your size assumptions for the kaiju are all off by a factor of three, as are the masses (and both are officially established)

    Your description of the kaiju volume is also off. A amphibious creature does not necessarily have to be neutrally buoyant, considering that it also spends much of its time on land. Furthermore, kaiju blood and body is made up of a foreign/silicone-based substance making density assumptions–given the point about neutrally buoyancy–hard to justify. Either way, a kaiju could not come even close to fitting into an Olympic-sized swimming pool. It would be probably 100 feet too short and 100 feet not deep enough (http://en.wikipedia.org/wiki/Olympic-size_swimming_pool). Even if the density calculation were correct, only a finely-crushed kaiju could fill the pool, not an animal with a complex body layout and lots of negative space.

    I agree with you about the pointless angle grinders, but many of the workers were welding–totally justifiable.

    A container ship would never shatter. Steel doesn’t fail like glass–it yields and bends. I doubt the jaeger could even pick it up, and it would surely deform, but not shatter.

    Without actually looking at the math on the chalkboard, it’s hard to say whether or not it is accurate or logical. Shows like The Big Bang Theory make a point about having real equations on the white boards. Without checking, can you conclude otherwise for Pacific Rim?

    Totally agree with you on the kaiju flight, the alloy point, and the analog confusion.

    I would have to see your numbers, but again, all the pressure calculations are off because of your incorrect mass and height values. Substantially reducing both (as the canon would dictate) would reduce the pressure on the feet and make them more structurally sound and resistant to “splattering” (which iron doesn’t do under yield stress).

    For speed, your numbers are still off. An 100m arm would be 50 feet longer than the official height of the jaeger itself, making it look rather like an orangutang. Also, the average person punches not much faster than 30 miles per hour. Given that the jaeger arm, officially, is no longer than 120 feet and that in the film it takes maybe 3 seconds to land some of the larger punches, the jaeger arm doesn’t move very fast even in absolute terms. Extending a 120 foot arm in 3 seconds is 27 miles per hour, not Mach 2.1 as you suggest.

    I’m not sure when in the movie you saw a jaeger jump 500 feet in the air (150m and well taller than any of the kaijus), but the numbers are off here too. Getting the 20m result from your jumping calculation should have told you something was off.

    You’re also right on the helicopter point (http://www.wired.com/wiredscience/2013/07/how-would-you-carry-a-jaeger-from-pacific-rim/) and the re-entry point.

    Sorry for busting some engineering chops here, but it’s what I do (http://blogs.scientificamerican.com/overthinking-it/).


  6. I have been pointed to the wiki where they list the sizes and it confused me. See above the observations from the film by which I measured the monsters and jaegers. But if I am wrong, which is entirely possible, then very little changes.
    The kaiju still don’t weigh enough.
    The jaeger still only jumped 20m
    The Hull would fare better if the jaeger only weighed the listed 1980 tons except that it could be no more than 5cm (2″) thick, which assumes the entire mass of the jaeger is in its hull. That would stop a bullet quite easily, but wouldn’t even slow down a monster that can shred the golden gate bridge.
    The helocopters still couldn’t lift them.
    The arm extension calculation was only illustrative anyway, and you can just quarter the value, which would bring it below the speed of sound.

  7. Kyle,
    I’ve already addressed the height and weight thing. I guessed at the height from watching the movie. I have a feeling that they may have made them bigger in certain situations for dramatic purposes. For example, the skeleton of one of the first, smaller kaiju took up more than half of the deck of an aircraft carrier which would make it at least 400 feet long.

    Steel does shatter if you hit it hard enough. Maybe not like glass, but it will shatter. Regardless the simile with the fluorescent light bulb was meant to illustrate relative fragility, though, not failure mode. Perhaps I lacked clarity on that.

    Close to neutral bouyancy is required to swim about comfortably underwater. At least three of the kaiju do this. That is what I based my assumption on for their density.

    Reread the section about the punch. I’m talking about the time it takes to punch, not the velocity at which I punch. I’m explaining why it makes sense for giant monster fights to “look” like they’re in slow motion.

    I’m happy bust your chops right back, though I like your article on the nuclear blast. I regretted not covering it here, but you did a better job than I would have anyway.

  8. Observations based on passing glimpses of skyscrapers is inherently less reliable than published specifications. The movie’s special effects producers also describe crafting the cinematography around these true values.

    The kaijus only don’t weigh enough if your assumptions about density are correct, which I pointed out likely aren’t. If you are going to guess about density, why not use the official weights and work form there?

    Sure, based on the time you give, the 20m doesn’t change, but you are using this 20m value to make a point about the 150m jump. The value doesn’t change, but it does render your next comparison incorrect (of an 11s jump time).

    A jaeger *is* easily shredded by the kaijus. We see loss of limbs and nearly an entire torso in the film. So, being easily bitten through by a kaiju does not invalidate the design of the robot.

    Yes, I agreed with you about the helicopters.

    The arm calculation was misleading. Even if you did quarter the value to bring it below the speed of sound, you have a value of 400mph. Just from looking at the film (http://www.youtube.com/watch?v=lLuZPIc8nSk) we can see it goes nowhere this speed.

  9. Alright all you grumblers on and off the blog, I added a section re-evaluating things based on the published values for height and weight.

  10. Hey Ryan,

    Nice additions. I do see where you’re coming from with the promotional poster heights. Interesting hull analysis too. (And thanks for the link love!)

    Thanks for the back and forth.

  11. This article is great, and it’s fun to point out every goofy science-wrongness the movie put out there, but we all recognize that the science is awful on purpose, right? The major influence for Pacific Rim is kaiju monster movies and mecha anime, which are traditionally absurd when it comes to science and logic. From Godzilla to Jet Jaguar, PacRim is one long love-letter to the radiation-loving, illogic spouting, cheesy and goofy movies that inspired it.

    …but then I just couldn’t get over the angle grinders in theater myself. 🙂

  12. I’m not sure that the science was awful on purpose. I’m sure they knew that some of it was impossible, but I think some of it was bad due to a lack of interest in getting it right. The alloys part, I think, is a good example.

  13. Well summarized, but you missed my favorite oddity. The EMP took out all ‘digital’ systems, but somehow Gypsy Danger was “analog…nuclear.” These two engineering choices have nothing to do with one another, and secondly, I’d be astounded that we’d build a machine so astoundingly complex using analog systems! Never mind the digital displays, advanced AI, and weapons systems that just scream digital control…

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