Really, instead of three one-hundred-metre robots, why not use the resources to build one three-hundred-metre goliath (yeah yeah, didn't think it through. It would just be really skinny!) to send the monsters packing?

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    I am going to let Paul enjoy his reputation and just add this chestnut. Seeing how these robots defy so many of the laws of physics, it's hard to imagine they couldn't have built even larger ones, but we are supposed to imagine these devices to be the penultimate weapons designs of the era. If it were possible to build something larger, they would have. Since the Jaegers are all about the same size minus their specializations, we are to assume, they don't get any bigger than this. Look up the Square-Cube Law Commented Oct 29, 2014 at 0:31
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    @Thaddeus Haha, I just posted an answer about that, within about 1 minute of the posting of this comment. Nice!
    – Nerrolken
    Commented Oct 29, 2014 at 0:34
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    Because that wouldn't be an entertaining film.
    – Ian Newson
    Commented Oct 29, 2014 at 12:46
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    Gee thanks Ian Newson... You've just found a generic answer for 90% of the questions on this site...
    – Finnball
    Commented Oct 29, 2014 at 13:26
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    Stop making sense. Commented Oct 29, 2014 at 20:35

8 Answers 8

  1. It might not be possible to build a robot of that size that can support its own weight, or function properly. (As noted by @MarkGabriel in the comments, see this question on the Physics Stack Exchange).

  2. Even if it were, the weight/strength of such a robot might still not be enough to crush a kaiju.

  3. Such a robot might also be slower, and thus not able to intercept the kaiju before they reach population centres.

  4. And if you just build one big robot, if it gets taken down, you’ve got nothing. If you build three smaller robots, you can lose one and still have a chance of the remaining two defending you by utilising the mad skillz of the pilots.

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    @JoeL., aircraft carriers are the reason nobody builds battleships anymore. And aircraft carriers are still getting bigger. I guess it isn't the motion of the ocean that does it...
    – gowenfawr
    Commented Oct 29, 2014 at 2:35
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    @JoeL. I don't know about other navies new carriers, but the hull of the Ford-class is very similar to the Nimitz, basically the same length (1.2% longer) and same ~100,000 ton displacement.
    – Nick T
    Commented Oct 29, 2014 at 4:20
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    As for point #1, please refer to this link : physics.stackexchange.com/questions/139092/…
    – Zaenille
    Commented Oct 29, 2014 at 4:36
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    @MarkGabriel: you’re mixing facts in with my pure speculation there, I’m not sure that’s wise. Commented Oct 29, 2014 at 11:44
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    @Gaius The prior size of UK aircraft carriers wasn't down to engineering concerns; rather political expediency. The Invincibles were formally titled "through-deck cruisers" because aircraft carriers were considered a boondoggle, and also the UK's maritime role in NATO at the time was hunting Soviet submarines in littoral waters; rather than blue-water, expeditionary operations. tl;dr: it's interesting trivia, but not really a valid data point.
    – Tom W
    Commented Oct 29, 2014 at 12:25

The same reason we don't build tanks the size of buildings, or carriers the size of island chains: it was considered the most efficient cost/benefit ratio by the designers at the time. Bigger doesn't always mean better, it often means slower, heavier, more expensive and more unwieldy. Lifting a heavier arm means needing more powerful engines, which in turn make it heavier, requiring even more powerful engines, etc. The size they finally settled on must have been the one that the designers decided was the best trade-off, as with any construction project.

Also, it's worth noting that three robots of normal size don't necessarily equal one robot of three times that size: double the dimensions of a square, and you'll end up with four times the surface area. Similarly, building a 3x Jaeger might have taken the resources of 3 or 5 or 10 normal Jaegers, and at a certain point that becomes not worth it anymore.

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    Ref. Panzer VIII Maus, Landkreuzer P.1000 Ratte. ;-)
    – DevSolar
    Commented Oct 29, 2014 at 11:53
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    @DevSolar Of course, those are a great example of why we don't do these kinds of things - it nicely illustrates the diminishing returns of scaling the same technology up. Even the Tigers where pushing the limits, and were famously unreliable. We could probably build a workable Maus-sized tank today, but it would arguably be even more useless - kinetic penetrators aren't the likeliest threat to tanks anymore. Even with the thick armour of the Maus/Ratte, an anti-tank missile would go through it easily.
    – Luaan
    Commented Oct 29, 2014 at 14:53
  • @Luaan: Actually, neither the Tiger nor the Panther were exceptionally prone to failure if handled and maintained well. Unfortunately, by the time they appeared on the battlefield the quality of crews had already begun to deteriorate sharply by attrition, and supplies were getting scarce. But yes, they (and the Maus / Ratte) are very good real-life examples why "bigger" isn't automatically "better". The T-34 and M4 Sherman, one on one, were much inferior tanks, but being able to build lots of them was what made them excellent weapons.
    – DevSolar
    Commented Oct 29, 2014 at 15:11
  • @DevSolar It's trickier than that. A lot of them were completely disabled by hits that didn't even get close to penetrating their armour, and their range was laughable compared to tanks like T-34 and the M4. It wasn't just the numbers - it was the whole issue of logistics (and maneuverability) that made T-34 and M4 great tanks, even if a look at the specs wouldn't really tell you so. This is an effect you can see even when buying a new PC - specs aren't enough :D
    – Luaan
    Commented Oct 29, 2014 at 15:15
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    @DevSolar Well, even the specs on wiki agree, and those are the official specs, not the real ones - Tiger had an operational range of 120km, while the T-34 had 400km and the M4 had almost 200km - and that's just the fuel, not including reliability issues and maintenance. But yeah, this discussion is wildly off topic :D It does still have points, though - logistics are also much more complicated as you get bigger, and reliability often suffers as well. The M4 was half the mass of the Tiger, and it shows on the stress on transmission and suspension. Jaegers would have more stress - bipedal sucks
    – Luaan
    Commented Oct 29, 2014 at 15:43

It's actually laid out in the beginning of them film (around 2:45 - 3:15):

The Jaeger program was born. There were setbacks at first - the neural load to interface with the Jaeger proved too much for a single pilot. A 2 pilot system was implemented... left hemisphere-right hemisphere pilot control. We started winning.

Splitting control of a Jaeger two ways, apparently doable. Three ways, apparently possible, although it isn't clear to me that the third pilot of Crimson Typhoon controlled anything but the third arm, and presumably it was no coincidence that triplets were piloting it (...and that triplets are more capable of unity in the drift. In fact, I have triplets, and I can tell you that's completely untrue in real life).

How many ways can you split that control? If getting two pilots to drift together is as difficult as is implied throughout the film, then isn't three, four, five, six much harder?

This also shows up in the differences between generational Jaegers - newer ones seem to be better armed, have better materials, or have better technology, but they aren't bigger that I noticed. There's a scalability problem.

I think it's a reasonable in-universe explanation that the size of the Jaegers was limited by the ability to control them, and that that was limited by the combination of technology and human capacity to drift.

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    "I have triplets, and I can tell you that's completely untrue in real life" You've tested drift technology on your own children?
    – Scott Odle
    Commented Oct 29, 2014 at 2:01
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    Legally, and for the record - no. Such "testing" would be "illegal" and "unethical". So I can assure you I "haven't" done that.
    – gowenfawr
    Commented Oct 29, 2014 at 2:28
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    Is there any reason to think that a bigger Jaegar would require more pilots unless you added more arms, joints in the arms, weapon systems etc. That would require more thought power I would assume size was just a purely mechanical thing.
    – Chris
    Commented Oct 29, 2014 at 13:50
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    That's a fair question, @Chris, and we don't know. I'm operating on the assumption that since it's implied that the neural interface technology worked in earlier, smaller applications, and only "proved too much for a single pilot" at the Jaeger scale, that there's some size issue involved.
    – gowenfawr
    Commented Oct 29, 2014 at 14:02
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    @Chris all we have is 7:34 - 7:46: "The drift. Jaeger tech. Based on DARPA jet fighter neural systems. Two pilots, mind-melding through memories with the body of a giant machine."
    – gowenfawr
    Commented Oct 29, 2014 at 15:25

Keep in mind that initially the Kaiju were smaller than the Jaegers. They were already oversized so it would be easy to simply crush them. Bigger Kaiju came over time - thus the classification of size.

So as far as I can tell, the answer to your question is, "They did. The Kaiju got even bigger."


A) The makers did not know that Kaiju's were bound to get bigger (category n) after every event or so
B) It's difficult to implement neural load sharing among more than two pilots as it is equally difficult to find pilots that are drift compatible
C) The govt hoped Anti kaiju wall would be a viable alternative and therefore diverted funds meant for Jaeger program. So the military poured whatever's left into creating digital jaegers that are fast and effective (unaware of category 4 kaiju Leatherback)


This is an engineering problem. Let's say it takes x amount of force for a Jeager of average size to move its leg y distance in order to walk. Using proportions, it would take a Jeager 3 times average size & weight 3x in order to move y/2


Probably same reason why the opposing side did not grow even larger Kaijus to crush all Jaegers easily: there are limits on how large the things could be.


Assuming Jaeger follow a cube-power law - that is: because they're three dimensional the mass, and thus resources, go up to the third power of height - pooling the resources from three 100m robots won't get you a 300m robot, it'll get you a 150m robot. Moreover since the robots are built in humanoid fashion you're still only getting two arms to attack with; the three 100m robots are therefore going to be able to deal three times as many blows on the Kaiju - albeit blows of lower power.

Another thing to consider is that the film explicitly calls out the early Jaeger being bigger and bulkier. Of the remaining Jaeger the bigger is also the oldest; this suggests that refinement of Jaeger design in the world as led towards smaller, faster Jaeger being a more optimal solution compared to oversized behemoths.

Finally, the real reason is none of this - let's face it, Jaeger don't make engineering sense - the reason for having smaller Jaeger is that it makes the film more enjoyable. Watching the Jaeger fight monsters as big or bigger than them is more visually engaging that watching a Mega-Jaeger crush tiny Kaiju, and having multiple Jaeger makes for a better storyline.

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