Questionable Math: Pacific Rim
Long ago I watched Pacific Rim and thoroughly enjoyed it. However sometimes I get distracted when movies (or books, or whatever media) give me concrete details that don’t make any god damn sense. Its like they’re inviting me to consider what they’ve done. I mean, the did do it; they went and put it in the movie and showed it to me.
The image that I have in mind is where 8 helicopters were carrying the jaeger out to the ocean battle. 4 helicopters strapped to each shoulder. Lets not even get into the weird physics of how they were all connected together like a bunch of balloons. For this exercise I’ll ignore that bit and treat them like they can all lift strait up very effectively.
 The helicopters make me ask: How heavy is a jaeger?
The heaviest lift helicopter I was able to find was one with a lifting capacity of 20,000 kg
That gives an upper bound on the weight of the jaeger of 160,000 kg (20,000 kg * 8). But is that a lot for a giant battle robot?
Lets look at density to figure out what the jaeger could maybe be made of.
A quick google tells me that a jaeger is 76 m tall and that an average person height and weight of 1.8 m and 80 kg would not be an unreasonable approximation. The jaeger is approximately 42 times taller than the person (76/1.8) so using the cube rule a jaeger sized person would be 74,088 times heavier (42^3). The inverse is true and if we scale down a jaeger to person size it would weigh 2.16 kg (160,000 kg/74,088). This is clearly an unhealthy weight for a person sized object.
Some more googleing to find the volume of a person gave a pretty wide range (unsurprisingly) and so I’ve settled on calling the average person that I’ve constructed at 78 L as the density of a human body is 985 kg/m^3. The density of the jaeger is 0.0278 kg/L (2.16kg/78L) which converts to 27.8 kg/m^3
So it can’t be solid balsa wood and is only 10 times denser than the least dense solid ever made.
But maybe I’m being unfair, it isn’t a solid chocolate jaeger after all, it does have air spaces in it. So how does it compare to real sturdy military vehicles? An M1 Abrams tank has a length, width, and height, of 7.93 m, 3.66 m, and 2.44 m respectively and a weight of 54,000 kg which gives it a minimum density of about 763 kg/m^3. Its a minimum density because I calculated a maximum volume given its length, width, and height so it was actually smaller its density would increase. The tank density of 763 kg/m^3 is about 10% of steel, which I assume is what a lot of a tank is made of. With that ballpark density modifier I’m happy to say that the jaeger could be arguably made from a material of up to 278 kg/m3 and very happily indeed I have discovered that the density of aluminum is 270 kg/m3 so there we have it!
The jaegers as depicted being hoisted by the 8 powerful helicopters could plausibly be constructed from aluminum; plausibly with respect to weight alone, and only if they were 90% void spaces internally.
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