I’ve heard building mechas is really difficult but there is no problem in building small humanoid robots (Boston Dynamics). So can’t we just upscale them and make mechas this way?
In: Engineering
Boston Dynamics’ robots are not easy to build. Nor are they easy to power. Nor are they inexpensive.
The big problem is what is often called the “square-cubed-law”. It’s called that because some properties of an object increase with the area (square), whereas others increase with its volume (cubed).
In other words: If you make something twice as big, it’s less than twice as strong. For example, ants are strong enough to lift objects that look ridiculously large in relation to their body size, even though they have tiny legs. But if you scale an ant up to the size of an elephant, its legs would just collapse under its own weight – which is why elephants have legs like tree trunks.
For engineering, this means that making things bigger is often difficult. A hobbyist can make a scale model of a passenger airliner using nothing but styrofoam, whereas Boeing has to use strong materials like aluminum and carbon composite for the real thing. And likewise, a boston dynamics robot scaled up into a mecha sized war robot would probably crumble under its own weight.
“Just upscaling” doesn’t work because of the [square-cube law](https://en.wikipedia.org/wiki/Square%E2%80%93cube_law) – if you take a working robot design and double its scale you’re moving 8 times more material with motors that are only 4 times stronger. Eventually your materials fail because of the weight on them, or the motors are unable to move the robot.
Square-Cube law is a bitch.
If you take a human, and increase them in volume so that length width and height are all 2x bigger, they will be 8 times the volume, but the area of their footprint will only be 4 times as big. The surface area of an object scales squared, while the volume scales by its cube.
This means that the weight per square inch of foot will increase significantly.
There are other similar reasons why things don’t just scale up, but most come back to square cube law in some form.
In addition to the Square-Cube law, you also have limits on materials. As you have much higher weights, the torques becomes much higher, the ground pressure spikes a lot more, the heat dispersion becomes more problematic and so on. Also the reason as of why you want to have such a colossus needs to be answered. The rule of cool does not apply to economic realities.
Bigger is not always better :/
Well, like others said there is the square-cube law, but that’s not the only reason.
– Small humanoid robots are not easy to build. They are expensive and usually great at only a limited amount of things. For example, most of boston dynamics robots are good at moving on legs. They have great equilibrium, can move in different terrain, etc. But they can’t relly lift much than small object, they have limited dexterity, etc.
– Almost if not all humanoid robots are just demonstrator, test, prototype. They exist to improve our know how and show to public/investor for companies to get more investment. Upscaling them to make mecha is just upscaling cost, with little demonstration that it would bring them more money.
– Mecha are not a good idea. People like them because they are cool looking and that’s why we see them in fictional stories, but in real life even if they would be cheaper, barely anybody would pay for them. They are simply almost always a better machine to do the job.
It is a mistake to think we have “no problem” building those kinds of robots. Boston Dynamics makes cool stuff, but they have been at it a while and there is a reason we are don’t see their robots running around everywhere. They have a very limited battery life, and right now, they are so expensive you are better off with a traditional robot or even just hiring a guy to follow you around and do stuff.
Even if we had the technology for mecha (we don’t) they question would be, the question would be, what is a more effective military option, one mecha or six fighter jets and twenty tanks?
A lot of people have covered the square cube law, that’s a significant engineering barrier. However theres also the issue of practicality. The first significant problem with a large biped robot as a weapons platform is that it can fall over. How much damage would the top part of it receive if a 50ft tall robot just like tripped? Never mind the insane difficulty of just designing something that size that can be mobile.
If you can just mount missiles and cannons on tanks, artillery, warships and planes why bother with a hugely complicated giant walking robot?
Pacific Rim looked cool, but if we got attacked by actual Kaiju the solution would be to just blast them with missiles launched from literal miles away. It would probably only take one. They make bunker buster missiles that can penetrate multiple layers of steel reinforced concrete THEN explode. Nothing organic could hope to withstand that.
This is why we don’t have giant insects the size of elephants. ExoSkeletons work great at smaller creatures but the weight/muscle ratio does not work at larger sizes.
Picture a giant crane. It allows us to lift thing to a certain height but is a bitch to move. Even when we put wheels on it. It would tip over if we try to move it. etc…
Sounds really cool, but in reality huge mechs would be easy targets, difficult to field maintain, etc. I think the future of robotic warfare lies in smaller more nimble machines. Wheeled/tracked, flying, maybe some walkers.
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