What is the earliest depiction of realistic (hard sci-fi) giant humanoid mechas or robots?

Question

The usual depiction of giant humanoid mecha/robots is very unrealistic. They disregard the square/cube law, inertia, to just name a few violations of the rules of physics.

The most realistic depiction I've seen is the 1987 novel Fiasco from Stanisław Lem.

The mechas there were driven by a pilot suspended in a harness and controlling the (humanoid) mecha with his own limb movements. The nearly 2000 ton and nearly 10-story tall vehicle could run quite fast, but if you wanted to stop or turn with it, you would need a lot of place, just like driving a battleship. Sudden movements would lead to great structural damage, so the controls are designed in a way to limit the maximum acceleration of actuators depending on the load the appendages have to bear. There was even an emergency switch to allow the appendages to move with slightly higher acceleration and with higher force than allowed, but it could lead to permanent damage to the mecha. _{Even the emergency cryogenics system installed in them was the most realistic I've ever read in a sci-fi novel.}

Are there other such realistically depicted mechas or robots in sci-fi? What was the earliest one?

Answer 1

Depending on your definition of "giant", the Mobile Infantry suits from Starship Troopers (1959) would fit the bill. The dimensions of a suit as described in the book are:

• Size: "Gorilla sized"

  you look like a big steel gorilla, armed with gorilla-sized weapons

• Mass: at least 1 ton empty and up to 2000lb with full load-out:

  Two thousand pounds of it, maybe, in full kit...

  ...You do not repeat not move when surrounded by a ton of metal with your power dead

  ... and me with a couple of hundredweight of ammo and sundry nastiness still on me that I just had to find time to use up.

  ... A bare man weighs less than the ammo and stuff you've expended.

Heinlein went to some level of technical detail to explain how these exoskeletons functioned, especially the controls. Not Lem levels of detail, but definitely not Transformers implausibility either.

But here is how it works, minus the diagrams. The inside of the suit is a mass of pressure receptors, hundreds of them. You push with the heel of your hand; the suit feels it, amplifies it, pushes with you to take the pressure off the receptors that gave the order to push. That's confusing, but negative feedback is always a confusing idea the first time, even though your body has been doing it ever since you quit kicking helplessly as a baby. Young children are still learning it; that's why they are clumsy. Adolescents and adults do it without knowing they ever learned it — and a man with Parkinson's disease has damaged his circuits for it. The suit has feedback which causes it to match any motion you make, exactly — but with great force.

Controlled force . . . force controlled without your having to think about it. You jump, that heavy suit jumps, but higher than you can jump in your skin. Jump really hard and the suit's jets cut in, amplifying what the suit's leg "muscles" did, giving you a three-jet shove, the axis of pressure of which passes through your center of mass. So you jump over that house next door. Which makes you come down as fast as you went up . . . which the suit notes through your proximity & closing gear (a sort of simple-minded radar resembling a proximity fuse) and therefore cuts in the jets again just the right amount to cushion your landing without your having to think about it.