AT-AT

The whole point of a troop transport is to get fighters and their equipment to the front lines without exhausting them in the process. To do it, a troop transport needs range and speed to achieve the element of surprise during an advance, and armor to protect the troops and gear inside. Which makes us wonder what the Star Wars weaponeers were thinking when they debuted the AT-AT in The Empire Strikes Back. The name stands for "All Terrain All Transport," but even with all these longstanding rules for making a good ride, the designers gave the Empire a bunch of top-heavy four-legged walkers that are vulnerable, slow and easy to spot.

I don't want to come off like someone who doesn't support quadruped robots on the battlefield. There's a time and a place where this design makes complete sense, such as the four-legged robots that could serve as battlefield mules for foot soldiers to haul gear or wounded troops. Four legs is an advantage to a robot mule that needs to keep up with Marines on a long-range combat patrol through rough terrain.

However, they are not well suited for front-line action. Scaling up a 4-legged design to mammoth AT-AT walkers brings few advantages, and numerous disadvantages. Sure, the AT-AT could step over many obstructions, like trees and boulders. But steeper inclines and the inability to roll upright—it's awfully boxy for such a maneuver; a barrel shape would help—makes this a dangerous ride.

Although the engineers of the Star Wars universe have perfected dynamic stability, allowing a legged robot to recalibrate its balance after each step just like a person does, we're still left with a nagging question. Why choose legs at all? The walker advances at a ponderously slow pace, making a ton of noise in the process. AT-ATs are so large they can be spotted visually and on radar. Since there's no element of surprise here, an Imperial general might as well fly a large ship or hovercraft to the target. Of course, the movie explains that the walkers' mission is to take down the Rebels' shield generator, but why that shield doesn't extend to the ground—allowing the mammoth AT-ATs to get through—confounds me. If they can walk through, why couldn't the Empire simply launch low-flying aircraft or high-speed hovercraft to ferry troops?

The AT-AT even fails at its primary advantage, the fact that it's armored vehicle. Sure, it's built solidly. But these things have such well-known weak spots that rebels arm their fighters with harpoon cables to trip them up. (What else are they good for, hunting space whales?) Yes, Hoth fell to the Empire, but the invasion would have been quicker, easier, and more effective with waves of smaller, conventional ground vehicles backed by close air support.