BigDog

The robot that could walk where wheels couldn't. Funded by DARPA, BigDog was a four-legged machine designed to carry 340 pounds of gear over rough terrain alongside soldiers. Its hydraulically actuated legs could handle slopes up to 35 degrees, walk through snow and mud, and recover from kicks and slips. BigDog pioneered dynamic balancing and terrain-adaptive locomotion that led directly to Boston Dynamics' later successes. Though ultimately too loud for military deployment, it proved that legged locomotion was viable for real-world tasks and launched a new era of mobile robotics research.