In 2005, Boston Dynamics unveiled its robot "mule," Big Dog. Now it has a smaller, nimbler littermate called Spot that can take a good kick. Weighing in at 160 lb (72.5 kg), the electrically-powered, hydraulically-actuated, four-legged robot made its debut in a YouTube video released by the company on Tuesday.

Boston Dynamics isn't releasing many details about Spot beyond saying that it's designed for indoor and outdoor operation; preferring to let the video speak for itself. However, the footage does provide a few clues.

For one thing, Spot is the smallest of Boston Dynamics' quadruped robots (outside of the lab-bound LittleDog) and shows the cleanest engineering. It's nimbler than Big Dog, though the two may be related, and the electrical/hydraulic system, which may be derived from the company's Atlas humanoid robot, is much quieter than the internal combustion engines used by the larger robots.

Another improvement is the configuration of the legs. Where Big Dog and its derivatives use a forward-angled leg design, Spot's is angled backwards like the legs of a goat, and it hops about like one. The efficacy of this arrangement is shown in the video, which shows Spot, standing about a meter high, navigating the narrow corridors of the Boston Dynamics offices… and receiving a swift kick by one of the office workers along the way. The company's robots are well known for keeping their balance, but Spot holds its feet with only a quick, remarkably lifelike stagger.

The video indicates that it uses some sort of scanning LIDAR for navigating. It also shows Spot negotiating a rough hill, climbing a flight of stairs, running with a man, moving in tandem with another Spot, and walking alongside the company's biggest robot, the LS3.

The latter raises the question of what Spot is for. Previous Boston Dynamics quadrupeds were developed as part of a contract to create robotic pack mules to assist soldiers with their gear in rough country. That makes sense for a machine the size of a mechanical bullock, but a robotic goat is another matter. Perhaps it's designed as a robot scout or an autonomous guard dog. Or maybe the company is expanding into the mechanical pet market. We'll have to wait until Boston Dynamics tells us a bit more.

The video showing Spot in action is below.

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