Darpa is really literal when it means that the LS3 has to operate like a mule. It needs to haul up to 400 pounds, walk 20 miles and operate for 24 hours without human intervention. The program’s been undergoing tests for years, and Darpa and Boston Dynamics have put out numerous videos showing the gangly metal beast climbing woodlands, recovering from being kicked over, and running on treadmills. The Fort Pickett tests show much of the same. Only this time, the robot is way quieter — emitting “less noise than any combustion-engine system out there that’s tactically relevant,” Hill says — and its rounded back and spindly legs allow it to climb out of the uneven terrain that troops in, say, Afghanistan encounter. The LS3 can now also put its feet on uneven surfaces like logs, whereas before it labored to avoid them.