Survey: turning in midair to land safely

Whether a quadruped can turn its body during a fall to land on its feet, and what Pupper's legs allow. Pupper can level a tilted body during a fall but cannot turn over from its back, so the posture at touchdown matters more than rotation.

• With legs alone, one quadruped has turned during an Earth-gravity fall on hardware: Mini Cheetah, carrying 532 g on each foot, turned up to 90° in pitch within 0.5 s. Turning fully over has needed a flexible spine: a 3.27 kg robot flipped 180° in 0.6 s in 19 of 20 drops from 2.8 m
• Tails turned 7–12 kg legged robots by 90° in 0.3–0.4 s. RHex gives the only comparison with and without one: with its tail inactive, its front legs snapped
• Pupper's legs are 52.5 % of its 3.17 kg, so one 115° stroke of the hips pitches the body about 30°, but a roll stroke turns it only 8–21°; a 0.3–1 m fall lasts 0.25–0.45 s
• In a 1 m drop the overrun knee would generate roughly 51 V, against the 40 V maximum in a retailer listing for the GIM4305. Whether the DeWalt pack accepts that charge and whether the power board passes reverse current are unknown, so the bus voltage is to be measured before any real drop