A drone you cannot see is not hiding. It is simply moving faster than your eyes can resolve. Northwestern University engineers have built the Phantom Twist, a single-rotor aircraft that spins its entire body between 15 and 25 times per second. Presented at Robotics: Science and Systems 2026 in Sydney, it is roughly ten times harder to see in flight than a quadcopter of the same size. The trick is not camouflage. It is persistence of vision. The human eye integrates light over roughly 100 milliseconds before handing a scene to the brain. Anything rotating faster than that window is smeared across its own path and averaged into the background. It is the same effect that turns a ceiling fan into a translucent disc. Conventional quadcopters cannot exploit this. Their propellers blur, but the frame stays rigid and still, and that stationary silhouette is exactly what the eye locks onto. Phantom Twist deletes it. - One motor, one propeller, no control surfaces - The propeller turns one ...