Phantom Twist spinning drone blurs into invisibility at 25 rotations per second

Stealth drone spins so fast that it disappears | New Scientist

Stealth bombers use exotic materials to lower their radar signature and spy satellites orbit earth far outside human sight, but a new drone avoids detection in an altogether simpler way: spinning so fast that it blurs into the background. Emma Alexander and colleagues at Northwestern University created the drone, called Phantom Twist. It spins at 25 revolutions a second to hide itself in a motion blur like the blades of a fan. But unlike a fan which has fixed parts that remain clearly visible - the central axle, controls, a stand - every single part of Phantom Twist whirs in circles. The unusual single-motor design was arrived at by a complex, multi-stage and entirely automated process. First, a computer created a list of millions of designs, which was whittled down to around 20,000 that were theoretically able to fly. Next, an AI slightly tweaked the placement of each component in every design to minimise visibility, on average, from all viewing angles. Finally, another AI model that mimicked human sight assessed the visibility of each shortlisted design in front of various backgrounds. The researchers simply stepped in at the end to build the best, final design. That winning design spread the components around so that none visually overlapped when spinning, was small enough to fit in the palm of the hand and weighed just 30 grams. "The motion blur essentially turns all of the mechanical components into this slight haze," says Alexander. "And if you're not paying attention you might really miss that slight change in the brightness of the environment." David Whitaker at Cardiff University, who studies optical perception, says that although the human visual system can detect changes up to 60 times a second in some situations, such as when observing a flashing LED, this rotating drone is moving fast enough that the brain simply merges its parts and the background together - not becoming invisible, but blurring enough that it can be missed if the background closely matches its own colour. "Imagine a cooling fan, spinning round and round. If it spins fast enough you lose appreciation of the blades. The visual system can't cope," says Whitaker. "When things are moving fast the visual system merges those moving objects with the background, so they become relatively invisible." Peter Lee at the University of Portsmouth, who was not involved in the research, says that stealthy drone technology has obvious military applications, but that this design - while deploying a nifty optical illusion - has serious limitations. The optical trick relies on a very spindly and sparse design, so adding any additional sensors or payloads would make it more visible, says Lee. And adding weight or scaling the design up in size would also lead to much higher centrifugal forces, potentially making flight impossible or causing the drone to break apart. Added to this, the gyroscopic effect of a spinning drone would make quick changes of direction extremely difficult. "This style of drone is not manoeuvrable in the way that quadcopters are highly manoeuvrable. So because of the rotation, it won't be able to bank at steep angles," says Lee. "It would slow the speed of the rotation, and therefore it would become more visible and it's probably getting unstable." The researchers admit that the drone is not highly manouverable - it can currently only hold a steady hover - and that it can still be heard easily even if not seen. But they believe that choosing transparent components rather than opaque ones, such as the black carbon fibre rods that make up the structure, could further reduce visibility. And changes to the AI design process to take into account the visibility of even the smallest components on the device could also bring further gains. The researchers are presenting their work at the Robotics: Science and Systems 2026 in Sydney, Australia.

Tiny drone hits invisible mode by twisting faster than eye can detect

This drone is 10 times less visible than a standard quadcopter, according to the study Engineers at Northwestern University have built a drone that vanishes without camouflage or transparent panels. Its trick is spinning so fast that your eyes simply give up trying to focus, a stealth edge that could turn surveillance into something almost invisible. The aircraft, nicknamed Phantom Twist, rotates up to 25 times per second, a rate that outpaces how quickly our visual system can process sharp detail. Instead of true invisibility, the drone dissolves into a faint, ghostly blur that blends into whatever is behind it. The work, led by associate professor Michael Rubenstein, was presented on July 16 at the Robotics: Science and Systems 2026 conference in Sydney, Australia, under the title Computational Design of a Low-Visibility UAV Using Human-Aligned Perceptual Metric. "Most efforts to hide drones focus on making them look like their surroundings," says Rubenstein. "Instead, we asked whether we could design the drone itself around the way humans perceive motion. This idea of low visibility through persistent motion is something few people have explored." That distinction matters because drones are increasingly used to watch wildlife, check aging infrastructure, or survey wetlands, but their mere presence changes the behavior of whatever they're observing. Birds scatter, animals flee, people act differently. A drone that's hard to spot could do the same job without that side effect. Prior attempts at motion-based concealment offer useful context here. The Northwestern paper points to an earlier project nicknamed the Boomerang Drone, covered in a 2006 New York Times Magazine piece, which tried a similar high-speed rotation trick but couldn't spin fast enough to fully exploit the blur effect, leaving it largely visible. The paper authors also trace the broader idea of active concealment back to the "Yehudi light," a counter-illumination project developed by the National Defense Research Committee in 1944 to hide Allied sea-search aircraft from enemy view. The Phantom Twist itself takes a very different shape from those earlier attempts. Rather than a typical quadcopter with four separate rotors, it runs on a single motor and a single propeller, with the propeller spinning one way while the rest of the drone's body spins the opposite way. "For a typical quadrotor drone, the propellers are spinning, but the robot is stationary," Rubenstein explains. "So, you still see its body. For our drone, the whole thing is rotating, so there are no stationary parts." To reach that layout, the team's computer model generated roughly 20,000 possible drone configurations capable of stable flight, then used artificial intelligence and optimization algorithms to repeatedly rearrange the motor, propeller, circuit board, counterweight, and batteries. Each design was simulated spinning mid-flight and overlaid on 100 real-world backgrounds, then scored by a perceptual model built to mimic human vision, where a lower score meant better camouflage. The 500 best-scoring designs were run through the optimizer again to squeeze out further gains before a final version was built. Emma Alexander, an assistant professor of computer science and one of the study's co-authors, explains the underlying physics. "The human eye takes time to accumulate signals, roughly analogous to the exposure time of a camera," she says. "When an object spins quickly, we perceive it as blurring out and losing distinct features. Because this new drone is almost entirely transparent, its few opaque components are visually averaged with the background for an overall appearance of a slight haze." According to the paper's visibility metric, the finished drone is about 10 times harder to spot than a standard quadcopter. But the spinning trick has real limits that make this drone far from being completely unnoticeable. The propeller still makes an audible whir that gives the drone away even when the eye can't, and its support wires and rods remain partly visible. The paper's authors suggest future versions could lean on more transparent materials and quieter propulsion, edging the drone ever closer to true - and somewhat scary - invisibility. After all, the same trick making a drone less impactful on wildlife could just as easily help it sneak around for reasons that aren't so friendly.

New spinning drone is 10 times less visible than standard quadcopters

Northwestern University in the US has developed a low-visibility drone called the "Phantom Twist." It achieves low visibility by spinning itself into visual oblivion and rotating up to 25 times per second. That is far too fast for the human eye to process. Interestingly, this motion blur transforms the drone into a faint, semi-transparent smudge that blends into its surroundings rather than achieving total invisibility. "Most efforts to hide drones focus on making them look like their surroundings," said Michael Rubenstein, who led the work. "Instead, we asked whether we could design the drone itself around the way humans perceive motion. This idea of low visibility through persistent motion is something few people have explored." Conventional drones often disrupt wildlife and human behavior simply by being noticed. Scientists have tried everything from high-tech light-bending optics to transparent plastics and hyper-realistic camouflage. But a team of roboticists at Northwestern University decided to stop trying to hide the drone. The idea was to focus on altering a drone's physical appearance to change how it is perceived. In this development, the standard stationary-body quadcopter design was replaced with a single-motor system where the propeller and the entire drone body spin in opposite directions to minimize visibility. Quadcopters remain highly visible because their bulky central bodies stay completely stationary while only rotors spin, but the Phantom Twist mimics a fast-spinning ceiling fan. Rotating its entire structure allows the drone to blur its body into a semi-transparent disc. Emma Alexander, a computer vision expert and co-author on the study, explains that the human eye behaves a lot like a camera with a fixed exposure time. "The human eye takes time to accumulate signals, roughly analogous to the exposure time of a camera," said Alexander. "When an object spins quickly, we perceive it as blurring out and losing distinct features. Because this new drone is almost entirely transparent, its few opaque components are visually averaged with the background for an overall appearance of a slight haze." The development, of course, was not straightforward. The parts just can't be mounted on a spinning stick and expect it to fly straight; balancing the entire structure is incredibly difficult. To solve this, the team handed the keys to artificial intelligence. The automated design pipeline first generated 20,000 mathematically stable configurations. Then, an optimization algorithm repeatedly rearranged the drone's heavy essentials, such as the battery, the circuit board, and the counterweights. The goal was to ensure the components never visually overlapped while spinning. The AI then simulated these designs against 100 real-world backgrounds, scoring them using a metric modeled after human vision. The lower the score, the harder it was to see. According to the study's testing, the new design is ten times harder to see than a conventional quadcopter. In the future, these types of drones could help in ecological and industrial surveys. Drones are vital tools for counting nesting birds, mapping wetlands, or inspecting cracked bridges. But the loud, buzzing, mechanical presence often panics wildlife and alters natural behavior. A drone that blends into the sky could watch animals without scaring them away. It is not entirely perfect yet. For instance, its propeller sound can still be heard, and if someone look incredibly closely, you can occasionally spot the faint outline of its carbon-fiber support rods. But the team is already working on the next generation. The goal is to incorporate acoustic dampening and fully transparent materials to make the drone truly vanish. The findings were presented at the Robotics: Science and Systems 2026 conference in Sydney, Australia.