A drone developed by researchers at Northwestern University is paving the way for a new generation of aircraft that are difficult to detect with the naked eye.
It relies on a principle different from traditional camouflage techniques, which is based on rotating its entire structure at a very high speed that makes it appear almost to disappear.
The researchers named the aircraft "Phantom Twist," and it spins at speeds of up to 25 revolutions per second—a speed beyond the human eye's ability to distinguish details. While not completely invisible, tests showed it to be about ten times less noticeable than current quadcopter drones.
Researcher Michael Rubenstein, the team leader, says that most attempts to conceal drones have focused on making them resemble their surroundings, but his team chose a different approach: designing the drone to match the way the human eye perceives movement, so that its continuous rotation blurs its visual features.
To achieve this, the researchers began by generating about 20,000 different designs using a computer, then used artificial intelligence techniques to test hundreds of possible arrangements of aircraft components, before arriving at the final design that met the requirements for performance and flight capability.
The design of the Phantom Twist differs significantly from traditional drones. Instead of four engines and four propellers, it relies on one engine and one propeller, while the entire structure rotates during flight, which eliminates the presence of fixed parts that can be easily detected by the eye.
Rubinstein explains that traditional drones keep their airframe stationary while only the propellers rotate, making them highly visible. In the new design, however, the complete rotation of the airframe allows its details to blend visually into the background, giving the drone the appearance of a blurry or "ghostly" patch, as the team describes it.
Researcher Emma Alexander explains that the human eye needs a fraction of a second to process an image, and when an object moves very quickly, its details become blurred. Because the new aircraft is made mostly of transparent materials, the few opaque parts blend visually into the background, making them even harder to notice.
Despite the promising results, the aircraft still has some limitations. Its wiring and support rails are still visible, and it produces a high level of noise during operation, which may limit its use in some missions.
Researchers hope that this technology will contribute in the future to the development of drones used for monitoring wildlife, conducting environmental surveys, and inspecting infrastructure, while reducing the visual noise caused by traditional aircraft.
Conversely, experts believe the design still faces technical challenges. Peter Lee, a researcher at the University of Portsmouth, says that adding new sensors or equipment to the aircraft would make it more visible, and any increase in weight would affect its balance and centrifugal forces, potentially hindering its flight capabilities.
He added that this type of aircraft is less maneuverable compared to quadcopters, as its steep angles slow its rotation, making it more visible and potentially affecting its stability during flight.
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