American students built a drone using Leonardo da Vinci's sketches
In the late 1480s, Leonardo da Vinci sketched an ingenious design for a single-seat helicopter powered by an "air screw." You may have seen his sketches and wondered whether one of these helicopters could ever fly. Now we know the answer. The Italian genius was right.
Starting in 2019, a group of engineers at the University of Maryland developed and tested the basic technology as part of a design competition. Then team member Austin Prete built the Crimson Spin quadcopter drone using da Vinci's screw-like design and sent it on several short flights.
"I was completely surprised that it worked," said Prete, an aerospace engineering graduate student who built the device for his master's degree. At first, he and other team members were skeptical, but after some computer simulations and 3D-printed propeller prototypes showed promising trends, they became more excited about da Vinci's design.
He presented his results and the first video of the aircraft's flight at the Transformative Vertical Flight 2022 conference in San Jose, California, last week.
This project is a good example of how modern technology diverges from the design of conventional airplanes and helicopters, although it is unlikely that a 15th-century flying device will deliver an Amazon package anytime soon. The conference featured a collection of exotic aircraft that can take off vertically like a helicopter and then fly horizontally like an airplane.
Companies such as Kitty Hawk, Airbus, Transcend Air and Jaunt hope to revolutionize this industry and carry people in air taxis.
Although Prete built only a small drone, this technology could work with an aircraft large enough to carry a person. "I really believe it should be able to scale quite well," Austin said.
The Maryland graduate student benefited from materials that da Vinci could not access. Renaissance building materials such as wood and leather were too dense for aircraft. Da Vinci also had no compact energy sources.
Prete had access to aluminum, plastic, electric motors, batteries and computer control systems, which made the air screw design possible. Computer-aided design and computational fluid dynamics software, which the engineer used to develop prototypes and simulate aerodynamics inside the computer, also proved useful.
Modern quadcopter technology also helped make the design practical. They control subtle changes in propeller rotation speed that somehow tilt the drone. According to Prete, it would have been much harder to try to build a single-rotor design like a conventional helicopter. Helicopters use complex transmissions and controls to continuously adjust the tilt of each rotor blade as it spins.
However, there are many challenges, including the greater weight of the air screws and potential instability. Prete found that some strange aerodynamics were likely helping keep the Crimson Spin in the air.
Delta-wing aircraft, such as the supersonic Concorde, create a swirling vortex just behind the leading edge of the wing. This vortex creates a low-pressure zone that can increase lift. Simulations show that a similar vortex forms along the outer edge of the flat surface of the air screw, spiraling down the entire structure and creating upward thrust.
One result of this aerodynamics is that the air screw produces less downward airflow than conventional propellers. According to the graduate student, this means there will be less dust, sand and other blown material underneath it. It is also likely much quieter.
This working air screw is a small drone about the size of a DJI, but Prete believes it can be improved through "geometry optimization and performance studies across different flight modes." Although he will no longer work on this project, the engineer believes the research could continue at the University of Maryland if there is interest and funding.
“This could be a practical hovering machine capable of potentially scaling up to carry a person, but I do not see its use in current company developments until additional research into features, reliability and performance is conducted. However, it may ultimately work in the same positions as ducted rotors”
A drone inspired by da Vinci's sketches is capable of taking off and moving around. During flight, the unusual propellers generate noise uncharacteristic of unmanned aerial vehicles, which sounds more like a drill.
