Shinji Suzuki met Takuo Toda in 1999, atop Mt. Yonami in the southern city of Jinseki-Kogen, Japan. Toda, the chairman of the Japan Origami Airplane Association, was there to launch a large paper plane from a tower he had built on the mountaintop for just that purpose.
Toda persuaded the local city council to build the 85-foot-tall tower—with 360-degree views of Mount Daisen, Mount Dogo, and the Hiba Mountains—as a monument to paper airplane hobbyists. The first floor of the tower includes a showcase of precisely folded paper plane models, while the top floor opens into a veritable launch pad. When Suzuki first met Toda, he was launching the almost-seven-foot-long paper plane—modeled after the space shuttle Discovery—off that very flight deck. “He told me that he would like to launch this paper plane from the space station,” Suzuki, now an emeritus professor in aviation at the University of Tokyo, says. “Everybody laughed at him.”
Toda’s lofty dream inspired Suzuki to take action, and in 2008, the pair announced a project to launch paper airplanes from the International Space Station (ISS). Critics suggested these planes would burn up on their descent back to Earth, Suzuki says. However, he predicted that with a protective coating and a controlled trajectory, they might actually be able to avoid burning up on reentry into Earth’s atmosphere. Another challenge? Figuring out where exactly the planes would land.
While Suzuki plotted the planes’ journey to the ISS, Toda would chart another path, racking up Guinness World Records for his paper airplane designs. For decades, he’s aimed to break the 30-second record for time aloft of a paper plane. He’s come close multiple times.
At a Japan Airlines hangar near Tokyo’s Haneda Airport in 2009, Toda sent a paper plane soaring for a whopping 26.1 seconds. And he holds the current time aloft record, which he set in 2010 with a rectangular design that lingered in the air for an astonishing 29.2 seconds. There are other records to be broken, too. As of April 2023, a trio of aerospace engineers currently hold the title for longest-distance throw of a paper airplane. Their dart-shaped plane traveled 289 feet and 9 inches, beating the previous record by almost 40 feet.
Our obsession with testing the boundaries of folded flight is relatively recent, but our desire to explore and explain the complex world of aerodynamics goes back much further.
Chinese engineers are thought to have invented what could be considered the earliest paper planes around 2,000 years ago. But these ancient gliders, usually crafted from bamboo and paper or linen, resembled kites more than the dart-shaped fliers that have earned numerous Guinness World Records in recent years.
Leonardo da Vinci would take a step closer to the modern paper airplane in the late 14th and early 15th centuries by building paper models of his aircraft designs to assess how they might sustain flight. But da Vinci’s knowledge of aerodynamics was fairly limited. He was more inspired by animal flight and, as a result, his design for craft like the ornithopter—a hang-glider-size set of bat wings that used mechanical systems powered by human movement—never left the ground.
Paper airplanes helped early engineers and scientists learn about the mechanics of flight. The British engineer and aviator Sir George Cayley reportedly crafted the first folded paper plane to approach modern specifications in the early 1800s as part of his personal experimentation with aerodynamics. “He was one of the early people to link together the idea that the lift from the wings picking up the aircraft for stable flight must be greater than or equal to the weight of the aircraft,” says Jonathan Ridley, PhD, the head of engineering and a scholar of early aviation at Solent University in the U.K.
More than a century later, before their famous 1903 flight in Kitty Hawk, North Carolina, the Wright Brothers built paper models of wings to better understand how their glider would sustain flight, explains Ridley. They then tested these models in a rudimentary, refrigerator-size wind tunnel—only the second to be built in the U.S.
Paper planes are still illuminating the hidden wonders of flight. Today, these lightweight aircraft serve as a source of inspiration not only for aviation enthusiasts but also for fluid dynamicists and engineers studying the complex effects of air on small aircraft like drones.
At Cornell University, in a lab run by physics professor Jane Wang, PhD, paper gliders plunge, swoop, and flutter through the air. What might look like child’s play to the untrained eye is actually part of a serious experiment conducted by Wang and her colleague Leif Ristroph, PhD, an associate professor of mathematics at New York University. Once the planes land, Wang and Ristroph analyze data from their flight and apply weights to change the balance of these gliders. They hope doing so will help them better understand how lightweight objects soar—something that could one day inform the future of miniature drones and other robotic craft.
The team’s most recent study, published in the Journal of Fluid Mechanics in February 2022, explored the mechanics of gliding and identified new ways for paper gliders to achieve stable flight. Insights gleaned from this research have practical applications, but they also shed light on the aerodynamic principles that keep paper airplanes thrown by enthusiasts up in the air. All planes —powered and unpowered —are controlled by the four forces of flight: lift, weight, thrust, and drag. Lift is the aerodynamic force produced by the forward motion of an object through a fluid—in this case, air. Weight, or the force of gravity, is the opposing force and pulls the airplane toward Earth. Where the engines or propellers on a passenger aircraft generate thrust, the force of a paper plane pilot’s throw gives the aircraft the forward momentum. Drag, caused by the friction a plane experiences as it moves through the air, acts in opposition to thrust.
Traditional airplanes have airfoil-shaped wings with a round leading edge. Air that passes over the wing conforms to its shape. Air flowing above the wing moves faster than air below the wing, forming a low-pressure zone above the wing that generates lift.
But the wing of a paper glider is flat, and air does not flow smoothly around it. Instead, that air forms a small, low-pressure vortex immediately above the leading edge of the wing. “This little vortex ends up changing a lot of the aerodynamic characteristics of the plane,” Ristroph says. “One thing it does is give the plane a natural stability, meaning that, in principle, it can and will glide.”
As the angle at which a glider’s wing cuts through the air—known as the angle of attack—changes, so too does the size and location of the vortex above the wing. This affects where the center of pressure, or the precise location where lift is focused, lies along the wing and how responsive it is to disturbances. If, for example, the plane encounters a gust that pushes its nose down, the center of pressure will slide forward, pushing the nose back up and into a stable position.
“The magic of a paper airplane is that all of these little flight corrections are happening continuously throughout its flight,” Ristroph says. “The plane is hanging under a vortex that is constantly swelling and shrinking in just the right ways to keep a smooth and level glide.”
The center of pressure for an airfoil, however, is locked in place and does not change with the angle of attack. This means it has trouble self-correcting if destabilized. Ristroph says the team tested this in some of their experiments by folding the sheets into an airfoil. These sheets quickly crashed after brief, erratic flights because they could not stabilize after being perturbed.
This phenomenon changes at different scales, Ristroph adds. For instance, if you were to construct a paper plane the size of a Boeing 747, the vortex above the wing would be much larger and behave differently. “That vortex would not just stay on the plane and sit there, it would jump off, reform again, and do something a little turbulent and a little crazy,” he says. “You might not be able to rely on that vortex to give you stability because it may not always be there.” Conversely, if you created a paper airplane less than, say, a millimeter long, the aerodynamics would change—along with the behavior of that vortex.
The central focus of Ristroph and Wang’s work—and, as their research suggests, the true secret to a stable glide—is identifying and making adjustments based on a glider’s center of balance. The center of balance lies at the point where a plane would be perfectly balanced if suspended in midair. (You can locate the center of balance on a paper airplane by balancing it between the tips of your thumb and forefinger.) For an unfolded sheet of paper like the ones Wang and Ristroph tested, the center of balance is directly in the middle of the page.
The team experimented with tweaking the center of balance by placing strips of copper tape on their paper gliders and studying their flight. If the weights were placed too close to the center of the sheet, the gliders would tumble uncontrollably to the ground. If the weights were placed too far forward, they would immediately nose-dive.
Through trial and error, they discovered that placing these weights halfway between the middle of the sheet and the leading edge created a stable glide, meaning that even if the glider was disturbed during its flight, it would still be able to right itself. Wang says this discovery was particularly surprising because previous work done on this topic had only ever identified “neutrally stable” modes of flight, which become unstable if perturbed and cannot self-correct.
Ristroph hopes the findings from their work will help engineers design new types of small aircraft that take advantage of passive modes of flight like, say, windsurfing craft that sail high above cities to monitor air quality. “Over the last 20 years, there’s been increasing interest in smaller-scale flight,” Ristroph says. “Small-scale flying robots [could] do things like ride on the wind rather than having some kind of engine or spinning rotors like a helicopter.”
The push to develop low-cost and low-impact alternatives to traditional aircraft has grown in recent decades. For example, in 2017 the San Francisco–based research and development firm Otherlab announced it had won a grant from the Defense Advanced Research Projects Agency (DARPA) to work on a lightweight cardboard glider that could someday deliver blood, vaccines, or other critical cargo to remote locations inaccessible via other modes of transportation.
The gliders, constructed from flat-packed pieces of cardboard, would be released from an airplane and, with the help of an onboard computer, navigate to a preprogrammed set of coordinates. Otherlab and DARPA shelved the project, but the central idea—tapping into the realm of unpowered flight to solve difficult problems—lives on.
Future small aircraft may also veer away from mimicking airplanes altogether, Wang says. In addition to studying paper gliders, much of her research focuses on forms of passive flight and gliding we already find in nature, such as insects and seeds that twirl off tree limbs. Using these techniques to create small craft could create even more possibilities in years to come.
Even after locating a glider’s center of mass, Wang cautions that this discovery won’t necessarily make solving future problems facing paper craft experts or engineers any easier. She and colleagues are attempting to solve these problems mathematically. Applying these mathematical revelations to a working glider? Well, that’s another challenge entirely.
Paper airplane enthusiasts, she suggests, might have better luck crafting gliders using intuition and experimentation instead. “People can make very, very good paper airplanes now,” Wang says. “It’s a fine art. They build their intuition by making them.”
Suzuki, Toda, and their collaborators spent 18 months testing multiple designs. They coated each plane in a protective glasslike substance that would raise the heat resistance but still allow for crisp, complex folds. With this design, Suzuki hoped that they might be able to test applications for other small-scale reentry vehicles.
The team then tested a prototype glider in the University of Tokyo’s hypersonic wind tunnel, subjecting the plane to speeds as high as Mach 7 and temperatures of almost 450°F—conditions similar to those a paper plane might face when reentering Earth’s atmosphere.
With these tests under their belt, the team reached out to Japan Aerospace Exploration Agency, who agreed to fund the project. One of the agency’s astronauts, Koichi Wakata, even expressed interest in launching them from the orbiting outpost himself. Ultimately, due to budget cuts, Suzuki and Toda’s paper planes never made it to space.
As researchers explore the field of aerodynamics, and new technology continues to model this type of flight, there’s still a chance we could see paper gliders pushing boundaries in years to come.
Weird Ways to Generate Lift
Here’s how strangely shaped objects—from Frisbees to honeybees—generate lift to soar through the air.
Frisbees
→ The lift produced by a Frisbee as it flies through the air is similar to the lift generated by an airplane’s wings. The perfect throw helps the disc push air downward without generating too much drag. In return, air pushes the Frisbee back up, generating additional lift. In 2005, researchers at MIT calculated the ideal throw angle for a Frisbee—12 degrees—to achieve maximum distance. (While the disc may travel greater heights with a larger angle, drag will shorten the distance traveled.)
Helicopter Seeds
→ The maple tree’shelicopter-like seeds, called samara, are specifically designed to fall and spin long distances away from the large, shady canopies of their parent trees. Their long, sail-like wings help balance the weight of the asymmetrical seeds. As the seed spins, the wider end of the wing moves faster than the air closer to the seed, generating lift to keep it airborne. Veins along the wing’s edge create turbulence, forming a small vortex above the wing that reduces pressure and generates even more lift.
Birds
→ Birds rely on their airfoil-shaped wings to generate enough lift force to equal and surpass their weight. But different types of birds rely on different modes of flight to generate lift force. (Hummingbirds hover thanks to a vortex that forms above their flapping wings.) Birds generate thrust by flapping their wings in a figure-eight motion. On the downstroke, air hits the bottom of the wing and is deflected past the bird, propelling it forward. Increasing the depth of each wingstroke increases airspeed and lifts the bird.
Bees
→ Bees have two sets of wings that they use to generate lift. As a bee rotates its wings back and forth, a small vortex forms above the wings’ leading edge, creating the lift force needed to keep the bee aloft. These soft and malleable wings move incredibly quickly, too, up to 230 beats per second. Compared to other insects of their size, this wingbeat is unusually fast. A fruit fly, for instance, is one eightieth the size of a honeybee and flaps its wings only 200 beats per second.
Sarah is a science and technology journalist based in Boston interested in how innovation and research intersect with our daily lives. She has written for a number of national publications and covers innovation news at Inverse.
Jennifer Leman is a science journalist and senior features editor at Popular Mechanics, Runner's World, and Bicycling. A graduate of the Science Communication Program at UC Santa Cruz, her work has appeared in The Atlantic, Scientific American, Science News and Nature. Her favorite stories illuminate Earth's many wonders and hazards.
