How tossing paper airplanes guided the career of an aerospace engineer.
- By Giles Lambertson
- Air & Space magazine, November 2008
While only in elementary school, Ken Blackburn settled on airplane design as a life study and began to shape his future in paper. He crafted reams of paper airplanes to learn the rudiments of aerodynamics. Experimenting for years with variations on a fundamental airplane made from a square sheet of paper, he learned about concepts that most people don’t encounter until they train to be pilots or study aerodynamics: dihedral angles, sink rates, and lift-to-drag ratios.
Through generations of folded aircraft, the youngster’s ideas evolved. He added pinpricks to wings, for example, to produce turbulent airflow so air wouldn’t “stick” to wing surfaces; later the tiny holes were dropped in favor of horizontal wing creases, which eventually gave way to diagonal creases.
In 1983, a year before earning a bachelor’s degree in aerospace engineering from North Carolina State University, Blackburn earned a spot in the Guinness Book of World Records for longest paper airplane glide time. He subsequently raised that Guinness standard three times, and his last record-setting flight—27.6 seconds—has stood for a decade. In 1994 he published several of his designs in The World Record Paper Airplane Book (Workman Publishing Company).
By some measurements, Blackburn has progressed little. Today a 45-year-old designer of military unmanned aerial vehicle prototypes, he works on pilotless craft so tiny their weight is measured in ounces and so slow they test the lower limits of aerodynamics. He and other engineers at the Air Force Research Laboratory, located at Eglin Air Force Base in Florida, labor in a branch of aeronautical engineering that in recent years has grown exponentially: Thousands of hand-launched UAVs, small enough to be carried in backpacks, have been deployed on surveillance missions in Iraq and Afghanistan.
Only a few inches in wingspan and about 15 ounces separate Blackburn’s recent professional project—BATCAM, an acronym alluding to the craft’s mission as an airborne battlefield camera—from the gliders he creates out of 8- by 11-inch sheets of paper. And, in fact, the bedeviling exigencies of low-speed flight are common to both types of craft and are studied and resolved in strikingly similar ways.
Blackburn, for example, designed paper airplanes systematically: A model was folded and flown, its flight assessed and its design tweaked accordingly. Then the redesigned airplane was flown, followed by more tweaking and more flying. Blackburn called it trial and error.
BATCAM, developed for the Research Laboratory’s Munitions Directorate, was engineered in much the same way, but professionals call it “the spiral method.” This development process also relies on iteration, albeit a more sophisticated variety, with an initial prototype being computer-designed, built, and tested, then an improved prototype built and tested, then a third, and so on.
When Blackburn joined Jacobs Engineering at Eglin, the original BATCAM prototype had been delivered. He helped develop the first improved model. Air Force Special Forces stationed at Hurlburt Field, Florida, tested eight of the aircraft in 2006.
“The Air Force and I are in agreement that you learn a lot by going out and testing,” Blackburn says. “I can generate a new tail shape, design it on the computer, and within a week have a prototype constructed and ready to fly. When you are working on a small airplane, and have all the tools, prototypes can come very quickly.” (Blackburn’s experience with flight is not limited to tiny aircraft. He has flown ultralights and at least once a week flies his Piper Warrior.)
Paper airplanes taught Blackburn that air is a real drag on light, slow-moving airframes. In order to be useful in the field, a small UAV must have an engine powerful enough to produce maneuvering thrust in buffeting winds. “Wind is a problem,” says Blackburn, and an especially daunting one for micro-vehicles. “For a bug, I guess going with the wind is okay,” he says, “but if you want to see what’s on the other side of the hill, an unmanned vehicle sometimes has to fly against the wind.”
Weighing less than a pound, BATCAM features wings with a 21-inch span that are flexible enough to wrap around its carbon graphite fuselage so the craft can be stashed in a backpack tube. (The wings spring back into shape when the UAV is removed from the tube.) The airplane’s battery-powered motor spins a propeller that pulls the GPS-guided craft a thousand feet into the air. From that vantage point, two TV cameras send images to a ground controller’s computer screen.
For all its sophistication, BATCAM looks a lot like a toy. In fact, the softly serrated trailing edge of its wing puts one in mind of Batman. But Blackburn politely rejects the notion that the miniature aircraft is a plaything.
“I think a fair number of people do have the opinion that it is more of a recreational device than a tool,” says Blackburn. “Where I became convinced otherwise is talking to soldiers and hearing them describe how it saved lives.”
Unmanned air vehicles were not a priority in the Department of Defense in the 1980s, when Blackburn began work in St. Louis with McDonnell Douglas, later acquired by Boeing. His first engineering job was on full-size aircraft like the AV-8 Harrier jump jet. Only toward the end of his 19 years in St. Louis did Blackburn lead research in UAV development.
For the paper airplane enthusiast, it was a return to building aircraft small enough to hold in his hands. Boeing’s UAV was a military “loiter craft” named Dominator, a 60-pound aircraft with a 12-foot wingspan capable of carrying several weapons. At one point, the engineering team puzzled over how to refuel Dominator in flight.
“It’s too small for a KC-135 tanker,” Blackburn drolly explains. “So what I did was to help define a concept for refueling.”
From his paper airplane tinkering, Blackburn learned to avoid preconceptions about fuselage and wing performance. “Sometimes the shapes surprise me,” he says of his hand-folded airplanes. “I think, ‘Well, this shape should do really well,’ and sometimes it doesn’t. Sometimes I come up with a shape that I think, ‘Well, it looks good but it won’t fly well,’ and then it does fly well. You learn by doing. More than anything else, this has made me appreciate having an open mind.”
Blackburn had experimented with asymmetrical designs in paper airplanes and knew that such configurations, while not particularly maneuverable, can be stable in flight. His colleagues warmed to his unorthodox idea and asked for a demonstration.
So Blackburn carried to a meeting an oddly configured paper airplane with a stabilizing canard on the right front of the fuselage and, on the left rear, a conventional wing with an upturned tip. With a quick toss, he floated it unwobbling across the conference room and into management acceptance as a concept vehicle for a UAV tanker.
While the Dominator has yet to be deployed, the prototype set the standard for endurance and performance in small air vehicles. Its asymmetrical-winged refueler—for which Blackburn was presented a Boeing Meritorious Invention Award—remains on the drawing board.
In the end, Blackburn’s paper airplanes helped him land his current job at Jacobs Engineering. He came across an online job posting for an engineer with miniature-airplane credentials. “It combined my two passions in life—aeronautical engineering and small aircraft—and I saw an opportunity to boost my résumé with my paper airplane experience,” Blackburn says.
Two weeks after an interview at Jacobs, he was working at Eglin. “For me, just as a hobby, I’ve tried to find every technical paper I can find to research small and very slow flying aircraft. That turned out to be the very knowledge I needed for my current job, and the people at Jacobs recognized it.”
By tomorrow’s UAV standards, the Dominator with its 12-foot wings and even the one-pound BATCAM are archaically oversized. Half-pound micro-vehicles are already flying. The Defense Advanced Research Projects Agency is funding research on airfoils with radically better lift-to-drag characteristics and powerfully efficient propulsion systems, all on an infinitesimal scale. Projects include insect-size flying robots fabricated at the University of California at Berkeley, and a nano-scale air vehicle at Oklahoma State University in Stillwater that weighs less than 10 grams and is only three inches long. Compared to such nanotechnology, paper airplanes are clunky contraptions.
“In the end, you do have to obey the laws of physics,” Blackburn says, though he concedes that “there comes a time when engineering for these vehicles does start to lose basic aerodynamic principles, but that size is really, really small, when your wing is on the scale of molecules.”
Blackburn’s work and the more immediate goals of engineers at the Munitions Directorate are focused on airplanes bigger than a molecule but small enough to require basic research into their handling qualities and components. To be effective, a small air vehicle must be compact enough—and its wings large enough—to make slow-speed hand-launching possible for a soldier who probably has not studied biomechanics and shot-put techniques, as Blackburn did to maximize his Guinness airplane launches. The quest for the next-generation mini-UAV has formed another work-and-play connection at Jacobs Engineering: “Almost everyone in our group flies radio-controlled airplanes,” says Blackburn. He calls the technologies in today’s radio-controlled toys “remarkable” and adds, “Our job is to make sure we’re not missing something” in RC components that could be used for military UAVs.
Blackburn’s experience with toy airplanes, both plastic and paper, has taught him a final lesson: “It becomes progressively more difficult to make a useful airplane as it gets smaller.” So attention, fourth-grade teachers: Don’t just confiscate the paper glider that smacks into the blackboard while your back is turned. Encourage the designer. He or she may be the one to solve tomorrow’s problems in low-speed, lightweight, unmanned flight.
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