Ben Balsley, CIRES Scientist in the Field
And Balsley, an atmospheric dynamics expert whose kite was more than two miles skyward that summer of 1990, had a peculiar feeling. "It was so far out of sight we couldn't even see it with the binoculars," he recalls. "I was pulling on a string that seemed to go off into eternity."
Balsley and his colleagues flew the kite -- which was really two large parafoils strung together in a line -- for four days and nights in the tropical Pacific trade winds, gathering meteorological data with instruments attached to the string. Mission accomplished, they returned home, convinced a renaissance was in the air.
Franklin's 1752 experiment was not the first kiting effort in the name of science, says Balsley, noting that a creative Scotsman undertook the first experiments in 1749. The use of kites for atmospheric research grew through the 1800s and into the early 1900s, when the U.S. Weather Service used piano wire to loft and tether meteorological box kites at 18 field stations east of the Mississippi.
Research balloons and aircraft gradually displaced the more romantic kites as experimental vehicles, however, and they faded into memory by the onset of World War II. But the allure of kites as effective research tools -- especially their ability to hover in one location for long periods -- was not lost on Balsley, a fellow at CU's Cooperative Institute for Research in Environmental Sciences (CIRES).
Casual discussions between Balsley and other atmospheric scientists in 1989 led to an exploratory research proposal by the CU researcher to the National Science Foundation. The NSF program manager for physical meteorology, who described the project as "just crazy enough to be successful," also approved it. Balsley and three colleagues touched down on Christmas Island the following August.
Set in the middle of the Pacific southwest of the Hawaiian Islands, Christmas Island was discovered on Dec. 24, 1777, by Captain James Cook. It turned out to be one of his final accomplishments, however, as Cook was slain by Hawaiian Island natives in 1778 shortly after he discovered their islands.
Chosen by Balsley for its steady trade winds, clear weather and conspicuous lack of air traffic, the 25-mile-long atoll in the Republic of Kiribati exudes a quaint charm, he says. Passengers on the once-a-week airplane flight from Honolulu are generally headed for London, Poland or Banana -- the island's three villages.
Since the effort demanded an exceptionally large and sturdy kite to loft the instruments and withstand the relentless winds, Balsley enlisted the help of noted kite designer William Tyrrell and aerodynamics expert Joe Williams of Doylestown, Pennsylvania. The result was two 8-by-17-foot nylon parafoils, one spaced about a mile above the other, and tethered by Kevlar string one-tenth of an inch in diameter.
Unlike most kites, the frameless parafoils consist of a series of hollow tubes resembling a raft that are inflated by the wind as the kite rises, explains Balsley. The space-age Kevlar material used to weave the tether -- the same material used in bulletproof vests -- has high strength but low shear, so even the tiniest knot in the line can snap it like a twig.
The researchers launched the tandem kite system -- which was spooled by a hand-powered winch -- from an abandoned runway near the southern edge of the shoe-shaped island. The 2.2-mile height attained by the upper kite proved to be a new world record for parafoils. "Once it was up it just stayed there," he marvels. "It became obvious there is a natural niche for research kites."
Balsley had one adrenalin-filled moment when the lower parafoil got soaked during a rare squall, then nose-dived into a nearby lagoon dubbed the Bay of Wrecks. Undaunted, he waded out about 100 yards in chest-deep water to retrieve it.
"I could see the guys were waving for me to come back," remembers Balsley. "What I didn't see at the time was the shark fin going in circles around me."
Despite the unexpected encounter with the curious six-foot fish, the project went swimmingly. The volleyball-sized instrument packages riding on the string worked as expected, relaying information on temperature, humidity, air pressure and electrical fields to a laptop computer stashed inside a ground tent.
In August 1993, a Balsley-led team took to the air once again, this time from Cape Sable Island off the southern coast of Nova Scotia. Accompanying Balsley were CU chemistry Professor John Birks and two graduate students.
"As soon as I heard about this project I got excited," recalls Birks, who was working with chemistry graduate student Karl Knapp to scale down the size and power needs of pollution-measuring instruments. "It seemed like a natural, so I jumped on the train."
The goal this time was to measure ozone concentrations in the lower atmosphere as part of the North Atlantic Regional Experiment, or NARE, a multi-year project to monitor the spread of industrial pollutants eastward from North America. While natural stratospheric ozone shields Earth from potentially harmful ultraviolet radiation, the ground-based ozone under study at Cape Sable is largely man-made, created when car and factory emissions react with oxygen in the presence of sunlight.
The team successfully tested a new system at Cape Sable consisting of a single parafoil (made of waterproof Mylar this time) and a second kitelike device known as a "wind tram" designed by aerospace engineering graduate student Mike Jensen. About twice the size of a child's kite, the triangular wind tram was designed to fly up and down the main tether while lugging a 10-pound instrument box to measure pollution concentrations at varying altitudes.
With the main parafoil acting as "a stationary sky hook to grab onto space," the wind tram had no trouble flying up the string on its own power, notes Balsley. "It was a thrill to watch it run up the tether and disappear through the clouds."
Although the tram was supposed to glide back down the string in response to electronic commands, there were a few glitches early on, remembers Birks. After the tram repeatedly became stuck high on the line and refused to descend, a weathered fisherman who was watching the show offered a piece of advice.
He suggested a technique for remotely shifting the weight of the instrument box to the wings of the troubled tram, which would then collapse and send the entire payload zipping back down the string. "It worked quite well," recalls Birks. "Fishermen tend to know a lot about pulleys, winches and lines."
This spring, the kite team is headed for the Azores, a tiny group of islands in the North Atlantic about 1,200 miles west of Portugal. While that work will be a continuation of the NARE experiments, the team may be packing a heftier spool of the 900-pound-test Kevlar line in anticipation of flying higher than ever before.
In fact, the world kite record -- set by a German team that strung together eight box kites to reach a height of six miles in 1919 -- could well fall. "We could have challenged the record at Christmas Island," says Balsley. "We just ran out of string."
Computer modeling by Jensen indicates that, in the right place and time, such parafoils could fly up to 11 miles high -- putting them into the lower margin of Earth's stratosphere and home of the protective ozone shield, says Birks. Above that altitude, diminishing winds and increasing atmospheric drag and tether weight preclude extended kiting.
"When you get that high, the weight of the kite is trivial compared to the drag and the weight of the line," explains Birks. Eleven miles of the lightweight Kevlar kite line still tips the scales at more than 100 pounds, roughly 10 times as heavy as one parafoil.
But the kiting expeditions have their "lighter" moments. The tension of the straining tether at Cape Sable, for instance, allowed those grasping the string to "bound across the beach as if we were jumping on the moon," says Balsley.
The researchers hope to upgrade the winch system used to lower the kite from extreme altitudes this spring, says Birks. Since rapid changes in winch speed are critical for keeping descending kites airborne, Birks enlisted the help of his automotively inclined father to design a system that attaches to a car wheel and takes full advantage of the brake and gear systems.
They plan to test the concept on Billy Goat Hill near his father's home, "the best place to fly a kite near Afton, Oklahoma," Birks says.
The premier places in the world to fly research kites may well be Earth's equatorial and near-polar regions, says Balsley. Both are of intense interest to atmospheric scientists, feature relatively light air traffic and boast steady, predictable breezes. "If we can get them in the lower stratosphere, there is no reason they should not stay up for months," Balsley says.
As part of an extensive computer modeling project, Jensen has compiled a kite-flying atlas of sorts that features, month-by-month, some of the windiest and most isolated places in the world. "It gives us a way to pick out the best places to fly and when to go," says Birks.
Eventually, Balsley and Birks hope to take the kite project to developing countries in South America and Africa. They recently began discussions with a group of former chemical company executives to identify areas of concern and evaluate their potential for kite research. Since the research "is fairly low-tech, it would be a natural way to involve local scientists and technicians in environmental monitoring procedures," notes Balsley.
In Brazil, for example, Birks envisions the kites floating over the tropical rain forests to study fluctuations in carbon dioxide levels caused by slash-and-burn agriculture and accompanying deforestation.
Kites lofted from boats in the middle of the Amazon River could provide "vertical profiles" of the gas for weeks on end, helping researchers better understand the mysterious carbon cycle. With the river flowing to the east and the wind blowing from the east, "we could conceivably fly for many days," says Balsley, also a researcher in the electrical and computer engineering department.
Not surprisingly, the subject of kites has become a passion for Balsley. He recently embarked on a project with undergraduate Sue Hornby to compile a detailed history of atmospheric kite research around the world. And the two have turned up some surprising information.
Many schoolchildren, for example, know Ben Franklin proved the true nature of lightning by snaring an electrical charge in a jar during his famous 1752 kite flight. What most don't know is this, says Balsley: Franklin's choice of a kite as a vehicle for his historic experiment appears to have been an afterthought.
Weary of waiting for a new steeple to be erected atop Philadelphia's Christ Church -- where he had originally planned to conduct his electricity tests -- Franklin abruptly changed his mind and sent a kite floating into the stormy heavens. "It looks like he just ran out of patience," says Balsley.
More than two centuries later, Balsley and Birks are dreaming of a kite renaissance that even the visionary Franklin might have found astonishing. They can see it now: An armada of soaring platforms deployed around the globe to tackle crucial global change questions from rising greenhouse gases and industrial pollution to our dwindling ozone shield.