Stanford students claim new altitude record for tiny, autonomous planes
A small Stanford battery-driven airplane flies itself to an altitude of 7,000 feet, apparently setting a world record.
BY DAVID ORENSTEIN
In what began as a class project and ended with an apparently successful quest to establish the world altitude record for a small, self-piloting airplane, a band of Stanford Aeronautics and Astronautics students learned how tricky it can be to come between the winds of Mother Nature and the rules of Uncle Sam.
Early in the morning Sept. 11, one of the team’s "autonomous" miniature airplanes reached an estimated altitude of 2,177 meters (7,142 feet), creating an unofficial record. The flight set the mark for aircraft in the 5-kilograms-or-less weight class that use electronics and software to fly by themselves rather than by remote control.
On an arid lakebed at NASA's Dryden Flight Research Center at Edwards Air Force Base, the students flew four sorties of their one-pound balsa-wood and foam planes.
"We established a reasonable record, of around 7,000 feet, which is pretty impressive for an electrically powered model airplane," said Geoff Bower, a doctoral student and teaching assistant for the class. "The students got to do a fast-paced project in which they went from a blank sheet of paper to testing out what their objective was and then achieving it. The goal was to set a new altitude record and they did."
The National Aeronautic Association is in charge of making the record official in the United States, based on the report of an observer who attended the tests. The world record must be certified by the Federacion Aeronatique Internationale.
Although the band of graduate students that Bower led as a teaching assistant for Professors Juan Alonso and Ilan Kroo expressed pride in creating a record, team members couldn't help but feel a little disappointed at the end of the day’s flights that the battery-powered, propeller-driven planes didn't soar even higher. They had lived a bittersweet day.
Zouhair Mahboubi, an aeronautics and astronautics graduate student, launches a one-pound, autonomous model plane in an attempt to establish a world altitude record for self-piloting planes in the under 5 kilogram weight class.
The first test, flown by a plane named Cero Suave, ended seconds after takeoff when it spun out of control because of a communication failure and smacked nose-first next to a road through the brushy Mojave Desert terrain of the base.
The second try, this time with Blue Panther, ultimately proved to be the best. The plane climbed as high as about 2,177 meters, the provisional new record, but when it lost contact with the ground-control station – a pair of laptops on a folding table – it went into an automatic landing mode and came down smoothly.
The students felt they could do better, and test three, again with Blue Panther, was almost as successful, coming within meters of the second flight. But the plane's promising climb was stunted when a stiff breeze began to push it toward the southern edge of the airspace allocated to the students. The Dryden Center at Edwards Air Force Base is in constant use – later that day the students got to watch the Space Shuttle Discovery land at the base – and so NASA could allocate only a 3-mile by 4-mile box for the Stanford planes to roam.
To keep Blue Panther inside the box, the students had to move toward the center and then land. It complied with a gentle swoop of a landing.
For the final sortie they launched Blue Panther a mile north of the point where the first three flights originated. The idea was to get more climbing time before the wind could blow the plane south, out of the box.
The plan worked – for a while. The plane punched through the atmosphere to an altitude of more than 2,490 meters (8,169 feet) until the winds shifted and blew it west, fully outside of its airspace. At that point, as a safety measure, the plane went into an automatic crash, or "flight termination" mode and plummeted back to the sun-baked sands at about 78 mph. The plane was recovered from a bush with a broken wing and tail. Blue Panther's higher altitude likely will not count as a record because the plane's return to Earth was, however nobly sacrificial, still a crash.
"Overall this was a great learning experience," said Zouhair Mahboubi, a master’s student, who like his teammates, had logged dozens of hours testing planes on Stanford’s own dry lakebed, Lake Lagunita. "We started with these planes about six months ago, and from the first days when we could hardly just launch them and we'd get only 10 meters before we had to land. We've come a long way."
The students' class was a year-long track of three courses, starting with design theory, conceptual design and then construction and testing of real planes to meet the goal of flying high on limited battery power.
The course has been offered most of the last six years, said Professor Alonso, but this year all four teams of students proved so successful that the professors and teaching assistant Bower arranged for them to attempt the record at NASA Dryden, in Southern California.
"The amazing thing is that the students were able to design, build, and test several aircraft that were capable of performing their entire mission, from take-off to landing, completely autonomously and without intervention," said Alonso. "The technologies necessary to do something like this in such a small package have only been available in the last five years."
In the end, much more was gained, both for pedagogy and posterity, than was lost. Each plane cost only about $500 in parts to build.
Although the planes were developed as a class exercise, small, inexpensive autonomous planes that fly thousands of feet in the air could have a wide variety of applications. Fitted with cameras, for example, they could monitor traffic, look for fires, sample the atmosphere, or conduct other surveillance, Alonso said.
So-called "micro" unmanned aerial vehicles could fill niche roles that larger drone planes are too large and expensive to fill, said Brendan Tracey, a second-year masters student. In particular, he envisions autonomous planes equipped with environmental sensors to monitor air pollution.
"You can build 500 $2,000 airplanes for $1 million," he said. "These sort of surveillance vehicles could really help do more research more cheaply and we could start finding out a lot more about the world in which we live."
Other members of the team, and prospective record holders, were graduate students Sean Copeland, Patrice Castonguay and Meir Messingher, and recent graduates Ismail Robbana and Henry Lee.
David Orenstein, public affairs, School of Engineering
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