The Ultimate Paper Airplane
Japan's bid to launch an origami aircraft from the space station
Ichiko Fuyuno
Testing a small-scale prototype of the space paper airplane in the University of Tokyo's hypersonic wind tunnel. Shinji Suzuki
Earlier this year, when astronauts attached the first section of Japan's Kibo research laboratory to the orbiting International Space Station, most people probably didn't notice the small symbol painted on the module's side—an airplane made of Japan's traditional folded-paper origami. Shinji Suzuki did notice. The University of Tokyo aerospace engineer hopes to watch real paper airplanes "launch" from the space station next year.
The idea started with Takuo Toda, president of the Origami Paper Airplane Association in Japan, who asked Suzuki a few years ago to study the possibility of a paper airplane re-entering the atmosphere from orbit. "At first, many aerospace engineers thought it would burn out," says Suzuki. Objects returning from space begin their atmospheric re-entry at speeds of Mach 20. By the time the shuttle drops to an altitude of 37 miles, temperatures on parts of its surface reach as high as 2,900 degrees Fahrenheit. But a much lighter paper aircraft would slow to Mach 6 earlier in its descent—at altitudes of 62 miles or so, where the air is thinner. As a result, the aerodynamic heating wouldn't be as severe.
Suzuki knew of a method developed by a small Japanese company to coat paper with a kind of glass that would increase its heat resistance while still allowing it to be folded easily. In February, he decided to test his creations. A three-inch-long origami airplane made of specially-coated paper and folded like a space shuttle was placed in a Mach 7 airflow inside the University of Tokyo's hypersonic wind tunnel. It withstood aerodynamic heating up to 400 degrees Fahrenheit for 10 seconds—enough to give Suzuki the confidence to move forward.
Last year Japanese astronaut Koichi Wakata expressed an interest in joining the project, after he'd learned that some materials made of paper—including a flight diary and notes taken by Israeli astronaut Ilan Ramon—had survived space shuttle Columbia's violent breakup on reentering the atmosphere in 2003. Suzuki now had a means to launch his aircraft from orbit. Wakata or one of his crewmates will release about 30 eight-inch-long origami airplanes during a spacewalk planned for his STS-127 shuttle mission early next year. The Japanese Space Agency, JAXA, recently announced its support for the research, one of four projects that will receive a combined total of 30 million yen ($285,700) a year for a maximum of three years. Success could pave the way for designing lightweight space reentry vehicles, says Suzuki.
Astronauts have flown paper airplanes inside spacecraft (see the video link on this page), but have never dropped one overboard to see what happens. This won't be the first high-altitude flight, however. "We have some true stories, and some we hope are true because they are so cool," says Andy Chipling, author of Flying Paper Airplanes and president of the Paper Aircraft Association. He himself has "let one or two go while paragliding," and once dropped a paper airplane from a hot air balloon 7,000 feet over Kenya. ("We started at 5,000 feet ground height, so it's cheating, I think!")
Then there was the time, recalls Chipling, that someone in the United States "let one go down a mountain. It was said that half an hour later, when he drove into the lower parking at the bottom of the mountain, the aircraft landed at about the same time. It sounds far-fetched, but it is not impossible, as thermals could have slowed its descent."
For Suzuki, the biggest challenge was figuring out how to predict the landing point for a paper airplane dropped from orbit. Basically, he can't. No one can determine with any precision where or when the origami airplanes will come down, except that they have a good chance of falling into the ocean. A bigger airplane would be more visible, but could pose a hazard to the space station or to people on the ground. Attaching an electronic transmitter would increase the airplane's weight and make it more subject to aerodynamic pressure. Therefore, says Suzuki, "I decided to expect someone on earth to pick it up" rather than try to track its flight.
If all goes well, the paper airplanes will land on Earth a few months after they're released. "I will write messages in several languages on the planes to ask the finder to let me know," Suzuki says.
Tony Reichhardt | READ MORE
Tony Reichhardt is a senior editor at Air & Space.