This altitude is higher than any propeller-driven aircraft has ever flown and about 9000 feet higher than the previous altitude record set by Pathfinder in 1997. The record flight was the 39th consecutive successful flight test of the Pathfinder platform.
The Pathfinder airplane is a technology demonstration platform proving the viability of solar-powered aircraft for high-altitude, long-endurance flight. Derivatives of this aircraft, incorporating energy storage for nighttime flight, will be capable of continuous flight for weeks or months at a time at altitudes of more than 60,000 feet.
The successful record flight is one more milestone on the way to commercial solar-powered aircraft acting as low-cost complements to satellites.
According to Bob Curtin, AeroVironment's Pathfinder program manager, high-altitude solar planes will be cost-effective for many applications currently performed by satellites. "They can relay communications signals. They can take photos. They can track hurricanes. They can do exactly what a satellite does for many applications, but more flexibly and with less investment."
For some communications applications, Pathfinder and its descendants have critical advantages over satellites: distance, location and recovery. Geo-stationary satellites orbit 25,000 miles above the earth's surface, requiring costly, high-power transmitters and adding delay to communication signals. Low-earth orbit (LEO) satellites cannot remain stationary over targets, and are still at least 400 miles away.
At less than 15 miles altitude, solar airplanes allow use of much cheaper transmitters and reuse of scarce frequency spectrum. Because solar airplanes can land and take off as needed, their payloads can incorporate the latest technology before it is qualified for an unrecoverable satellite payload.
At well under $10 million each in production, solar airplanes will also be much cheaper than satellites, which can cost more than $100 million to build and launch. Given these advantages and the success of the Pathfinder development, the commercial future for solar airplanes looks very promising.
Ray Morgan, vice president of AeroVironment, believes "it's inevitable that, in the future, solar-powered aircraft will be operating routinely as stratospheric satellites in the lower latitudes."
With an IMAX camera crew filming, the Pathfinder began its record flight at 8 a.m. carrying 68 pounds of simulated payload. Climbing steadily through the day, the airplane passed through 80,000 feet around 3:15 p.m. and reached a peak altitude of approximately 80,400 feet. Almost 15 hours after takeoff, the Pathfinder touched down for a safe landing at 10:45 p.m.
Jeff Bauer, deputy program manager from NASA's Dryden Flight Research Center, said the flight was "just picture perfect." NASA has sponsored development of the Pathfinder under the Environmental Research Aircraft and Sensor Technology (ERAST) program.
This marks the last flight for the Pathfinder as a testbed for the ERAST program and the focus of development now moves to a similar aircraft known as Centurion. With a wingspan of 206 feet, much longer than the current 121-foot Pathfinder, Centurion will be capable of reaching and sustaining an altitude of more than 100,000 feet. Low-altitude flight testing of Centurion will begin in October, and high-altitude flights are planned to begin in the summer of 1999.
AeroVironment has long been known for its development of efficient vehicles. Pioneering air vehicles have included the human-powered "Gossamer Albatross," and the solar-powered "Gossamer Penguin" and "Solar Challenger."
In 1981, the Solar Challenger flew 163 miles, from Paris to England, at altitudes up to 11,000 feet powered only by the sun. Solar Challenger is now owned by the Smithsonian Institute's National Air and Space Museum. Groundbreaking land vehicles have included the "Sunraycer" solar-powered car and the "Impact" electric car, forerunner of the General Motors EV1.