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Pathfinder Photo Gallery Contact Sheet Pathfinder Photo Gallery Contact Sheet

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Formats: Low Resolution Image Contact Sheet (143 KBytes)
Medium Resolution Image Contact Sheet (143 KBytes)
High Resolution Image Contact Sheet (143 KBytes)


These are the image contact sheets for each image resolution of the NASA Dryden Pathfinder Photo Gallery.

Pathfinder was a remotely controlled, solar-powered flying wing, designed and built as a proof of concept vehicle for a much larger aircraft capable of flying at extremely high altitudes for weeks at a time. It was built by AeroVironment, a California company that developed the human-powered Gossamer Condor and Gossamer Albatross lightweight aircraft during the 1970s, and later made the solar-electric powered Gossamer Penguin and Solar Challenger.

The basic configuration and concepts for Pathfinder were first realized with the HALSOL (High Altitude Solar) aircraft, built in 1983 by AeroVironment and the Lawrence Livermore Laboratory. Pathfinder was constructed of advanced composites, plastics, and foam, and despite a wingspan of nearly 100 feet (ft), it weighed only about 600 pounds. The wing was very flexible, which enabled it to distribute the load almost entirely along its span. It was propelled by 6 electric motors, each turning a composite propeller. Current from solar arrays provided power during daylight, while stored energy allowed flight after dark. The batteries allowed an endurance of about two hours in darkness.

On September 13, 1995, the aircraft achieved a major milestone in the ERAST program when it was flown to an altitude of 50,567 ft during a nearly 12-hour mission. The previous altitude record for a solar-powered aircraft was 14,000 feet. It then achieved an unofficial record of 67,350 feet, reached during the tests from the Navy's Pacific Missile Range Facility. Pathfinder was resuming test flights from the U.S. Navy's facility on the Hawaiian island of Kauai in mid-1997. Kauai's lower latitude provided a better angle for Pathfinder's solar cells to absorb radiation from the sun, and its prevailing northerly winds allowed Pathfinder to be oriented to the best sun angle for longer periods.

Pathfinder was one of several unpiloted prototypes under study by NASA's ERAST (Environmental Research Aircraft and Sensor Technology) program, a NASA-industry alliance which is helping develop advanced technologies that will enable aircraft to study the earth's environment during extremely long flights at altitudes in excess of 100,000 feet. Pathfinder flew very slowly, within a narrow speed range. Takeoff was at about 17 mph, cruise speed was about 21 miles per hour (mph), and it climbed at 150 feet per minute (fpm). Pathfinder pilot Dave Ganzer said, "It's like flying underwater, because everything happens at such a slow time scale." Because of its slow speeds Pathfinder flights were meticulously planned around the weather. Winds during takeoff and landing needed to be less than 12 mph. Mission simulations are flown before, and even during a flight to negotiate changing weather. Winds aloft often made the aircraft fly backwards or stationary (relative to the ground), but winds that can adversely affect the Pathfinder usually diminish above 30,000 feet.

Pathfinder mostly flew by autopilot, with a pilot and flight test engineer commanding the mission from the ground. Although the pilot had a control stick, the aircraft was usually "flown" using rotary switches that changed aircraft headings and turn rates via the autopilot. It was described as an easy plane to land: its normal descent rate of 70 fpm was lowered (by throttle) to 40 fpm and the plane was steered into the wind until touchdown.

Pathfinder was a lightweight, solar-powered, remotely piloted flying wing aircraft used to demonstrate the use of solar power for long-duration, high-altitude flight. Its name denotes its mission as the "Pathfinder" or first in a series of solar-powered aircraft that will be able to remain airborne for weeks or months on scientific sampling and imaging missions.

Solar arrays covered most of the upper wing surface of the Pathfinder aircraft. These arrays provided up to 8,000 watts of power at high noon on a clear summer day. That power fed the aircraft's six electric motors as well as its avionics, communications, and other electrical systems. Pathfinder also had a backup battery system that could provide power for two to five hours, allowing for limited-duration flight after dark.

Pathfinder flew at airspeeds of only 15 to 20 mph. Pitch control was maintained by using tiny elevators on the trailing edge of the wing while turns and yaw control were accomplished by slowing down or speeding up the motors on the outboard sections of the wing. On September 11, 1995, Pathfinder set a new altitude record for solar-powered aircraft of 50,567 feet above Edwards Air Force Base, California, on a 12-hour flight. On July 7, 1997, it set another, unofficial record of 71,500 feet at the Pacific Missile Range Facility, Kauai, Hawaii.

In 1998, Pathfinder was modified into the longer-winged Pathfinder Plus configuration and on Aug. 6, 1998, Pathfinder Plus set an altitude record (for propeller-driven aircraft) of approximately 80,285 feet at the Pacific Missile Range Facility. The goal of the Pathfinder Plus flights was to validate new solar, aerodynamic, propulsion, and systems technology developed for its successor, the Centurion, which was designed to reach and sustain altitudes in the 100,000-foot range. The Centurion was succeeded by the Helios Prototype with a goal of reaching and sustaining flight at an altitude of 100,000 feet and flying non-stop for at least 4 days above 50,000 feet.

Major activities of Pathfinder Plus's Hawaiian flights included detection of forest nutrient status, forest regrowth after damage caused by Hurricane Iniki in 1992, sediment/algal concentrations in coastal waters, and assessment of coral reef health. Pathfinder science activities were coordinated by NASA's Ames Research Center, Mountain View, California, and included researchers from the University of Hawaii and the University of California. Pathfinder is part of NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program managed by NASA's Dryden Flight Research Center, Edwards, California.

Pathfinder was designed, built, and operated by AeroVironment, Inc., Monrovia, California. Pathfinder had a 98.4-foot wing span and weighed 560 pounds. Pathfinder Plus has a 121-foot wing span and weighs about 700 pounds. Pathfinder was powered by six electric motors while Pathfinder Plus has eight. Pathfinder's solar arrays produced approximately 8,000 watts of power while Pathfinder Plus's solar arrays produce about 12,500 watts of power. Both Pathfinder aircraft were built primarily of composites, plastic, and foam.

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Keywords: Pathfinder; solar-powered; ERAST; Environmental Research Aircraft and Sensor Technology; AeroVironment; high-altitude; world record; Gossamer Condor; Albatross; Solar Chanllenger; HALSOL; High Altitude Solar; Hawaii; Kauai

Last Modified: February 6, 2002
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