The Pathfinder was a lightweight, solar-powered, remotely piloted flying wing aircraft that is demonstrating the technology of applying solar power for long-duration, high-altitude flight. It is literally the pathfinder for a future fleet of solar-powered aircraft that could stay airborne for weeks or months on scientific sampling and imaging missions.
During 1998, the Pathfinder was modified into the longer-winged Pathfinder-Plus configuration. On Aug. 6, 1998, the modified aircraft was flown to a record altitude of 80,201 feet for propeller-driven aircraft on the third of a series of developmental test flights from PMRF on Kaua’i. The goal of the flights was to validate new solar, aerodynamic, propulsion and systems technology developed for the Pathfinder’s successor, the Centurion/Helios Prototype, which was designed to reach and sustain altitudes in the 100,000-foot range.
Essentially a transitional vehicle between the Pathfinder and the follow-on solar wings, the Pathfinder-Plus is a hybrid of the technology that was employed on Pathfinder and developed for Centurion/Helios.
The most noticeable change is the installation of a new 44-foot-long center wing section that incorporates a high-altitude airfoil designed for Centurion/Helios. The new section is twice as long as the original Pathfinder center section and increases the overall wingspan of the craft from 98.4 feet to 121 feet. The new center section is topped by more-efficient silicon solar cells developed by SunPower Corp., Sunnyvale, CA, that can convert almost 19 percent of the solar energy they receive to useful electrical energy to power the craft’s motors, avionics, and communication systems. That compares with about 14-percent efficiency for the older solar arrays that cover most of the surface of the mid- and outer wing panels from the original Pathfinder. Maximum potential power was boosted from about 7,500 watts on Pathfinder to about 12,500 watts on Pathfinder-Plus.
In addition, the Pathfinder-Plus is powered by eight electric motors, two more than powered the previous version of Pathfinder. Designed for the Centurion/Helios Prototype follow-on solar wings, the motors are slightly more efficient than the original Pathfinder motors. The Pathfinder-Plus also validated a new flight control system for the Centurion/Helios Prototype, although only the Pathfinder’s own system actually controlled the motors and control surfaces…Learn more
The Pathfinder Plus is currently on display at the Udvar-Hazy Center, part of the Smithsonian National Air and Space Museum in Chantilly, Virginia.