Editing NASA Pathfinder (section)

===Development===
In 1983, AeroVironment obtained funding from an unspecified US government agency to secretly investigate a [[unmanned aerial vehicle|UAV]] concept designated "High Altitude Solar" or HALSOL. The HALSOL prototype first flew in June 1983. Nine HALSOL flights took place at  [[Area 51|Groom Lake]] in Nevada. The flights were conducted using radio control and battery power, as the aircraft had not been fitted with solar cells. HALSOL's aerodynamics were validated, but the investigation led to the conclusion that neither [[photovoltaic]] cell nor energy storage technology were mature enough to make the idea practical for the time being, and so HALSOL was put into storage.<ref name=goebel12>{{usurped|1=[https://web.archive.org/web/20090211170130/http://www.vectorsite.net/twuav_12.html Goebel, Greg, "The Prehistory of Endurance UAVs", ''Unmanned Aerial Vehicles'', chapter 12. Exists in the public domain.]}}</ref>

In 1993, after ten years in storage, the aircraft was brought back to flight status for a brief mission by the [[Ballistic Missile Defense Organization]] (BMDO). With the addition of small solar arrays, five low-altitude checkout flights were flown under the BMDO program at NASA Dryden in the fall of 1993 and early 1994 on a combination of solar and battery power.<ref name=pathfinderfactold2/>

In 1994 the aircraft transferred to the [[NASA ERAST Program]] to develop science platform aircraft technology. It was renamed "Pathfinder" because it was "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".<ref name=pathfinderfactold2>[https://web.archive.org/web/20030810185046/http://www.dfrc.nasa.gov/Newsroom/FactSheets/FS-034-DFRC.html NASA Pathfinder fact sheet, archived at archive.org]</ref> A series of flights were planned to demonstrate that an extremely light and fragile aircraft structure with a very high [[aspect ratio]] (the ratio between the wingspan and the wing chord) can successfully take-off and land from an airport and can be flown to extremely high altitudes (between {{convert|50000|ft|m}} and {{convert|80000|ft|m}}) propelled by the power of the sun. In addition, the ERAST Project also wanted to determine the feasibility of such a UAV for carrying instruments used in a variety of scientific studies.<ref name=pathfinderfactold>[https://web.archive.org/web/20030620174825/http://www.dfrc.nasa.gov/Research/Erast/pathfinder.html NASA Pathfinder fact sheet, archived at archive.org]</ref>

On October 21, 1995, the aircraft's fragility was aptly demonstrated when it was severely damaged in a hangar accident, but was subsequently rebuilt.<ref name=pathfinderfactold/>