AeroVironment Helios Prototype

The AeroVironment Helios Prototype was a solar‑electric, high‑altitude, long‑endurance (HALE) aircraft developed by AeroVironment in partnership with NASA and the U.S. Department of Energy during early 2000s. Designed to demonstrate the feasibility of continuous, stratospheric flight using only sunlight, the Helios began as a modified Twin Otter platform, evolving into a distinctive wing‑leg configuration with six elongated booms supporting a 75‑meter wingspan. Its skin was covered with photovoltaic cells that generated up to 30 kilowatts of power, feeding electric motors that drove twin pusher propellers. Energy storage relied on lightweight lithium‑ion batteries, allowing the aircraft to operate through night hours for up to 30 days in theory, though actual flight tests achieved several weeks of endurance. First flown in 2001, Helios set multiple records, including the longest sustained flight by an unmanned aircraft and the highest altitude for a solar‑powered vehicle, reaching over 30 km. Although the program ended after a 2003 crash, its technology paved the way for subsequent solar UAVs such as NASA’s Pathfinder and the commercial Solar Impulse series. Helios remains a landmark in aviation, proving that renewable‑energy power can sustain prolonged, high‑altitude operations and inspiring a new generation of persistent aerial platforms for communications, surveillance, and climate monitoring.