AeroVironment Helios Prototype
Solar-powered flying wing that set a world altitude record.
The AeroVironment Helios Prototype was the fourth and final aircraft in an evolutionary series of solar- and fuel-cell-system-powered unmanned aerial vehicles developed under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. It was built to develop technologies for long-term, high-altitude flight as an atmospheric satellite, performing research and serving as a communications platform. The Helios Prototype was derived from the NASA Pathfinder and NASA Centurion aircraft.
Quick Facts
- Aircraft Type
- Unmanned aerial vehicle
- Manufacturer
- AeroVironment
- Primary User
- NASA ERAST Program
- Number Built
- 1
- First Flight
- September 8, 1999
- Developed From
- NASA Pathfinder, Pathfinder Plus and NASA Centurion
Facts from the source article.
Lore & Background
The Helios Prototype was created by modifying the NASA Centurion with a sixth 41 ft wing section and a fifth landing gear and systems pod, becoming the fourth configuration in the series of solar-powered flying wing demonstrators. Its larger wing accommodated more solar arrays for sun-powered development flights. The aircraft could be configured in two ways: HP01 focused on altitude using batteries and solar cells, while HP03 optimized endurance with solar cells, storage batteries, and a hydrogen–air fuel cell system, reducing motors from 14 to ten. The maiden flight occurred on September 8, 1999, followed by battery-powered development flights to validate wing performance and handling qualities. The Helios Prototype was an ultra-lightweight flying wing with a 247 ft wingspan, longer than a C-5 or Boeing 747, constructed mainly of carbon fiber, graphite epoxy, Kevlar, Styrofoam, and transparent plastic skin. It had 72 trailing-edge elevators for pitch control and used differential motor power for yaw and pitch control. From 2000 to 2001, HP01 received upgrades including new avionics, high-altitude environmental control systems, and a SunPower solar array with over 62,000 rear-contact solar cells.
Reader's Guide
The Helios Prototype demonstrated the potential of solar-powered flight for high-altitude, long-endurance missions. On August 13, 2001, it reached 96,863 ft, a world record for sustained horizontal flight by a winged aircraft, spending over 40 minutes above 96,000 ft. This achievement advanced the ERAST program's goals of sustained flight near 100,000 ft and endurance of at least 24 hours. However, on June 26, 2003, during a systems checkout flight in preparation for an endurance test, the aircraft broke up and fell into the Pacific Ocean about 10 mi west of Kauai. The mishap investigation reported that turbulence caused a persistent high dihedral configuration, leading to pitch instability and airspeed excursions that exceeded design limits, resulting in structural failure. The crash highlighted the challenges of controlling ultra-lightweight, flexible aircraft in turbulent conditions. Despite its loss, the Helios Prototype's record and design influenced subsequent high-altitude, solar-powered UAV concepts.
Did You Know?
- The Helios Prototype had a wingspan of 247 ft, longer than a Boeing 747 or C-5 transport.
- It reached a world-record altitude of 96,863 ft on August 13, 2001.
- The aircraft could be configured with either 14 or 10 motors depending on mission goals.
Frequently Asked Questions
What is the AeroVironment Helios Prototype?
It was a solar- and fuel-cell-powered flying wing that served as the fourth and final aircraft in NASA's ERAST program. Built by AeroVironment and evolving from the Pathfinder and Centurion designs, it aimed to prove that an unmanned aircraft could loiter at high altitude for weeks on renewable energy alone.
What altitude record did the Helios Prototype set?
On August 13, 2001, the aircraft climbed to 96,863 feet, establishing a world altitude record for an unmanned vehicle. That single flight made it the highest-flying solar-powered UAV ever recorded.
What was the Helios Prototype designed to do?
Its mission was to act as an atmospheric satellite, staying aloft for extended periods to gather environmental research data and double as a communications relay. The ultra-light structure—just 1,600 pounds at gross weight spread over 1,976 square feet—let it hover on sunlight and stored fuel-cell energy.
How big is the AeroVironment Helios Prototype?
The flying wing stretched 247 feet tip to tip with an aspect ratio of 31-to-1, making it one of the most slender wings ever built. Despite that enormous span, the entire airframe weighed only about 1,600 pounds, giving it a wing loading of roughly 0.81 lb per square foot.
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