Helios Prototype is the name of a solar- and fuel cell system-powered uninhabited aerial vehicle that NASA tested. AeroVironment, Inc. developed the vehicle under NASA's Environmental Research Aircraft and Sensor Technology program. In August, 2001, it set an unofficial world record for sustained altitude by a winged aircraft. It sustained flight at above 96,000 feet for forty minutes, and at one time it flew as high as 96,863 feet. Later, in June, 2003, the Prototype fell into the Pacific Ocean about ten miles west of the Hawaiian Island Kauai.

Significance and goals

NASA claimed if the concept the Prototype embodied proves itself, then multi-month flight will become possible. Accordingly, Helios was a forerunner of what some call artificial "atmospheric satellites". NASA claimed such atmospheric satellites might someday replace conventional artificial satellites.

NASA established two major goals for the Helios Prototype, as follows.

1. Reach an altitude at or near 100,000 feet with a small payload on a single-day flight. NASA could apply the knowledge gained therein firstly to carry scientific instruments to high altitudes, and secondly when designing aircraft for, or completing missions on, Mars. NASA claimed that a vehicle so capable could also carry larger payloads to lower altitudes. This versatility would enhance the Prototype's worth.
2. Achieve extreme duration. Initially, plans called for the aircraft to maintain, by the year 2003, flight for ninety-six uninterrupted hours, most of which would have occurred at an altitude greater than 50,000 feet. Later, NASA delayed those plans by three years. Meanwhile, it sought to maintain, by September, 2003, flight for forty hours, with at least fourteen of those hours above 50,000 feet.

Design

Sunnyvale, California-based Sunpower Corporation supplied solar cells for Helios. The cells featured a rear-contact cell design that placed wires on the underside of the cells, so as not to obstruct the cells' exposure to solar radiation.

The fuel cell systems designed for the Helios Prototype included both regenerative and non-regenerative designs.

See also

• Electric vehicle

External links

• NASA's Helios Project

References

• Current Projects - Helios Prototype
• NASA Dryden Fact Sheets - Helios Prototype
• "Photovoltaic Finesse: Better Solar Cells—with Wires Where the Sun Don't Shine", an article by Daniel Cho on page thirty-three of the September, 2003 issue of Scientific American