Solar aircraft heading toward market

Transfer of solar aircraft technology to the commercial market has moved a step closer with the recent signing of an agreement between NASA’s Dryden Flight Research Centre and AeroVironment.

Transfer of solar aircraft technology to the commercial market has moved a step closer with the recent signing of an agreement between NASA’s Dryden Flight Research Centre and AeroViroment, Inc, to jointly sponsor further development of AeroVironment’s Helios Prototype and Pathfinder Plus solar-electric flying wings.

The Joint Sponsored Research Agreement (JSRA) was signed recently by Kevin Petersen, director of NASA Dryden, and Timothy Conver, president and chief executive officer of AeroVironment. The signing took place on the occasion of the final flight in a three-mission series of high-altitude telecommunications relay demonstrations by the Pathfinder Plus from the US Navy’s Pacific Missile Range Facility (PMRF) on the Hawaiian Island of Kauai.

At the same time, the two entities revealed that a second supplemental energy system is being perfected by AeroVironment that will give the Helios the ability to fly multi-week missions at high latitudes.

Commercialisation of high-altitude remotely piloted or autonomously operated unmanned aerial vehicles (UAVs) has been a high priority for partners of the Environmental Research Aircraft and Sensor Technology (ERAST) alliance since its inception in late 1993. The new agreement builds upon a similar JSRA pact between NASA and several small high-technology firms that forms the basis for the ERAST project.

As part of the agreement, AeroVironment will provide program management personnel; expertise in energy storage systems, fuel cell propulsion and solar-electric airframes; design and flight teams; and facilities, such as their UAV Development Centre, Fuel Cell Lab, and Mobile Test Facility.

The agreement calls for NASA Dryden to maintain safety oversight for flight and ground testing for all solar aircraft as well as for energy storage and power systems, stationary and mobile ground support systems.

Dryden will also provide support for flight demonstrations, including provision of the Pathfinder Plus and Helios Prototype aircraft and their flight kits, support for technology development for next-generation Helios aircraft and components, and facilities and equipment such as PMRF, environmental test, simulator facilities and range equipment.

Initially, AeroVironment, its SkyTower subsidiary and NASA are commercialising two versions of the Helios solar/electric extreme-endurance UAV.

One version will be able to fly at lower latitudes for up to six months without landing by employing a regenerative fuel cell-based energy storage system to provide power at night.

The regenerative system uses excess power from the solar arrays during the daytime to power an electrolyser that breaks down water into its component gases, hydrogen and oxygen, which are then stored in pressurised tanks. At night, the process is reversed, with fuel cell stacks recombining the gases into water, producing electricity as a by-product to power the aircraft.

The other version will use a similar fuel cell-based energy system without the regenerative feature to power the aircraft at night. Designed to allow Helios to fly for one to two weeks at all latitudes any time of the year, this system combines stored hydrogen with oxygen collected from the atmosphere.

Initiated by AeroVironment and now a joint effort by NASA and the Monrovia, California -based firm, development of the non-regenerative system has accelerated rapidly over the past nine months. AeroVironment is currently operating developmental versions of both fuel cell-based energy systems at its California development facility.

‘Fundamentally, affordability is why we’re building the Helios,’ said Robert Curtin, vice-president and director of AeroVironment’s UAV Design Development. ‘Cost is very important to potential military and commercial users. The extreme endurance of Helios will result in a short logistics ‘tail,’ a very small operational infrastructure and low operational costs. The bottom line is much lower operational costs than any conventional UAV.’