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PEM Fuel Cell History

photo of Helios research aircraft taking off, 2003.

NASA - Aerovirment Helios research aircraft in 2003
Image #ED03-0152-1 from NASA

The NASA Helios aircraft broke apart during testing before designers had the opportunity to test the planned regenerative fuel cell concept. As it turns out, technical difficulties and time constraints had already led the team to replace the regenerative system with a system using hydrogen from two tanks. Use of the alternate fuel cell system changed the weight distribution along the span of this flying wing which then failed when the remotely-piloted aircraft flew into unexpected wind conditions. The following information is from the Investigation of the Helios Prototype Aircraft Mishap, Volume I, Mishap Report, January 2004, pages 21-22. The report is available online at:

  "Fuel Cell Development: In late 1998, NASA and AeroVironment (AV) started the preliminary design and development of the Regenerative Fuel Cell System (RFCS) for the long endurance demonstration planned for 2003. A conceptual design review for the aircraft with a RFCS was held in May 1999 and a preliminary design review (PDR) was held in September 1999. NASA and AV committed to the development of the RFCS in October 1999 and, soon after, AV and two fuel cell subcontractors started the development of the RFCS. By the summer of 2001, a prototype, full-scale fuel cell pod was built, but the hydrogen-oxygen fuel cells and electrolyzers under development were not working reliably. It was clear at that time that designing, building, and testing two flight weight RFCS pods for the long endurance demonstration would not be possible with the time and budget remaining to the program.

"During October-November 2001, NASA and AV sponsored independent technical reviews to assess the progress in the RFCS development. Based on these assessments, AV approached Dryden Flight Research Center management with a proposal to change from a RFCS to a consumable primary fuel cell system (PFCS). The primary motivation for the proposed change was two-fold: 1) a PFCS, derived from existing fuel cell components in the automotive industry, could be designed, built, and tested within the current schedule and budget constraints, and 2) a Helios unpiloted aerial vehicle with a PFCS would have a 7-14 day duration capability. This latter factor was important because AV thought that they could attract other commercial and Department of Defense (DOD) customers and bring this high-altitude, long-endurance capability to market sooner. In December 2001, NASA and AV decided to switch to the PFCS and began the development and modifications needed to the HP01 aircraft for the 2003 demonstration. Since 2003 was the last year of the Environmental Research Aircraft and Sensor Technology (ERAST) program, a major milestone had to be accomplished without the possibility of schedule or budget relief. This contributed to the decision to switch to the primary fuel cell as a risk reduction."


Image of Helios aircraft following in-flight breakup, 26 June 2003

Helios research aircraft during in-flight breakup
26 June 2003

Image from NASA

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