AeroVironment's Global Observer was being developed as a JCTD, funded by no fewer than six U.S. government agencies, and was to fly with the Air Force's Joint Aerial Layer Network (JALN) payload, designed to allow multiple tactical communications systems to talk to one another and connect to distant command centers. AeroVironment says it is still talking to its customers.
The U.K.'s solar-powered Qinetiq Zephyr was developed through a series of larger and more ambitious prototypes, and set a number of flight-endurance records in 2010—including a 336-hr. flight—after which nothing more was announced publicly. Qinetiq says it has no further progress or plans to report.
A much more ambitious solar-electric program, the Defense Advanced Research Projects Agency's (Darpa)Vulture, was cut back last April from a flight demonstration to research into critical technologies, 18 months after an $89 million contract award to a Boeing team. Vulture was designed to demonstrate a five-year operational endurance: one of the original competitors envisaged a vehicle that would be carried to altitude by an aerostat and recovered by parachute after a single mission, with its components being recycled as possible. However, the program is now focusing on solar-cell materials and fuel-cell technology.
Lighter-than-air craft have been faring no better, as contractors fail to deliver on their promises because of technical problems, schedule delays and cost overruns.
Of four Pentagon programs launched to develop and demonstrate long-endurance surveillance airships, one has crashed, one has been terminated, one scaled back substantially and one survives on only a trickle of funding. All have come to grief in the process of developing the air vehicle itself.
The first of the four airship programs to spring a leak was HALE-D, begun by the Missile Defense Agency in 2003 and taken over by Army Space & Missile Defense Command (SMDC) in 2008. At 232 ft. long, HALE-D was a subscale demonstrator for an unmanned airship designed to stay aloft at 65,000 ft. for more than 30 days. But after the prototype's crash, there was no more money, and the program ended.
Another stratospheric airship brought down to Earth is Darpa's Integrated Sensor Is Structure (ISIS), an ambitious program to integrate a dual-band active-array radar into a 1,000-ft.-long solar-electric airship capable of staying aloft for 10 years, tracking hundreds of air and ground targets from 70,000 ft. Started in 2004, ISIS encountered problems with the radar array and regenerative power system, and plans for Lockheed Martin to build a 510-ft.-long demonstrator capable of flying for a year were put on hold. For now, the program is focusing on radar and airship risk-reduction while Darpa reassesses the plan with the Air Force, says the Government Accountability Office (GAO).
Next to be punctured was the Air Force's Blue Devil 2 program, launched in 2010 to meet an urgent requirement to provide persistent multisensor surveillance in Afghanistan. The goal was to take a commercial airship, make it unmanned and install multiple video, radar and signals-intelligence sensors, communications links and onboard processing to create an ISR “fusion node.” The 370-ft.-long Blue Devil 2 was intended to fly for up to four days at 20,000 ft. with a payload up to 2,500 lb.
The Air Force set an aggressive schedule and awarded the integration contract to virtually unknown Mav6. Then the problems began. Based on a TCOM Polar 1000 airship, the program had problems with the envelope, overweight tail fins that failed structural testing, and flight-control software that did not scale up from a smaller version of the craft. The Air Force canceled Blue Devil 2 in June 2012, before the airship could fly, to avoid further delays and increasing costs, says the GAO.