Boeing has flown the Phantom Eye high-altitude long-endurance (Hale) unmanned aircraft system powered by liquid hydrogen (LH2). The 150-foot-wingspan, all-composite aircraft flew for 28 minutes from the NASA Dryden Flight Research Center at Edwards AFB in Southern California on June 1, reaching an altitude of slightly more than 4,000 feet. “This flight puts Boeing on a path to accomplish another aerospace first–four days of unrefueled, autonomous flight,” said Boeing Phantom Works president Darryl Davis.
Two years ago, Davis predicted a first flight for the Phantom Eye in early 2011. But the development of LH2-powered aircraft has challenged aerospace engineers for generations. On April 1 last year, the hybrid LH2/electric-powered Aerovironment Global Observer crashed at Edwards during its ninth test flight. Two weeks later, the company was ordered to stop work after $120 million of U.S. government funding ran out. The first flight of the Phantom Eye also ended with an accident, when the landing gear dug into the lakebed and broke. To save weight in a vehicle that is designed to fly at 150 knots at 65,000 feet with a 450-pound payload, the Phantom Eye takes off from a dolly and lands on skids and a nosewheel.
Boeing is self-funding the Phantom Eye, saying that the program helps the company develop future ISR, strike and bomber programs. The demonstrator, a 60-percent-scale version of Boeing’s ultimate design, is powered by two 150-hp Ford truck engines that are turbocharged and are fed the vaporized LH2 via an accumulator tank. Two eight-foot-diameter tanks in the forward fuselage hold the liquid fuel supply. LH2 requires four times more tank capacity than an energy-equivalent amount of conventional kerosene. Boeing notes that the Phantom Eye’s propulsion system is “environmentally responsible” and creates only water as a byproduct.
The first flight demonstrated initial handling and maneuverability, said Boeing program manager Drew Mallow. “When we fly again, we will enter more demanding envelopes of high-altitude flight.”
Aerovironment told AIN that it is trying to secure funding to finish the second, nearly completed Global Observer. The company understands what caused the loss of the first air vehicle, and has developed and tested a solution.