HYDROGEN FUEL CELLS have had a hard time making inroads as power sources for ground-based electric vehicles, but things are starting to look up for the zero emission propulsion tech. A new air taxi startup, Alaka’i Technologies, this week unveiled a liquid-hydrogen-powered, five-passenger electric aircraft that it claims will be more efficient and powerful than the battery-powered aircraft its many, many competitors are developing.
The Massachusetts-based “flying car” company, led by veterans of NASA, Raytheon, Airbus, Boeing, and the Department of Defense, unveiled a mockup of the six-rotor aircraft, called Skai, in Los Angeles at the offices of BMW Designworks, with which it partnered on the aircraft’s design. Alaka’i says the final product will be able to fly for up to four hours and cover 400 miles on a single load of fuel, which can be replenished in 10 minutes at a hydrogen fueling station. It has built a functional, full-scale prototype that will make its first flight “imminently,” a spokesperson says.
It wouldn’t be the first fuel cell-powered plane; Boeing made that happen in 2008. But it would be the first of its kind. Skai’s boxy configuration doesn’t have the aerodynamic look of prototypes from the likes of Lilium, Bell, and yes, Boeing. It tops out at just 118 mph, while other eVTOL (that’s electric vertical takeoff and landing) concepts promise speeds of over 150 mph. The Skai is designed, rather, for efficiency, which matters more than top speed if it’s going to make dozens of short hops daily. “Our goal was to keep it simple, and we focused on accommodating a certain mission profile that’s repeatable over an entire day,” says NASA veteran engineer Bruce Holmes, who serves on Alaka’i’s board of directors.
The argument for fuel cells boils down to energy density: One pound of compressed hydrogen contains over 200 times more energy than one pound of battery, says Alaka’i founder Brian Morrison. That means the Skai can meet the speed, range, and payload requirements that Alaka’i thinks will make it competitive, while saving a lot of weight—a top line consideration for anything that flies. Though the company won’t reveal specifics surrounding the power system, it suggests that it and its fuel cell provider (also not disclosed) have made “breakthroughs” with the technology that enable this performance.
Hydrogen fuel cells are proving themselves able to significantly boost run times for vehicle systems, with certain small unmanned aircraft jumping from 30- to 45-minute run times with batteries to more than two to four hours with fuel cells, says Thomas Valdez, a chemical engineer with Teledyne Energy Systems. And they offer a safety benefit by eliminating the risk of thermal runaway. Even a punctured tank is no big deal: “Pressurized hydrogen would very quickly dissipate in the air, so it won’t pool or catch fire the way conventional fuels do,” Valdez says.
Of course, as with all air taxi startups, many challenges remain for Skai. Foremost among these is ensuring it can achieve FAA certification in a timely manner, no guaranteed thing for a new propulsion system in a new kind of aircraft. Holmes thinks that a simple design will help. “We have vastly fewer parts compared to traditional aircraft, and half the number of requirements that have to be checked out by the FAA,” he says. The Skai doesn’t have a tail rotor, and a ballistic parachute means it doesn’t have to rely on autorotation to land safely if the power gives out. The six rotors, which generate a combined 450 hp, sit in a fixed position, instead of pivoting between vertical and horizontal flight.
To get this thing off the ground, Alaka’i intends to look to non-air taxi service early on, including flying for emergency services, search-and-rescue missions, and hauling cargo, roles that don’t require the same certification standards as passenger flight. Holmes’ extremely optimistic estimate: Certification will take just a few months (and be done by the end of 2020), instead of the standard five to 10 years.
Hydrogen, of course, has its downsides, namely the fact that there’s not much of it around. A lack of fueling infrastructure has hindered hydrogen ground vehicles, but aircraft may have an easier time. Instead of relying on fueling stations on every corner, aircraft can have more centralized fueling centers supplied by tanker trucks.
Another potential roadblock could be hardware costs. “Hydrogen fuel cells have been used in spacecraft for quite a long time. They are proven technology,” says Charles Eastlake, a professor emeritus of aerospace engineering at Embry-Riddle Aeronautical University. “The show-stopper is cost.” He notes that one electric airplane project the university undertook in 2011 involved a fuel cell that would have cost $250,000 on the open market, all to power a relatively small 40 horsepower electric motor. While the technology has improved since then and costs come down, it likely won’t be by that much given that most of the R&D dollars have been going to batteries, Eastlake says.1
Alaka’i says the first aircraft will be piloted, with highly automated and fully autonomous operation coming later. It’s targeting a price around $200,000, though early models will likely be much pricier, and an annual production volume on the order of 10,000. That’s a huge number—no manufacturer makes more than 700 aircraft annually—but consistent with what other air-taxi developers say will be needed to make an Uber-like system economically viable. Eventually, Alaka’i wants to see versions available for private ownership in the same general financial category as high-end luxury cars. Key difference, of course, being that these cars can fly.