Revolution.Aero Uplift: A new hydro-generation of aircraft

Deep Dive

If it is batteries versus hydrogen, for Hydroplane the universe’s most abundant element wins every time.

The company is a pioneering, California-based start-up, backed by the US Air Force, that begins flight testing its modular hydrogen fuel cell power plant for general aviation, UAM and vertical lift platforms later this year.

“Hydrogen has a much higher energy density,” Dr Anita Sengupta (pictured), founder and CEO, Hydroplane tells Revolution.Aero. Energy density is the energy in watts per kg of weight. At that calculation, hydrogen has an energy density of 35,000 watts per kg, while lithium-ion batteries come in at around 200 watts per kg.

“With almost all aviation use cases you want to fly for an extended period of time, so as you increase your endurance requirements, batteries become less and less of an option. If you want to fly for more than an hour, batteries don’t work. You can take a look at the battery-powered aircraft on the market — there’s not many, take the Pipistrel, it flies for an hour and can hold two people. That’s really the limit with what you can do with battery-powered aircraft right now,” says Sengupta.

So, hydrogen allows you to have a much higher energy density. “Essentially, you only need one hydrogen battery, which is a fuel cell stack and then you increase your range by carrying more fuel,” says Sengupta. The ceiling on your distance is how much fuel the aircraft can carry.

This approach allows Hydroplane to keep to the existing endurance of aircraft currently in production. “We configure the feed system to couple to the endurance requirement of the platform it will power.”

Another “huge advantage” of hydrogen is aircraft ground time, according to Sengupta. Rather than waiting the 30-45 minutes, possibly an hour, to charge a battery-powered aircraft, you can fuel-up and go. “I have a hydrogen fuel cell car, its exactly the same as fuelling a conventional, gasoline powered car. You pull up to the pump, you connect the nozzle to your car, you fuel in three to five minutes and you move on.”

“Operationally, aviation would prefer to see a solution which is a fuelling operation versus a charging operation,” says Sengupta.

Hydroplane is just two years old. In that time, it has secured two contracts, worth $750,000 each, to the USAF’s Small Business Technology Transfer, is developing a retrofittable 200kW modular power unit solution and is on track to fly its demonstrator aircraft next year.

AFWERX (part of the USAF venture arm) Agility Prime programme is the USAF’s initiative to accelerate development of the commercial AAM industry. Technologies, such as Hydroplane’s, that have both military and civilian applications can achieve military-standard certification through the programme. They can then take that to the FAA to assist the certification process for civil use.

“We are starting off with single-engined aircraft like Cessna, Piper and Cirrus class. We are not yet trying to address commuter or high altitude aircraft, the system we have in design is for 200-300 horsepower aircraft. [That said] it is modular, in terms of the power plant, so we would like to produce a future generation system which can go up to a megawatt class [of aircraft],” says Sengupta.

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