As the country shifts toward a decarbonized and renewable energy future, research teams, companies and government agencies are exploring how to use liquid hydrogen to fuel large-scale vehicles like locomotives, maritime vessels and aircraft. One such company is Eternium Corporation in Novato, CA, which is currently developing a long-range, multi-role all-electric aircraft.
The implications of Eternium’s prospective aircraft represents a greater shift in an aviation industry already exploring an alternative-fuel future, with similar projects being undertaken by organizations like Airbus and NASA in recent years. While Airbus and NASA’s research developments are geared specifically toward passenger aircraft, Eternium also sees potential in other non-passenger applications for its aircraft.
“The idea is for the structure of the aircraft to lend itself to modularity,” Jared Semik, founder and CEO of Eternium Corporation, said. “So the multimodal aspect of [the aircraft] ended up morphing into close in-air support, semi-autonomous fire suppression and cargo variants.”
For Semik, an eight-year military veteran of the Marine Corps and Army with 24 years of experience as an aerospace professional, the idea of applying semi-autonomous and liquid hydrogen fueled aircraft specifically for the purpose of wildfire response began after watching the air traffic of large fire-suppression aircraft from ridgelines in northern California.
“It is well-known in the industry how dangerous it is for the pilots, the aircrew and ground crew to fight fires,” Semik said. “If one of the [planes] crashed, it could also become an accelerant to the fire. From my experience in the aviation sector and the military, I saw what it took to have combat air control, and the same paradigms extend over into fire suppression.”
In theory, a forward air controller on the ground would connect to a semi-autonomous lead aircraft that would map the topography of a wildfire area using advanced technologies such as LiDAR (Light Detection and Ranging), infrared sensors or satellite imagery. The lead aircraft would then draw a flight path for additional aircraft to follow and drop fire retardants on the target area.
“The forward-looking infrared can tell you exactly where the hotspots are and where the fire is with respect to the topography of the landscape and then you can build a fire suppression package based off of that. In essence, you would then nest and stagger multiple aircraft in the air behind [the lead aircraft] and close in formation, so you have capabilities in terms of width for fire suppression that you can’t get from a single aircraft,” Semik said.
Additionally, using semi-autonomous aircraft would bring some flexibility in terms of how many aircraft are needed to respond, based on the size and characteristics of a fire.
“Each aircraft can work autonomously or you can buy multiple units and nest them, so it’s just a matter of the requirements of whatever fire department or fire suppression organization is using them,” Semik explained. “They would probably be regionally-responding, because you’re not just going to have a base in any specific spot. You’d have a unit of them where you can say, ‘Okay, we only need one unit because the fire is in its infancy.’ But when you need to overwhelm [the fire] you could have 2, 3, 4 or however many aircraft you’d end up needing because the sky’s really the limit.”
A fire-suppression strategy with semi-autonomous aircraft would present a number of solutions that could address common risks inherent to fighting wildfires from the air.
“It removes the potential miscommunication by forward air controllers about what the actual status of the fire is on the ground,” Semik said. “Ideally we want something where we don’t have to worry about the danger for the pilots and also, since we’re hydrogen fueled, we’re not necessarily having to worry about a fuel explosion. Liquid hydrogen has different burning characteristics than petroleum fuels, so it’s a little less dangerous in that regard.”
In order to bring this idea to life, however, Semik and his team have had to start with a ground-up approach in building out their aircraft. But as their research and development phase has come along, they’ve had to regularly adapt and revise their aircraft to optimize its potential.
“What we’re currently working on is the aerodynamic body on top of the other systems. We’ve ironed out the majority of the propulsion system with our patent-pending superconductive motor and the cryogenic system associated with it, which is why we ended up switching to liquid air and liquid hydrogen [fuel],” said Semik. “Originally, we had a liquid nitrogen system and then compressed hydrogen before moving onto liquid hydrogen.”
Semik refers to the superconductive motor as the aircraft’s cornerstone, being its biggest patent-pending technology. Due to this extremely high torque density motor, it capitalizes on an electrical aircraft’s critical need for maximum energy and usage density, without being bogged down by its own size and weight.
“The problem in aviation is the fact that we’re mass-dependent and we have a mass-penalty for everything that you put on the aircraft,” Semik said. “In order to create a motor with high enough torque, battery technology is prohibitively high and prohibitively massive. You can’t just throw a bunch of batteries on an aircraft, slap a very inefficient motor on with a very inefficient fan section and call it a day. It’ll fly, but it won’t go very far.”
Additionally, several energy sources are being tested and utilized together for the aircraft’s overall power system.
“Since we don’t have a lot of energy density to play with in batteries, we went with liquid hydrogen [fuel] to better capitalize on the mass energy density of liquid hydrogen and the efficiency of the fuel cells. Then we put gallium arsenide solar cells on the top to round out the charging of the battery, so we hybridized the power system with three separate power modes of storage battery, fuel cell and solar.”
Semik believes that this multi-power system, coupled with the superconductive motor, will bring the capabilities of his aircraft on par with the hydrocarbon-based jets predominantly used today.
One additional element, however, could actually propel these liquid hydrogen fuel-based aircraft ahead of its hydrocarbon counterparts: streamlining the supply chain by conveniently generating its own liquid hydrogen fuel nearby.
“We’re also working on a 100 percent solar-driven, high-temperature, high-pressure, alkaline electrolysis and liquefaction system,” Semik said. “So if we can take that and modularize it in a place like an airport, then we would just have to supply it with water [to produce liquid hydrogen].”
With an ability to produce its own hydrogen fuel through an electrolysis and liquefaction system from a nearby water source, the need for oil would essentially be voided, according to Semik.
“Unless you’re in the middle of the desert, water is in abundance and even if you’re in the desert in Arizona or Nevada, you still have the Colorado River running through a lot of those states so you still have ambient water sources. So if you just feed the system water, filter it, heat it up, electrolyze it and then liquefy it all by using the solar energy that you’re getting in abundance in some of the desert areas, you would have a supply of fuel for your aircraft and you’re not beholden to anything.”
If the need for oil and petroleum energy sources are voided, energy prospects for the whole aviation industry could evolve.
“We’ve lived on this energy glut for so long because petroleum is a great energy source as it’s very energy dense and very versatile,” according to Semik. “But once we start getting the motor technology more dense and understand how to more efficiently squeeze every ounce of energy out of a less dense fuel, the lines between a petroleum-based aircraft and our aircraft are going to be blurred. I’m actually anticipating superiority, because there is a slight advantage with some of the alternative energies that petroleum-based vehicles don’t have.”
Once the aircraft is fully developed and able to fly, there will be an additional hurdle that will need to be overcome in the permitting process by the Federal Aviation Administration (FAA). Semik, however, believes the FAA will be receptive to his liquid hydrogen fueled aircraft, particularly as his team has designed their aircraft from the ground-up with the FAA in mind.
“With all my experience in aerospace as an engineer, I’m not aware of any limitations the FAA places on [liquid hydrogen fuel aircraft], the only limitations are basically our own ability to engineer it. This isn’t the first certification process I’ve gone through professionally with the FAA and generally speaking, they’re extremely fair with the advent of new regulations and new restrictions and specifications of things. They just want to know that it’s safe.”
So with an eye on how these innovative technologies can shape the future of aviation, Semik is confident in the holistic, all-encompassing approach his team has had in designing their aircraft.
“We’ve had a completely holistic approach through this entire process particularly with this paradigm shift in mind,” Semik said. “Instead of trying to take current off-the-shelf technology and just shoehorn it into old, outdated airframes and propulsion systems, we’re taking a lot of leaps in technology while paying a lot of attention to the relationships between subsystems so that they lend themselves to safety, manufacturability, maintenance and cost-reduction. All of that has basically been baked into our organization and our technology from the very beginning.”
Consequently, the research and development process Semik and his team at Eternium are utilizing is evident of the greater shift in re-evaluating our society’s relationship with energy. When asked if he envisions a fuel-alternative future in aviation, Semik asserts that it’s that very idea that is driving this process forward.
“It’s the impetus behind this entire company and it’s not just alternate fuels for the environment, but also alternate fuels in terms of their potential to allow individual autonomy. An interesting byproduct of pulling ambient energy in nature is you no longer have to be beholden to somebody that has to put in capital investment to create petroleum fuel. So it has political, geopolitical and financial ramifications for individuals and what we’ve been doing here is really taking it down to the raw fundamentals from an energy perspective of what an aircraft needs and going from there,” said Semik.
Ultimately, with the innovative technology now available and ongoing research and development to make a liquid hydrogen aviation industry feasible, the most significant hurdle in advancing liquid hydrogen fuel may be quite surprising to some.
“Our biggest hurdle, honestly, is public perception,” Semik said. “There’s not a lot of public understanding of the science with respect to liquid hydrogen fuel and the complexity of superconductive motors because for a lot of people it’s science fiction and they don’t realize how mature the technology actually is, even though it hasn’t been done yet in this specific capacity. Then there’s pushback from the political bureaucracy in terms of allowance and safety regulations if they don’t know enough about it, so you’re going to be constantly fighting these battles with perception that this is an unsafe thing.”
In the meantime, Semik and his team at Eternium are continuing their research and development to support a fuel-alternative aviation future in which wildfire-response may be just one of many purposes their aircraft can serve.
“We are at a high-technology readiness level in our propulsion system and power system and we are getting into the actual builds and our engineering design reviews now and then all that’s going into a test phase. The passenger capacities are going to take a heck of a lot more finagling with the FAA, because their regulations are pretty extreme with passengers. But the non-passenger variants, like the brush-fire variant, you can most likely see them in about 3-4 years.”
Scott King writes about science and the environment for the Ally. Support his work.
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Liquid Hydrogen, Innovative Technologies Merging in Race to an Alternate-Fuel Future in Aviation - The Sierra Nevada Ally
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