Mobility is a crucial part of our everyday life, and aviation is a key component of this ability to travel from one place to another at speed.
By enabling people and goods to travel miles within a few hours, the aviation industry connects people like no other mode of transportation can. This makes it a significant contributor to global economics, accounting for 3.5% of the world’s gross domestic product (GDP).
The industry also supports a total of 86.5 million jobs globally, with an estimated market size of the global airline industry exceeding $760 billion.
Notably, airlines worldwide are projected to have carried approximately 9.5 billion passengers in 2024, representing a 104% increase from 2019 levels and a 9% rise from 2023, according to ACI World. This growth is expected to accelerate at a greater speed, with global passenger traffic projected to reach 19.5 billion by 2042.
The aviation industry is clearly expanding, and its future is indeed bright. Having said that, it is also contributing to greenhouse gas (GHG) emissions to a considerable extent.
While aviation accounts for a relatively small share of global emissions at 2.5%, it grew faster than rail, road, or shipping between 2000 and 2019. This increased demand for international travel after the Covid-19 pandemic actually led to aviation emissions reaching nearly 950 Mt CO2.
Not only are aviation emissions growing at a rapid pace, but they are also one of the most challenging sectors to decarbonize, posing a critical environmental challenge.
As a result, the industry’s focus is currently on decarbonizing its operations and achieving the Net Zero objective, which involves reducing CO2 emissions to a level that nature can absorb by 2050.
Unlocking Hydrogen’s Promise for Emission-Free Aviation
With aviation contributing a notable portion of global carbon dioxide and contrail emissions, it is becoming extremely important to develop advanced and comprehensive solutions to meet the industry’s climate goals.
One promising solution is hydrogen, the lightest and most abundant chemical element in the universe, which constitutes about 75% of all normal matter.
This chemical element has emerged as a popular and valuable decarbonization tool thanks to its clean combustion. It’s a clean-burning fuel as it only produces water vapor as a byproduct when combusted.
Moreover, the gravimetric energy density, or the available energy per unit mass of a substance, of hydrogen is approximately 2.8 times higher than that of conventional aviation fuel, kerosene. Hydrogen actually has the highest gravimetric energy density of all known substances, i.e., ~120 kJ/g. In contrast, kerosene-based jet fuel has an energy density equal to 43 MJ/kg.
However, hydrogen has a low density at ambient conditions, i.e., 0.08 kg/m3. This presents major storage challenges, especially for long-haul flights.
A practical alternative to this is storing the colorless, odorless, and tasteless gas in a liquid form at 20 K. This form increases hydrogen’s density to 𝜌𝐿𝐻2 = 70.8 kg/m³, which has emerged as a solution for aviation applications.
Companies have also explored various aspects of liquid hydrogen (LH2) integration in aircraft, including thermal management, pressure control mechanisms, insulation strategies, and the design of cryogenic tanks.
However, a holistic system that integrates LH2 storage, thermal management, and transfer control in a form that is scalable to aircraft design is still underexplored.
So, a team of researchers from the FAMU-FSU College of Engineering, which is a joint college of engineering of Florida A&M University and Florida State University, has designed a liquid hydrogen storage and delivery system that can help the aviation industry realize its zero-emission objective.
With support from NASA, the study outlined a scalable, integrated system that addresses multiple engineering challenges by enabling the use of hydrogen as a clean fuel. It is also used as a built-in cooling medium for critical power systems aboard electric-powered aircraft.
The team showed that liquid hydrogen can be stored efficiently, transferred safely, and used to cool critical onboard systems while supporting the power demands of the aircraft during takeoff, cruising, and landing phases.
According to the corresponding author of the study, Wei Guo, who is a professor in the Department of Mechanical Engineering:
“Our goal was to create a single system that handles multiple critical tasks: fuel storage, cooling, and delivery control. This design lays the foundation for real-world hydrogen aviation systems.”
Hydrogen Hybrid-Electric Aircraft: Scalable Propulsion Solution
Published in Applied Energy1, the study undertakes the task of reducing the aviation industry’s carbon and contrail emissions, which are key contributors to climate change, by proposing an innovative design for a system to store liquid hydrogen, thermal management, and control its transfer, which is customized for Integrated Zero Emission Aviation (IZEA).
The IZEA is an academic-industry collaboration aimed at achieving zero greenhouse gas emissions from commercial aviation. Industrial partners include Raytheon Technologies, Boeing, and Advanced Magnet Laboratories.
In particular, this collaboration examines hybrid power production through a combination of fuel cells and turboelectric generators, utilizing hydrogen with either concentrated oxygen or ambient air.
The goal of IZEA is to figure out just how to use liquid hydrogen as fuel as well as increase efficiency and power without increasing weight.
They selected the FAMU-FSU College of Engineering to help develop the sustainable aviation system in late 2022, as part of a five-year, $10 million project.
To fulfill the national agenda for energy systems and commercial aircraft propulsion to cut down the aviation industry’s harmful emissions, the FAMU-FSU team will work with researchers from the University of Kentucky, the University at Buffalo, Georgia Tech, and industry partners, as announced IZEA two and a half years ago.
Now, the collaboration has addressed the lack of a holistic system by building a scalable and comprehensive hydrogen-based propulsion system for future aircraft.
The project begins with short-distance regional flights in order to assess the near-term feasibility of aviation powered by liquid hydrogen. The focus here is on a prototype aircraft with a blended wing body configuration, which can carry 100 passengers.
The hybrid-electric aircraft draws power from both hydrogen fuel cells and high-temperature superconducting (HTS) electric generators, which are driven by combustion turbines fueled by hydrogen.
Fuel cells offer a solution to avoid NOx emissions and contrails, hence the reason organizations like Airbus and CHEETA are also looking into aircraft powered by fuel cells. However, the problem with the current stacks of fuel cells is that they are extremely bulky, making it difficult to power a large aircraft throughout its various phases, particularly during takeoff. As a solution to this problem, the team introduced the dual power source.
Fuel cells are utilized during low-load conditions, such as taxiing and cruising, with a maximum power of approximately 6.8 MW. Meanwhile, hydrogen turbine-driven superconducting generators supply the additional power (9.4 MW) needed during takeoff. This combination brings the total power to a 16.2 MW peak and enhances resiliency by providing power redundancy.
To address the challenge of density, hydrogen being less dense and hence taking up a lot of space unless it’s stored at -253°C as a super-cold liquid, the researchers designed cryogenic tanks and their associated subsystems using a new gravimetric index.
The index is the ratio of the fuel mass to the full fuel system, but the team’s index includes the mass of the hydrogen fuel, tank structure, heat exchangers, insulation, working fluids, and circulatory devices.
In order to find the configuration that gives the maximum fuel mass relative to total system mass, the researchers continued adjusting the key parameters like vent pressure and heat exchanger dimensions until they came upon the optimal one.
The ideal layout achieved a gravimetric index of 0.62. This means that 62% of the system’s total weight is usable hydrogen fuel, representing a significant improvement over conventional designs.
For thermal management, the other key function of the system, the researchers didn’t install a separate cooling system but rather routed the extremely cold hydrogen via heat exchangers. These exchangers, arranged in a staged sequence, remove the wasted heat from components like cables, motors, superconducting generators, and power electronics. Absorbing this heat gradually increases the temperature of hydrogen.
Optimizing Hydrogen Delivery & Thermal Management in Flight
When it comes to delivering liquid hydrogen throughout the aircraft, it presents its own challenges. For instance, pumps bring not only extra weight but also complexity to the system and can bring forth unwanted heat under cryogenic conditions.
To overcome these challenges, the team developed a pump-free system that utilizes tank pressure to control the flow of hydrogen fuel.
The pressure is increased by injecting hydrogen gas from a regular high-pressure cylinder and decreased by venting hydrogen vapor. For real-time adjustment of pressure, a feedback loop connects pressure sensors to the power demands of the aircraft, which ensures the accurate rate of hydrogen flow across all flight phases.
The system, according to the simulations, is capable of delivering hydrogen at rates of up to 0.25 kilograms per second. This delivery rate is sufficient to meet the 16.2-megawatt electrical demand during takeoff or in the event of an emergency, where the aircraft must go around.
With heat exchanges organized in sequential order, as hydrogen moves through the system, the gas first cools components that are operating at cryogenic temperatures, like cables and HTS generators. Then, it absorbs heat from higher-temperature components, such as motors and power electronics. At last, before hydrogen reaches the fuel cells, it is preheated to match the optimal conditions of the fuel cell inlet.
It is this staged thermal integration that enables liquid hydrogen to be used as both a fuel and a coolant, thereby maximizing the system’s efficiency while minimizing the complexity of the hardware.
“Previously, people were unsure about how to move liquid hydrogen effectively in an aircraft and whether you could also use it to cool down the power system component. Not only did we show that it’s feasible, but we also demonstrated that you needed to do a system-level optimization for this type of design.”
– Guo
The focus of the study here was on design optimization and system simulation. In the next step, researchers will do experimental validation. For this, the team will build a prototype system and then run tests at FSU’s Center for Advanced Power Systems.
In their future work, the researchers will also focus on the heat exchangers’ design, which is present in every circulation loop, and transfers heat from the components to the working fluid. The current study lacks detailed specifications for the material, size, and thermal properties of these components.
Innovative thermal management strategies will also be the focus to cool the fuel cell stacks and address the significant heat generation during operation. These advancements, the study noted, are crucial to refining the overall thermal management architecture and ensuring the practical implementation of zero-emission aviation technologies.
Investing in Hydrogen-Powered Aviation Technologies
When it comes to investing in the aviation sector, RTX (RTX +0.03%)offers a high-potential opportunity. The world’s largest aerospace and defense company is a core industry partner in the IZEA collaboration. It also has extensive R&D programs targeting sustainable aviation technologies, including fuel cell and hydrogen-powered systems.
RTX Corp. (RTX +0.03%)
RTX operates through three main segments:
- Collins Aerospace provides technologically advanced aerospace and defense products to commercial airlines, civil and military aircraft manufacturers, and space operations.
- Pratt & Whitney segment supplies aircraft engines to military, general, and commercial customers.
- Raytheon develops missiles, smart weapons, and advanced air and missile defense capabilities.
Through Collins Aerospace and Pratt & Whitney divisions, RTX is actively involved in developing and testing hydrogen-powered aircraft and related technologies.
This includes the HySIITE program, which is working on allowing the aviation industry to use hydrogen at scale. Sponsored by the DOE’s Advanced Research Projects Agency-Energy, the project is optimized for liquid hydrogen and is wrapped up in December 2024. The HySIITE rig tests showed a 99.3% reduction in NOx compared to a GTF engine and up to a 35% improvement in energy efficiency.
Its two other projects, meanwhile, are ongoing to drive the future of hydrogen in aviation. The Hydrogen Advanced Engine Study (HyADES), supported by Canada’s joint industry-government initiative, INSAT, is working on advancing the use of hydrogen for turboprop aircraft. COCOLIH2T, meanwhile, is supported by the EU’s Clean Hydrogen Joint Undertaking and is developing a way to store fuel.
When it comes to Raytheon’s market performance, its stocks have been flying high. The company’s shares, with a market capitalization of $183.64 billion as of writing, have been trading above $137.50, a new all-time high (ATH) and representing year-to-date (YTD) gains of 18.7%.
RTX Corporation (RTX +0.03%)
There has been constant growth for RTX shares over the last three decades. The shares are also up about 21% since the April lows. With that, its EPS (TTM) is 3.41 and the P/E (TTM) is 40.31. Raytheon also offers an attractive dividend yield of 1.98%.
As for company financials, it reported strong performance in the first quarter of 2025 with sales increasing by 5% from the previous year to $20.3 billion and adjusted EPS being $1.47. Raytheon’s operating cash flow during this period was $1.3 billion, and free cash flow was $0.8 billion, while the backlog is $217 billion, including $92 billion in defense and $125 billion in commercial.
“We are off to a strong start to 2025. The current environment is clearly very dynamic, but our company is well positioned to perform operationally and our teams remain focused on executing on our commitments and delivering our robust backlog.”
– RTX President and CEO Chris Calio
For the entire 2025, the company projects adjusted sales between $83-$84.0 billion, adjusted EPS to be between $6.00 and $6.15, and free cash flow of $7-$7.5 billion while noting that these estimates do not cover the impact of the recently enacted tariffs.
Amidst all this, the company was awarded a $536 million contract from the U.S. Navy just this week for the SPY-6 family of radars, which are now installed on two of their ships, with three more ready for installation. Over the next decade, radars will be deployed on more than 60 U.S. Navy ships.
As part of the contract, Raytheon will provide continued support through training, installation, integration, and testing, in addition to software upgrades to boost radar capabilities.
“SPY-6 is the most advanced radar in the U.S. naval fleet, providing ships a new level of defense against evolving threats.”
– Barbara Borgonovi, president of Naval Power at Raytheon.
The 13th AN/TPY-2 missile defense radar has also been delivered to the U.S. Missile Defense Agency, marking the first unit to feature a fully GaN-based array, which significantly enhances the system’s sensitivity and performance.
A $1.1 billion contract has also been secured by the company for the manufacturing and delivery of AIM-9X Sidewinder missiles. With this award, Raytheon continues its long-term support of the Sidewinder program, a widely used short-range missile system globally.
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Final Thoughts: Hydrogen’s Role in Sustainable Aviation
The aviation sector is rapidly growing and contributing to global economic and social development, but at the same time, it is creating a pressing need to address the problem of carbon and contrail emissions. Here, hydrogen, with its high specific chemical energy, has emerged as a promising clean fuel alternative.
With that in mind, the latest study presents a comprehensive framework for designing and optimizing a liquid hydrogen storage, thermal management, and transfer-control system, demonstrating its potential to advance efficient and sustainable aviation technologies.
By leveraging hydrogen’s positive impact on climate change and air quality, the aviation industry now has a viable pathway to reduce its carbon footprint, paving the way for a future where long-distance travel no longer comes at the expense of the planet.
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Studies Referenced:
1. Virdi, P. S., Guo, W., Cattafesta, L. N. III, Cheetham, P., Cooley, L., Gladin, J. C., He, J., Kim, C., Li, H., Ordonez, J., Pamidi, S., & Zheng, J.-P. (2025). Liquid hydrogen storage, thermal management, and transfer-control system for integrated zero emission aviation (IZEA). Applied Energy, 355, 126054. https://doi.org/10.1016/j.apenergy.2025.126054