In the race towards greener propulsion systems, LiquidPiston's X-Engine emerges as a disruptive force challenging the dominance of hydrogen engines. The X-Engine operates on a revolutionary High Efficiency Hybrid Cycle, combining the best features of traditional cycles to achieve up to 30% higher thermal efficiency than conventional engines. Unlike the Wankel engine, the X-Engine's design features a stationary combustion chamber and apex seals, leading to improved fuel combustion, lubrication, and reduced emissions. Its compact size and multi-fuel capabilities, including jet fuel, make it an ideal choice for various applications from drones to hybrid-electric vehicles. LiquidPiston's collaboration with the U.S. Department of Defense highlights the X-Engine's potential in the aerospace and defense sectors, especially with its ability to run efficiently on jet fuel. The engine's weight advantage over diesel engines opens up possibilities for eVTOL aircraft, UAS, and mobile generators. By utilizing supercomputers and simulations, LiquidPiston has developed a robust platform with customization options for ignition systems and fuel types, ensuring adaptability to diverse needs. While hydrogen engines face infrastructure challenges and high costs, the X-Engine offers a practical alternative with immediate readiness for conventional and alternative fuels. LiquidPiston's innovation signifies not just an evolution but a revolution in rotary engines, promising a greener and more efficient future for propulsion systems.