Advancing Space Travel: The Promise of Multimode Propulsion

Researchers at the University of Illinois Urbana-Champaign have made significant strides in enhancing spacecraft efficiency for lunar missions through a cutting-edge propulsion approach known as multimode propulsion. This innovative method combines both chemical high-thrust and electric low-thrust propulsion using the same propellant, aiming to optimize spacecraft operations on missions to the Moon. Funded by NASA, the team examined four real mission scenarios to demonstrate the practical applications of this technology.Aerospace engineering Ph.D. student Bryan Cline emphasized the project's groundbreaking nature: “This is the first high-fidelity analysis of multimode mission design for lunar missions relevant to NASA, particularly utilizing CubeSats.” By employing a standard 12-unit CubeSat, the team was able to explore various mission profiles effectively.One of the primary benefits of multimode propulsion lies in its ability to significantly reduce the spacecraft's dry mass. Cline explained that utilizing a single fuel tank streamlines mass and volume, which is a distinct advantage over traditional hybrid systems that require multiple propellants. “With multimode systems, the flexibility to switch between high-thrust and low-thrust modes allows for better maneuverability and reduced fuel consumption,” he noted.Cline's team manually determined when to employ high-thrust or low-thrust during their mission simulations, which resulted in suboptimal trajectories. To enhance this process, he developed an algorithm that automatically identifies the optimal moments to switch thrust modes, ensuring the most efficient flight path. “We created the first indirect optimal control technique tailored for multimode mission design, enabling us to achieve specific objectives such as minimizing fuel use and transfer time,” Cline stated.The researchers successfully tested this method on both two-dimensional transfers between Earth and Mars and three-dimensional transfers to geostationary orbit. Cline highlighted the versatility of the approach: “The method is adaptable to a wide range of mission design challenges, ensuring optimal solutions through variational calculus.”Cline remarked on the potential of multimode propulsion as an emerging technology that enhances mission capabilities. “This advancement provides greater flexibility and adaptability, allowing for missions that were previously unattainable,” he said. “We are at an exciting juncture for multimode propulsion, working to translate our laboratory research into practical applications that will benefit the broader space community.”