Actively pulsed dual heating in vaporizing liquid microthrusters: An integrated analysis combining numerical simulations and experiments

The advancement of Micro-Electro-Mechanical Systems technology has driven significant interest in micropropulsion systems for small satellites (total mass < 10 kg) used in Earth observation missions, where precise attitude control is essential. Among the various microthruster concepts, vaporizing liquid microthrusters stand out for their simple design and ability to use liquid propellants, enabling compact and lightweight propulsion systems. These microthrusters can achieve nominal thrust levels between 0.1 and 10 mN with specific impulses exceeding 100 s when using water as a propellant. However, their Technology Readiness Level remains below 5 due to flow boiling instabilities, which significantly affect thermal and propulsive performance and limit device lifetime. To address these challenges, a novel dual-heating microthruster concept has been developed in collaboration with the Institute for Microelectronics and Microsystems of the National Research Council, based in Lecce (Italy) and KU Leuven (Belgium), led by the Aerospace Propulsion group at the University of Salento. The new design integrates two independent heating chambers, each equipped with dedicated heating elements and microsensing capabilities (thermistors and vapor quality capacitive sensors). This approach decouples the boiling and superheating phases, leading to improved control over the vaporization process and reducing thermal stresses. A numerical and experimental investigation was conducted to assess the impact of actively controlled dual pulsed heating on the devices thermal and propulsive behavior. A 1D numerical model was developed to analyze different heating strategies and optimize energy efficiency, while experimental validation provided critical insights into real-world performance. The results demonstrate that the dual-heating strategy enhances stability, increases operational efficiency, and extends the device's lifetime. These findings highlight the potential of adaptive control techniques in optimizing vapor–liquid microthruster operation, bringing microelectromechanical systems-based microthrusters closer to practical satellite applications.