Numerical study of MEMS-Based vaporizing liquid microthruster for CubeSats

In the last decade, the interest in CubeSat had been increased dramatically. The low deployment cost and the capability to operate in low Earth orbit enable it to become one of the most attractive tools for different space missions such as remote sensing and communications. However, the information about the technology of the CubeSat in terms of the design and the propulsion system is still limited or characterized as classified data. The focus of this work is mainly on the enhancement of the performance of the vaporizing liquid microthruster (VLM) propulsion system of a CubeSat. The development in propulsion systems' miniaturization has generated a proliferation entailing both nano- and microsatellite designs. Consequently, the microelectromechanical systems (MEMS) technology has diversified into various applications. Recently, MEMS have been applied in the domain of micropropulsion for miniaturized satellites. The VLM is amongst several MEMS microthrusters which is established newly, has gained research attention for its capability to produce continuously variable thrust in the micronewton (µN) to millinewton (mN) range. In this thesis, 3D model simulations were conducted to numerically investigate the fluid flow behaviour of MEMS-VLM thruster with the aid of the Computational Fluid Dynamics (CFD) technique. The computational domain consists of an inlet channel, distributer, microchannels, chamber and in-plane converging-diverging (C-D) nozzle. The geometry's modification aims to achieve maximum thrust force by controlling the VLM chamber heating power at a constant inlet propellant flow rate. The computational simulations of the proposed design were performed for two phases: subsonic section (inlet-distributor-microchannel-chamber) and supersonic section (planar convergent-divergent micronozzle). The numerical results demonstrate a 38% increase in the thrust force and a 22% decrease in the heating power compared to the design proposed by Kundu et al. [Pijus Kundu et al. 2012 J. Micromech. Microeng. 22 025016]. In conclusion, the geometrical modification remarkably increases the underlying thrust with comparatively low input power. The proposed VLM modification can yield up to 1.38 mN thrust and a specific impulse of 70 s by utilizing 2 W heating power at a 2 mg/s water flow rate, which is within the capability of the CubeSat power budget and fuel amount. Moreover, the current design could reduce the possibility of propellant pumps failure that resulted from the boiling of the water within the inlet part of the VLM, and hens reduce the thrust instability. Finally, a comparative evaluation with other published VLM research shows that the current design can produce relatively more thrust force by utilizing less input power.