Development of a measurement and control system for a biphasic fluid evaporator

In recent decades, countless small satellites have been launched in space with a trend that is expected to significantly scale up in the near future. The reasons that spurred their rapid growth in space industry are related to the compact dimensions, high versatility and flexibility and cost-effectiveness that characterize the miniaturized satellites, such as CubeSats. Nevertheless, ground-breaking propulsion systems must be designed to comply to the size and manufacturing costs of these space assets so as not to compromise the several benefits of small satellites. Among the different categories of thrusters, the cold gas system is one of the most suitable engines for CubeSat missions due to its simplicity and reliability, even if the straightforward operating principle entails low thrust and efficiency. To mitigate these drawbacks, the T4i company has developed a cutting-edge cold gas system which innovation consists in storing the propellant inside a pressurized tank in liquid form reducing volume and costs. An evaporator plays a key role in the proper functioning of the system since it aims to completely vaporize the propulsive fluid in any initial condition generating a suitable thrust. Furthermore, the microtubes technology employed to realize the evaporator and the physical properties of the selected propellant contribute to enhance the efficiency of the whole system. The purpose of the thesis is to develop a data acquisition and control system for the evaporator with a particular focus on the hardware and software implementation. An appropriate apparatus, called TRAP experiment, has been designed to test and certify the evaporator in microgravity environment during a suborbital flight planned by Virgin Galactic. However, test bench experiments have been carried out implementing a communication interface between the system control board and a Client PC in order to send telecommands and receive the telemetry. After all the electronic boards have been designed, assembled and tested, suitable wires and connectors have been chosen to proper connect sensors and actuators to the experimental apparatus. Subsequently, a software, based on a finite state machine, has been developed to automatically control the whole experiment with a particular emphasis on the dedicated thermal control system of the evaporator, implemented according to a suitable control law. In addition, the development of a Graphical User Interface for a Client PC has allowed to perform specific operations manually by means of telecommands and to receive information acquired by sensors. Finally, several tests have been carried out to verify, firstly, the proper functioning of the entire electronic system, and secondly, the validity of the thermal control algorithm of the evaporator.