• design
• electrothermal
• thruster
• vaporizing
• water

Nowadays, the increasing mission complexity of small orbiting satellites requires them to have an on-board propulsion system. However, there are some differences between these propulsion systems and those of larger spacecraft. The systems must be low cost, low volume, and safe. Traditionally cold gas nitrogen systems have been used as they provide a simple solution, combining high reliability with low cost and heritage. Nevertheless cold gas thrusters tend to be limited by fairly low specific impulses and poor storage densities. A possible way to increase their performance is to heat the propellant to achieve higher specific impulses and thus extending the mission life. When this
is done electrically with resistance heaters the thruster is known as resistojet. In the past, resistojets have primarily utilized hydrazine as the propellant because it represented the best compromise between performance in terms of specific impulse and storage and distribution. Finding alternative propellants to standard fuels is vital for space agencies around the world. Another propellant that seems interesting for its particular properties it's pure water.
Water is inexpensive, non-toxic and can be stored in liquid form. It is also an abundant resource in the solar system. Its relatively small molecular mass makes it possible to achieve a high level of specific impulse. The disadvantages of using water are that it
must be very pure and, as most standard propellants, It must be kept from freezing. Additional power must be supplied to vaporize water either in the resistojet or in a separated vapor generator. The subject of this thesis is the design, manufacturing and testing of a preliminary prototype water resistojet with a separate vaporization chamber. In the first phase of this work, research was carried out into all the water fed electrothermal thrusters alternatives in the literature, after that the prototype has been designed and built. The entire system is designed in a modular manner, tank, vaporization chamber and nozzle head completely separate; this will allow various types of configurations to be tested, e.g. various nozzle geometries and the use of the vaporization chamber to supply water vapour to other types of electric thrusters. The thruster control system has been also designed, both hardware and software. System control and data acquisition are carried out by two microcontrollers of the ATmega family mounted on two arduino boards respectively.