• Electric Propulsion
• Cathode
• Feeding system HET
• Iodine Fed HET
• Control unit
• Alternative propellants

Electric Propulsion is considered the technology of the future for spacecraft propulsion. It uses electrical energy to produce thrust. This can be achieved by using electric and magnetic fields to accelerate charged species (i.e. plasmas) or by using electric power to heat a neutral gas.

The leading technologies used today are Hall thrusters. These devices are characterized by high specific impulse and less propellant consumption to achieve the desired total impulse. Hollow cathodes have been the standard electron source for Hall thrusters (HETs) for decades. It usually operate on the same propellant as the companion thruster, typically noble gases, specifically Xenon (Xe) and Krypton (Kr).

Many other propellants have been investigated in the laboratory over the last years, in particularly Iodine (I), due to its many advantages. Iodine generally is stored in solid state at room temperature and at a density at least three times higher than noble gas-gased propellants; it also have a first ionization energy lower than Xenon. However, it needs to be vaporized at temperature of 80-100 ◦C to deliver it to the thruster unit or before the cathode operation, without requiring pressurized vessels or high-pressure propellant management components, as vapour is directly generated within the storage by sublimation. So it is essencial a feeding system to sublimate and deliver the vapor iodine.

This thesis work was carried out to optimize the control unit of the whole feeding system and test the mass flow meter integrated in the apparatus.
The basic feeding system architecture is that proposed by UniPi, consisting essentially of sublimator assembly, an ON/OFF valve, a laser flow meter and a thermal throttle. The entire feed system must be maintained at an elevated temperature to prevent iodine vapor from redepositin. Therefore it is necessary a positive temperature gradient between the sublimator and the thermal throttle, maintened through a control unit.