To understand Electric Propulsion, we first need to understand the concept of Specific Impulse. It can be defined as the total impulse per unit weight of the propellant. It directly relates to the thruster’s efficiency. In chemical propulsion we try to extract the internal energy of a propellant by combusting it and breaking bonds. But, what if we could take a propellant and supply with external energy with no theoretical limit. More the energy content more work can be done. This is the basic goal of electric propulsion.