The unmanned aerial vehicles (UAVs) have become a part and parcel of the military and commercial sector. It has also invaded the entertainment and recreational sector with the advent of nano drones. The advantages associated with the UAVs have surpassed any other available technology in the market, and thus, the development in the UAV technology has been witnessing a constant rise with the passing time. The UAVs have become more versatile for consumer and industrial market with the reductions in their power, components and form, which enable them to carry heavier payloads. The increasing applications of UAVs across military and commercial sector have necessitated the development of UAVs with increased fuel efficiency and flight endurance. Hence, the propulsion system is a key component of UAVs in achieving the mentioned features.