Studies focus on the characteristics of steam and carbon dioxide as major constituents of a biowaste stream, and typically use cubic zirconia as a heating element.
Both methods, however, suffer from some limiting drawbacks: Hydrazine, the most commonly used monopropellant, is highly expensive and due to its volatile nature unsuitable for smaller satellites that are sent to space as secondary cargo.
Cold gas thrusters, while utilizing relatively cheap, inert and therefore "safe" gasses like nitrogen, suffer from low specific impulse in comparison to monopropellant motors.
Resistojets are designed to bridge the gap between these two methods of propulsion, offering the safety of an inert propellant coupled with specific impulse nearing that of hydrazine.
[4] The main disadvantage of a resistojet design in comparison to simpler cold gas thrusters is the need for a power supply, which takes up space and is therefore sometimes a prohibitive factor for Microsat missions.