Nonpropellants

Nonpropellants are substances or systems that do not generate thrust in propulsion contexts. They are used in a variety of fields to support operation, safety, or delivery without acting as the main propulsive force. In aerospace and rocketry, for example, nonpropellants include inert gases or liquids used for purging, pressurizing, cooling, or providing an inert atmosphere in tanks and lines. They may also serve as ballast or shielding media and can help prevent unwanted reactions or fires by displacing oxygen or flammable vapors.

Common nonpropellant gases used in propulsion-related applications are nitrogen, helium, and argon. Nitrogen is often employed to purge tanks and feedlines, helium for pressurization and cryogenic handling, and argon for electrical arc suppression and inerting in sensitive environments. Nonpropellants can also support cooling loops, vibration isolation, or protective atmospheres within spacecraft during assembly, fueling, or storage. While propellants produce controlled exhaust to move a vehicle, nonpropellants fulfill ancillary roles that enable safe and reliable operation.

Beyond aerospace, nonpropellant delivery systems appear in consumer and industrial contexts. Some devices expel contents without a gaseous propellant, using mechanical pumps or compressed gas drives to dispense liquids or pastes. This class of systems avoids reliance on volatile propellants and is chosen for environmental, regulatory, or handling considerations. Overall, nonpropellants are defined by their lack of thrust contribution, while still playing essential roles in support, safety, and delivery across multiple technologies.