coldgas

Coldgas refers to a class of spacecraft propulsion that uses the controlled expulsion of a stored gas to generate thrust without chemical reactions. The term commonly applies to cold gas thrusters used for attitude control and small propulsion tasks on satellites, spacecraft, and rovers. The approach is valued for simplicity, reliability, and cleanliness.

In a typical coldgas system, a gas such as nitrogen, helium, carbon dioxide, or air is stored at moderate pressure in a tank. A regulator and a fast-acting valve admit the gas into a nozzle, converting stored pressure into a directed jet. The thrust results from conservation of momentum as mass leaves the vehicle. Because there is no combustion, exhaust is non-toxic and primarily inert, and the system can operate with little risk of contamination.

Performance: thrust is small, usually millinewtons to newtons, depending on nozzle size and gas. Specific impulse is modest, typically tens of seconds. System design emphasizes low mass, simple plumbing, and long life. Gas choice affects performance; nitrogen is common due to availability and non-reactivity, while helium provides higher exhaust velocity but lower propellant density, which can require larger tanks.

Applications include attitude control, formation flying, and small orbital maneuvers on satellites and CubeSats. Coldgas thrusters offer rapid response and easy integration but are limited by low thrust and propellant mass requirements for large delta-v. They are often used in clusters or as supplementary propulsion alongside other propulsion types.