What propellant does JWST use for its thrusters?

JWST uses hydrazine as the fuel for its thrusters.

The telescope carries a conventional storable, hypergolic chemical-propulsion system for major trajectory corrections and orbit station-keeping near the Sun–Earth L2 point. Its engines use hydrazine fuel together with dinitrogen tetroxide oxidizer; the two ignite on contact, avoiding a separate ignition system.

Hydrazine is not used to power Webb’s scientific instruments or its main electrical systems. A solar array supplies electricity, while hydrazine propulsion provides carefully controlled changes in velocity and orientation. Smaller thrusters help manage attitude, while larger engines perform course corrections and station-keeping.

A common mix-up is choosing nitrogen or xenon. Nitrogen can be used in some spacecraft systems, and xenon is associated with ion propulsion, but neither is Webb’s thruster fuel. Dinitrogen tetroxide is also part of the propulsion system, but it is the oxidizer rather than the stored answer’s fuel.