The Cluster Reaction Control Subsystem (RCS) is configured as a conventional bi-propellant system, based on a single 400 Newton main engine and eight 10 Newton thrusters. It is arranged in two redundant branches (with the exception of the main engine), each of which is capable of performing a complex mission profile. Electrical cross-coupling permits the operation of either of the two branches from either redundant half of the Attitude Determination and Control Electronics (ADCE).
The propellant is stored in six titanium tanks - three for the nitrogen tetroxide oxidiser (NTO) and three to hold the monomethylhydrazine (MMH) fuel - pressurised by helium which is stored in two smaller spherical tanks. Pressure-regulation and propellant-delivery systems manage the pressurant and propellant conditioning and distribution functions.
During launch, the pressurant, fuel, oxidiser and the manifold will be isolated from each other by pyrotechnically operated valves, to comply with launch-vehicle safety requirements. After each manoeuvre, the main engine and thrusters will also be isolated by additional latching valves, thereby increasing reliability by eliminating potential leak paths.