Reaction control system

The Mercury space capsule and Gemini reentry module both used groupings of nozzles to provide attitude control.

The Gemini capsule was also capable of adjusting its reentry course by rolling, which directed its off-center lifting force.

In-orbit attitude control was achieved by firing pairs of eight 25-pound-force (110 N) thrusters located around the circumference of its adapter module at the extreme aft end.

Lateral translation control was provided by four 100-pound-force (440 N) thrusters around the circumference at the forward end of the adaptor module (close to the spacecraft's center of mass).

The clusters were located near the craft's average centers of mass, and were fired in pairs in opposite directions for attitude control.

[citation needed] The suborbital X-15 and a companion training aero-spacecraft, the NF-104 AST, both intended to travel to an altitude that rendered their aerodynamic control surfaces unusable, established a convention for locations for thrusters on winged vehicles not intended to dock in space; that is, those that only have attitude control thrusters.