Gimbaled thrust is the system ofthrust vectoring used in mostrockets, including theSpace Shuttle, theSaturn V lunar rockets, and theFalcon 9.
In agimbaled thrust system, the engine or just the exhaustnozzle of the rocket can be swiveled on two axes (pitch and yaw) from side to side. As the nozzle is moved, the direction of the thrust is changed relative to thecenter of gravity of the rocket.
The diagram illustrates three cases. The middle rocket shows the straight-line flight configuration in which the direction of thrust is along the center line of the rocket and through the center of gravity of the rocket. On the rocket at the left, the nozzle has been deflected to the left and the thrust line is now inclined to the rocket center line at an angle called the gimbal angle. Since the thrust no longer passes through the center of gravity, a torque is generated about the center of gravity and the nose of the rocket turns to the left. If the nozzle is gimbaled back along the center line, the rocket will move to the left. On the rocket at the right, the nozzle has been deflected to the right and the nose is moved to the right.
Thrust vectoring for manyliquid rockets is achieved by gimbaling the wholeengine. This involves moving the entirecombustion chamber and outer engine bell as on theTitan II's twin first-stage motors, or even the entire engine assembly including the relatedfuel andoxidizer pumps. TheSaturn V and theSpace Shuttle used gimbaled engines.[1]
A later method developed forsolid propellantballistic missiles achieves thrust vectoring by deflecting only thenozzle of the rocket using electric actuators orhydraulic cylinders. The nozzle is attached to the missile via aball joint with a hole in the centre, or a flexible seal made of a thermally resistant material, the latter generally requiring moretorque and a higher power actuation system. TheTrident C4 andD5 systems are controlled via hydraulically actuated nozzle. TheSTS SRBs used gimbaled nozzles.[2]