TVC Controller

This is the current TVC geometry of Osiris. This geometry was largely driven by the slew rate requirement, which defines how fast the actuators can move the engine in the pitch and yaw axes. However, the geometry is constrained by structures, as the necessary arrangement of load cells, instrumentation, and gimbal joints currently results in a non-optimal geometry. However, the current geometry still exceeds the requirements for a complete circle gimbal profile in 10 seconds. Between now and CDR, we aim to improve the geometry to achieve a slew rate of at least 20 degrees per second, which is a lower bound estimate of what's necessary for a liquid lander.

The maximum force on the actuator is when the pitch and yaw axes are maxed. An important note here is that this force is not from the thrust of the engine, but rather from the reaction force that the actuators feel when pushing the engine (which has some moment of inertia) in a certain direction. When the engine is at a neutral state, the actuators have the best torque leverage on the engine; however, as the engine moves in the pitch and yaw axes, the actuator has to impart more force to generate the same moment. The length of the actuator is, unsurprisingly, at its longest when the pitch and yaw axes are maxed.

As we can see below, the actuator specs meet the computed requirements.