Angular momentum

[tmf97]

Summary

Converts the attitude dynamics implementation to track angular momentum as the state, instead of angular velocity. Moves angular velocity to the derived state. Propagates all changes to existing unittests.
(Angular velocity is a bad state to track because it is coupled with the moment of inertia of the spacecraft, which changes significantly as fuel gets used up throughout the mission. Tracking angular momentum makes state propagation much easier, even if the initial conditions may be a bit confusing)

Testing

• Existing unittests.

• Running a sim with D_T=0.1 gives a reasonable output when looking at plot_quat():
  

• Nothing else 😅

Notes

This will make implementing the ACS actuator model significantly easier when we get around to it.
The math that's implemented here is based off of my MAE 4060 notes, which are at Team Docs > References > Spaceflight course handouts (MAE 4060)

Comments

• Add an x between the brackets if you commented your code well!