Are there any plans to extend the SDF specification such that one can specify a full 6x6 inertia matrix as the inertial property of a link? Currently, it is only possible to specify the centre of gravity, a scalar mass and a 3x3 rotational inertia matrix. However, for systems such as ships and underwater vehicles, the full inertia matrix is not block diagonal and hence additional parameters are required. The default physics engine DART has support for specifying 6x6 inertia matrices.

The current solution in ignition gazebo with the hydrodynamics plugin is not optimal. This is due to the fact that the added mass forces are calculated at the next timestep by numerically differentiating the velocity.