Title pretty much says it all. If I have a model with a freejoint, which has some rotation around all axes, and I prescribe some angular velocity Ω on this joint, will this velocity be in inertial frame or body-fixed frame? So, looking at the image below, does angular velocity in the freejoint (1,0,0) spin around X_I or X_v?
Nevermind, it's body-fixed. This was easily tested with a simulation of a floating body and setting an initial orientation and angular velocity. And body-fixed orientations and velocities is the only thing that makes sense for a developper.