I've been working on a hobby space simulator of my own for some time now and have recently implemented a flight dynamics model for atmospheric flight based on stability derivatives. I derived rigid body equations of motion within the rotating planet frame (think of ECEF) since it simplifies several aspects of the simulation. Since I am in the rotating frame, I also add fictitious centrifugal and Coriolis forces, neglecting the Euler force. This seems to all work beautifully for atmospheric flight.
I have also derived equations of motion for space flight, which are in the planet inertial frame (ECI). The plan is to switch to these at some cutoff altitude, which is how I believe Kerbal Space Program handles it (I've never played, but its wiki pages lists Rotational/Inertial Transition altitudes for planets). The rotating frame state (position, velocity, etc.) can easily be transformed into the inertial frame state at this point.
However, I'm not sure if this is the best solution. I've been wondering how Orbiter handles this internally? With the high rotational speeds, especially near the equator (~465 m/s for Earth, or nearly 8 meters! per frame at 60 fps), I can't imagine that keeping everything in the inertial frame would be very stable in a simulation. Just wanted to do a quick sanity check before I go too deep into this!
I have also derived equations of motion for space flight, which are in the planet inertial frame (ECI). The plan is to switch to these at some cutoff altitude, which is how I believe Kerbal Space Program handles it (I've never played, but its wiki pages lists Rotational/Inertial Transition altitudes for planets). The rotating frame state (position, velocity, etc.) can easily be transformed into the inertial frame state at this point.
However, I'm not sure if this is the best solution. I've been wondering how Orbiter handles this internally? With the high rotational speeds, especially near the equator (~465 m/s for Earth, or nearly 8 meters! per frame at 60 fps), I can't imagine that keeping everything in the inertial frame would be very stable in a simulation. Just wanted to do a quick sanity check before I go too deep into this!
