We all know that rockets have thrust along with a large mass flow, meaning that their mass is constantly depleted. For ground launcher rockets, the propellants form a large part of the mass and this changes over time in their flight. How does a trajectory simulation account for this? Since most of them are dynamically shifting throughout the flight. Even the jettisoning changes the centre of mass abruptly. How does one account for suchchanges, and how does it affect the moments experienced by the vehicle.