We now know factually that the rear starboard yaw thrusters activated before the mystery piece broke off, and that there was some sort of problem with them as reported by Dittemore. That possibly could have turned the orbiter sideways.
What sort of force do you figure broke off the vertical stab if it wasn't caused by a yawing force?
The aft RCS jets maneuver the spacecraft until a dynamic pressure of 10 pounds per square foot is sensed; at this point, the orbiter's ailerons become effective, and the aft RCS roll jets are deactivated. At a dynamic pressure of 20 pounds per square foot, the orbiter's elevators become effective, and the aft RCS pitch jets are deactivated. The orbiter's speed brake is used below Mach 10 to induce a more positive downward elevator trim deflection. At Mach 3.5, the rudder become activated, and the aft RCS yaw jets are deactivated (approximately 45,000 feet).Entry flight control is maintained with the aerojet DAP, which generates effector and RCS jet commands to control and stabilize the vehicle during its descent from orbit. The aerojet DAP is a three-axis rate command feedback control system that uses commands from guidance in automatic or from the flight crew's RHC in control stick steering. Depending on the type of command and the flight phase, these result in fire commands to the RCS or deflection commands to the aerosurfaces.
In the automatic mode, the orbiter is essentially a missile, and the flight crew monitors the instruments to verify that the vehicle is following the correct trajectory. The onboard computers execute the flight control laws (equations). If the vehicle diverges from the trajectory, the crew can take over at any time by switching to CSS. The orbiter can fly to a landing in the automatic mode (only landing gear extension and braking action on the runway are required by the flight crew). The autoland mode capability of the orbiter is used by the crew usually to a predetermined point in flying around the heading alignment cylinder. In flights to date, the crew has switched to CSS when the orbiter is subsonic. However, autoland provides information to the crew displays during the landing sequence.