Entry interface is considered to occur at 400,000 feet altitude approximately 4,400 nautical miles
(5,063 statute miles) from the landing site and at approximately 25,000 feet per second velocity.
At 400,000 feet altitude, the orbiter is maneuvered to zero degrees roll and yaw (wings level) and at
a predetermined angle of attack for entry. The angle of attack is 40 degrees. The flight control
system issues the commands to roll, pitch and yaw reaction control system jets for rate damping.
The orbiter's speed brake is used below Mach 10 to induce a more positive downward elevator trim
deflection. At approximately Mach 3.5, the rudder becomes activated, and the aft reaction control
system yaw engines are deactivated at 45,000 feet.
Entry guidance must dissipate the tremendous amount of energy the orbiter possesses when it enters
the Earth's atmosphere to assure that the orbiter does not either burn up (entry angle too steep) or
skip out of the atmosphere (entry angle too shallow) and that the orbiter is properly positioned to
reach the desired touchdown point.
During entry, energy is dissipated by the atmospheric drag on the orbiter's surface. Thus, descent
rate and down ranging are controlled by bank angle. The steeper the bank angle, the greater the
descent rate and the greater the drag. Conversely, the minimum drag attitude is wings level. Cross
range is controlled by bank reversals.
The entry thermal control phase is designed to keep the backface temperatures within the design
limits. A constant heating rate is established until below 19,000 feet per second.
The equilibrium glide phase shifts the orbiter from the rapidly increasing drag levels of the
temperature control phase to the constant drag level of the constant drag phase. The equilibrium
glide flight is defined as flight in which the flight path angle, the angle between the local horizontal and
the local velocity vector, remains constant. Equilibrium glide flight provides the maximum downrange
capability. It lasts until the drag acceleration reaches 33 feet per second squared.
In the transition phase, the angle of attack continues to ramp down, reaching the approximately
14-degree angle of attack at the entry Terminal Area Energy Management (TAEM) interface, at
approximately 83,000 feet altitude, 2,500 feet per second, Mach 2.5 and 52 nautical miles (59
statute miles) from the landing runway. Control is then transferred to TAEM guidance.
During the entry phases described, the orbiter's roll commands keep the orbiter on the drag profile
and control cross range.
Snopercod...looks like we have a possible scenario from putting together press reports.
If the impact on launch hit the gear doors, you could lose the gear door latching mechanisms due to tile damage. If the vehicle loses enough TPS, you could compromise the frame underneath.
The shuttle TPS system has several layers, but if the layers were compromised prior to entry interface, you could get a slow melt of the airframe and the loss of integrity that engineers have always feared with the vehicle.