Entry: The de-orbit burn and entry targeting were accomplished using well-established Mission Control Center procedures. There were no problems identified with this process.
On the morning of February 1, space shuttle Columbia entered with unknown damage to an RCC panel or T-seal in the left wing RCC panel 5-9 area. Hardware forensic analysis and a review of MADS temperature and strain measurements on the left wing leading edge structure point to the RCC panel 8/9 area as the most likely area of damage. The forensic evidence indicated the RCC panel 8/9 area was subjected to extreme entry heating over a long period of time, leading to RCC rib erosion, severely slumped carrier panel tiles, and substantial metallic slag deposition on the RCC panels nearest the damaged area.
MADS data indicated the RCC cavity temperature and the temperature behind the wing leading edge spar began to rise at approximately 8:49:00 EST. This indicates that hot gas flowed into the RCC cavity between entry interface 8:44:09 EST and 8:49:00 EST. Three minutes later, at 8:52:00 EST, temperature and strain measurements indicated that hot gas penetrated the internal part of the wing via a breach in the wing leading edge spar. Immediately, the hot gas inside the wing began to heat wire bundles containing real-time telemetry and MADS data. A MADS upper left wing pressure measurement was the first to fail at approximately 8:52:16 EST. Over the next four minutes, 164 other measurements fail, with the last failure at approximately 8:56:24 EST. Most measurements failed very quickly, within the first two minutes of the breach.
Space shuttle Columbia’s flight control system began to sense increased drag on the left wing due to the damage at 8:52:05 EST. The vehicle easily compensated for the initial aerodynamic disturbance. A significant change in the vehicle aerodynamics was observed at 8:54:20 EST, indicating a change in the damage to the left wing. At the same time several very bright debris events were seen in ground-based videos.
Soon after the hot gas entered the space shuttle left wing multiple debris events were captured on video by observers on the ground. These video images begin at 8:53:46 EST (20 seconds after California coastal crossing) and end with Columbia’s final break-up. The exact source of the debris may never be fully understood. However, upper wing skin and Thermal Protection System (TPS) parts are possible candidates. Damage to the internal aluminum wing structure was most probable during this timeframe as well. These debris events appeared to affect orbiter communication. There were 13 unexplained communication dropouts in this timeframe.
By 8:56:16 EST hot gas had penetrated the space shuttle wheel well wall as indicated by an off-nominal rise in hydraulic line temperatures. Another significant change in space shuttle Columbia’s aerodynamics occurred at 8:58:09 EST, accompanied by several more debris events. The vehicle responded to this event with a sharp change in its aileron trim. Additionally, by 8:58:56 EST all left main gear tire pressure and temperature measurements were lost, indicating a rapid progression of damage inside the wheel well. A continual progression of left wing damage caused another abrupt change in the vehicle’s aerodynamics at 8:59:29 EST. Columbia attempted to compensate by firing all four right yaw jets. By 8:59:32 EST the Mission Control Center had lost all telemetry data. MADS recorder data was lost at 9:00:14 EST. Based on video imagery, main space shuttle aerodynamic break-up occurred at 9:00:23 EST.