THE KIRTLAND IMAGE

¶As Columbia passed over Albuquerque, New Mexico, during re-entry (around EI+795), scientists at the Air Force Starfire

¶Optical Range at Kirtland Air Force Base acquired images of the Orbiter. This imaging had not been officially assigned, and the photograph was taken using commercial equipment located at the site, not with the advanced Starfire adaptiveoptics telescope.

¶The image shows an unusual condition on the left wing, a leading-edge disturbance that might indicate damage. Several analysts concluded that the distortion evident in the image likely came from the modification and interaction of shock waves due to the damaged leading edge. The overall appearance of the leading-edge damage at this point on the trajectory is consistent with the scenario.

¶were high enough to substantially damage the wing skins, wing leading edge spar, and the wheel well wall, and melt the wingʼs support struts. Once structural support was lost, the wing likely deformed, effectively changing shape and resulting in increased lift and a corresponding increase in drag on the left wing. The increased drag on the left wing further increased the Orbiterʼs tendency to yaw left.

¶Loss of Vehicle Control (EI+612 through EI+970)

¶A rise in hydraulic line temperatures inside the left wheel well indicated that superheated air had penetrated the wheel well wall by EI+727. This temperature rise, telemetered to

¶Mission Control, was noted by the Maintenance, Mechanical, and Crew Systems officer. The Orbiter initiated and completed its roll reversal by EI+766 and was positioned left-wing-down for this portion of re-entry. The Guidance and Flight Control Systems performed normally, although the aero-control surfaces (aileron trim) continued to counter- act the additional drag and lift from the left wing.

¶At EI+790, two left main gear outboard tire pressure sensors began trending slightly upward, followed very shortly by going off-scale low, which indicated extreme heating of both the left inboard and outboard tires. The tires, with their large mass, would require substantial heating to produce the sensorsʼ slight temperature rise. Another sharp change in the rolling tendency of the Orbiter occurred at EI+834, along

¶Lower Left wing debris Lower Right wing debris Figure 3.7-1. Comparison of amount of debris recovered from the left and right wings of Columbia. Note the amount of debris recovered from areas in front of the wheel well (the red boxes on each wing) were similar, but there were dramatic differences in the amount of debris recovered aft of each wheel well.

¶with additional shedding of debris. In an attempt to maintain attitude control, the Orbiter responded with a sharp change in aileron trim, which indicated there was another significant change to the left wing configuration, likely due to wing deformation. By EI+887, all left main gear inboard and outboard tire pressure and wheel temperature measurements were lost, indicating burning wires and a rapid progression of damage in the wheel well.

¶At EI+897, the left main landing gear downlock position indicator reported that the gear was now down and locked. At the same time, a sensor indicated the landing gear door was still closed, while another sensor indicated that the main landing gear was still locked in the up position. Wire burn-through testing showed that a burn-induced short in the downlock sensor wiring could produce these same contra- dictions in gear status indication. Several measurements on the strut produced valid data until the final loss of telemetry data. This suggests that the gear-down-and locked indica- Figure 3.7-2. Each RCC panel has a U-shaped slot (see arrow) in tion was the result of a wire burn-through, not a result of the back of the panel. Once superheated air entered the breach the landing gear actually deploying. All four corresponding in RCC panel 8, some of that superheated air went through this proximity switch sensors for the right main landing gear re- slot and caused substantial damage to the Thermal Protection mained normal throughout re-entry until telemetry was lost. System tiles behind this area.

¶Post-accident analysis of flight data that was generated after telemetry information was lost showed another abrupt change in the Orbiterʼs aerodynamics caused by a continued progression of left wing damage at EI+917. The data showed a significant increase in positive roll and negative yaw, again indicating another increase in drag on and lift from the damaged left wing. Columbiaʼs flight control system attempted to compensate for this increased left yaw by firing all four right yaw jets. Even with all thrusters firing, combined with a maximum rate of change of aileron trim, the flight control system was unable to control the left yaw, and control of the Orbiter was lost at EI+970 seconds. Mission Control lost all telemetry data from the Orbiter at EI+923 (8:59:32 a.m.). Civilian and military video cameras on the ground documented the final breakup. The Modular Auxiliary Data System stopped recording at EI+970 seconds.

¶Findings:

¶F3.6−1 The de-orbit burn and re-entry flight path were normal until just before Loss of Signal. F3.6−2 Columbia re-entered the atmosphere with a preexisting breach in the left wing. F3.6−3 Data from the Modular Auxiliary Data System

recorder indicates the location of the breach was in the RCC panels on the left wing leading edge.

¶F3.6−4 Abnormal heating events preceded abnormal aerodynamic events by several minutes. F3.6−5 By the time data indicating problems was teleme-

tered to Mission Control Center, the Orbiter had already suffered damage from which it could not recover.

¶Recommendations:

¶R3.6-1 The Modular Auxiliary Data System instrumen-

tation and sensor suite on each Orbiter should be maintained and updated to include current sensor and data acquisition technologies.

¶R3.6-2 The Modular Auxiliary Data System should be

redesigned to include engineering performance and vehicle health information, and have the ability to be reconfigured during flight in order to allow certain data to be recorded, telemetered, or both, as needs change.