Throughout February, March, and April of 2003, truckloads of Columbia’s debris retrieved in East Texas arrived at the reconstruction hangar at Kennedy Space Center. In the first month or so, several truckloads arrived every week. By April, those deliveries were beginning to tail off as searchers completed clearing the debris field.
Workers in the field knew that NASA was conducting important analyses on the material they’d found and shipped to KSC, but they had no concept of the scope of the operation until they saw the reconstruction hangar themselves. NASA’s Mike Ciannilli (who now runs NASA’s Columbia Recovery Office and the Apollo 1, Challenger, and Columbia Lessons Learned Program) worked as an aerial spotter in East Texas during the recovery period. He said, “We had no clue what was going on at KSC. The first time I went to the hangar, I was blown out of the water. I was just mesmerized by it.”
By the end of April, the debris had begun to tell a very clear story about Columbia’s demise. Almost all of the debris showed the effects of extreme heat, oxidation, and mechanical stress to varying degrees. But what damage happened before the ship broke apart, and what happened afterward? Painstaking forensic analysis was required to gradually tease apart the sequence of the accident.
Reconstruction workers initially used a computer graphics package (originally developed to track the process of waterproofing the tiles during launch processing) to plot which of the insulating tiles had been recovered from Columbia’s wings. It quickly became obvious that the software was inadequate to provide the information needed for the forensic analysis. Which tiles were damaged? How were they damaged? Were there larger-scale patterns of burns, pitting, or other damage?
The solution was to lay the tiles out on a large, elevated table on which was drawn the outline of the wing and the location and part number of every single one of the 2,800 silica tiles on the left wing. As tiles were recovered and identified (sometimes based only on a few millimeters of thickness), engineers lay them in place on the table.
Patterns quickly emerged.
The carrier panel tiles, which formed the closeout between the leading edge and the rest of the wing, showed where the breach in the wing occurred. The carrier panel tiles behind Panel 9 on the leading edge were slumped and coated with metallic deposits from structures in the interior of the wing.
Burn patterns showed that plasma entering the breach in the wing at thousands of miles per hour pressurized the wing cavity and blew out vents in the upper and lower surfaces of the wing.
As the hot plasma entered and melted its way through the wing’s interior, its heat caused the adhesive that held the tiles onto the wing surface to fail. Those tiles—designed to take heat from the outside surfaces, not from where they were glued onto the ship—peeled off of the wing.
The wing was clearly baking from the inside out.
Finally, the tiles found farthest west in the debris field—those which had come off the earliest in the moments leading to the breakup, as the shuttle was flying from west to east across Texas—were all from the left wing, and all from the area behind leading edge panels 8 and 9.
Leading Edge Frames
Boeing’s Mike Gordon and NASA structures engineer Lyle Davis spent many long hours examining the recovered pieces of the reinforced carbon-carbon (RCC) panels on Columbia’s wing’s leading edges. These pieces ranged in size from larger than one square foot to smaller than a thumbnail.
Since the RCC panels were U-shaped and several feet long, it was impractical to lay them out two-dimensionally. Kennedy Space Center’s shops constructed a set of clear Lexan frames that held the pieces of each RCC panel and its underlying structure, allowing people to see in three dimensions what the front edge of the wing looked like.
The RCC frames also told a compelling story about the accident. Panels 1 though 7, and from Panel 10 outboard, were fractured from forces after the shuttle disintegrated. Their metallic attachment fittings were still partially intact.
However, at Panels 8 and 9, no metallic fittings were recovered. The stainless steel support structure—which melts at 2,500°F—had melted away and was deposited as slag onto the interior of adjacent panels on the wing. The retrieved pieces of RCC from Panels 8 and 9 were knife-edged and heavily eroded, providing evidence that plasma at over 3,000°F was acting as a blowtorch at high pressure on those panels for a prolonged period. This was the only place on the wing where this pattern was observed.
Materials scientists analyzed the cross-section of the slag deposits inside the left wing panels. This analysis showed what the metals were (insulating blankets, aluminum from wing spars, Inconel and steel from fittings, etc.) and how the deposits were laid down. It clearly told the story of the wing’s failure in time sequence.
As with the tiles, the location of the leading edge components in the debris field also gave the sequence of the accident. The leading edge components from the middle to the tip of the left wing (Panels 8 to 22) were found farthest west, between Dallas and Palestine. Pieces of the leading edge of the left wing closest to the shuttle’s fuselage (Panels 1 to 7) were found farther east, between Palestine and Nacogdoches. The right wing leading edge pieces were all found farther east. This provided evidence that the left wing failed before the right wing, with the most likely point of failure being at Panels 8 and 9.
NASA now had the evidence to prove how Columbia broke up.
NASA announced in early May that only one single failure scenario explained all of the evidence contained in the debris, the OEX recorder, and the telemetry received in Houston. Something—most likely the piece of foam from the external tank during ascent to orbit—caused a breach in the leading edge of the left wing, allowing plasma to penetrate the wing during reentry and erode it from the inside out.
Whether the foam actually punctured the RCC at the leading edge, or whether it pushed the spacers apart and created a gap in the panels, will never be conclusively known.
The last truckload of debris arrived at the reconstruction hangar on May 6. Wreckage that had been strewn over thousands of square miles of forest and field—pieces that had been carefully collected by tens of thousands of searchers working in tough conditions for three months—was all here in this one place. The twisted, burned, and shattered debris had told an important story, one that would have been impossible to write without the collective efforts of so many dedicated people in East Texas and Louisiana and of the nation’s wildland firefighting teams.
“Each piece was evidence of how hard Columbia fought to come home to us,” astronaut Pam Melroy said. “We saw every recovered piece as a victory.” Every piece of debris moved the reconstruction team closer to their goal: We will find the problem, fix it, and move forward in their honor.
[Portions excerpted from “Bringing Columbia Home,” © 2017 by Mike Leinbach and Jonathan Ward.]