Lock the doors: Remembering Columbia’s final homecoming (2020)

Lock the doors: Remembering Columbia’s final homecoming (2020)
Space Telescope (HST) four times and had begun building the sprawling International Space Station (ISS) in low-Earth orbit.

The shuttle remained an inherently dangerous vehicle, although the robustness of the four surviving orbiters—Discovery, Atlantis, Columbia herself and the “baby” of the fleet, Endeavour—had been amply demonstrated and their shortcomings were well-understood. Or so it seemed. Those shortcomings came home to roost with horrifying suddenness on the morning of 1 February 2003.

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video falling from the External Tank at T+82 seconds and hitting Columbia’s left wing—at precisely the spot where Reinforced Carbon Carbon (RCC) would later guard the ship against the most severe re-entry temperatures—concern was elevated, but ultimately dismissed. It would prove to be a dismissal as ill-judged as declaring the Titanic to be unsinkable.

The video footage from STS-107’s launch on 16 January offered little indication of what, if any, damage the foam strike had caused, save for a huge shower of particles. It was unclear if these particles originated from the impact of the foam itself or from shattered pieces of the RCC panels. If it was the latter, this did not bode well for Columbia’s re-entry, for the panels helped to guard the vehicle against the brunt of 3,000-degree-Celsius (5,400-degree-Fahrenheit) extremes during the hypersonic return to Earth. Senior managers doubted that a foam strike—an event which had occurred on earlier missions—could possibly be a “safety of flight” issue.

Space Center’s (JSC) flight control team of the kind of data “signature” they could expect to receive in the event that the worst should happen. Let’s suppose, said McCluney—outlined in depth by Michael Cabbage and William Harwood in their harrowing book about the tragedy, Comm Check—that a large hole had been punched through one of the shuttle’s RCC panels, enabling super-heated plasma to enter the airframe. “Let’s surmise,” he told them, “what sort of signature we’d see if a limited stream of plasma did get into the wheel well [of Columbia’s main landing gear], roughly from entry interface until about 200,000 feet (60 km); in other words, a 10–15-minute window.” Little could McCluney possibly have guessed that his “signature” would almost exactly mirror the dreadful events which befell Columbia on the morning of Saturday, 1 February 2003.

“First would be a temperature rise for the tires, brakes, strut actuator, and the uplock actuator return…”

At 8:52:17 a.m. EST, nine minutes after entry interface—the point at which the shuttle began to encounter the tenuous upper traces of the “sensible” atmosphere—Entry Flight Director LeRoy Cain and his team saw the first unusual data on their monitors. Cain had begun his shift on console earlier that morning, with an up-tempo “Let’s go get ’em, guys,” before giving STS-107 Commander Rick Husband the go-ahead to perform the irreversible de-orbit burn to drop Columbia out of orbit and onto an hour-long path to land at the Kennedy Space Center’s (KSC) Shuttle Landing Facility (SLF) at 9:16 a.m. EST. Much of the entry profile was controlled by the shuttle’s General Purpose Computers (GPCs), as was normal protocol, but with 23 minutes remaining before touchdown, Maintenance, Mechanical, Arm, and Crew Systems (MMACS) Officer Jeff Kling saw something peculiar in his data.

It was what flight controllers termed an “off-nominal event”.

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Video Credit: NASA/Matthew Travis/YouTube

As later described by Cabbage and Harwood, Kling noticed that two downward-pointing arrows appeared next to readings from a pair of sensors deep within Columbia’s left wing. They were designed to measure hydraulic fluid temperatures in lines leading to the elevons. A few seconds later, two more sensors also failed. The attention of Kling and his team was instantly captivated; it looked for all the world that the wiring to all four sensors had been cut.

They tried to fathom a common “thread” to explain the fault, but none was forthcoming.

Kling spoke directly to Cain. “FYI, I’ve just lost four separate temperature transducers on the left side of the vehicle,” he began, cautiously. “Hydraulic return temperatures. Two of them on System One and one in each of Systems Two and Three.”

“Four hyd return temps?” queried Cain.

“To the left outboard and left inboard elevon.”

news, for STS-107 was a “heavyweight” mission with the fully-loaded Spacehab module and experiment pallet. A “wheels-up” belly landing was not expected to be survivable. The astronauts would need to perform a never-before-tried bailout, utilizing an escape pole system implemented after Challenger, but this could not be attempted until Columbia was at much lower altitude and at much lower relative airspeed.

“Data loss would include that for tire pressures and temperatures, brake pressures and temperatures,” concluded McCluney.

After hearing Jeff Kling’s report, astronaut Charlie Hobaugh—the lead Capcom on duty that morning and the man responsible for talking directly to the STS-107 crew—called Husband to inform him of the anomalous tire pressure messages. Hobaugh also asked Husband to repeat his last comment. There was no reply from the rapidly-descending Columbia. By now, LeRoy Cain was pressing Kling for answers on whether the messages were due to faulty instrumentation, but was advised that all associated sensors were reading “off-scale-low”—they had simply stopped working.

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Video Credit: NASA/Matthew Travis/YouTube

Seconds later, at 8:59:32 a.m., Husband tried again to contact Mission Control. These were to be the last words ever received from Space Shuttle Columbia.

“Roger,” he said, presumably acknowledging Hobaugh’s earlier pressure call, “uh, buh…” At that point, abruptly, his words were cut off in mid-sentence, together with the flow of data from the orbiter. Communications were never restored. Thirty-two seconds after Husband’s partial transmission, a ground-based observer with a camcorder shot video footage of multiple debris contrails streaking like tears across the Texas sky.

With the telemetry thus broken, the atmosphere in Mission Control was becoming increasingly uncomfortable. Kling told Cain that there was no common thread between the tire pressure messages and the earlier hydraulic sensor failures; moreover, other instrumentation for monitoring the positions of the orbiter’s nose and main landing gear had also been lost. As the seconds of radio silence stretched longer, Cain asked Instrumentation and Communications Officer (INCO) Laura Hoppe how long she expected the intermittent “comm” to last. She admitted that she expected some ratty comm, but was surprised and puzzled by how protracted and “solid” it was.

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“Simplicity, patience, compassion.
These three are your greatest treasures.
Simple in actions and thoughts, you return to the source of being.
Patient with both friends and enemies,
you accord with the way things are.
Compassionate toward yourself,
you reconcile all beings in the world.”
― Lao Tzu, Tao Te Ching