Columbia

Will Collier — who I might have to make a guest-blogger while I’m under the weather — sent in this Newsday story on the last minutes of the Space Shuttle Columbia. As Will noted, it’s tough reading, especially the part describing exactly what NASA thinks happened during re-entry.

Excuse the lengthy extract:

. . .even as the Columbia astronauts chatted about the light show outside, the hole in Columbia’s left wing was disrupting that boundary layer. Ever more air molecules were shooting into the inside of the wing at RCC panel 8 and slamming into the insulation protecting the panel attachment fittings, swirling through the cavity and spreading out to either side. At that altitude, the effect was small. But the shuttle was descending, and the air was getting thicker with each passing second. With Columbia in a 40-degree nose-up orientation, the plume entering the breach in RCC panel 8 was aimed at the upper attachment fittings and insulation. The insulation began melting, and the front face of the left wing’s aluminum honeycomb forward spar — the only barrier between the plume and the interior of the wing — began heating up.

At 8:48:39 a.m., just four minutes and 30 seconds after Columbia had dipped into the atmosphere, a sensor mounted behind the forward spar, near the point where RCC panel 9 was bolted to the other side, measured an unusual increase in stress. The spar was softening.

About a minute later — five and a half minutes after entry interface — the shuttle’s flight computers ordered a turn to the right. Up until this point, the shuttle had simply been falling into the atmosphere, wings level, nose up and pointed straight ahead. Now, the ship’s flight computers began actively guiding the shuttle toward Kennedy’s runway. The shuttle’s nose smoothly swung 80 degrees to the right.

Less than 20 seconds after the maneuver, sensors mounted on Columbia’s left rear rocket pod measured an unusual change in temperature. Wind tunnel testing would later show some of the hot air blasting into the RCC cavity was exiting through the vents on the upper surface of the wing, carrying thin clouds of metallic vapor from melted insulation.

The firestorm inside the RCC cavity was rapidly increasing in intensity. The boundary layer around the leading edge breach was severely disrupted, and the flow of super-heated air over the lower surface of the wing exposed the protective tiles there to much higher temperatures than they were designed to withstand. Insulation and RCC panel support fittings behind the breach continued to burn away.

Within a few seconds of 8:52:16 a.m. — the exact time is unknown — the deadly plume burned its way through the forward wing spar and into the interior of the wing.

The shuttle was still 300 miles from the coast of California. The crew still had no idea anything was wrong.

But with the boundary layer disrupted, the temperature of the atoms and molecules blasting into the wing probably exceeded 8,000 degrees near the leading edge breach itself. Hot gas began flowing into the wheel well through vents around landing gear door hinges. At 8:52:17 a.m., the first unusual sensor reading flashed on a computer screen in mission control: a slight increase in temperature in the hydraulic fluid running through a brake line leading to the left main landing gear.

Columbia’s left wing was burning up from the inside out.

Now go read the whole thing.