Why did Space Shuttle Columbia disintegrate/explode?

Question

I have never understood this.

Answer 1

According to the Columbia Accident Investigation Board, the cause of the accident was a hole in the leading edge of the left wing of the shuttle. The hole was caused by a piece of the insulating foam that separated from the External Tank during launch. With the wing punctured, hot gases could penetrate the wing, causing the shuttle to break apart.

Answer 2

During the launch, a piece of insulating foam from the main external fuel tank came loose and struck the wing of the orbiter. This created a hole in the protective thermal tile cover on the wing. During launch, the Shuttle has gotten through the thicker part of the atmosphere before gaining most of its speed, so this did not cause any problems then, but the ship's fate was sealed unless the damage were detected in time. Had it been, the shuttle could have remained docked to the ISS and a separate vehicle could have been launched (either another shuttle, or a Russian Soyuz) in order to give them a ride home.

During re-entry, spacecraft use the friction with the Earth's atmosphere to literally burn off their speed so that they may slow down enough to land safely. This is why our craft use heat shields. Since Columbia's protective tiles on its wing were damaged, some of the hot plasma gases leaked inside the wing, where there was no protection against such temperatures.

The high heat melted support structures, which caused the wing to break off due to the huge aerodynamic forces on it. This of course changes the aerodynamic profile of the craft, as well as shifting its center of gravity. This sudden change, combined with the high velocity caused it to jolt out of its stable position. The structure of the orbiter was not strong enough to withstand this jostling, and high-velocity winds were also now hitting the orbiter in places where it was not designed to withstand the forces. This simply ripped it to pieces.

This is basically the same fate as the Challenger. Most people remember the Challenger as having exploded, but what actually destroyed the Challenger was aerodynamic forces ripping it to pieces as it tumbled due to the break in the side booster's support structure. This same effect broke up the main tank as well, which contained lots of fuel at the moment. This released fuel was ignited by the flames from the boosters, and this is the 'explosion' that people remember, but it was actually an after-effect of the actual shuttle destruction.

Of course, at the speeds of the space shuttle, neither of these craft went tumbling end over end or anything - they were instantly ripped to shreds. Imagine a hollow aluminum rod, planted in the ground, and something VERY heavy balanced on top of it. It may be strong enough to hold that weight up so long as the weight is directed length-wise along the rod. If you were to tap the side of the rod with a hammer hard enough to dent the rod, it would crumple under the weight of the heavy load it was holding. That is essentially what happened to Columbia - it got ripped apart by forces coming at it in ways that it was not able to withstand.

All of this happened because of some small thing in both cases - a piece of foam hitting the wing during takeoff in Columbia's case, and a frozen o-ring in Challenger's case. NASA procedures have been changed in each case to prevent similar failures from causing further fatalities. (The shuttle is inspected from the ISS for damage before docking, and weather conditions around launch are required to be much better now than they were prior to Challenger).

Answer 3

There was a loose heat shield panel. It supposedly (can't really be proved) was jostled when it hit something during launch, but the shuttle wouldn't burn up during launch because leaving the atmosphere is easier than reentering. When they reentered they atmosphere, the heat panel theoretically came off and created a weak spot where the 1000+ degree heat just melted a hole into the shuttle and ignited the fuel, etc and blew up the shuttle from the inside.