Columbia Space Shuttle Explosion

On Saturday morning, February 1st, Columbia was scheduled to land at Kennedy Space Center on one of the largest runways (15,000 feet long and 300 feet wide) in the world. It was a good day for the orbiter to return, according to NASA's shuttle team. The weather was excellent. Everything seemed to be going perfectly.

Flying over the Ocean, approaching Hawaii, Columbia's crew watched the effects of reentry as they discussed how "amazing" and "bright" the light show was outside the shuttle's window. (See the second part of the video, recovered after the disaster, depicting crew members as they prepared for landing.) One of the astronauts observed that he "definitely wouldn't want to be outside now."

But as Columbia continued her reentry into Earth's atmosphere, ground controllers noticed weird readings from some of the temperature sensors. (This glossary of NASA acronyms will aid in understanding the data.) First there was a loss of temperature measurements for the shuttle's left-wing hydraulic systems. Then a gauge showed excessive structural heating.

At the first press conference following the disaster, Ron Dittemore describes what ground controllers saw:

• At 7:53 a.m. CST (8:53 a.m. EST), there was a loss of temperature measurements. The readings were neither high nor low - they were off-scale.



• At 7:56 a.m. CST, sensors showed a 20-30 degree temperature rise in the main-gear tire wheel well on the left side of the shuttle. Although the temperature reading was higher than normal, there appeared to be no cause for alarm.



• At 7:58 a.m. CST, three temperature sensors for the shuttle's left-wing area were off-scale again.



• At 7:59 a.m. CST, the left inboard and outboard temperatures showed an off-scale load. One of these measurements was sensed by Columbia's on-board computer.



• While Rick Husband was responding - likely to acknowledge the measurements - his transmission was cut off.



• Immediately thereafter, mission control lost all contact with Columbia.

Further, according to Dittemore, the left side of the fuselage, above the wing, experienced an abnormal temperature rise of about 60 degrees over five minutes while the right-side temperature increased a normal 15 degrees (given the shuttle's reentry mode). All the readings came from sensors underneath the heat tiles, on the aluminum hull of the craft.

When the temperature of the shuttle rises, one can expect increased drag on the spacecraft. When drag is increased, the shuttle's automated flight system will correct for that increase. Columbia's adjustments were so large that "we have never seen it to this degree," according to Dittemore. Notwithstanding, the corrected flight path was still within Columbia's capabilities.

At the time of the last transmission (this video includes recreations), the shuttle was hurtling to Earth at a speed of Mach 18.3 and an altitude of 207,135 feet. When they lost the data, mission controllers instantly knew they "had a bad day."

"It was," said Dittemore, "as if someone had cut the wire."