Space Shuttle Columbia is the 14th episode of Seconds from Disaster resolves why the oldest shuttle got destroyed.
As the Space Shuttle Columbia lifts off from the Kennedy Space Centre 16 days before re-entry, a piece of insulating foam breaks off the external fuel tank and damages the left wing of the shuttle. As it enters the Earth's atmosphere during the return trip, it disintegrates under the massive heat and slams onto a field in Texas, just like an asteriod, killing all astronauts on board.
Initial InvestigationEditNASA Space Shuttle Program Manager Ron Dittemore reported that "The first indication was loss of temperature
The investigation focused on the foam strike from the very beginning. Incidents of debris strikes from ice and foam causing damage during take-off were already well known, and had damaged orbiters, most noticeably during STS-45, STS-27, and STS-87. Tile damage had also been traced to ablating insulating material from the cryogenic fuel tank in the past. The composition of the foam insulation had been changed in 1997 to exclude the use of freon, a chemical that is suspected to cause ozone depletion; while NASA was exempted from legislation phasing out CFCs, the agency chose to change the foam nonetheless. STS-107 used an older "lightweight tank" (a design that was succeeded by the "superlightweight tank", both being upgrades from the original space shuttle external tank) where the foam was sprayed on to the larger cylindrical surfaces using the newer freon-free foam. However, the bipod ramps were manufactured from BX-250 foam which was excluded from the EPA regulations and did use the original freon formula. The composition change did not contribute to the accident. In any case, the original formulation had shown frequent foam losses, as discussed earlier in this article.
Independent Investigation BoardEdit
Following protocols established after the loss of Challenger, an independent investigating board was created immediately following the accident. The Columbia Accident Investigation Board, or CAIB, was chaired by Air Force Brigadier General Duane W. Deal and consisted of expert military and civilian analysts who investigated the accident in great detail.
Columbia's flight data recorder was found near Hemphill, Texas on March 20, 2003. Unlike commercial jet aircraft, the space shuttles do not have flight data recorders intended for after-crash analysis. Rather the vehicle data are transmitted in real time to the ground via telemetry. However, since Columbia was the first shuttle used in space, it had a special flight data OEX (Orbiter EXperiments) recorder, designed to help engineers better understand vehicle performance during the first test flights. After the initial Shuttle test-flights were completed, the recorder was never removed from Columbia and was still functioning on the crashed flight. It records many hundreds of different parameters and contained very extensive logs of structural and other data which allowed the CAIB to reconstruct many of the events during the process leading to breakup. Investigators could often use the loss of signals from sensors on the wing to track how the damage progressed. This was correlated with forensic debris analysis conducted at Lehigh University and other tests to obtain a final conclusion about the probable events.
On July 7, 2003 foam impact tests were performed by Southwest Research Institute, which used a compressed air gun to fire a foam block of similar size and mass to that which struck Columbia and at same estimated speed. To represent the leading edge of Columbia''s left wing, RCC panels from NASA stock, along with the actual leading-edge panels from Enterprise, which were fiberglass, were mounted to a simulating structural metal frame. Over many days, tens of these blocks of foam were shot at the wing leading edge model at various angles, aimed at different specific RCC panels, most of which produced only cracks or surface damage to the RCC. In the final round of testing, a block fired at the side of an RCC panel created a hole 41 by 42.5 centimeters (16 by 16.7 in) in the protective RCC panel. The tests clearly demonstrated that a foam impact of the type Columbia sustained could seriously breach the thermal protection system on the wing leading edge.
On August 26, the CAIB issued its report on the accident. The report confirmed the immediate cause of the accident was a breach in the leading edge of the left wing, caused by insulating foam shed during launch. The report also delved deeply into the underlying organizational and cultural issues that led to the accident. The report was highly critical of NASA's decision-making and risk-assessment processes. It concluded the organizational structure and processes were sufficiently flawed and that compromise of safety was expected no matter who was in the key decision-making positions. An example was the position of Shuttle Program Manager, where one individual was responsible for achieving safe, timely launches and acceptable costs, which are often conflicting goals. The CAIB report found that NASA had accepted deviations from design criteria as normal when they happened on several flights and did not lead to mission-compromising consequences. One of those was the conflict between a design specification stating the thermal protection system was not designed to withstand significant impacts and the common occurrence of impact damage to it during flight. The board made recommendations for significant changes in processes and organizational culture.
On December 30, 2008 NASA released a further report, entitled Columbia Crew Survival Investigation Report, produced by a second commission, the Spacecraft Crew Survival Integrated Investigation Team (SCSIIT). NASA had commissioned this group, "to perform a comprehensive analysis of the accident, focusing on factors and events affecting crew survival, and to develop recommendations for improving crew survival for all future human space flight vehicles." The report concluded that: "The Columbia depressurization event occurred so rapidly that the crew members were incapacitated within seconds, before they could configure the suit for full protection from loss of cabin pressure. Although circulatory systems functioned for a brief time, the effects of the depressurization were severe enough that the crew could not have regained consciousness. This event was lethal to the crew."
The report also concluded:
- The crew did not have time to prepare themselves. Some crew members were not wearing their safety gloves, and one crew member was not wearing a helmet. New policies now give the crew more time to prepare for descent.
- The crew's safety harnesses malfunctioned during the violent descent. The harnesses on the three remaining shuttles were upgraded after the accident.
The key recommendations of the report included that future spacecraft crew survival systems should not rely on manual activation to protect the crew.
Possible emergency proceduresEdit
The CAIB determined a rescue mission, though risky, might have been possible provided NASA management took action soon enough. The CAIB determined that had NASA management acted in time, two possible contingency procedures were available: a rescue mission by shuttle Atlantis, and an emergency spacewalk to attempt repairs to the left wing thermal protection.
Normally a rescue mission is not possible, due to the time required to prepare a shuttle for launch, and the limited consumables (power, water, air) of an orbiting shuttle. However, Atlantis was well along in processing for a March 1 launch on STS-114, and Columbia carried an unusually large quantity of consumables due to an Extended Duration Orbiter package. The CAIB determined that this would have allowed Columbia to stay in orbit until flight day 30 (February 15). NASA investigators determined that Atlantis processing could have been expedited with no skipped safety checks for a February 10 launch. Hence if nothing went wrong there was a five-day overlap for a possible rescue. As mission control could deorbit a shuttle but could not control the orbiter's reentry and landing, it would likely have sent Columbia into the Pacific Ocean; NASA has since developed the Remote Control Orbiter system to permit mission control to land a shuttle.
NASA investigators determined on-orbit repair by the shuttle astronauts was possible but risky, primarily due to the uncertain resiliency of the repair using available materials. Columbia did not carry the Canadarm, or Remote Manipulator System, which would normally be used for camera inspection or transporting a spacewalking astronaut to the wing. Therefore an unusual emergency Extra-Vehicular Activity (EVA) would have been required. While there was no astronaut EVA training for maneuvering to the wing, astronauts are always prepared for a similarly difficult emergency EVA to close the external tank umbilical doors located on the orbiter underside, which is necessary for reentry. Similar methods could have reached the shuttle left wing for inspection or repair.
For the repair, the CAIB determined the astronauts would have to use tools and small pieces of titanium, or other metal, scavenged from the crew cabin. These metals would help protect the wing structure and would be held in place during re-entry by a water-filled bag that had turned into ice in the cold of space. The ice and metal would help restore wing leading edge geometry, preventing a turbulent airflow over the wing and therefore keeping heating and burn-through levels low enough for the crew to survive re-entry and bail out before landing. Because the NASA team could not verify that the repairs would survive even a modified re-entry, the rescue option had a considerably higher chance of bringing Columbia's crew back alive.