Space Shuttle Columbia
Submitted by Jamie, June 22, 2006, 8:28 pm
Wreck Type: Aviation
Wreck Location: Texas
Date of Wreck: February 1, 2003
Wreck Details:
The Space Shuttle Columbia disaster was the disintegration of the Space Shuttle Columbia over Texas on February 1, 2003, during reentry into the Earth's atmosphere on its 28th mission, STS-107. All seven members of the crew died.
The loss of the Columbia was caused by damage sustained during launch when most of the left bipod foam ramp broke off of, or was "shed" from, the main propellant tank under the aerodynamic forces of launch and struck the orbiter's left wing's leading edge. During this debris strike, one or more thermal protection system (TPS) panels on that wing was damaged. While the shuttle was still in orbit, some engineers suspected damage to the thermal protection, but NASA managers limited the investigation, feeling that nothing could be done even if damage was found.
The damage to the TPS panel(s) allowed the hot gasses of reentry to penetrate and destroy the internal wing structure and, fairly quickly, the entire vehicle. A massive ground search primarily in Texas recovered crew remains and many vehicle fragments.
U.S. manned space flights did not resume until over two years later, but the foam shedding problem continued. Despite these setbacks, the International Space Station continues to operate with a skeleton crew transported and supplied by Russian space vehicles.
There have now been two such losses of a space shuttle and crew. The first was the Challenger disaster in 1986.
Crew:
Commander: Rick D. Husband, a US Air Force colonel and mechanical engineer, who piloted a previous shuttle during the first docking with the International Space Station.
Pilot: William C. McCool, a US Navy commander
Payload Commander: Michael P. Anderson, a US Air Force lieutenant colonel and physicist who was in charge of the science mission.
Payload Specialist: Ilan Ramon, a colonel in the Israeli Air Force and the first Israeli astronaut.
Mission Specialist: Kalpana Chawla, an Indian-born aerospace engineer on her second space mission.
Mission Specialist: David M. Brown, a US Navy captain trained as an aviator and flight surgeon. Brown worked on a number of scientific experiments.
Mission Specialist: Laurel Clark, a US Navy captain and flight surgeon. Clark worked on a number of biological experiments.
Debris strike during launch:
STS-107 had been delayed 18 times over the course of two years (despite its designation as the 107th mission, it was actually the 113th mission launched) from its original launch date of 11 January 2001 to its actual launch date of 16 January 2003. A well-publicized launch delay due to cracks in the shuttle's propellant distribution system occurred one month before a 19 July 2002 launch date, but the Columbia Accident Investigation Board (CAIB) determined that this delay had nothing to do with the catastrophic failure six months later.
The Left Bipod Foam Ramp is an approximately three-foot (one-meter) piece made entirely out of foam, as opposed to being a metal ramp that is merely coated with foam. As such, the foam, not normally considered to be a structural material, is required to bear some aerodynamic loads. Because of these special requirements, the casting-in-place and curing of the ramps may be performed only by a senior technician. Apparently, even the best technical servicing available could not compensate for this fatal design flaw.
Bipod Foam Ramps had fallen off on at least three previous Shuttle flights, with at least one previous Shuttle strike but no serious damage. The euphemism used by NASA management to refer to this phenomenon was "foam shedding." As with the O-ring erosions that ultimately doomed the Challenger Shuttle, NASA management seemed to grow complacent and accustomed to these phenomena when no serious consequences resulted from these earlier episodes.
Video taken during lift-off was routinely reviewed two hours after the launch and revealed nothing unusual. The following day, higher-resolution film that had been processed overnight revealed that a piece of insulation foam fell from the external fuel tank 81.9 seconds after launch and appeared to strike the shuttle's left wing, potentially damaging the thermal protection on the Space Shuttle. The exact location where the foam struck the wing could not be determined due to the low resolution of the tracking camera footage.
Initial investigation:
NASA Space Shuttle Program Manager Ron Dittemore reported that "The first indication was loss of temperature sensors and hydraulic systems on the left wing. They were followed seconds and minutes later by several other problems, including loss of tire pressure indications on the left main gear and then indications of excessive structural heating". Analysis of 31 seconds of telemetry data which had initially been filtered out because of data corruption within it showed the shuttle fighting to maintain its orientation, eventually using maximum thrust from its reaction control system jets.
The focus of the investigation centered 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 actually damaged orbiters, most noticeably during STS-45, STS-27, and STS-87 [9]. Tile damage had also been traced to ablative insulating material from the solid rocket motors in the past. The composition of the foam insulation had been changed in 1997 to exclude the use of freon, a chemical that causes ozone depletion; while NASA was exempted from legislation phasing out CFCs, the agency chose to change the foam nonetheless. This led to many statements linking the foam strike to environmental pressures. STS-107 used an older "lightweight tank" where the foam was sprayed on to the larger cylindrical surfaces using the newer no freon foam. However the bipods 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.
Was rescue or repair possible?
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.
Rescue:
The CAIB determined a rescue mission, though risky, might have been possible provided NASA management took action soon enough.
Normally a rescue mission isn't possible, due to the time required to prepare a shuttle for launch, and the limited consumables (power, water, air) of an orbiting shuttle. However in this case Atlantis was well along in processing for a March 1 launch. Also Columbia carried an unusually large quantity of consumables due to an Extended Duration Orbiter (EDO) package. 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.
Repair:
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 Remote Manipulator System which would normally be used for camera inspection or transporting a spacewalking astronaut to the wing. Therefore an unusual emergency 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. During launch these doors are open for the propellant feed lines from the external tank to supply the main engines in the orbiter tail. If they fail to close after jettisoning the external tank, it constitutes a thermal protection breach which would destroy the orbiter upon reentry. This requires an emergency EVA to close them manually. Similar methods could have reached the shuttle left wing for inspection or repair.
For the repair, astronauts would have to use tools and small pieces of titanium, or other metal, scavenged from the crew cabin. These heavy 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.
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