Report Details Causes Of Space Shuttle Columbia Disaster
A new report from a study panel details the causes leading to the Space Shuttle Columbia disaster in 2003, with the panel recommending many corrective and preventive moves to avert further tragedies, while also concluding that some factors in the tragedy will remain unknown.
As Columbia lifted off and headed to the International Space Station, a piece of foam insulation broke off from the external fuel tank and punched a hole in a wing of the orbiter vehicle.
Later, during an attempted return to Earth, searing hot gases of reentry entered the wing, melted structural components and caused the loss of the ship and crew of seven.
As we have reported in many previous issues, NASA already has taken many of the steps recommended in the report, such as removing foam insulation from the external fuel tank, using better materials to lessen chances of icing on the tank, and much more.
The final report includes 30 recommendations to improve spacecraft design and crew safety. The recommendations cover a broad range of subjects from crew training, procedures, restraints and individual safety equipment to spacecraft design methods and recommendations regarding future accident investigations.
NASA already has implemented some of the report’s recommendations and is evaluating others. A fact sheet describing actions that have been taken or are in work by both the Space Shuttle Program and Constellation Program as a result of the investigation is available at the same web link as the report.
This was the first-ever in-depth crew survival study of a spaceflight accident. The investigation was conducted by a multi-disciplinary NASA team based at Johnson Space Center. The study team also consulted experts outside of NASA for portions of its work.
To view the Spacecraft Crew Survival Integrated Investigation Team report in full, please go to http://www.nasa.gov/reports on the Web.
To view the report details on fault tree elements not closed, please go to http://www.nasa.gov/columbia/caib/PDFS/VOL2/D04.PDF on the Web.
These are some of the still-unanswered questions that the report panel was unable to resolve. ET means external fuel tank. RCC is reinforced carbon carbon, a material that can withstand the high heat of reentry, shielding the shuttle orbiter vehicle.
Table 1: Fault Tree Elements Not Closed, and Likely Contributed to the Accident.
| BRANCH | ELEMENT NUMBER | DESCRIPTION OF FAULT TREE ELEMENT |
| Orbiter | SFOML-WING-11-5 | ET Debris Impact on Ascent. Launch photography and onboard sensors indicated that bipod foam struck the underside of the left wing leading edge. |
| Orbiter | SFOML-WING-11-66 | Loss of RCC Panel Due to T-Seal Failure. The T-seals between RCC panels 7 and 8 and 8 and 9 could have been the initial location of the breach. |
| Orbiter | SFOML-WING-12-9 | RCC Damage Due to Impact Caused Sneak Flow Causing Loss of Panel. Damage could have been initiated at the RCC panel or an adjoining T- seal. |
| ET | 1.1.1.4.1.1.1.1 | BX-250/Forward Bipod Fittings/Inadequate Design Methodology. Forward bipod fitting assembly debris due to an inadequate design methodology. |
| ET | 1.1.1.5.1.1.1.1 | SLA-561/Forward Bipod Fittings/Inadequate Design Methodology. Forward bipod assembly Super Light Ablator application with inadequate design methodology causes debris. |
| BRANCH | ELEMENT NUMBER | DESCRIPTION OF FAULT TREE ELEMENT |
| ET | 1.1.1.5.1.2.1.1 | SLA-561/Plate Connector-Bipod Fitting/ Inadequate Design Methodology. Forward bipod fitting plate connector Super Light Ablator application with inadequate design methodology causes debris. |
| ET | 1.1.1.4.1.1.3.2.1 | BX-250/Forward Bipod Fittings/Debris Due to Inadequate Manufacturing Process Plan. Forward bipod fitting assembly debris due to an inadequate manufacturing process plan. |
| ET | 1.1.1.4.1.1.3.3.6 | BX-250/Forward Bipod Fittings/Debris Due to MAF Material Processing. Forward bipod fitting assembly debris due to inadequately defined acceptance testing during Machoud Assembly Facility Processing. |
| ET | 1.1.1.4.1.1.3.7 | BX-250/Forward Bipod Fittings/Undetected Anomaly. Forward bipod fitting assembly debris due to undetected anomaly during Machoud Assembly Facility processing. |
| Integration | B561 | Transport Mechanism. There are transport mechanisms to facilitate debris striking the orbiter left wing area from viable debris sources (ET, orbiter, and SRB). |
The "likely contributed to the accident" entries address the release of debris from the ET and the impact of this debris on the orbiter wing RCC panels or T-seals. Although the Super Light Ablator has not been implicated in the foam release, it cannot be ruled out.
Table 2: Fault Tree Elements Not Closed, and Possibly Contributed to the Accident.
| BRANCH | ELEMENT NUMBER | DESCRIPTION OF FAULT TREE ELEMENT |
| Orbiter | SFOML-WING-8-51 | RCC Panel Improper Installation. Addresses improper installation of the wing leading edge RCC as an initiating cause. |
| Orbiter | SFOML-WING-8-54 | RCC Processing/Material Defect. Addresses the possibility that an initial manufacturing or material defect was present in the RCC from the original manufacturing that led to failure. |
| Orbiter | SFOML-WING-8-57 | RCC Substrate Failure Due to Mission Cycles. The lack of NDE inspection leaves this possibility suspect. |
| Orbiter | SFOML-WING-8-58 | RCC Substrate Failure Due to Ground Cycles. The lack of NDE inspection leaves this possibility suspect. |
| Orbiter | SFOML-WING-8-59 | RCC Failure Due to Aging. Investigates the question of RCC aging over time versus mission cycles. |
| Orbiter | SFOML-WING-12-3 | Micrometeoroid Impact on Orbit. Based on the orbiter orientations, the chance of a micrometeorite or orbital debris hitting the RCC leading edge is 1 in 13,800. |
| Orbiter | SFOML-WING-12-4 | Orbital Debris Impact on Orbit. Based on the orbiter orientations, the chance of a micrometeorite or orbital debris hitting the RCC leading edge is 1 in 13,800. |
| Orbiter | SFOML-WING-11-8 | SRB Debris Impact on Ascent. The SRB bolt catcher and the SRB separation motors are possible sources of debris. |
| SRB | B.1.3.4.4.3.1 | Debris Due to Failure of Attach Fasteners, LMC Supplied. |
| SRB | B.1.3.4.4.3.2 | Debris Due to Failure of Bolt Catcher Structure. |
| SRB | B.1.3.4.4.3.3 | Debris Due to Failure of LMC ET Thrust Fitting or Inserts. |
| SRB | B.1.3.4.4.3.4 | Debris Due to Failure of Insulation (SRB/LMC). |
The "possibly contributed to the accident" include a number of different means to cause damage to the wing leading edge. The effect of aging (both operational and calendar) of the RCC is uncertain at best. Certain debris sources are listed here as they could lead to relatively heavy objects hitting the wing leading edge. Micrometeoroids and space debris can also cause a large enough hole in the RCC to allow superheated air to enter the wing