Crystallographic Oxide Phase Identification of Char Deposits Obtained from Space Shuttle Columbia Window Debris

Analyzing the remains of Space Shuttle Columbia has proven technically beneficial years after the vehicle breakup. This investigation focused on charred deposits on fragments of Columbia overhead windowpanes. Results were unexpected relative to the engineering understanding of material performance in a reentry environment. The TEM analysis demonstrated that the oxides of aluminum and titanium mixed with silicon oxides to preserve a history of thermal conditions to which portions of the vehicle were exposed. The presence of Ti during the beginning of the deposition process, along with the thermodynamic phase precipitation upon cool down, indicate that temperatures well above the Ti melt point were experienced. The stratified observations implied that additional exothermic reaction, expectedly metal combustion of a Ti structure, had to be present for oxide formation. Results are significant for aerospace vehicles where thermal protection system (TPS) breaches cause substructures to be in direct path with the reentry plasma.

Characterization of Deposits on Glass Substrate as a Tool in Failure Analysis: The Orbiter Vehicle Columbia Case Study

In connection with the accident investigation of the space shuttle Columbia, an analysis methodology utilizing well established microscopic and spectroscopic techniques was implemented for evaluating the environment to which the exterior fused silica glass was exposed. Through the implementation of optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, and electron diffraction, details emerged regarding the manner in which a charred metallic deposited layer formed on top of the exposed glass. Due to nature of the substrate and the materials deposited, the methodology proved to allow for a more detailed analysis of the vehicle breakup. By contrast, similar analytical methodologies on metallic substrates have proven to be challenging due to strong potential for error resulting from substrate contamination. This information proved to be valuable to not only those involved in investigating the break up of Columbia, but also provides a potential guide for investigating future high altitude and high energy accidents

Failure Analysis in Space: International Space Station (ISS) Starboard Solar Alpha Rotary Joint (SARJ) Debris Analysis

This slide presentation reviews the debris analysis of the Starboard Solar Alpha Rotary Joint (SARJ), a mechanism that is designed to keep the solar arrays facing the sun. The goal of this was to identify the failure mechanism based on surface morphology and to determine the source of debris through elemental and particle analysis

The Space Shuttle Columbia Accident Investigation: Forensic Tools, Techniques, and Results

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Materials Analysis: A Key to Unlocking the Mystery of the Columbia Tragedy

Materials analyses of key forensic evidence helped unlock the mystery of the loss of space shuttle Columbia that disintegrated February 1, 2003 while returning from a 16-day research mission. Following an intensive four-month recovery effort by federal, state, and local emergency management and law officials, Columbia debris was collected, catalogued, and reassembled at the Kennedy Space Center. Engineers and scientists from the Materials and Processes (M&P) team formed by NASA supported Columbia reconstruction efforts, provided factual data through analysis, and conducted experiments to validate the root cause of the accident. Fracture surfaces and thermal effects of selected airframe debris were assessed, and process flows for both nondestructive and destructive sampling and evaluation of debris were developed. The team also assessed left hand (LH) airframe components that were believed to be associated with a structural breach of Columbia. Analytical data collected by the M&P team showed that a significant thermal event occurred at the left wing leading edge in the proximity of LH reinforced carbon carbon (RCC) panels 8 and 9. The analysis also showed exposure to temperatures in excess of 1,649 C, which would severely degrade the support structure, tiles, and RCC panel materials. The integrated failure analysis of wing leading edge debris and deposits strongly supported the hypothesis that a breach occurred at LH RCC panel 8

DYNAMIC FRACTURE-BEHAVIOR OF SIC WHISKER-REINFORCED ALUMINUM-ALLOYS

This paper presents a study of dynamic fracture initiation behavior of 2124-T6 aluminum matrix composites containing 0, 5.2, and 13.2 vol pct SiC whiskers. In the experiment, an explosive charge is detonated to produce a tensile stress wave to initiate the fracture in a modified Kolsky bar (split Hopkinson bar). This stress wave loading provided a stress intensity rate, K1, of about 2 x 10(6) MPa square-root m/s. The recorded data are then analyzed to calculate the critical dynamic stress intensity factor, K(Id), of the composite, and the values obtained are compared with the corresponding quasi-static values. The test temperatures in this experiment ranged from -196-degrees-C to 100-degrees-C, within which range the fracture initiation mode was found to be mostly ductile in nature. The micromechanical processes involved in void and microcrack formation were investigated using metallographic techniques. As a general trend, experimental results show a lower toughness as the volume fraction of the SiC whisker reinforcement increases. The results also show a higher toughness under dynamic than under static loading. These results are interpreted using a simple dynamic fracture initiation model based on the basic assumption that crack extension initiates at a certain critical strain developed over some microstructurally significant distance. This model enables us to correlate tensile properties and microstructural parameters, as, for instance, the interspacing of the SiC whiskers with the plane strain fracture toughness.X1129sciescopu

The minimum volume fraction of SiC reinforcement required for strength improvement of an Al-Cu based composite

10.1007/BF00356073Journal of Materials Science30205223-5227JMTS