Materials Characterization of a Payload Bay Latch Roller and x0582 Ring Frame Bulkhead Recovered From Space Shuttle Columbia

Tuesday, May 24, 2016: 1:30 PM
407 (Meydenbauer Center)
Mrs. Ngozi Ubani Ochoa , University of Texas at El Paso, El Paso, TX
Dr. Stephen W. Stafford , University of Texas at El Paso, El Paso, TX
Darren Cone , University of Texas at El Paso, El Paso, TX
Dr. John Olivas , University of Texas at El Paso, El Paso, TX
The National Aeronautics and Space Administration (NASA) Shuttle Transportation System Mission 107 lifted off on January 16, 2003, for a 16-day research mission. During re-entry, the Space Shuttle Columbia was destroyed and the seven crew members aboard lost their lives. This tragic event was later found to be a result of damage to the thermal protection system (TPS) on the wing leading edge, incurred during launch ascent. Although previous analysis has addressed the root cause of TPS damage, additional study is warranted to investigate material behavior of the sub-structural components exposed to the conditions of the re-entry environment.

This paper details the materials characterization performed on components recovered from the Space Shuttle Columbia debris: a portion of the x0582 ring-frame bulkhead, immediately aft of the crew module, which includes a port-side payload bay door latch roller.  The latch roller itself exhibits localized areas of extensive thermal damage in close proximity to regions that appear unaffected. The latch roller construction is comprised of concentric sleeves of varying alloys, including titanium alloy (Ti-6Al-4V), a nickel-based superalloy (Inconel 718), and a super austenitic stainless steel (Incoloy A286). The attached bulkhead is composed of an aluminum alloy (Al 2024), which contains evidence of unique delamination fracture surfaces. Though infrequently referenced in literature, these ‘broom straw’ fracture characteristics have been observed during other aerospace accident investigations, but the mechanism behind this fracture mode has not been fully described.

Previous analysis of aluminum and titanium char-layer deposits found on crew module overhead windows of Columbia revealed indications of an unexpected material response of titanium to the re-entry environment. These windows are in close proximity to the bulkhead and latch rollers, so investigation of these components is useful in determining the possible sources of the metals deposited on the windows and the conditions in which deposition occurred.

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