| Back |
Space Shuttle
Summary
Although the loss of the Space Shuttle Columbia and its crew was tragic,
the circumstances offered a unique opportunity to examine a multitude of
components which had experienced one of the harshest environments ever
encountered by engineered materials: a
break up at a velocity in excess of Mach 18 and an altitude exceeding 200,000
feet (63 KM), resulting in a debris field 645 miles/ 1,038
KM long and 10 miles/16 KM
wide. Various analytical tools were employed to
ascertain the sequence of events leading to the disintegration of the Orbiter
and to characterize the features of the debris.
The testing and analyses all indicated that a breach in a left wing
reinforced carbon/carbon composite leading edge panel was the access point for
hot gasses generated during re-entry to penetrate the structure of the vehicle
and compromise the integrity of the materials and components in that area of
the Shuttle.
The analytical and elemental testing
utilized such techniques as X-Ray Fluorescence (XRF), Energy Dispersive X-Ray
(EDX) dot mapping, Electron Micro Probe Analysis (EMPA),
and X-Ray Photoelectron Spectroscopy (XPS) to characterize the deposition of
intermetallics adjacent to the suspected location of the plasma breach in the leading
edge of the left wing, Fig.1.
FIGURE 1. Micrograph
of a Left Wing Carrier Panel Slag Deposit.
Cummings [1]
Fractographic and metallographic analyses of
several pieces of debris, Fig. 2, were
performed to characterize such fracture characteristics as broomstrawing and
feathering of aluminum alloys; suspected stress-assisted grain boundary
oxidation (SAGBO) of Inconel components; and intergranular high temperature
fracture features observed on several A286 stainless steel spar fittings.
FIGURE 2. Interior view of aluminum drag chute canister. Parker [2]
The examination of the debris’ fracture surfaces
and of metallographically-prepared specimens harvested from the debris was
performed via scanning electron
microscope. The resultant
features and characteristics were compared to those of laboratory exemplars of
similar base materials. The observed featrues,
along with the results from the elemental analytical testing, helped the Space
Shuttle Columbia accident investigation team reconstruct the mishap and help
determine the sequence of events which ultimately led to the loss of the
vehicle.
References
1. Cummings, V. J.,
XPS, Metallographic and SEM X-Ray elemental Dot Map
Analysis of STS-107 Debris Sample 24543-1, National Aeronautics and Space Administration,
KSC-MSL-2003-149, 2003.
Received his degree in Materials Science and Engineering, with a
specialization in metallurgical engineering, from the University of
Florida. Professional career began as a
Materials Engineer performing failure analysis and crash investigations of navy
and marine rotor-wing and fixed-wing aircraft.
Later, transferred to the Kennedy Space Center and began performing failure
analysis and accident investigations of Space Shuttle, Space Station, and
ground support equipment hardware and components for NASA. Presently serves as Chief of the Failure
Analysis and Materials Evaluation Branch at the Kennedy Space Center. Significant accomplishments include being awarded
the NASA Exceptional Achievement Medal and serving as an editor and contributor
to the American Society for Materials Failure Analysis Handbook.
| Back |