Chapter 12
2003: Columbia Space Shuttle
Explosion
145
THE REPORTED STORY
The New York Times Abstract:
Space shuttle Columbia breaks up on re-entry to earth’s atmosphere,
killing all seven astronauts aboard: Col Rick D Husband, mission commander,
Capt David M Brown, Dr Kalpana Chawla, Cmdr William C McCool, Lt Col
Michael P Anderson, Dr. Laurel Salton Clark and Col Ilan Ramon, an Israeli;
breakup occurs 40 miles above Earth and only minutes before scheduled land-
ing at Kennedy Space Center in Florida; shower of fiery debris falls across
Texas and Louisiana; NASA will activate board of independent outside
experts, led by Harold W Gehman, to oversee parts of investigation; how large
a setback the loss of Columbia will pose for shuttle is difficult to assess.
(Sanger, 2003)
THE BACK STORY
The Columbia was the first of the original four orbiters launched.
Between its first launch in 1981 and final launch (mission STS-107) on
January 16, 2003, it went through numerous upgrades, including a glass
cockpit and second-generation main engines. However, more than 44% of
its tiles and 41% of the 44 wing leading edge reinforced carbon-carbon
panels were original equipment.
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146 Engineering Ethics: An Industrial Perspective
LO2 Ice/Frost Ramps
PDL 1034
LO2 PAL Ramp
BX-250
Tank Fittings
BX-250 with PDL-1034
closeouts
LO2 Feedline
BX-250 & SS-1171 with
PDL-1034 closeouts
LH2 Ice/Frost Ramps
PDL-1034
LH2 PAL Ramps
BX-250
Aft Interfaces/Cable
Trays/Covers
BX-250
Bx-265 (unique
for ET-93
)
Aft Struts
BX-250
LH2 Tank Dome
NCFI 24-57
Apex Closeout
BX-250
Fwd and Aft InterTank Flange
Closeouts
BX-250
LH2 Tank Fwd Dome
BX-250
InterTank Closeouts
BX-250 and PDL-1034
LO2 Tank Dome
BX-250
InterTank Acreage (Machined
/ Vented)
NCFI 24-124
LO2 Tank Ogive/Barrel
Thick/thin spray
NCFI 24-124
Ogive Cover Plate
BX-250
LH2 Tank Barrel
Thick
/ thin spray
NCFI 24-124
Figure 12.1 Locations of the various foam systems used on ET-93, the external tank used
during Columbia’s final flight.
Reprinted from NASA, 2003.
EXTERNAL TANK INSULATION
The shuttle system design, consisting of a reusable orbiter, an expendable
external fuel tank carrying liquid propellants for the orbiters’ engines, and
two recoverable solid rocket boosters, is discussed extensively in Chapter 5.
In this section, we highlight the design of the external tank insulation
(Figure 12.1).
The external tank is built by Lockheed Martin. It is coated with two
insulation materials: dense composite ablators for dissipating heat and
low-density closed-cell foams for high insulation efficiency. Closed-cell
materials consist of small pores filled with air and blowing agents that are
separated by thin membranes of the foam’s polymeric component. The
insulation maintains an interior temperature that keeps the oxygen and
hydrogen in a liquid state and an external temperature high enough to
prevent ice and frost from forming on the surface.
Metallic sections that will be insulated with foam are first coated with
an epoxy primer. In areas such as the bipod hand-sculpted regions, foam is
directly applied over ablator materials. Where foam is applied over cured
or dried foam, a bonding enhancer called Conathane is first applied to aid
in adhesion. After foam is applied in the intertank region, the larger areas
of foam coverage are machined down to a thickness of approximately
1 inch.
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2003: Columbia Space Shuttle Explosion 147
Figure 12.2 Cutaway drawing of the bipod ramp and its associated fittings.
Reprinted from NASA, 2003.
Because foam applied over the bipod fittings may not provide enough
protection from the high heating of exposed surfaces during ascent, the
bipod fittings are coated with ablators. The bipod is one of the main
connections between the external tank and orbiter. Foam is sprayed by
hand over the fittings, allowed to dry, and manually shaved into a ramp
shape (Figure 12.2). Only visual inspections of the bipod at the assembly
facility and at the Kennedy Space Center are conducted.
EARLY PROBLEMS
Originally the bipod foam ramps on external tanks 1 through 13 possessed
a 45-degree ramp angle. However, after foam was lost from the bipod ramp on
mission STS-7, subsequent wind tunnel testing showed that shallower angles
were aerodynamically preferable. This result caused ramp angle modification
to between 22 and 30 degrees. For tanks 76 and later, a slight modification was
also made to the ramp impingement profile.
Foam loss occurred on more than 80% of the 79 missions for which
imagery was available. Foam was specifically lost from the left bipod ramp
on nearly 10% of missions where the left bipod ramp was visible following
external tank separation. For about 30% of all missions, foam loss could
not be determined either because of night launch or because the external
tank bipod ramp area was not in view when images were taken.
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