Date: April 17, 2003
Contact: Lt. Col Woody Woodyard, 281-283-7520 or 713-301-2244
Contact: Terry N. Williams or Patricia Brach, 281-283-7520
Columbia Accident Investigation Board Issues Preliminary Recommendations to Improve
Inspection and Testing of RCC Components, Shuttle Imaging on Orbit
Houston, Texas -- The Columbia Accident Investigation Board today issued two
preliminary recommendations to NASA. Additionally, the Board issued several facts
regarding the shuttle program.
Recommendation One: Prior to return to flight, NASA should develop and
implement a comprehensive inspection plan to determine the structural integrity
of all Reinforce Carbon-Carbon (RCC) system components. This inspection plan should
take advantage of advanced non-destructive inspection technology.
This recommendation was issued because of the board's finding that current inspection
techniques are not adequate to assess structural integrity of RCC, supporting
structure, and attaching hardware.
Recommendation Two: Prior to return to flight, NASA should modify its Memorandum
of Agreement with National Imagery and Mapping Agency (NIMA) to make on-orbit
imaging for each Shuttle flight a standard requirement.
This recommendation was issued because of the board's finding that the full capabilities
of the United States Government to image the Shuttle on orbit were not utilized.
Facts Regarding RCC Components -- The board will include the following
facts in its final report:
- The Reinforced
Carbon-Carbon (RCC) system (including all RCC, supporting structure and attaching
hardware) is an essential component of the Space Shuttle Orbiter Thermal Protection
System (TPS) and has a Criticality Rating of 1 (loss of crew - loss of vehicle).
- The RCC
composite consists of a reinforced carbon-carbon substrate that carries the
structural loads, a tetraethyl orthosilicate impregnation that reduces inherent
substrate porosity, a silicon carbide treatment that protects the substrate
from oxidation, and a sealant coating that provides additional oxidation protection.
These composite structures are attached to the shuttle by a metal support
initial manufacturing acceptance, the integrity of production composites used
in the RCC system is checked at various points in production by physical tap,
ultrasonic, radiographic, eddy current, weight gain, and visual tests. In
addition, a flat plate control panel made in parallel with the production
piece is destructively tested at various points in the production process.
- A projected
design mission life has been established for each RCC component. These projections
are based on analysis correlated to simulated flight load testing, and assume
the presence of sound composite material and metal support structure.
external inspections and tactile checks are the only specified post flight
inspections of RCC composite components. The planned interval for removing
RCC composite components for more thorough inspection is typically many flights,
unless their removal is dictated by an observed visual surface condition or
necessitated by the requirement to provide access for other operations.
testing of some post-flight RCC components has shown indications of RCC material
defects not previously identified by visual inspection methods currently employed.
Facts Regarding Shuttle Imaging -- The board will include the following
facts in its final report:
- The U.S.
Government has the capability to image the Shuttle on orbit.
- A Memorandum
of Agreement exists between NASA and NIMA regarding on-orbit imaging of the
the flight of STS-107, there were no on-orbit images taken of sufficient resolution
to assess the Orbiter's condition.
The CAIB issued these recommendations and findings in advance of their appearance
in the final report. The board's final report will be issued later this summer.
It will include the probable cause of the accident, contributing factors, findings
and additional recommendations.