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INVESTIGATION REPORT#21-03



Submitted by Arthur - N1ORC  
 
For Immediate Release
CAIB PA 21-03

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 system. 


During 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. 


Visual 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. 


Non-destructive 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 Shuttle. 


During 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. 



 
 
      
 


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