Don James
Headquarters, Washington, D.C.                                                                       
May 14, 1991
(Phone:  202/453-2754)
 
H. Keith Henry
Langley Research Center, Hampton, Va.
(Phone:  804/864-6120)
 

RELEASE: 91-75
 
NASA TO TEST FLIGHT-WEIGHT AERO-SPACE PLANE COMPONENT

   NASA is preparing to test a structural component made of 
advanced carbon-carbon composite material as part of the X-30 
National Aero-Space Plane (NASP) program.  Carbon-carbon is an 
advanced heat-resistant, non-metallic material that may be used 
on the NASP flight research vehicles in the mid-1990s. 

   The NASP mission profile demands much greater performance 
from its structures and materials than does the Space Shuttle, 
which travels through the atmosphere in a relatively short 
time.  Engineers expect that the X-30 will experience 
structural loads at extreme temperatures and sustained high 
temperatures in high-altitude cruise through the atmosphere. 

   Design and fabrication of this major NASP flight-weight 
component follows years of technology development.  The 
carbon-carbon material is stronger than metal at high 
temperatures.  It's also lighter than aluminum, making it a 
good alternative in areas where active cooling can be avoided. 

   The component is part of a full-scale wing control surface 
from a generic NASA aerospace plane design.  The structure was 
shipped to NASA's Ames-Dryden Flight Research Facility, 
Edwards, Calif. last week for extensive tests to begin this 
Fall.  The flap-like component first will be tested for its 
ability to withstand mechanical loads similar to those on a 
vehicle that takes off from a runway like an airliner and flies 
into orbit.  

   Thermal trials are scheduled to start in Fall 1992.  Initial 
tests will be limited to state-of-the-art strain measurement 
capabilities -- about 600 degrees F.  Researchers hope to 
achieve test temperatures exceeding 2000 degrees F. by 1993. 


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   The Missile Division of LTV Corp., Grand Prairie, Texas, 
designed and built the NASP test component under contract to 
NASA's Langley Research Center, Hampton, Va.  LTV's successful 
fabrication of the somewhat stiff composite represents a major 
milestone in materials technology development.

   "The fabrication was challenging," said Dr. Wayne Sawyer of 
Langley's Structural Mechanics Division.  "It is a big part 
that requires a series of fairly high-temperature thermal 
cycles in the fabrication process.  These thermal cycles result 
in material deformations in some way or another.  It shrinks 
and expands and tends to warp.  Just being able to make a big 
part or several big parts that will fit together is very tough 
and requires good control of the tolerances and the fabrication 
process."    

   The rib-stiffened NASP component is about 56 inches long, 39 
inches wide, 14 inches thick at the leading edge and 6 inches 
thick at the trailing edge.  It is patterned after part of a 
flight control surface called an elevon, which is mounted at 
the back of some aircraft and the Space Shuttle orbiter to 
provide pitch and roll control.     

   "To our knowledge the component is made of some of the most 
complicated carbon-carbon parts ever fabricated," said 
Langley's Dr. Don Rummler, also of the  Structural Mechanics 
Division.  The need for a  load-bearing tube with multiple 
layers and many holes and cutouts complicated the fabrication 
task.  High-temperature requirements dictated that even simple 
parts like fasteners were made of carbon-carbon. 

   Extra care was taken to overcome the potentially serious 
problem of delamination of the materials, which is almost 
impossible to repair.  Technicians built up the test structure 
one thin layer at a time; it has 42  layers, or plies, at its 
maximum thickness. 

   The component parts were heated to high temperatures several 
times and densified to increase their strength, in a process 
Rummler likens to "burning toast."  Strength went up with each 
processing cycle, as epoxy-like material was used to densify 
the material by filling tiny voids in the carbon matrix between 
heat treatments.  A final coating protected exterior surfaces 
against oxidation.

   Just where, how and if advanced carbon-carbon will be used 
in the X-30 has yet to be decided.  "The material and the 
advanced fabrication procedures developed to make the elevon 
structure represent an option that we did not have at the 
beginning of the National Aero-Space Plane program," explained 
Rummler.  "It is a design-efficient, light-weight alternative." 

                             -end-