1441. The Shuttle Orbiter Structural Weight Reduction Potential With Advanced Composites Application

Paper

Abstract

The application of advanced composites offers potential Shuttle orbiter structural weight reduction and
performance gain. Savings 17 to 30 percent of the total structure and thermal protection system (TPS) weight
can be realized by taking advantage of the high-temperature (600$infty$F) composite structural allowable. The
concept of bonding ceramic TPS tiles directly on graphite/polyimide (GR/PI) structure (the feasibility of
which has been demonstrated) is presented. The direct-bond tile concept eliminates the strain isolation pad,
which is indispensable with the 350$infty$F allowable aluminum structure TPS that are the present orbiter design.
The GR/PI composite and the ceramic tiles are thermally compatible (similar thermal expansion coefficients),
resulting in small thermal stresses. The large stiffness-to-weight ratio of GR/PI allows design of a lightweight
structure with sufficient stiffness to preclude TPS tile fracture caused by structural deflection. This paper
emphasizes weight-saving concepts for orbiter structural components that are retrofittable: the body flap, elevons, vertical stabilizer, main landing gear
door, and thrust structure. The total estimated weight saving is 3255 pounds. The nonretro-fittable items are also
presented-the orbiter wings, forward fuselage, mid fuselage, and aft fuselage-for a total estimated weight saving
of 9666 pounds. All structures are proposed to be constructed of graphite/polyimide composite except the thrust
structure, which will be graphite/epoxy because it is relatively protected from the thermal environment.