Nonlinear Behavior of Space Shuttle Superlightweight Liquid-Oxygen Tank Under Prelaunch Loads

The new Space Shuttle superlightweight external fuel tank e ew for the e rst time on 2 June 1998 (Space Transportation System-mission 91 ). We present results of elastic linear-bifurcation buckling and nonlinear analyses of one of its major components; that is, the liquid-oxygen tank. The contents include an overview of the structure and a brief description of the e nite element code that was used to conduct the analyses. Results are presented that illustrate three distinctly different types of nonlinearresponsephenomena for thin-walled shells that aresubjected to combined mechanical and thermal loads that launch-vehicle shell designers may encounter. A procedure is demonstrated that can beused by structural analysts and designers to obtain reasonable, conservative estimates of linear-bifurcation, buckling-load knockdown factors for shells that are subjected to complex loading conditions or to characterize the effects of initial geometric imperfections on nonlinear shell response phenomena. Results are also presented that show that the superlightweight liquid-oxygen tank can carry loads in excess of twice the values of the operational prelaunch loads considered and that a e uid-e lled launch-vehicle shell can be highly sensitive to initial geometric imperfections. Presentedherearee vepapersonlarge-scaleanalysesofacomplexshellstructure.Thee rst,longerpaper,“ NonlinearBehaviorofSpaceShuttleSuperlightweight Liquid-OxygenTankUnderPrelaunchLoads,” coversthestructure,theanalysistechnique,someloading cases,andexperimentalverie cationonthemethod.Itis followed by a companion paper, “ Modeling and NonlinearStructural Analysis of a Large-ScaleLaunch Vehicle,” which goes into greaterdepth on themethods, and then by three shorter papers, “ Effects of Welding-Induced Imperfections on Behavior of Space Shuttle Superlightweight Tank,” “ Nonlinear Behavior of Space Shuttle Superlightweight Tank Under Booster Ascent Loads,” and “ Nonlinear Behavior of Space Shuttle Superlightweight Tank Under End-of-Flight Loads,” covering interesting behaviorunder differing load cases. Thesepapersare intended to stand ontheir own (and hencehavesomeredundant introductory material) but are complementary to one another, and so they are presented here together.