Drop tank

Abstract: A double walled tank is provided for the storage of hazardous materials. The tank comprises an internal tank substantially contained inside an external tank, and substantially reduces the use of internal reinforcements between the two tanks that would disrupt the flow of fluids through the interiors of the tanks. The tank is also provided with a pair of spill boxes that surround access openings to the double walled tank and catch and contain any hazardous material that should leak or spill when loading or unloading the tank.

Abstract: Results of buckling and nonlinear analyses of the Space Shuttle external tank superlightweight liquid-oxygen (LO2) tank are presented. Modeling details and results are presented for two prelaunch loading conditions and for two full-scale structural tests that were conducted on the original external tank. The results illustrate three distinctly different types of nonlinear response for thin-walled shells subjected to combined mechanical and thermal loads. The nonlinear response phenomena consist of bifurcation-type buckling, short-wavelength nonlinear bending, and nonlinear collapse associated with a limit point. For each case, the results show that accurate predictions of non- linear behavior generally require a large-scale, high-fidelity finite-element model. Results are also presented that show that a fluid-filled launch-vehicle shell can be highly sensitive to initial geometric imperfections. In addition, results presented for two full-scale structural tests of the original standard-weight external tank suggest that the finite-element modeling approach used in the present study is sufficient for representing the nonlinear behavior of the superlightweight LO2 tank.