Finite element modeling and analysis
NASA tasked Dynamic Concepts (DCI) with assessing the structural dynamics of the rollout process, whereby the space shuttle orbiter, external tank, and solid rocket booster assembly is moved via a crawler transporter from the Vertical Assembly Building to the launch pad. DCI used Femap finiteelement modeling software from Siemens PLM Software (Plano, TX) to create an integrated model of all the shuttle components, and used Siemens’ NX Nastran to analyze the simulated vibration environment. The analysis helped NASA resolve issues with support structures and determine target rollout speeds that minimized potentially damaging vibration.
NASA also engaged DCI to develop a more detailed finiteelement model of the space shuttle’s external tank. Much of the computer-aided engineering work on the space shuttle for the past two decades has used a finite-element model of the tank that, alone, was not sufficient to meet the current needs for detailed analysis of local components. DCI created much of the new finite-element model directly from drawings, using Femap modeling and NX Nastran analysis tools. When complete, the new model will be structurally resolved to the current model, and will work in a plug-and-play fashion with other component models. NASA engineers will use the model for sensitivity and what-if analysis.
DCI is also supporting development of nextgeneration rocket engines that will power the return to the Moon. The Ares I launch vehicle in NASA’s Constellation program includes the J2-X, a new upper-stage engine. DCI worked with NASA to define the dynamic environment for simulations that will be used in the J2-X design. DCI devised a vibration test bed using an actual surplus engine suspended on bungee cords and attached to several shakers that provided the random force inputs. Accelerations and strains were measured at several critical locations on the engines. A finite-element model of the engine, adapted to the test bed configuration, was then used to simulate the results with NX Nastran.