Finite Element Model Correlation and Evaluation of the Design of a Structural Support for the DLR Shell Lander

Kurzfassung

The current work is a correlation between models of finite element analysis and laboratory test models. The second task of this work involves the evaluation of the design of a rigid interface frame requirement for a concept study of an asteroid lander -a freely falling scientific object. The lander in onsideration is similar in size, shape and mass to that of the Mobile Asteroid Surface Scout (MASCOT). The development of the lander concept has led to the requirement of having an outer protective covering (cushion) that acts as an energy absorber in order to protect the internal instruments when impacted on a hard surface. This cushion is a sandwich panel with aluminum honeycomb core and Dyneema composite face sheet. The advancement on study of cushion geometry has opened to two models. The efficiency of the cushion as energy absorber is experimented at DLR laboratory with test setups for different impact conditions. Major difference in the surface on which the cushion impact considered, is on a flat surface target and a penetrator target. The performance of the cushion is also tested by varying the number of face sheets glued over the core. Crash analysis by finite element model of the cushion is developed for the laboratory test condition and the properties of the core and the face sheet is optimised. These finite element models are correlated with laboratory test condition for the first model of the cushion. On impact, cushion absorbs energy up to its absorption capacity. The load transfer results in the deflection of the sandwich cushion panel. A possible solution to over come this deflection was to provide a rigid frame support. The frame is designed with the requirement to accommodate a load cell to measure the impact force and to provide attachment points between the cushion and the housing. An evaluation on the provision of the frame to prevent the bending is predicted with the second model of the cushion.