Design, Test and Comparison of mechanical support principles to increase the robustness of deployable thin shell CFRP Booms of the deorbiting device ADEO

Kurzfassung

In the industry led ESA project ADEO, a truncated pyramid shaped configuration for a drag augmentation device, is accomplished using DLR´s thin shell, rollable CFRP booms combined with four sail segments as a so called drag sail. Realizing a boom root deployment enables the boom tip to be pushed out of the housing and to deploy the sails. Due to this principle a transitional zone forms from the flattened to the fully deployed boom cross section. Thus reducing the second moment of area and therefore local stiffness of the boom, the transitional zone needs to be mechanically supported. Realizing this with a boom-support-guide device, this supportive structure fulfills a secondary function of guiding the deploying boom from the boom hub into the destined direction away from the spacecraft. However, for a successful operation the boom system needs to provide certain stiffness, buckling load capacity and robustness. In this paper the influence of the mechanical support & guiding device on the buckling behavior and stiffness of a boom during deployment and in deployed configuration is studied. To do so the mechanical characteristics of the initial and for two alternative designs of the boom guide & support devices are investigated and compared. Experimental data is acquired by combined mechanical boom bending and compression tests in a vertical test stand with booms mounted onto a realistic deployment unit. By simulating occurring sail and deployment loads with a certain spectrum of angles of attack and according boom lengths, values for boom buckling, collapse and boom tip deflections are acquired and analyzed in typical load-deflection curves. Finally the acquired experimental data and characteristics of the different designs are compared and discussed.