Deployable Hexapod Using Tape-Springs
ALCATEL SPACE INDUSTRIES CANNES LA BOCCA (FRANCE)
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In the near future of space observation systems several technical challenges come into light like multi-pupil systems conceived as free flyers or extremely high resolution EHR systems with large dimensions and high agility requirements. To be able to face these challenges the Alcatel Space Research Department is studying innovative structural concepts for future observation instruments. One of these concepts is based on an hexapod whose legs are deployable coiled tape-springs. This hexapod is stowed in a favorable mechanical configuration for launch and self- deployed once in orbit. The deployment errors and long-term instabilities can be corrected thanks to six actuators located under the feet of the hexapod and the final optical performance is reached thanks to adaptive optics. The main advantages of this concept compared to classical hyper-stable telescope structures are -a reduced volume during launch allowing large systems design -a very strong reduction of dimensional stability requirements during launch thanks to the actuators and the adaptive optics which will correct the geometric instabilities of the structure after deployment. This allows to build very light structures sized only by orbital life with quite classical CFRP or metallic materials. - a mass and inertia reduction which leads to an agility gain of the system. This concept is currently examined with ESA Innovative Triangle Initiative support. The goal of this study is to develop and build a representative breadboard of an hexapod using this technology and to evaluate its deployment precision and correction capabilities. This paper presents the optimal design algorithm based on interval analysis and used to define the geometry of the breadboard in order to maximize its correction capabilities and to insure its workspace. Then the structure design and the 6 tape-spring mechanisms are described. The paper ends with the results of the deployment and correction tests.
- Machinery and Tools