multifunctional dimentionally stable flexible composite for space applications

Paper number

IAC-08.C2.4.6

Author

Dr. Leri Datashvili, Technische Universität München, Germany

Year

2008

Abstract

Antenna reflectors usually consist of stiffened or sandwich shells, thus leading to high stiffness and high reflecting surface (RS) accuracy. On the other hand they are difficult to stow densely and then deploy in orbit if their characteristic in-orbit size exceeds that of the accommodation space available in a launcher. This is easier for reflecting surfaces consisting of (metallic) meshes to be tensioned in orbit into its reflecting shape by its deployable backside structure. Because of the inherent approximation of such meshes to an e.g. parabolic shape and other possible disturbances like pillow effects, these mesh reflectors are primarily applicable in the lower RF range. 
So, reflecting surfaces are desirable for increased precision requirements for applications in the higher RF frequency bands. In order to keep the stowability advantages of meshes but enhancing shape accuracy, reflecting surfaces composed of Carbon fibre reinforced silicones (CFRS) are developed and investigated. Due to their small bending stiffness induced by the silicone matrix they can be manufactured in relatively straightforward processes with double curvature and nearly ideal parabolic shape, and they can also be stowed quite densely. Compared to the conventional stiff matrix composites, which give high accurate double curved reflecting surfaces, an additional functionality is acquired by using a flexible silicone matrix and easy stowing and deployment is achieved. 
Because of the C-fibers CFRS is characterized with a very low thermal expansion (measured in the range of  0.36e-6/°C), with no moisture absorption or micro-cracking effects even under strong environmental cycles pointing to a high dimentional stability of the material. Results obtained from different thermo-mechanical and RF characterization tests for such CFRS surfaces will be shown which confirm the expected behaviour. For RF characterization measured properties for insertion loss, cross-polarization and reflectivity will be presented. 
Several application examples are discussed further in the paper. SMART reflector concept developed for the use of CFRS reflecting surface is presented. The advantage of the SMART concept is that it uses similar material for the stiffening ribs as the RS for achieving low thermal expansion due to compatibility and similarity of the thermo-elastic properties of the ribs and RS. An umbrella-type deployable reflector is discussed next. Advantage of such a reflector consists in the capability of the folding/deployment scheme to use high modulus fibres in CFRS RS in order to reach high RF as even Ka-band.

Abstract document

IAC-08.C2.4.6.pdf

Manuscript document

IAC-08.C2.4.6.pdf (🔒 authorized access only).

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