Title: Kinematic analysis of a lightweight periodic dielectric structure of pearls for RF coaxial power cables for space applications

Authors: Gerald Kress; Holger Karstensen; Michael Mattes; David Raboso

Addresses: CMASLab, Department of Mechanical and Process Engineering, ETH Zürich, CH-8092 Zürich, Zürich, Switzerland ' Karstensen Consulting, Hubertusstr. 2, D-85662 Hohenbrunn, Bavaria, Germany ' Department of Electrical Engineering, Technical University of Denmark, Ørstedts Plads 348, DK-2800 Kgd. Lyngby, Denmark ' European Space Agency, Universidad Politécnica Valencia, Camino de Vera s/n, CPI (Edificio 8G – Acceso B – Planta B), 46022 Valencia, Spain

Abstract: The desire to reduce the mass per unit length and to increase phase stability of coaxial radio-frequency (RF) power cables for space application motivates a new design idea, namely to replace solid dielectric with a periodic chain of hollow pearls. The design of the dielectric pearls must allow for bending flexibility of the cable even if they are made from a stiff material such as silicon glass. An important requirement of RF power cables for space applications is their phase stability, which is influenced by the material-dielectric-constant tolerance over a large temperature range as well as by changes in geometry. This paper presents an original closed-form model based on rigid-body motion to predict the kinematic response of dielectric pearls to the bending of the cable. Particularly, the model maps the eccentricity of the inner and outer conductors with respect to each other and the axial strain of the bent cable along its centreline. The model results indicate that mass reductions of the periodic hollow-pearl design over conventional solid PTFE dielectrics are significant.

Keywords: co-axial RF power cable; space application; high power; high temperature range; multipactor; periodic dielectric structure; bending kinematics; closed-form modelling.

DOI: 10.1504/IJSPACESE.2020.10032053

International Journal of Space Science and Engineering, 2020 Vol.6 No.1, pp.28 - 48

Received: 06 Sep 2019
Accepted: 01 Feb 2020

Published online: 22 Sep 2020 *

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