A Caltech Library Service

Design of one-kilometer-long antenna sticks and support structure for a geosynchronous satellite


Freeman, Janet Elizabeth (1986) Design of one-kilometer-long antenna sticks and support structure for a geosynchronous satellite. Engineer's thesis, California Institute of Technology. doi:10.7907/0cpe-gh28.


This study develops a preliminary structural design for three one-kilometer-long antenna sticks and an antenna support structure for a geosynchronous earth-imaging satellite. On each of the antenna sticks is mounted a linear array of over 16,000 antenna elements. The antenna sticks are parallel to each other, and are spaced 1 km apart so that they form the corners of an imaginary triangular tube. This tube is spinning about its long axis. Antenna performance requires that the position of each antenna element be known to an accuracy of 0.5 cm, and that the spacecraft's spin axis be parallel to the earth's spin axis within one degree. Assuming that the position of each joint on each antenna stick is known, the antenna sticks are designed as beams under a uniformly distributed acceleration (due to spacecraft spin) to meet the displacement accuracy requirements for the antenna elements. Both a thin-walled round tube and a three-longeron double-laced truss are considered for the antenna stick structure. A spacecraft spinrate is chosen by considering the effects of environmental torques on the precession of a simplified spacecraft. A preliminary truss-like support structure configuration is chosen, and analyzed in quasi-static equilibrium with control thrusters firing to estimate the axial loads in the structural members. The compressive loads found by this analysis are used to design the support structure members to be buckling-critical three-longeron double-laced truss columns. Some tension-only members consisting of Kevlar cord are included in the design to eliminate the need for bulkier members. The lateral vibration modes of the individual structural members are found by conventional analysis -- the fundamental frequencies are as low as 0.0066 Hz. Finite element dynamic analyses of the structure in free vibration confirm that simplified models of the structure and members can be used to determine the structural modes and natural frequencies for design purposes.

Item Type:Thesis (Engineer's thesis)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Babcock, Charles D.
Thesis Committee:
  • Unknown, Unknown
Defense Date:16 December 1985
Record Number:CaltechETD:etd-03242008-104934
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1100
Deposited By: Imported from ETD-db
Deposited On:04 Apr 2008
Last Modified:16 Apr 2021 23:23

Thesis Files

PDF (Freeman_je_1986.pdf) - Final Version
See Usage Policy.


Repository Staff Only: item control page