A Composite Structural System for a Large Collapsible Space Antenna

Abstract

Satellite systems of the future will have to cope with an ever-increasing number of small ground terminals of reduced cost. The use of these small and low-powered ground terminals will demand improved space craft radio frequency performance which will lead in turn to the use of large antennas.

A number of space missions have been proposed incorporating reflectors of very large diameter. These applications include mobile satellite systems, broadcast satellites, electronic transmission of mail and data sharing. Reflectors up to 50 m diameter may be used in the next decade.

The role of the structural engineer in the design of large space antennas is to ensure that the structure is capable of withstanding all possible load conditions without failure, to minimise deviations from the perfect geometry and so ensure high-quality performance, to produce a minimum mass and minimum package volume for low cost transportation using the space shuttle and orbiting transfer vehicle, and to devise very reliable methods for the deployment or construction of the satellite in space.

This chapter illustrates an erectable reflector, based upon the General Dynamics Corporation’s extendable truss antenna, which is deployed at low earth orbit and then transported to geostationary orbit. A suitable composite material of construction for the manufacture of the reflector is suggested and the manufacturing process of this carbon fibre polyethersulphone tube is given.

Finally, compressive and buckling tests on, and mechanical properties of, the composite are discussed when it has been exposed to normal atmospheric conditions and when it has been degraded by temperature cycling in high vacuum. The temperature limits are at present between + 50°C and −95°C. The initial indications are that, within the limits of the test parameters, the composite material is structurally satisfactory. However, because the environment of space is very hostile and the temperatures are extreme many more tests will have to be undertaken.