Self-Deploying Foam Antenna Structures

Inflatable or self-deployable systems offer the only practical way to achieve space deployed antennas with low mass at large aperture. In this Phase I program, open-celled rigid polyurethane foams were developed for use in self-deploying antenna structures. Advantages of such a system relative to current systems include high volumetric efficiency of packing, inherent restoring force, low (or no) outgassing, low thermal conductivity, high dynamic damping, mechanical isotropy, infinite shelf life, and easy fabrication with methods amenable to construction of large structures (i.e., spraying).In Phase I, it was demonstrated that rigid polyurethane foams with a variety of glass transition temperatures (Tgs) can be easily formulated using commercially available urethane components; foam systems with Tgs ranging from 30 to 150?C were prepared. The ability to tailor the system Tg is a critical element in tailoring the deployment of these systems on-orbit. The ability to create open cells in rigid polyurethane foams was also demonstrated; a sample was prepared with greater than 50% open cell content. Open-celled foams are critical for achieving high packing efficiency and maintaining dimensional stability of the structures during thermal cycling. It was also demonstrated during the course of the Phase I program that metallized open-celled foams can perform well for antenna applications. RF insertion loss testing in the frequency range 12-17 GHz on foam samples coated with approximately 3.5 microns of metal indicated a minor loss of 0.2 dB, clearly demonstrating the promise of metallized foams for antenna applications.