Deployment of large structures such as solar sails relies typically upon electromechanical mechanisms, mechanically expandable or inflatable booms, launch restraints, controls, and other mechanisms that drastically increase the total mass, stowage volume, and areal density. The primary performance parameter for solar sails is areal density, which determines the acceleration of the sail. Present technology allows the solar sail areal density to be around 20 g/m2, and that permits only nearby demonstration missions.
A new ultra-lightweight solar sail concept uses a “boomless” microporous membrane structure deployed by shape memory effect and elastic recovery. It can enable the development of solar sail structures with areal densities close to 1 g/m2 that, in turn, will make fast trips to the helio-pause, early solar storm warning, and ultimately interstellar missions possible.
The use of shape memory polymer (SMP) micro-foam thin structure reinforced with carbon nanofibers is considered for solar sails. Prior to launch, the structure is warmed up above ambient temperature to allow packaging and stowing, and then cooled back to ambient to induce a shape hibernation. In space, it “remembers” its original shape configuration and size when warmed up by solar radiation, and is then cooled by the space environment to achieve rigidization. The stiffness of rigidized membrane reinforced with carbon nano tubes should be high enough to support large deployed structures without any deployable booms or other support structures.
This technology concept represents the next generation of ultralight self-deployable solar sails. The solar sail structure is deployed by the shape memory and elastic recovery. It provides a simple end-to-end process for stowing, deployment, and rigidization that has benefits of very low mass, low stowage, low cost, and great simplicity. It avoids the complexities associated with existing deployment methods by eliminating booms, deployable mechanisms, launch restraints, and control systems that require typically >90% of the mass budget of the deployable structure.
The concept may launch a new paradigm in structure configurations and future mission architecture. The microporous membrane structure will enable highly integrated, multi-functional membranes with embedded thin-film electronics, sensors, actuators, and power sources that could be used to perform other functions such as communication, navigation, science gathering, and power generation.