Space flower: the bionic system for satellite thermal regulation

摘要

The paper presents a novel concept for spacecraft temperature control. The concept is inspired by the elegant bindweed flower (Convolvulus sepium). The characteristic of this trumpet-shaped flower is that it closes at each sunset and reopens the following day. We emulated this behavior with an artificial flower. Our artificial flower consists from a peduncle which is in firm thermal and mechanical contact with the spacecraft radiator panel. Six ribs which are actually Shape Memory Alloy (SMA) actuators are connected to the peduncle. The principal characteristic of SMAs is their ability to memorize their original configuration after they have been deformed. By heating SMAs above their "trained" transition temperature, they can recover large strains and hence their original form (shape memory effect). A very thin reflecting foil is stretched over the ribs. The artificial flowers are arranged in a 2-D hexagonal matrix over the entire radiator panel. When the sun irradiates the flower and/or the radiator temperature exceeds the preset value, the SMA actuators in the ribs bend and open the flower. In such a manner the flower exposes the highly reflective surface to the sun and shadows the spacecraft radiator until the sun sets again. The total mass of the flower per square unit is significantly lower than that of the contemporary used Venetian louvers. Further, the flower structure is without any friction-connected kinematic movements, thus the reliability of device should be high.