Flying Spiders: Effects of the length of a dragline and the spider mass in ballooning

Most spiders use a type of aerial dispersal "ballooning" to move from one location to another. By ballooning, spiders can reach distances as far as 3200 km and heights of up to 5 km. Though a large number of observations of spider ballooning have been reported, it remains a mysterious phenomenon. What dominate the three stages of spider takeoff, flight, and settling? There are many factors to consider, including a spider's mass, morphology, posture, the silken dragline properties, and local meteorological conditions. A thorough understanding of the roles of these critical parameters is not only of ecological significance but also critical to improving advanced technologies for bio-inspired innovations of airborne robotic devices. This preliminary test is to determine how the silk dragline length and spider mass affect the interaction in the freefall at Reynolds numbers of several thousand (based on the spider size and the relative wind speed), using recordings by a high-speed camera in a laboratory setting. The vertical velocities of the dragline and the induced flow structures are compared against numerical models of coupled fluid-structure interaction. Such results are expected to shed lights on the intriguing flow physics of spider ballooning and help to validate new models.