MEAM Seminar: “Photophoretic Levitating Structures Enabling Mesospheric and Martian Exploration”

Studying certain regions of the atmosphere is hindered by available propulsion technologies. For example, the mesosphere, ranging from about 50 to 80 km in altitude, has air too thin for aerodynamic and buoyant flight but air too dense for satellites and orbital flight due to drag. The Martian atmosphere is another region where no flight mechanisms currently operate besides the short-term flight of the Mars Helicopter. We propose a novel flight mechanism utilizing only light and no moving parts to allow macroscale structures to achieve photophoretic levitation. Photophoretic levitation refers to flight enabled through light-induced movement of gas particles that create lift forces and is optimized in the terrestrial mesosphere and on Mars. We previously demonstrated the possibility of levitating centimeter-scale disks and plates of microfabricated materials for early levitation testing, fabrication, and theory development. Now, we show the scalability of this mechanism to carry theoretical payloads of up to 10 kg in the upper atmosphere. This scalability is plausible by expanding the nearly 2D materials to meter-scale 3D structures like spheres and cones made of the same ultrathin, ultralight materials. We will discuss the architecture of photophoretic aircraft and their scalability to kg-size payloads, as well as the fabrication, testing, and simulations behind these discoveries. The applications include in situ measurements in the upper atmosphere through deployment from missions like current NASA balloons or sounding rockets. Ultimately, deploying an array of photophoretic aircraft represents new and cost-effective means of remotely sensing winds, temperature, and gas concentrations in the Martian atmosphere and the mesosphere through different sensing mechanisms.