Knudsen-Pump-Based Propulsion for Atmospheric and Martian Exploration

Photophoretic levitation refers to flight enabled through the light-induced movement of gas particles that create lift forces. The mesosphere is a region of the atmosphere with pressures too high for satellites and too low for balloons, so a sustained flight mechanism does not exist for this 50-80 km region. The photophoretic flight mechanism is optimized in the terrestrial mesosphere and can effectively carry milligram-mass payloads for ultrathin centimeter-scale plates. However, we have computationally shown that meter-scale 3D photophoretic aircraft constructed of these ultrathin materials lead to the scalability to kg-size payloads. The lift force combines solar balloon buoyancy and photophoretic forces, all powered with just sunlight, allowing flight from 0 to 80 km of altitude. We also present our early testing results for sea-level-pressure solar balloons and the next steps for lower-pressure testing at mesospheric air pressures, which act as proofs-of-concept for the analytical results. The optimized payloads are sufficient for GPS tracking of mesosphere winds, temperature measurements, and other properties which are difficult to measure in situ at such altitudes. Ultimately, deploying an array of microflyers represents novel and cost-effective means of remotely sensing winds, temperature, and gas concentrations in a region we currently struggle to observe.