An update on drone R&D and testing for Arctic ice preservation

We discuss recent and proposed unmanned aerial vehicles and flights, for the development and testing of SRM (marine cloud brightening, MCB; and stratospheric aerosol injection, SAI). Those discussed include flights conducted by the authors, and (where information is available) by other teams. We discuss tests various tests and technologies: 1) MCB based on Unmanned Aerial Vehicles (UAVs) spraying salt nanoparticles. These aerosols are created in a lab, using antisolvent precipitation of brine with ethanol. 2) Balloon flights (Make Sunsets and SATAN), using commercial balloons loaded with H2 or He, and an SO2 payload  3) Fixed wing SAI tests, using small UAVs to distribute SO2 or CS2 in the midlatitude lower stratosphere. Appraisal of the above techniques' implementation gives clarity on the potential for each to be useful in coming years for both research and deployment.