A 2025 update on engineering issues concerning stratospheric aerosol injection for geoengineering

Solar Radiation Management (SRM) geoengineering is a proposed response to anthropogenic global warming (AGW). Stratospheric aerosol injection (SAI) is one proposed method, reliant on lofting material into the stratosphere. This layer of the atmosphere is generally difficult to access using conventional fixed wing aircraft or - particularly in the tropics. Relevant technological progress in the last 5 years has been rapid, and a new review is now merited. We therefore qualitatively appraise recent groundbreaking technology developments, with potential applicability to SAI. While some previously promising technologies featuring in earlier reviews have been largely static during the 2020s (e.g. artillery) progress has been very rapid in the following areas. 1. Balloon SRM technology. 2. Reusable space launch. 3. Unconventional space launch. 4. Hypersonic aircraft 5. Supersonic passenger transport. 6. Unmanned aerial vehicles . Paying particular attention to commercial firms operating in each of these fields, we document the current state of the field. We therefore identify a range of technologies and firms likely to influence the SAI technology landscape in coming decades.