Aircraft retrofitting analyses

Most SAI modeling to date assumes deployment at altitudes above 20 km — for instance, the ARISE-SAI scenario (a widely used set of model simulations of SAI deployment) involves injections at ~22 km. However, a fleet of aircraft capable of reaching these altitudes does not currently exist.

The tropopause (the boundary between the lower atmosphere and the stratosphere) is lower at the poles, which means deployment at high latitudes and low altitude (~15 km) may be possible with existing aircraft. Current widebody jets have service ceilings up to 13 km, making a retrofit targeting 15 km plausible. Existing business jets could also reach 15 km, though with a relatively small payload (~10 tonnes), and further work is necessary to determine the trade-off between payload and altitude across different existing aircraft. In addition to supporting a better understanding of technically plausible deployment scenarios, some aircraft retrofit would be necessary for an aerosol microphysics experiment.

This activity performs desk research on which commercial aircraft are best suited for modification, and the associated costs and resources. The primary categories of modification to be considered are (1) airframe altitude capability, (2) excess thrust and engine suitability, (3) gross weight constraints, (4) lift coefficient and wing modifications, and (5) operational considerations and constraints. A comprehensive study must examine a wide range of aircraft, including large commercial aircraft — such as Boeing 747s — and business jets.

A preliminary study commissioned by Reflective from the aerospace company AeroTEC indicated that retrofit is feasible. Further analyses are required on specific risks — such as potential engine flameout at higher altitudes — to reduce remaining uncertainty. A similar study of business jets will provide the depth of information needed to assess aircraft modifications for an aerosol microphysics experiment or an aerosol evolution and transport experiment. Together with the clean-sheet aircraft feasibility study, these analyses will let decision makers compare the retrofit and new-aircraft pathways.