Environmental Design-for-Demise: Quantifying Stratospheric Emissions from High-Cadence SmallSat Re-entry

As European and global regulators move toward a zero-debris approach to satellite mission design, small satellites designed for demise have been viewed favourably, as they typically ablate during re-entry and pose minimal risk of ground casualties. However, the increasing flux of ablating satellites introduces a new regulatory concern through the injection of anthropogenic material into the upper atmosphere. A recent NOAA study found that approximately 10% of stratospheric aerosol particles now contain metals originating from spacecraft re-entry, indicating a measurable perturbation to stratospheric chemistry. Consequently, regulators have raised concerns that existing re-entry practices may lead to unacceptable atmospheric impacts. This study presents an end-to-end framework for quantifying the climate cost associated with satellite fleet de-orbiting.

While ablation modelling has traditionally focused on spacecraft survivability during re-entry, comparatively little attention has been given to the chemical by-products and their potential climate effects. We employ a multiscale computational framework to quantify satellite re-entry ablation by-products and assess their impacts on ozone depletion and radiative forcing. Near-surface re-entry flow conditions are first simulated for a representative satellite to constrain the thermodynamic inputs to reactive molecular dynamics simulations using the ReaxFF force field. The resulting particle size distributions and chemical compositions are incorporated into the Community Earth System Model (CESM), coupled with the Community Aerosol and Radiation Model for Atmospheres (CARMA), to predict atmospheric aerosol distributions and associated climate effects. Finally, we assess the sensitivity of climate perturbations to spacecraft material selection and re-entry trajectory design.