Redefining “Space Sustainability” for Launch Vehicles: Forecasting the Atmospheric Impact of the Commercial Space Launch Industry in 2050

Abstract

Discussions on “space sustainability” have largely centered on orbital debris, the burnup of vehicles during atmospheric reentry, and the resulting emissions. However, few studies have examined emissions from the launches themselves. Along with reentry burnup, rocket launches are the only source of high altitude anthropogenic emissions. At such high altitudes, emitted particles can remain in circulation for years. With the annual growth rate of the commercial launch industry averaging 14.6% in the last 4 years and over 211 launches in 2023 alone, our research on the atmospheric impact of launch vehicles comes at a crucial point in the policy debate on space sustainability.

This thesis outlines several potential future scenarios of the launch industry in 2050, with all the vehicles in each scenario using the same fuel type. We examine these four launch scenarios—a kerosene (RP-1) launch industry, a methane (CH4) launch industry, a hydrogen (H2) launch industry, and a control or “baseline” scenario without launches. For each scenario, we estimate the number of launches for a distribution of heavy-lift launch vehicles across origin spaceports. We simulate the chemical interactions of the launch plumes with the atmosphere using the global atmospheric chemistry model GEOS-Chem High Performance (GCHP). Finally, we quantify the steady state impact of launch emissions on stratospheric ozone and surface air quality.

We find that the black carbon emitted by kerosene and methane rockets causes an indirect increase in stratospheric ozone due to the removal of NOx, with ozone column change averaging 5.07 Dobson Units (DU) and 1.26 DU respectively; hydrogen rockets cause a net decrease in ozone column averaging -0.11 DU. The population-weighted average surface ozone impact is -0.286 ppb, -0.068 ppb, and 0.023 ppb for RP-1 rockets, CH4 rockets, and H2 rockets respectively. The population-weighted average surface PM2.5 impact is -0.031 μg/m3, -0.004 μg/m3, and 0.002 μg/m3 for RP-1, CH4, and H2 rockets respectively. Although RP-1 and CH4 rockets decrease surface ozone and surface PM2.5, H2 rockets have the smallest magnitude impacts on the atmosphere overall. Our findings have important implications for commercial launch providers, research institutions, and policymakers including the Federal Aviation Administration (FAA) and NASA.