"And the way things mix in the upper atmosphere means that the launch and reentry emissions are by far more impactful." What is worse, pollutants in the upper atmosphere remain much longer than those emitted by cars and factory chimneys close to the ground. "So, in terms of each rocket launch, the difference almost offsets. SpaceX's Starship megarocket launches on its 13th test flight, on July 24, 2026. Boley concurred: "We absolutely have to understand, and we have to understand that before we actually launch a million satellites.