Their unique breakthrough is relighting rocket engines in a hypersonic airflow. Everything else is shoulders-of-giants and design iterations and good project m

Their unique breakthrough is relighting rocket engines in a hypersonic airflow. Everything else is shoulders-of-giants and design iterations and good project management, but relighting rocket engines like that was an unknown. Landing is a critical prerequisite to reuse: we can't reuse what we discard. But the important reusability breakthrough comes in a few months when they do the first reflight of an orbital booster.