The four RS-25 motors of the SLS main stage. These engines are not new. They have already flown as Space Shuttle prime movers. To date, NASA has 16, which guarantees four SLS flights. Unlike SpaceX’s Starship Raptor engine, RS-25 engines are not reusable. © NASA, Corey Houston
This is the big day ! Nasa’s powerful SLS launcher finally shows itself tomorrow in full
