Encyclopedia entry SEP 903 Engine · France Part of SSBS S01 Original archive entry. The text, images and links below are kept as they were written. SEP solid rocket engine. SSBS S01 second stage. RelatedCountryFranceLaunch VehiclesSSBS S112, SSBS S01, SSBS S02, SSBS S2PropellantsSolidStagesSEP 903