Complex sentence: TSC's launch customer was Virgin Galactic, which contracted to purchase five SpaceShipTwos and two WhiteKnightTwos; Scaled Composites were contacted to develop and build prototypes of WK2 and SS2, of which TSC started full-scale production in 2008.
Split into simpler sentences: TSC's launch customer was Virgin Galactic, which contracted to purchase five SpaceShipTwos and two WhiteKnightTwos. To meet Virgin Galactic's requirements, TSC has contracted Scaled Composites to develop and build prototypes of WK2 and SS2, of which TSC started full-scale production in 2008.