Ending months of speculation, Blue Origin, a company owned by Amazon-founder Jeff Bezos, has won a milestone contract to provide first-stage rocket engines for a powerful new booster being designed by United Launch Alliance to replace its current fleet of Atlas and Delta launchers, the companies announced Thursday.

The Centaur upper stage destined to send Boeing’s CST-100 Starliner crew capsule into orbit on its first unpiloted test flight next year has arrived at Cape Canaveral after a sea journey aboard United Launch Alliance’s Mariner transport ship.

A United Launch Alliance Atlas 5 rocket will boost NASA’s Tracking and Data Relay Satellite-M, or TDRS-M, into space from Cape Canaveral on Aug. 18 at 8:03 a.m. EDT (1203 GMT).