The Delta D, Thrust Augmented Delta or Thor-Delta D was an American expendable launch system used to launch two communications satellites in 1964 and 1965. It was derived from the Delta C, and was a member of the Delta family of rockets.The three-stage core vehicle was essentially the same as the Delta C. The first stage was a Thor missile in the DSV-2A configuration, and the second stage was the Delta D, which was derived from the earlier Delta. An Altair-2 SRM was used as a third stage.