Delta D
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. The main difference between the Delta C and Delta D was the presence of three Castor-1 solid rocket boosters, clustered around the first stage.
Missions: 2
Successes: 2
Partial Failures: 0
Failures: 0
Success Streak: 2
Success Rate: 100%