 The end result was the Atlas SLV-3 and Agena D, standardized versions of the Atlas D core and Agena B which would be the same on every launch (at least as far as the Atlas was concerned, Agena Ds often still had customized setups, especially for DoD payloads).The Agena D first flew in July 1963 for DoD launches, but NASA continued using Agena Bs for the remaining Ranger missions.The Atlas SLV-3 meanwhile first flew in August 1964.