Delta's inexpensive, reliable, and versatile third generation upper stage

The need for larger diameter fairings to encapsulate spacecraft designed to use Delta's increased lifting capabilities resulted in hammer-head design configurations that would have unaccepably degraded vehicle flight characteristics. This situation led to the development of the Straight Eight configuration. The towed mode arrangement for the second stage negated the requirement for the engine compartment structure, thus establishing the potential for an improved packaging of the hydraulic and pneumatic systems. Therefore, with cost reduction and reliability improvement objectives, a second stage propulsion system improvement program was initiated. The paper will describe these improvements and their system benefits.