Delta improvement study - Hydrogen upper stage

Abstract

Introduction T HE Delta commercial launch vehicle has had a long and successful life. It was first launched May 13, 1960 and the mission was unsuccessful. The Echo 1A satellite was carried into orbit on the second Delta mission. Between May 1960 and November 1990, the Delta completed 189 of 201 missions successfully, giving it 94% reliability. The version of the rocket that was considered for upgrade in this study was the Delta II 7925. It first flew on Nov. 26, 1990. The Delta II 7925 consists of three stages and uses nine external solid rocket motors. Propulsion for stage 1 is provided by a liquid core engine burning RP-1 fuel and oxygen. Core stage 2 is a storable liquid core and uses nitrogen tetroxide and A-50 propellants. Stage 3 consists of a solid rocket motor used to insert the payload into geosynchronous transfer orbit (GTO). A payload of 4010 Ib can be placed into GTO using the Delta II 7925 with a 9.5-ft payload fairing. The study reported here is aimed at helping to reduce the use of toxic storable propellants. Special safety steps needed for these chemicals would be eliminated and operations costs would fall as a result. By using a hydrogen and oxygen upper stage, stages 2 and 3 could be eliminated from the Delta II. Figure 1 illustrates this modification. Five engines were examined in the course of this research for use in the hydrogen replacement stage. Included in the research were the following engines: an RL10C, an RL10A-4, an advanced technology low cost (ATLC) engine, an advanced expander cycle engine, and an engine with a simplified injector.