Design and Development of the MESSENGER Propulsion System

Abstract

A Mercury orbiter mission has been out of reach for over 20 years due to the thermal, Delta V, and resulting spacecraft mass constraints. MESSENGER’s ceramic cloth sunshade solves the thermal issue, its newly developed mission trajectory reduces the Delta V requirements, and the subject of this paper, MESSENGER’s integral propulsion system/composite structure, yields a missionenabling reduction in spacecraft mass. Propulsion system mass was further reduced via the development and qualification of a new propellant tank resulting in a tank dry/wet mass ratio of just 0.03. The use of a refillable, auxiliary tank for propellant settling and small Delta V maneuvers enabled the main tanks to be devoid of positive expulsion devices. The large (2300 m/sec) mission Delta V requirements of this interplanetary mission dictated the use of a regulated dual-mode propulsion system. A unique sequencing of individual tank outlet latch valves maintains the spacecraft X and Y center of mass well within the requirements of the mission during expulsion of the nearly 600 kg propellant load. The use of flightproven components, a sequential proto-flight test philosophy, and a small Integrated Product Team approach have resulted in the recent successful development, manufacture, test, and integration of the propulsion system into the spacecraft.