Layout and Design of a pressurised Structure for gelled Propellants for a Thrust controllable Sounding Rocket Upper Stage

Abstract

In-situ measurements in middle and higher atmosphere regions are often only possible by means of sounding rockets. The typical trajectory of a sounding rocket is a suborbital, elliptic flight path which practically leads to only several seconds during ascent as well as descent to perform the desired measurements. To improve scientific gain and provide longer measurement times in the relevant altitude regions, the Mobile Rocket Base (MORABA) and partners of the German Aerospace Center as well as industrial partners are working on a thrust controllable upper stage for sounding rocket applications. The upper stage will be powered by a gelled propellant engine and enable the payload to hover on a certain altitude level or perform different, non-ballistic flight paths. To achieve this, it will be equipped with an attitude control system consisting of a thrust vector control unit for the engine and additional cold gas thrusters. In this way, it would be possible to precisely target atmospheric phenomena and perform local measurements with an essentially extended local operating time in comparison to current sounding rocket concepts. The rocket engine will be pressure fed by the propellant tank system which is a key element of the upper stage, providing a sufficient fuel flow and pressure needed for the optimal combustion and different thrust levels. This paper concentrates on the development of a fuel tank for gelled propellants for the supply of the upper stage engine. The development process is described from defining the task over the concept development to a detailed CAD model concept. The peculiarities of this tank are the light and economical design as well as the integrated, pressure driven piston to feed the propellant. The focus of this work is the definition of the concept and the subsequent structural FEM analysis of the tank system.