Development and Qualification of ATV Propulsion Assemblies

Computer Science – Numerical Analysis

Scientific paper

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Scientific paper

In the frame of the development and operation of the International Space Station ISS, the European Space Agency ESA is not only contributing experiments and a laboratory module but also logistics capacity. This purpose of supplying the ISS shall be covered by an unmanned, Automated Transfer Vehicle (ATV) that will be launched for the first time in 2004 by Ariane 5. The development of the ATV is in close conjunction to the future Ariane 5 launch capacity of about 20 tons injected into low earth orbit. Thus this unmanned transporter will be a quite large space craft that is subjected to fulfil several mission objectives apart of only delivering cargo such as multiple automatic docking/de-docking, re-boost services and re-fuelling. For those reasons and due to its dimensions the propulsion sub-system is one of the most sophisticated in the field of space propulsion. Even safety issues of manned space flight have to be applied since the pressurised cargo section is part of the ISS when docked to the manned modules. This leads to by far the largest but also the most sophisticated propulsion system ever built in Europe. Astrium as one of the major partners of this european project is responsible for this major system that will be described in the paper. Focusing on the major core assemblies such as multi thruster platforms, pressure control system incl. safety and redundancy mechanisms as well as tanks and other components that completes a propulsion system. System Design and Qualification Starting from the basic criteria the paper will present the major performance requirements such as pressures, thrust levels and other parameters that led to the selection of major components of the system such as thrusters, valves, tanks, etc. Some of the component could be selected from off the shelve, whereas other core components such as the 200N Attitude Control and Braking Thrusters or Propellant Tanks had to be newly developed. The stepwise approach of development and careful qualification will be presented starting from components and assemblies up to sub- system. Exemplarily, the path of the 200N shall be described in more detail since requirements of various kinds are to be applied here. This thruster is used in a total of 28 engines located on 4 thruster cluster assemblies on the bottom and 4 on the front of the space craft delivering steady state thrust as well as impulse bit to the ATV and can be used also as backup for the main thrusters. Safety and thus redundancy is one of the major driver for the design. As a first step i.e. the thrusters are equipped with measures to detect malfunctions and problems by continuous measuring chamber temperature and combustion pressure. The layout of the thruster clusters arrangement in combination with control electronics are such are such that multiple independent branches are controlling the system by which each of them could to fulfil the whole operational objectives. The thruster clusters are also affected by most of the environmental constraints that require careful thermal or mechanical design. For example severe shock loads induced by the stage separation nearby as well as meteorites and debris have to be taken into account for mechanical design. Or large transient pressure spikes and water hammer caused by simultaneous operation of thrusters have to be considered for hydraulic design. As well as extreme conditions for thermal design facing high thermal loads both radiation and conductive during thruster firing and sun exposure of the externally mounted assembly as well as low heater budget and I/F flux limitations when exposed to deep space during long phases. Intensive test programs have been carried out or are under preparation as well as complementary numerical analysis are completing and supporting each step of the development. The paper will describe those design and qualification activities as well as the results as far as available to that time in order to give an overview of the status of the development of the whole propulsion system.

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