Conceptual Design of the Electrical Power Subsystem for the European Student Moon Orbiter Mission

Paper number

IAC-06-C3.1.07

Author

Mr. Steve Ulrich, Universite de Sherbrooke, Canada

Coauthor

Mr. François Landry Corbin, Universite de Sherbrooke, Canada

Coauthor

Mr. Hubert Nolet Côté, Universite de Sherbrooke, Canada

Coauthor

Mr. Alexandre Désilets, Universite de Sherbrooke, Canada

Year

2006

Abstract

The European Student Moon Orbiter (ESMO) mission is part of the Student Space Exploration and Technology Initiative (SSETI) program, which is under the supervision of the European Space Agency (ESA). The objective of ESMO is to send a satellite in orbit around the moon, perform innovative scientific experiements in lunar orbit and scan the lunar surface for future moon lander missions. Canada, represented by l’Université de Sherbrooke (Québec), is involved in the ESMO mission since June 2005. For this unique mission, Canada plays a major role by designing and building the Electrical Power Subsystem (EPS). The EPS is responsible for electrical power generation, energy storage for peak-power demands and eclipse periods as well as power regulation and control to prevent overcharging and undesired spacecraft heating. The Canadian team has conducted a conceptual design for the EPS by exploring many concepts and by analyzing their respective performance within the context of a mission to the moon. 

Primary battery cells, photovoltaic solar cells, static power sources (such as thermoelectric couple), dynamic power sources (such as radioisotopes) and fuel cells are considered as method for electrical power generation. Energy chemical storage technologies investigated for the spacecraft include Li-ion, NiCd, NiH2 and NaS batteries. The power regulation and control function can be breaked down into three distinctive subfunctions: power source control, bus voltage regulation and battery charging. Therefore, for every of these subfunctions, different options are analyzed in details (including unregulation, quasi-regulation, fully regulation, peak-power tracking (PPT), direct energy transfer (DET) with shunt regulation, parallel and independent charging concepts). 

Based on the mission context and requirements, the conceptual design reveals that GaAs photovoltaic solar cells will be used as primary power source. Although solar arrays can be mounted directly on the spacecraft structure, preliminary computations indicate that deployable solar panels will be necessary (mainly because of the high power demand from the propulsion subsystem and the payload). Li-ion battery is selected as the method of energy storage, based on its high depth-of-discharge, which is a critical factor for a mission to the moon, where many charge-discharge cycles are involved. Despite of the increased complexity, the EPS will provide a fully regulated bus voltage controlled by the DET technique, resulting in a low system mass. Finally, performance analyses show that an independent battery charging method, known as linear charge-current-control (LC3), consists in the best option for charging the Li-ion battery cells.

Abstract document

IAC-06-C3.1.07.pdf

Manuscript document

IAC-06-C3.1.07.pdf (🔒 authorized access only).

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