Battery for Extended Temperature Range Exomars Rover Mission

Abstract

The robotic exploration of Mars plans to deliver a European rover on the surface of Mars during the RSP (Rover & Surface Platform) mission. Exomars is a broad cooperation between ESA and Roscosmos, with important contribution from NASA.NASA already sent several rovers on Mars using RTG (Radio isotopic Thermoelectric Generator) to provide electricity on-board. RTGs are not used by ESA, therefore an electrochemical storage system is developed for this mission.Nevertheless, the rover is equipped with Radio-isotopic Heater Units (RHU) supplied by the Russians, which aim to prevent the internal temperature of the rover dropping below −40°C, whereas an external Rover temperature as low as −125°C, can be expected on the Martian surface. The drawback is that during the rover encapsulation and the cruise between the Earth and the red planet, the internal Rover temperature will reach +40°C to +50°C during months.The rechargeable battery designed for the rover shall then withstand the high temperatures exposure followed by charge / discharge cycles at low temperatures when on surface of Mars.Another point to highlight is that the mission objective is to try to find well-preserved organic material, particularly from the very early history of the planet, from the subsurface.Consequently, the contamination of the rover and all its equipment must be controlled similar to medical tools to avoid depositing spores that could pollute the samples during the on surface phase of the mission.This paper is presenting the innovative battery designed to withstand these extended operating temperatures while being able to power the rover during night and days (even during local sand storm).The thermal control of the battery was of the utmost criticality to answer to this wide temperature range.The rover design was well advanced when the battery development started, therefore adding challenging schedule and mass targets!