Radioisotope power systems utilising americium-241 as a source of heat have been under development in Europe as part of a European Space Agency funded programme since 2009. The aim is to develop all ...of the building blocks that would enable Europe to launch and operate deep space and planetary missions in environments where use of solar power or alternative power generation technologies is challenging. Although some technical and policy work activity predate the ESA programme, the maturity of the technology has now reached a level that it can be incorporated in mission studies and roadmaps targeting the period from the mid 2020s onwards. This paper describes the state of the art in European radioisotope thermoelectric generators and radioisotope heater units. This paper includes: the evolution of the technical programme in detail; descriptions of the design; evolution of RTG and RHU devices from laboratory prototypes to more advanced fully functional systems; and experimental data obtained to date. This paper also outlines the technical challenges and multidisciplinary skills required to develop what is a world leading, original, significant and transformative technology solution for planetary science and exploration missions from the mid 2020s onwards.
Radioisotope heater units (RHU) and radioisotope thermoelectric generators (RTG) are currently being developed for the ESA radioisotope power system program. The state-of-the-art for the USA and ...Russian systems is to use plutonium-238 as the radioisotope fuel; however, for the ESA applications americium-241 has been selected due to its availability and relatively cost-effective production in the European context. The proposed designs implement a multi-layer containment approach for safety reasons, with a platinum-rhodium alloy for the inner containment of the fuel and carbon-based materials for the outer layers. The Am-fueled RHU provides 3 W of thermal power, and makes this design competitive with existing models in relation to specific power. The heat source for the RTG has a 6-side polygonal shape, with a distributed 3-fuel pellet architecture: this configuration allows to maximize the specific power of the RTG, since Am-based fuels have a lower power density than Pu-based fuels. The heat supplied by the fuel is 200 W, with an expected electrical power output of 10 W provided by six Bi-Te thermoelectric modules. Finite element structural and thermal analyses have been performed to assess the theoretical feasibility of the components as initially conceived. Mechanical and electrically-heated prototypes for the systems have already been tested in a representative lab environment at the University of Leicester; these tests have provided initial estimates for the efficiency of the systems. Both the RHU and RTG architectures are currently undergoing a new design iteration process. This paper reports on the overall architecture and design of the Am-fueled RTG and RHU, the modelling results and the experimental data obtained so far.
Radioisotope thermoelectric generators (RTG) and heater units (RHU) systems are being developed in Europe as part of a European Space Agency (ESA) funded program. Aimed at enabling or significantly ...enhancing space science and exploration missions, these systems rely on the cost-effective production of americium-241 for the fuel. The use of an iterative approach and the application of lean methodologies for the development these systems have been the focus of this technology program. Isotope containment architectures and, in the case of RTG systems, bismuth telluride based thermoelectric generators are under development. At the small end of the scale, the RHU configuration is based on a 3 W thermal power output. The first version of this system has been designed and analysed. Electrically-heated and mechanical models have been produced and tested. The RTG heat source configuration is designed to deliver 200 W of thermal power output while minimizing the volume occupied by the fuel. A 5% total system conversion efficiency and a modular scalable design imply that electrical power output can range between 10 W and 50 W. Each RTG system could house up to 5 heat sources. An electrically-heated RTG system based on the 200 W heat source architecture has been designed, analysed and tested. The advancement in the design of the heat source for both RTGs and RHUs is currently the focus of the programme with the aim of advancing the technology readiness level of the containment structures. The most recent results of the programme will be presented.
Most of the visible universe is in the highly ionised plasma state, and most of that plasma is collision-free. Three physical phenomena are responsible for nearly all of the processes that accelerate ...particles, transport material and energy, and mediate flows in systems as diverse as radio galaxy jets and supernovae explosions through to solar flares and planetary magnetospheres. These processes in turn result from the coupling amongst phenomena at macroscopic fluid scales, smaller ion scales, and down to electron scales. Cross-Scale, in concert with its sister mission SCOPE (to be provided by the Japan Aerospace Exploration Agency—JAXA), is dedicated to quantifying that nonlinear, time-varying coupling via the simultaneous in-situ observations of space plasmas performed by a fleet of 12 spacecraft in near-Earth orbit. Cross-Scale has been selected for the Assessment Phase of Cosmic Vision by the European Space Agency.
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