1 LHP as strategic thermal control element for space and planetary missions By Alejandro TORRES 1) , Donatas MISHKINIS 1) and Tarik KAYA 2) 1) IberEspacio, Madrid, Spain 2) Carleton University, Ottawa, Canada Most of the components and subsystems of a spacecraft must operate in restricted temperature ranges. This makes thermal control a key matter in the design and operation of a spacecraft with a significant mass, power and cost impact in the overall spacecraft budgets. Spacecraft thermal control relies on the global spacecraft thermal balance: the heat loads must be rejected to deep space acting as thermal sink via thermal radiation through dedicated radiators installed on the satellite external surfaces. Large satellites must reject important heat loads through external radiators. The available area for these radiators is limited mainly due to limitations on the launchers dynamic envelope. Most of the dissipative equipment is installed on these radiators, so the density of equipment, and therefore power dissipation is increasing importantly. Added, there is other difficulty, namely to provide proper thermal conditions to even power dissipations and design temperature ranges. The paper presents a review of thermal architectures to provide design solutions to nowadays challenging requirements. An example of these new thermal architectures is the satellite thermal modular platform. A numerical model is presented and the results for two typical orbit scenarios are provided. Key Words: Spacecraft thermal control, Loop heat pipe, Thermal architectures. Nomenclature CCHP : Constant Conductance Heat Pipe CDL : Capillary Driven Loop CPL : Capillary Pumped Loop DHP : Diode Heat Pipe EO : Earth Observation GEO : Geosynchronous Earth Orbit HEM : Homogeneous Equilibrium Model HP : Heat Pipe Ka : K-above Ku : Kurz-unten (directly below microwave K-band) LEO : Low Earth Orbit LHP : Loop Heat Pipe MEO : Medium Earth Orbit MLI : Multi-Layer Insulation MPDL : Mechanically Pump Driven Loop OMUX : Output Multiplexer PRV : Pressure Regulating Valve SMTP : Spacecraft Modular Thermal Platform TPL : Two-Phase Loop VCHP : Variable Conductance Heat Pipe 1. Introduction The ever-increasing level of power, integration and complexity induced by new technologies characterizes the natural evolution of on-board equipments, antennas and sub-systems. Traditional thermal control techniques are reaching the limit of their potential. To accept the future challenge in term of performance and reliability, new architectures based on high performance heat transfer devices must be developed. The integration of such technologies within equipments, antennas or sub-systems could provide very efficient solutions for the next generation of products. The following types of Technologies to overcome the challenge are Two-Phase Heat Transport Systems. To structure the technology the following classification can be established: - Heat Pipes (HPs) - Constant Conductance Heat Pipes (CCHPs) - Variable Conductance Heat Pipes (VCHPs) - Heat Pipe Diodes (HPDs) - Two-Phase Loops (TPLs) - Capillary Driven Loops (CDLs) o Loop Heat Pipes (LHPs) o Variable Conductance LHP (VCLHP) o Capillary Pumped Loops (CPLs) - Mechanical Pump Driven Loops (MPDLs) 2. Thermal Control Technologies Survey. Besides the ability to easily dump the effects of the harsh environment on the design temperatures of the electronics, the thermal designer faces other challenging issues, having its origin in the telecommunication satellites and it is mainly due to two reasons. On one side, to increase the number of transponders per satellite to make more profitable each