Mathematical model validation of a thermal architecture system connecting east/west radiators by flight data Alejandro Torres a, * , Donatas Mishkinis a , Tarik Kaya b a IberEspacio, Madrid, Spain b Carleton University, Ottawa, Canada highlights  A novel spacecraft thermal control architecture is presented.  The eastewest radiators of a GEO communications satellite are connected using LHPs.  A transient mathematical model is validated with flight data.  The space flight data proved successful in-orbit operation of the novel architecture.  The model can be used to design/analyze LHP based complex thermal architectures. article info Article history: Received 9 August 2013 Accepted 23 January 2014 Available online 7 February 2014 Keywords: Spacecraft thermal control Heat pipes Loop heat pipes abstract A novel satellite thermal architecture connecting the east and west radiators of a geostationary tele- communication satellite via loop heat pipes (LHPs) is flight tested on board the satellite Hispasat 1E. The LHP operating temperature is regulated by using pressure regulating valves (PRVs). The flight data demonstrated the successful operation of the proposed concept. A transient numerical model specifically developed for the design of this system satisfactorily simulated the flight data. The validated mathe- matical model can be used to design and analyze the thermal behavior of more complex architectures. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction With the increasing power levels of the modern telecommuni- cations satellites, innovative thermal control methods are needed to remove the excess power. Currently, one of the biggest limita- tions of the satellite thermal control is the available radiator area due to the constraints on the dynamic envelope of the launchers. A novel spacecraft thermal control architecture connecting the east/west radiators is presented in this paper. In this architecture, the radiators are connected by loop heat pipes (LHPs) and the LHP operating temperature is regulated by using pressure regulating valves (PRVs). There are several advantages when using an LHP with PRV instead of a regular heat pipe (HP): 1. System accommodation: The HP length, number of bends and shape (i.e. 2D or 3D) limit system accommodation. The regular HP used in telecommunication satellites are typically non- flexible and its stiffness can be an important issue for certain equipment, for example Low Noise Amplifiers (LNA). LHP does not have this limitation since transport line routing can be very complex as the lines are flexible. 2. On-ground testability: Depending of the HP orientation and satellite ground test position with respect to gravity vector, some pipes can be either working in reflux mode or not working (evaporator above condenser). However, the LHP will work against gravity, so limitations are minimum. 3. Payload equipment temperature control and satellite power consumption saving: The diode effect of the LHP prevents overheating of payload equipment when a radiator is sun illu- minated. In the cases where the radiator is not sun illuminated, the PRV closes the fluid path to the radiator preventing payload equipment temperature to fall beyond minimum qualification temperatures. Therefore, no compensation heaters are needed and an important satellite power saving is achieved. 4. Power transport capability: The LHP can handle larger heat loads than heat pipes. 5. Radiator size and mass reduction: The LHP allows the use of a direct condensation condenser (condenser embedded into the * Corresponding author. E-mail address: ato@iberespacio.es (A. Torres). Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng http://dx.doi.org/10.1016/j.applthermaleng.2014.01.050 1359-4311/Ó 2014 Elsevier Ltd. All rights reserved. Applied Thermal Engineering 66 (2014) 1e14