Thermica and Thermisol

The Thermica application globally transforms the geometric model into a mathematical model and performs a complete thermal analysis of a space system orbiting around a planet or along an interplanetary trajectory. On this thermal model, Thermica computes all the elements needed to simulate the temperature. The temperature computation is then performed by a thermal solver which may be Thermisol, the solver of Thermica, or MSC SINDA. The description of the simulation transmitted to the temperature solver is based on a nodal description.

Here, the thermal analysis no longer requires any geometry. The main functions of Thermica are as follows:

• Geometry modeling and physical properties & meshing
• Mission modeling: orbit & pointing
• Physical simulation: radiative & conductive couplings, solar & planet fluxes, convection
• Translation of the geometrical problem to a nodal network problem

Thermica integrates a radiative exchange factors computation module based on an multi-threaded ray-tracing algorithm. It computes geometric view factors, extended view factors and radiative exchange factors, allowing to handle realistic thermo-optical properties in the UV and IR bands:

• Absorptivity / emissivity
• Specular / diffuse reflection
• Specular / diffuse transmission
• Refractive index
• Management of properties depending of the incidence
• Possibility to define wavelength dependent properties to handle non-grey bodies

Thermica allows for accurate contributions from the Sun and Planets contribution to flux budget:

• Solar fluxes computed as function of the position of the Sun with an efficient ray-tracing algorithm, using the same thermo-optical properties as for radiative exchange factors computation. The Sun can be considered at infinite distance or at finite distance

• Planet fluxes computation are done both in the IR and the UV spectrum (for albedo fluxes). These are computed from the radiative exchange factors. The IR emission is computed as either a black body emission, both uniform or non-uniform, and the Albedo with an albedo coefficient, either uniform or non uniform

Thermica accounts for conduction effects with two computational methods:

• The simplify RCN method, a first order method that suppresses edges and exports an easier node-to-node couplings topology for standard cases

• The RCN method, a second order method based on a quadratic temperature profile into each node that creates a new edge data-structure related to thermal nodes. It integrates Fourier's law on node's edges to determine the incoming and outcoming conductive fluxes.  This approach is compatible with the finite volume approach.

Thermica integrates a powerful temperature solver, Thermisol.

Thermisol computes temperature solutions automatically set from the Thermica following outputs: a nodal description, complementary items, couplings and fluxes, which combine in a detailed Thermal model without any limitation in terms of complexity.

Thermal models can be easily enriched thanks to a very accessible thermal modelling language (Mortran) and a powerful user library. This allows then for a fast, robust and smart temperature solver that offers both steady-state and transient analysis.