Set up a CubeSat thermal analysis from start to finish

This is an objective-based exercise. Instead of being provided a list of instructions, you are simply provided a scenario and problem statement to solve.

You will learn how to set up a CubeSat thermal analysis from start to finish in Simcenter 3D Space Systems Thermal. You will mesh the CAD geometry, assign materials and thermo-optical properties, and define boundary conditions for both conduction and radiation.

If you encounter difficulties while following the steps, refer to the Answer video: Set up a CubeSat thermal analysis from start to finish.

Download and extract the part files.

Scenario:

You are a thermal engineer working on a 3U Earth observation CubeSat mission in low Earth orbit at an altitude of 400 km.

You are provided with a CAD model of a 3U CubeSat that includes the following components:
  • Antennas (1) for communication with the ground.
  • Reaction wheels (2) that provide precise attitude control.
  • Solar panels (3) mounted on four sides, each containing seven panels that generate electrical power.
  • Sun sensors (4) that measure the Sun’s direction to determine the spacecraft’s attitude.
  • GPS antenna (5) to determine the satellite position in orbit.
  • Printed circuit boards (PCBs) (6) that host the spacecraft’s electronics and dissipate heat.
  • Batteries (7) that store electrical power for spacecraft operation.
  • Magnetorquer (8) that control attitude using Earth's magnetic field.
  • Observation camera (9) that captures images of the Earth.

Cutaway view of a 3U CubeSat with labeled components such as solar panels, antennas, sun sensors, GPS antenna, PCBs, batteries, attitude control devices, and a camera.

The spacecraft operates in low Earth orbit, where it is exposed to solar radiation, reflected radiation from Earth (albedo), Earth infrared radiation, and deep space cooling. At the same time, internal components generate heat that must be properly dissipated.

The mission team must ensure that all critical components operate within their allowable temperature limits throughout the orbit:

  • Battery: 5 °C to 25 °C
  • Payload (camera): −10 °C to 25 °C
  • Solar cells: −50 °C to 100 °C

Objectives:

You must determine whether the CubeSat design maintains all critical components within their allowable temperature ranges under realistic orbital conditions.

To complete the analysis, you will:

  • Create and use a custom FEM template with predefined material and thermo-optical properties.
  • Generate FEM models for all major components.
  • Mesh components using different techniques such as 3D, 2D, or simplified representations, depending on geometry complexity and required thermal accuracy.
  • Assign appropriate material and thermo-optical properties to each component.
  • Simplify selected components using idealized geometry by removing features that do not significantly affect the thermal results but increase the element count.
  • Assemble the full model and define thermal contacts between components.
  • Apply orbital heating conditions.
  • Define space radiation to a deep space environment at 4 K.
  • Apply internal heat loads from electronics and batteries.
  • Run a transient solution.
  • Post-process results to evaluate temperature distribution and heat flux.
  • Compare the predicted temperatures against allowable limits to determine whether the design meets thermal requirements.

Instructions:

Create a custom template

Create and add a custom template to the .pax file. You will update this file to add an entry that points to your custom FEM template. This template allows reuse of predefined material and thermo-optical properties across FEM files.

Template files store the analysis settings and FE modeling definitions used to create a new FEM or Simulation file. The .pax file is an XML file that lists the FEM and Simulation templates that the software loads automatically when you create a new part file from a template.

  1. From cube_sat/Template, open the SST_CustomTemplate.fem file and review the predefined material and thermo-optical properties.
  2. Copy SST_CustomTemplate.fem to the Simcenter 3D_installation/SIMULATION/templates directory.
  3. Copy an existing FEM template entry.
  4. Update the <Filename> value to point to SST_CustomTemplate.fem and the <Presentation> name to SST‑Custom Template.
    XML snippet defining a custom FEM template in Simcenter 3D Space Systems Thermal.

    Alternatively, you can redirect the default template directory to your current working folder to avoid modifying the default templates. To do this, set the UGII_TEMPLATE_DIR variable environment to the working folder. For more information, see the Automate meshing with selection recipes and template files tutorial.

  5. Restart Simcenter 3D.

Generate FEM models

Generate FEM models only for the major components. Ignore the remaining components in the thermal analysis because they do not affect the results.
  1. From the cube_sat folder, open Maya_3U_CubeSat.prt and review the assembly.
  2. Switch to the Pre/Post application.
  3. Create a new assembly FEM Maya_3U_CubeSat_assyfem1.afm in the Simcenter 3D Space System Thermal environment.
  4. In the Simulation Navigator, under Maya_3U_CubeSat.prt, observe that all components appear with the status Ignored because you have not yet added them to the assembly FEM.
  5. Before creating FEM files, unpack Side.prt x4, Solar_Panel.prt x28, PCB.prt x4, Wheel.prt x3and End_Plate.prt x3 so that each component appears as an individual node in the assembly tree.
    This allows each component to map to its own FEM.
  6. Create a separate FEM file for each major component listed in the table by using the Map New right-click command with the SST- Custom Template. Associate each part file with a new FEM as specified in the table.
    Do not create idealized parts for any components, except the Rail.prt. For the rail, you will simplify the model in the idealized part before meshing.
    Component Associated CAD part FEM file
    Side.prt (4) Side Side_fem1.fem
    Solar_Panel.prt (28)
    Note:
    Set Polygon Body Resolution to High.
    		 Solar_Panel Solar_Panel_fem1.fem
    Bottom_Plate.prt Bottom_Plate Bottom_Plate_fem1.fem
    PCB.prt (4) PCB PCB_fem1.fem
    End_Plate.prt (3) End_Plate End_Plate_fem1.fem
    Rail.prt
    Note:
    Select the Create Idealized Part check box
    		 Rail Rail_fem1.fem
    Battery.prt Battery Battery_fem1.fem
    Camera.prt Camera Camera_fem1.fem
    Wheel.prt (3) Wheel Wheel_fem1.fem
  7. For parts with multiple instances, after creating the FEM for one instance, find all matching components and automatically map them to the associated FEM models.

Mesh the parts

Mesh components using appropriate techniques depending on the component level of detail and its impact on the thermal results.
  • Use 3D meshes for thermally critical or volumetric components, for example, battery and structure.
  • Use 2D shell meshes for thin structures.
  • Use idealized geometry or primitives for simplified representations.
  1. For each FEM file listed in the table, create a 3D Swept Mesh with a 10 mm element size. Apply the material and thermo-optical properties specified in the following table.

    When you create Solar_Panel_fem1.fem, set Polygon Body Resolution to High.

    FEM Material properties Advanced Thermo-Optical properties
    Side_fem1.fem Create a new aluminum material with mass density of 2700 kg/m3, a thermal conductivity of 157 W/(m·K), and a specific heat of 929 J/(kg·K). Create a new thermo-optical property with emissivity and absorptivity set to 0.88.
    Solar_Panel_fem1.fem
    Note:
    Set % of Element Size to 0.
    		 PCB (generic) Solar Cells
    Bottom_Plate_fem1.fem Aluminum Bare Aluminum
    PCB_fem1.fem
    Note:
    Mesh the board only; do not mesh components.


    		 PCB (generic) PCB
    End_Plate_fem1.fem Aluminum White Paint - States
  2. Notice that the top End_Plate includes the GPS antenna. For simplicity, assign different thermo-optical properties to the region instead of creating a separate mesh.
    • Open the End_Plate_fem1.fem file.
    • Create a Surface Coat 2D mesh on the GPS antenna region using QUAD 4 Thin Shell elements.
    • Assign this mesh to the Null Shell mesh collector. There is no conduction and heat capacity.
    • In Thermo - Optical Properties, set Radiation to Top and select Black Paint.
  3. Use a more detailed 3D mesh for the battery since it is a thermally critical component because its temperature must stay within a narrow range and directly impacts mission safety. Create a 3D Swept Mesh with a 10 mm element size as shown in the table:
    Category PCBs Cells Connector Spacers
    Selection
    Properties Material: PCB (generic)

    Thermo-optical properties: PCB

    		 Material: Invar

    Thermo-optical properties: PCB

    		 Material: PCB (generic)

    Thermo-optical properties: Black Paint

    		 Material: Stainless Steel

    Thermo-optical properties: Bare SS
  4. For camera, use mixed meshing 3D and 2D shell to balance accuracy and performance as shown in the table:
    Category Board Spacers Camera Box
    Selection







    Properties 3D Swept Mesh with a 10 mm element size.

    Material: PCB (generic)

    Thermo-optical properties: PCB

    		 3D Swept Mesh with a 10 mm element size.

    Material: Stainless Steel

    Thermo-optical properties: Bare SS

    		 3D Hex Dominant Mesh with a 10 mm element size.

    Material: Aluminum

    Thermo-optical properties: Iridite

    		 2D Mesh QUAD 4 Thin Shell with 10 mm.

    Set Thickness is 2 mm

    Material: Aluminum

    Thermo-optical porperties: Top is set to Black Paint, Bottom is set to Bare Aluminum
  5. For parts where only mass representation is required and geometric detail is not needed, use primitives instead of meshing the full geometry. In Wheel.prt, create a primitive using the Extrude command. To do this:
    • Select the indicated face and extrude a box sized to preserve approximately the same radiating surface area.

    • Create a new FEM file, set Bodies to Use to Select and choose only the box.

    Alternatively, you can create a new FEM file for Wheel.prt and represent it as a box using Menu > Insert > Primitive > Box.

  6. Mesh the created box using a 2D Mesh with QUAD 4 Thin Shell elements and a 10 mm element size. Assign Aluminum as the material, set the Thickness to 2 mm, and in Thermo-Optical Properties, assign Black Paint to the top radiation, assuming internal radiation is not required.
    Note:
    To verify the top and bottom sides, right-click the mesh node and select Check > Element Normals. Arrows pointing outward indicate the top side.
  7. Associate all wheel components with their wheel_fem1.fem using the Map Existing command.
  8. For the rail, you created an idealized part so you can remove small geometric features that do not significantly affect thermal behavior but increase element count. Open and promote the idealized Rail_fem1_i.prt part.
    Working in the idealized part lets you modify the geometry without changing the original CAD model.
  9. Remove unnecessary details, such as small chamfers and faces on both sides of the rail using Delete as shown:

    7 faces selected

    2 faces selected

    32 faces selected
  10. Use the Replace command to remove the faces on the ends of the rail, as shown.


  11. Mesh the rail using a 3D Hex Dominant Mesh with a 10 mm element size. This method is used because the geometry is not suitable for swept meshing. Assign Aluminum as a material, and set Thermo-Optical Properties to Silver Teflon - States.
    The model is now meshed. Use Model Display Preferences to display the mesh based on thermo-optical properties visually verify that all meshed components have assigned properties.
  12. Return to the assembly model and verify that all components are associated with their FEM files.

Simulation setup

  1. Create a Simulation file using the Simcenter 3D Space System Thermal environment.
  2. Create a transient solution and define the following settings:
    • Set the run directory to Solution Name.
    • Set the parallel processing parameters to reduce solve time. In the Parallel Configuration Tool, select the GPU to use for radiation calculations.
    • Set the solution units to meters.
    • Set the space environment temperature to 4 K.
  3. Define orbital heating to apply solar flux, albedo, and Earth IR using the Orbital Heating simulation object with the following settings:
    • The Illuminate Selected Elements type.
    • For Top Side Illuminated Region, select the following 54 external faces that receive the sun light. You can ignore small faces for this tutorial.

    • GPU Computed Ray Tracing calculation method.
    • Number of rays is 15000.
  4. Define the classical Orbit using the following settings:
    • For the spacecraft orientation, set the first vector point toward Nadir, since the camera faces the Earth, and align the second vector with the X velocity vector, as shown.

    • The CubeSat rotates about its own axis. Specify the indicated vector (1) and point (2), and set the rotation to 360° over one orbit.

    • For the Sun planet characteristics, compute the solar flux for the December solstice Sun position and specify the solar flux in W/m2.
    • For the orbit parameters, specify:
      Minimum altitude: 400 km Orbit inclination: 25°
    • Set 12 intervals to calculate the satellite positions along the orbit. Increasing the number of intervals increases the solution time.
  5. Visualize the orbit using the Orbit Visualizer command.
  6. If a label conflict message appears, resolve it automatically as follows:
    • In the assembly file, right-click and select Assembly Checks > Assembly Label Manager.
    • In the Simulation file, right-click and select Simulation Label Manager.
  7. Define space radiation using the All Radiation type with the GPU Computed View Factor calculation method, and include the radiative environment in the definition.
  8. Define thermal contacts using Surface-to-Surface Contact with automatic face pairing. To do this:
    • Select the entire polygon body, creating 156 face pairs.
    • Activate thermal coupling and specify conduction with a heat transfer coefficient of 600 W/m2°C.

    The solver automatically identifies faces within the specified tolerance and creates corresponding face pairs.

    Alternatively, you can manually create thermal contacts using Thermal Coupling.

  9. To keep the model organized, create a folder named Contacts, and drug and drop all created face contacts into it.
  10. Apply heat loads using Thermal Loads on the following components:
    • 1 W on the first PCB board and 2W on the second PCB board.

    • 3 W on the battery cells.

  11. Edit and set up a transient solution using the following parameters:
    • Set the solution end time based on the orbit period.
    • Enable periodic convergence and instruct the solver to stop the solution when the temperature change between orbits is less than 1 °C.

      The solver compares the temperatures at the start and end of the orbit. If the difference is within the specified tolerance, it stops the solution.



    • Use a constant time step of 60 s.
    • Request 20 results per orbit and save results for the last orbit only.
  12. Solve a solution.

    You may encounter an error indicating that some contacts between bodies are not fully meshed. You can either return and mesh the entire model or remove these contacts. For this tutorial, ignore the error.

    To proceed, clear the Model Setup Check option and run the analysis again.

    The solution runs for approximately 20 minutes.

Review results

  1. Display the solar flux, albedo, and Earth IR results.
  2. Display the temperatures for battery, and compare the temperatures against allowable limits to determine whether the design meets thermal requirements.

    The temperature range is 28–49 °C, which falls outside the allowable range of 5–25 °C. The design does not meet thermal requirements and requires modification, such as adding heaters or changing material properties.

  3. Display the battery temperatures for the last orbit and plot the graph across iterations.
  4. Display the temperatures for solar cells and camera and determine whether they remain within the allowable limits.