Introducing multi-layer insulation:

Multi-layer insulation (MLI) is a type of thermal insulation commonly used in spacecraft and other applications where it is necessary to maintain a stable temperature within a structure.

MLI blankets consist of:
• Alternating layers of highly reflecting material. • Low conductivity spacer material or insulator.

In Simcenter 3D Space Systems Thermal, you can model multi layer insulation or MLI in different ways.

Modeling MLI layer explicitly:

To model each layer explicitly, you:
•Create top and bottom facesheetsof a honeycomb panel as separate 2D thin shells.
•Create a null shell for MLI with defined top and bottom thermo-optical properties.
•Define Thermal Couplingbetween 2D thin shells.
•Define Thermal Coupling-Radiationbetween the top facesheet and MLI using the specified effective emissivity.

Pros
•MLI and facesheets are explicitly modeled and are
available in post-processing.

Cons
:•A separate sheet for MLI needs to be created.
•An additional thermal coupling between MLI and 2D
thin shell needs to be defined.

Modeling MLI using two-layer shells

To model MLI using two-layer shells, you:
• Create top and bottom facesheets as separate 2D thin shells.
• For the top 2D thin shell, use the Create Top and Bottom as Two-Layer Shells option to create a thermal resistance between the top and bottom of the shell element.
• Reverse the top 2D thin shell element normals to point inside the panel.
• Define Thermal Coupling between 2D thin shells.

Pros:
• No need to create additional shells or layers.

Cons:
• Verify the element normals.
• Display results on bottom location, or on top and bottom locations with Backface Culling.

Modeling MLI using multi-layer shell

To model MLI using multi-layer shell, you:
• Create Multi-Layer Shell Non-Uniform for part or all of stack.
• Use the Coupling to Layer above option to specify the coupling magnitude. Optionally, you can create a
thermal coupling separately.

Pros:
• All layers are defined in a single shell.
• Can capture full stack or just top facesheet and MLI.

Cons:
• All layers, including MLI thickness and null material properties need to be defined.
• In post processing, you can view layer going from bottom (Ply 1) to top (Ply N).

Modeling MLI using effective thermo-optical properties

To model MLI using thermo-optical properties, you:
• Create top and bottom facesheets as separate 2D thin shells.
• Define thermo-optical properties, such as emissivity and absorptivity, for MLI on the top facesheet.
• Define Thermal Coupling between 2D thin shells.

Pros:
• No need to create additional shells or layers.

Cons:
• Need to compute effective properties.
• Shows less accurate results.