CubeSat Design

✓ Thermal analysis using ANSYS lead to the conclusion that a heat shield was required.

✓ A heat shield was designed, manufactured and integrated in a clean room.

✓ Vibration study showed that the CubeSat lower frequency participation factors are negligible and that the satellite is safe for launch.

✓ A complex CAD model was simplified and tailored for each type of analysis.

Vector Launch commissioned the Space Engineering Research Center with designing a CubeSat for their GalacticSky payload. The CubeSat bus is a MISC-2 and will uses flower petal configuration for primary solar array power. This satellite was designed to have the Sun shine directly on the solar panels throughout the Sun-synchronous orbit. I was in charge of the thermal design and analysis as well as the vibration analysis.

Pictures: (1) Steady-state analysis results with a reflective heat shield – the only place to install the heat shield was around the Sun Sensor (see green area). (2) Kapton

cutouts to perform a fit check and develop the manufacturing process (3) An Aluminum manufacturing plate was used to streamline the manufacturing process

1. THERMAL ANALYSIS & DESIGN

To make the analysis possible with a low-end computer, I simplified the CubeSat CAD by removing electronic connectors and defeaturing the electronic boards.

An adaptive meshing was selected as the default meshing. Thin bodies were meshed using uniform edge sizing to make sure there where more than one element through the thin axis.

Surfaces were defined to radiate and conduct heat. The batteries and other electronics were assigned volumetric heat generation according to the system engineer’s data. The thermal model was subjected to heat flux from different directions to check of any potential issues.

Analysis showed a high temperature area near the Sun-Sensor. Adding a reflective heat radiation to the model showed a 20-degree temperature reduction.

Design process:

I obtained the Sun Sensor CAD model from the general CubeSat model and 3D printed a low-density full-scale model in PLA. I sketched SolidWorks the first iteration of the heat shield dimensions and printed them on paper. This paper template was cut to resemble the heat shield and placed on top of the engineering adaptor plate that the real Sun sensor will be mounted on. The paper plate was used to cut out Kapton sheets with thicknesses similar to the Mylar and Aluminum materials in stock. Using an empirical formula from a cryogenic textbook, I concluded that 3 layers would be able to reduce the temperature by 20 degrees Celsius.

CubeSat

DESIGN

PROCESS

(1) Manufacturing

of one of two heat shields. Each MLI has 3 layers made up of Mylar and Aluminum

(2) The first heat shield weighs 2.5 grams. The 4 flaps in the perimeter have a dual role: 1) Mechanically attach the shield to the chassis and 2) Provide grounding

(3) Testing the shield for conductivity

(4) The CubeSat after final integration. The heat shield can be seen at the bottom of the CubeSat

2. VIBRATION ANALYSIS

The CAD model for the vibration model is different from the thermal model.

The vibration model is in a stowed configuration (the solar panels are stowed). Because the vibration study has to do with the stiffness and mass distribution across the assembly, a different approach was taken here. The internal electronics, which provide a key role in the thermal analysis, have a negligible structural impact. Their mass is what affects the vibrations simulation. Therefore, I chose to remove all the electronics and replace them with 3 point masses (image to the right).

The key thing from the vibration analysis results was that the participation mass factor for the low frequency modes, which are the most dangerous to the launcher and spacecraft, are negligible.

Pictures: (1) Point masses replaced the electronics in the payload, Attitude Determination and Control System (ADACS), and bus. (2) Mode 4, the first mode with a non-negligible participation factor. Notice the bottom area’s deformation