Appendix F: Concept Generation/Prototype for Integration/TVAC Jig (Jin Guang)

Concept Generation

Concept Design for Jig

Current approaches by CubeSat manufacturers primarily utilise rotating jigs and base plates with removable stands. Although there are several commercial MGSE options available, these solutions typically cost several thousand dollars each.

Rotating Jig

Fig. F-1 Rotating Jig Designs: Vertical (Source: Canadian Metal Working) and Horizontal (Source: EnduroSat)

Rotating jigs feature a circular base on a turntable (horizontal/vertical) with fixtures to hold the CubeSat, allowing easy access to all faces during CubeSat integration. However, they are complex/costly to manufacture, heavier (e.g., EnduroSat Rotary Jig weighs 8.5 kg, costs 7700 USD), require bearings, and require locking mechanisms to prevent unwanted rotation.

Base plate with Removable Stands

Fig. F-2 Base Plate with Removable Stands (Source: ISISpace)

These jigs feature an aluminum base with removable plastic/rubber stands, potentially allowing flexibility in CubeSat orientations. Without bearings or a turntable, they are simpler to manufacture, lighter, and more portable. Although there is no rotating turntable, as the CubeSat and Jig assembly is rather lightweight, it can be manually repositioned for access during integration and testing.

Table F-3 Decision Matrix
Base Plate with Removable Stands is selected as it is more lightweight/portable and less complex to manufacture. Fewer moving parts reduces points of failure and need for maintenance (such as lubrication of bearings).

Material Selection

Aluminium 6061, commonly available within NUS, is considered a suitable material for the base plate due to its sufficient mechanical strength and low outgassing properties.

However, parts in contact with the CubeSat (such as the stands/fixtures) need to additionally be ESD safe and ideally made of plastic to prevent damage to Galassia-5’s frame. The Jig must be temperature capable between –15°C to +55°C. This is derived from Simera Monoscope operating temperature, which has strictest operational limits of –10°C to +50°C. In accordance with ECSS‐E‐ST‐10‐03C, a qualification margin of 5°C is applied at both ends of the temperature range (ECSS, 2022).

According to ECSS‐Q‐ST‐70‐02C (ECSS, 2008), the following must be met to ensure low outgassing:

• RML <1.0%
• CVCM <0.10 %

A TML of below 1.0% is preferred, though this can be ignored under certain circumstances.

Some plastics were evaluated below:

Table F-4 Decision Matrix

ESD POM was ruled out as its TML is above 1%. While PEKK has better performance overall, the cost is 8 times that of ESD-ABS, which also fulfils all the requirements. Hence, ESD-ABS was chosen.

Two main manufacturing options are considered for the manufacturing of the plastic components: CNC machining and 3D printing. While both methods are viable, the in-house 3D printing of ESD‐safe plastics is not practical. ESD plastics typically contain carbon black or carbon nanotubes, which can release VOCs and fine particulates during the printing process. Printing these materials requires an isolated printing environment equipped with thorough filtration/ventilation systems for occupational safety and OSHA compliance. Thus, if 3D printing is chosen, this must be outsourced to qualified external vendors with proper control measures.

Detailed Design

Several designs were developed to optimise the jig for supporting the CubeSat.

First Iteration

The design consists of an Aluminum 6061 base plate of dimensions 400 x 260 x 100 mm. This allows enough space for the stands to be mounted, such that all 3 orientations (X/Y/ Z) of G5 can be supported.
Fig. F-5 Base Plate Version 1. The Red, Magenta and Green lines denotes the CubeSat position for each orientation.

Two types of stands are mounted to the base plate from underneath using countersunk M5 screws, to accommodate different orientations of Galassia-5:

• Corner towers (Vertical Orientation) – vertical ESD-ABS posts that interfaces with CubeSat rails at all 4 corners of the CubeSat, holding Galassia-5 in vertical orientation.
• Rail Blocks (Horizontal Orientation) – low-profile ESD-ABS blocks that interfaces with CubeSat rails. The Rail Blocks are spaced sufficiently far apart for the CubeSat rails at either edge of the CubeSat to fit snugly into the gap, holding Galassia-5 in horizontal orientation.

The stands are raised to allow a 50 mm clearance beneath the CubeSat for access to bottom components.

Fig. F-6 Corner Tower (Left) and Rail Block (Right)

To validate the concept, a 3D-printed prototype was fabricated. A fit test was conducted using a 3D-printed mock-up of Galassia-5, and it was verified that the CubeSat fit properly in both the horizontal and vertical orientations onto the stands on the jig.

Fig. F-7 Assembled Iteration 1 Jig with Galassia-5 3D-printed mockup (here shown in Vertical Orientation)

From the first prototype, some problems were observed:

• Based on CAD data, the total mass of the jig (if produced using the actual materials) would be close to 4kg (approx. 13kg with G5), which was deemed too heavy for portability.
• During installation, there was difficulty aligning the screw holes on the stand with those on the base plate.
• There is a possibility of the CubeSat Sliding/Toppling when being transported in the Horizontal Orientation.

Second Iteration

To reduce the weight of the Jig assembly, material was removed from the base plate by cutting out holes. This brought the final mass of the aluminium base plate down to 1.8 kg, a reduction of around 40% compared to the original.

Table F-8 Comparison of Overall Mass between First and Second Iterations

To facilitate precise alignment during assembly, 2 mm deep recesses matching the dimensions of the stands were machined into the base plate. This ensured that the screw holes would align accurately when the stands were placed into position. In accordance with Design for Manufacturing principles, T-bone fillets were incorporated into the recesses to provide suitable toolpaths for the milling cutter, ensuring machinability.

Fig. F-9 Base Plate Version 2. Note the holes cut and 2mm deep recesses.

To ensure that the holes cut would not affect the structural integrity of the Base Plate when subject to loads from G5, FEA was conducted. A total load of 180N (twice the intended load) was applied with both ends of the plate fixed, and a maximum stress of 5.27 *10^6 N/m^2 was recorded. This is far below yield stress of Al6061 (2.76*10^8 N/m^2).

Fig. F-10 FEA Screenshot (Shown here: Configuration with highest recorded stress). Other FEA Tests can be found in [Appendix B](/final-report/appendix-b)

To prevent the CubeSat from toppling/sliding off the rail blocks during transport, endblocks were designed, to be installed onto the ends of the rail blocks using M3 screws.

Fig. F-11 Endblock and hole interfaces on rail block

Fig. F-12 CAD Render of Galassia-5 in Horizontal Orientation on the Jig with Endblocks installed

4.4.3 Analysis of Proposed Jig Design

The proposed jig design demonstrates several unique features:

• Its modular design supports all 3 orientations of Galassia-5, providing flexibility during integration and testing.
• The jig is also Lightweight compared to other similar Jigs on the market, weighing only 2.6 kg compared to Endurosat’s 3.5 kg (EnduroSat, n.d.).
• The design supports testing of deployable components by providing sufficient clearance around critical areas.
• The Jig utilises materials with low outgassing properties, making it suitable for use in TVAC, eliminating the need for another Jig solely designed for TVAC use.
• The endblock allows G5 to be securely fastened during transport, preventing toppling or sliding.

Pictures of the assembled prototype are shown below.

CAD Renders

Fig. F-13 CAD Render of Jig (Iteration 2). Orientation: 2U/Z Face facing down

Fig. F-14 CAD Render of Jig (Iteration 2). Orientation: 3U/X Face facing down. The Endblocks are also shown in this CAD Render.

Fig. F-15 CAD Render of Jig (Iteration 2). Orientation: 6U/Y Face facing down

Images of Prototype

Fig. F-16 Assembled prototype from Laser-Cut Acrylic and 3D-printed PLA (Left: With Endblocks installed, Right: Without Endblocks)