Hang Jin Guang

Hang Jin Guang

Year 4 Mechanical Engineering

A0254475X

4. Mechanical Ground Support Equipment

4.1 Scope of Project

4.1.1 Problem

The development process of a CubeSat involves the following major stages:

  • Assembly and Integration;
  • Qualification and Testing (TVAC and Vibration Testing according to ECSS/Exolaunch requirements);
  • Delivery to the Launch Integrator (Exolaunch).

Specialised Mechanical Ground Support Equipment (MGSE) are required to support each process stage. Designing and fabricating the MGSE in-house ensures compatibility with Galassia-5’s custom frame/deployables, and testing/transportation requirements, which COTS options may not provide.

Fig. 4.1.1.1. CubeSat Development Timeline with corresponding MGSE required

4.1.2 Objective/Design Statement

  • Develop in-house, dedicated MGSE custom-designed for Galassia-5 that fully supports all phases of the CubeSat development process, including assembly, integration, environmental qualification, and transportation to the launch site.
  • The MGSE shall be specifically tailored to the custom frame, deployables, and testing/transportation requirements of G5, enabling safe handling of G5 from cleanroom through to launch vehicle integration.

Three MGSE were designed to support the major stages of G5’s development process:

  1. Combined Assembly/Integration and TVAC Test Jig
  2. Vibration Testing Fixture
  3. CubeSat Transport Box

4.2 Combined Assembly/Integration and TVAC Test Jig

COTS Assembly Jigs are costly (e.g., EnduroSat’s 3U Assembly Jig costs approximately $4,500 (EnduroSat, n.d.)) and involve long lead times. Additionally, the Bus Contractor (NuSpace) requires a Jig that can support all 3 orientations of G5 and accomodate its custom frame/deployables. Combining TVAC and integration functionality into a single jig eliminates the need for another TVAC testing fixture, further reducing cost and logistical complexity. Hence, a custom jig was designed in-house.

4.2.1. Design Requirements (Integration/TVAC Jig)

The Combined Assembly/Integration and TVAC Test Jig (the “Integration/TVAC Jig” or “Jig”) must fulfill the following operational requirements:

  • Dimensions/Orientation: Accommodate Galassia-5 (6U) in all 3 orientations.
  • Load Capacity: Carry Galassia-5’s full weight (~8.7kg) plus safety margin.
  • ESD Safe: Parts contacting Galassia-5 must be ESD-safe to prevent buildup and sudden discharge of static electricity, which can damage sensitive onboard electronics. ESD-safe materials ensure any charge is safely dissipated..
  • Low Outgassing: Materials must meet ECSS low-outgassing requirements (RML <1.0%, CVCM <0.1% per ECSS-Q-ST-70-02C) as the jig will be under vacuum in the TVAC chamber. Outgassing occurs when materials release trapped/volatile gases under vacuum, which can condense onto critical surfaces such as optics/sensors, possibly degrading instrument performance.
  • Portable within Cleanroom: Jig is lightweight for portability.
  • Clear Access to underside: Provide 50mm underside clearance (as requested by Bus Contractor) beneath the satellite for integration and component testing.
  • Ease of manufacture: Simple to manufacture, assemble, and cost-effective compared to market alternatives.

4.2.2. Detailed Design of Integration/TVAC Jig

Throughout the prototyping iterations, we continuously updated and improved our overall design. The final design was arrived at after three main iterations.

The Concept Generation/Material Selection process is available in Appendix F.

Fig. 4.2.2.1. Top view of Base Plate. Note the cutouts for weight reduction.

The final base plate is constructed from MIC-6 tooling plate (Fig. 4.2.2.1.), with dimensions of 420 mm x 270 mm x 12.7 mm. MIC-6 was selected because it is cast aluminium alloy with pre-processed flat surface, eliminating the need for additional post-processing or precision milling to achieve flatness.

This provides sufficient space to mount the modular stands, to support all three orientations of Galassia-5 (vertical, horizontal 3U/2U face down).

Engravings on the base plate indicate stand positions, facilitating accurate alignment during assembly.

The two types of modular stands (Fig. 4.2.2.2) are:

  • Corner Towers (Vertical Orientation): Vertical ESD-ABS posts that interface with CubeSat rails at all 4 corners of the CubeSat, holding Galassia-5 in vertical orientation.
  • Rail Holder (Horizontal Orientation): Low-profile ESD-ABS blocks that interface with the CubeSat’s side rails, spaced to hold Galassia-5 rails securely in a horizontal orientation


Fig. 4.2.2.2. Corner Tower (Left), Rail Holder (Right)

Both stand types provide 50 mm clearance beneath the CubeSat for unobstructed access to bottom components, and are secured by screws from above for easy removal/installation.

To prevent the CubeSat from toppling/sliding off the rail blocks during transport in horizontal orientation, the left-side rail holders feature integrated stoppers, and removable endstops can be installed onto the right-side rail blocks using M3 screws.

Fig. 4.2.2.3. Integrated stopper on Left Top (LT) rail holder (Left), and removable endstop mounted on right-side rail block (Right)

Aluminium handles are installed on the jig for easy transport within the cleanroom. As the handles may obstruct access to Galassia-5 from certain angles, they can be easily removed/ installed using M5 screws.

Fig. 4.2.2.4. Galassia-5 CAD Model on the jig in vertical and horizontal (3U face down) orientations.

4.2.3. Simulation and Testing (Integration/TVAC Jig)

Fig. 4.2.3.1. Static Simulation of Jig (Vertical Orientation gives largest stress value)

To ensure that weight-reduction cutouts would not compromise the structural integrity of the loaded jig, a Finite Element Analysis (FEA) was conducted under a total distributed load of 240N (twice the maximum weight of 6U CubeSat) with the handles fixed.

Peak stress of 1.65 *10^7 N/m^2 was recorded at the aluminium handles (Stress is lower at other points). This remains significantly below yield stress of Al6061 (2.76*10^8 N/m^2) and ESD-ABS (3.2x10^7 N/m^2), giving safety factors of 16.7 and 1.94 respectively. These results confirm the jig can safely support the weight of G5.

Following design finalisation, the jig was manufactured and a fit test conducted (Fig. 4.2.3.2.) using a structural model of Galassia-5. The satellite fitted successfully onto the jig with sufficient clearance for deployables.

Fig. 4.2.3.2. Assembled Jig with G5 Structural Model in all 3 orientations

4.2.4. Evaluation

Ultimately, the jig design demonstrates several unique features:

  • Its modular design supports all 3 orientations of Galassia-5, providing flexibility during integration and testing.
  • At 2.6 kg, it is lighter than comparable market alternatives such as EnduroSat’s (smaller) 3U Jig (3.5 kg).
  • Sufficient spatial clearance around critical areas supports testing of deployable components.
  • Low-outgassing materials make the jig suitable for TVAC environments, eliminating the need for a separate TVAC jig.
  • Endstops secure G5 during transport within cleanroom, preventing toppling or sliding.

4.2.5. Future Work (Integration/TVAC Jig)

Pending confirmation of the TVAC chamber to be used, the method of securing the jig (and locations of clamps) to the chamber floor will need to be determined.

4.3 Vibration Testing Fixture

During launch, CubeSats are subjected to severe dynamic loads, necessitating rigorous vibration testing. Qualification of the G5 Flight Model (FM) will be performed using the Exolaunch Nova Testpod; however, the Nova Testpod is expensive to rent and is typically only available for short periods during the final qualification phase.

This presents a challenge for preliminary testing of the G5 Engineering Model (EM). Without a dedicated test fixture, the team cannot perform iterative design validation or identify structural flaws early in the development cycle. COTS test fixtures can cost tens of thousands of dollars with long lead times. Likewise, the custom dimensions and deployables on G5 makes COTS testpods difficult to procure without modification. Hence, an in-house vibration testing fixture was therefore designed and fabricated.

4.3.1. Design Specifications (Vibration Fixture)

The Vibration Fixture (for preliminary testing of G5 EM) must fulfil the following requirements:

  • Dimensions: Accommodate the Galassia-5 EM, providing adequate clearance for X-face antennae/deployables, and Y-face solar panels (2 mm).
  • Modal Frequency: First fundamental resonance frequency above 1000 Hz (NuSpace requirement). This ensures rigid-body behaviour, i.e. the fixture transmits input loads to G5 without amplification from fixture’s resonances.
  • Transfer Function: Rigid clamping to achieve transfer function near 1.0, maximising energy transfer from the shaker table and preventing micro-slip or chatter.
  • Mass Optimization: Minimise dead mass to reduce the total mass accelerated by the shaker table and facilitate transport of fixture components.
  • Interface Compatibility: Base plate must interface with bolt patterns of shaker tables at shortlisted test facilities (currently TUV SUD and ST Satsys).
  • Test Standard Compliance: Withstand 3-axis random vibrations, meeting SpaceX rideshare PSD requirements (5.13 GRMS loading) (SpaceX, 2025).

4.3.2. Concept Generation and Prototyping (Vibration Fixture)

Two primary concepts were generated through a literature review and CAD prototypes were made and evaluated.

Concept A: Enclosed Testpod Design: Modelled after Exolaunch Nova Testpod and ESA PhiSat vibration fixture (ESA, 2020), this uses a fully enclosed aluminum box, either welded from plates or milled from a large block of stock material.

A CAD prototype of Concept A was produced and simulated. To achieve 1st modal frequency above 1000Hz, panel thicknesses of more than 20mm were required.

Fig. 4.3.2.1. CAD Prototype of Enclosed Testpod Design (Left, front panel removed to show frame inside) and ESA Phisat Test Fixture (Right) .

Fig. 4.3.2.2. Solidworks Frequency Simulation with 20mm thick panels. Modal Frequency: 998 Hz

From Mass Properties, the empty fixture weighs over 40kg. Substantial raw material is required for manufacturing, the heavy structure reduces portability, requires welding capabilities unavailable at NUS, and makes it difficult to design a clamping mechanism to internally clamp the CubeSat rails.

Concept B: Open-Frame Clamp Assembly: Inspired by the OreSat test fixture (OreSat, n.d.), this design clamps the CubeSat to the shaker table between two plates using bolts. It requires significantly less material, does not require welding, and is modular for easy transport.

Fig. 4.3.2.3. CAD Prototype of Open-Frame Clamp Assembly (Left) and OreSat Test Fixture (Right)

An initial prototype using two bolts per side yielded a first modal frequency of 978 Hz. Increasing to three bolts per side raised this to 1146 Hz.

Fig. 4.3.2.4. Two Bolt Assembly, Frequency Simulation (Modal Frequency: 978 Hz)

Fig. 4.3.2.5. Three Bolt Assembly, Frequency Simulation (Modal Frequency: 1146 Hz)

After evaluating both prototypes/concepts, and after consultation with the Bus Contractor (NuSpace), Concept B was selected for its manufacturability, lower mass, and ease of clamping. To incorporate a safety factor and achieve more uniform clamping of the CubeSat rail, the final design uses five bolts per side.

The choice of material was evaluated according to this decision matrix:

Evaluation Criteria Plastic (e.g. Delrin) Steel Aluminium (Al6061)
Elastic Modulus (higher is better, ability to withstand vibrations) Very Low (~3 GPa); Too low to withstand high vibration loads Very High (210 GPa) ✔ High (69 GPa) ✔
Density (kg/m^3) 1400 ✔ 7850; Makes assembly very heavy 2700 ✔
Machinability ✔   ✔
DECISION     ✔ Ideal strength to weight ratio

Table 4.3.2.6. Decision Matrix

4.3.3 Detailed Design (Vibration Fixture)

In the final detailed design, the G5 EM is clamped between a top plate and a base plate using ten M6 bolts.

Fig. 4.3.3.1. CAD Model of fully assembled Vibration Fixture with G5 CAD model inside.

  • The top plate features cutouts to accommodate the rails and externally mounted solar panels on the Y face.
  • A minimum material thickness of 20 mm is maintained throughout to ensure structural rigidity and resist bending moments induced by the shaker armature.
  • Sufficient clearance is provided along both X and Y axes to safely house all externally mounted deployables/solar panels.
  • The round base plate, measuring 550 mm in diameter, features M10 counterbore holes designed to interface with both the TUV SUD and ST Satsys shaker tables. Hole placements were confirmed against mechanical drawings obtained from each facility.
  • Design for Manufacturability (DFM): Instead of machining the guide rails directly from the base plate, which would require long machining time and generate excessive material waste, the guide rails were designed as separate modules that bolt onto the base plate.

Fig. 4.3.3.2. Round base plate with Guide rails (secured using M6 bolts)

4.3.4. Simulation and Testing Scope (Vibration Fixture)

Modal and random vibration simulations were conducted on the Vibration Fixture. Based on Exolaunch specifications, 2.7Nm torque (equivalent to 2183.5 N force on each rail) was applied to the 10x M6 bolts. The assembly was constrained using fixed supports at the M10 bolt holes, to replicate bolting the plate to the shaker table. The results are summarised in the table below. More details on the Simulation can be found in Appendix G.

Table 4.3.4.1. FEA Simulations on Vibration Test Fixture

The empty Fixture mass is approximately 23 kg. Together with the G5 EM (8.7kg), the total dynamic mass mounted to the shaker table is roughly 32 kg, within the operational limits of the intended shaker tables. Each individual component of the Fixture weighs no more than 15 kg, ensuring user-centricness as the parts are human-portable and easy to install.

At the time of writing, the physical prototype is under production and will arrive end-Week 12. Thereafter, a fit test will be conducted with the G5 structural model. This website will be updated after the fit test is conducted.

4.3.5. Evaluation

This vibration test fixture demonstrates several unique features:

  • The modular open-frame design allows easy installation/takedown, and the parts are sufficiently lightweight for user transport.
  • Open-frame design uses significantly less material than an enclosed testpod.
  • The design allows easy clamping of CubeSat rails. Bolt torque can be set precisely to apply a specific clamping force.
  • At approximately 2000 SGD, the fixture provides a cost-effective solution for EM testing, with the Nova Testpod only required once for Protoflight Model qualification. The design is also readily repeatable for future CubeSat programmes at NUS.

4.3.6. Shortcomings and Future Work (Vibration Fixture)

  • Bolt Relaxation: Under high vibration, localised plastic deformation beneath bolt heads or thread loosening can reduce pre-load, causing destructive chatter (impacting test results). Future iterations could incorporate mechanical retention methods such as Belleville washers or lockwire. Chemical thread-lockers (e.g., Loctite) are not advisable as they may complicate jig disassembly.
  • Simulation Limitations: Although FEA predicts resonance above 1000 Hz, simulation results may not perfectly replicate real-world dynamics. At the test facility, a low-level sine sweep (20-2000 Hz) on the empty fixture should be performed to validate FEA results, identify resonance peaks and any sub-1,000 Hz resonances before loading the G5 EM.

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4.4 CubeSat Transport Box

Transporting Galassia-5 to the launch integrator (Exolaunch) requires safe (cushioned from shock/impact) and dust-free transport conditions.

Taking reference from past Galassia missions, the CubeSat is placed in a transport box, which is then housed within a cushioned COTS Pelican Case to protect against shock loads during shipping. Due to custom requirements (e.g. ESD-safe, FPP Panel), a custom transport box for G5 needs to be designed and fabricated, and a suitable Pelican Case selected for shipping.

4.4.1. Design Specifications (Transport Box)

The CubeSat transport box must fulfill the following requirements:

  • Capacity & Dimensions: Fully accommodate Galassia-5, including all externally mounted antennae, solar panels and deployables.
  • Dust Resistance: Limit particulate ingress to protect sensitive optics and electronics when the Pelican Case is opened.
  • ESD-Safe: To allow engineers to safely power on the satellite while it remains secured inside the box.
  • Portability: Easily portable, with readily removable carry handles.
  • Transparent: Transparent box allows visual inspection of G5 without removal from the box.
  • FPP Access: Feature a dedicated slot to access the Flight Preparation Panel (FPP) without removing G5 from the box, to facilitate power-on tests and battery charging.

4.4.2. Concept Generation and Prototyping (Transport Box)

Aluminum, standard polycarbonate, and AC-300 ESD-safe acrylic were evaluated for the exterior panels according to the decision matrix below.

Evaluation Criteria Aluminum Panels Standard Polycarbonate AC-300 ESD-Safe Acrylic
ESD-Safe (for power on of CubeSat) ((10⁶ to 10⁸ Ω/sq)) ✔   ✔
Transparency (Visual inspection capability)   ✔ ✔
Weight (Lighter is better)   ✔ ✔
Strength ✔    
DECISION     ✔ AC-300 acrylic selected as it satisfies both ESD-safe and transparency requirements.

Table 4.4.2.1. Decision Matrix

For the internal guide rails, metal rods were initially considered but ultimately rejected due to the risk of metal-on-metal particulate generation when sliding against the aluminum CubeSat rails. Instead, ESD-safe polymers (PEEK/ABS/POM) were evaluated, with ESD-ABS selected for its suitability for 3D printing and a surface resistivity of 10⁶ to 10⁸ Ω/sq.

A CAD prototype using 10mm AC-300 acrylic was produced. It was found to be too heavy, with the empty box already weighing 7 kg.

Fig. 4.4.2.2. Prototype with 10mm AC-300

After static load simulations of different acrylic thickness, 5mm thickness was found to be sufficiently strong for the use case,reducing the empty box mass to 4.5 kg. Together with G5 mass of 8.7kg, the overall mass is 14.2 kg, which is sufficiently lightweight to be carried by 1-2 personnel.

The handle design was standardised to match those used on the Integration/TVAC Jig, simplifying inventory management. Handles can be installed/removed by using the same screws that secure the acrylic panels to the guide rails.

4.4.3. Detailed Design (Transport Box)

The 324 x 365 x 170 mm enclosure is constructed from 5mm thick laser-cut AC-300 acrylic plates, fastened together using M5 screws.

Fig. 4.4.3.1. Empty Transport Box (Note removable panels on the X face)

Fig. 4.4.3.2. G5 CAD model placed inside the Transport Box

Inside the enclosure, four ESD-ABS rods act as the primary guide rails, positioned to match the rail spacing of Galassia-5, ensuring a snug fit without lateral movement.

Additionally, individual panels on the X face of the box can be removed to access the FPP, allowing umbilical connections for power-on testing/battery charging while maintaining the integrity of the enclosure.

To ensure impact resistance and protect against shock during transport, the loaded transport box is placed inside a Pelican 1650 Protector Case with shock-absorbing foam customised to its dimensions. Shock sensors placed within the Pelican Case will record the shock loads experienced by G5 during transport.

Fig. 4.4.3.3. Pelican 1650 Protector Case

4.4.4. Simulation and Testing (Transport Box)

To validate the design, comprehensive simulation and physical testing was conducted.

  1. Finite Element Analysis (FEA): A SolidWorks simulation was performed by applying a 24kg static load (twice the maximum mass of a 6U CubeSat) to the guide rails with the handles fixed.
    A maximum stress of 2.02 × 10⁷ N/m² was recorded at the aluminium handles (Stress is lower at other points), below the yield stresses of AC-300 acrylic (6.9 × 10⁷ N/m²) and ESD-ABS (3.2 × 10⁷ N/m²), giving safety factors of 3.4 and 1.58 respectively, confirming the box can be safely carried by its handles under load. As ESD-ABS is anisotropic, it must be printed lengthwise for maximum strength.

    Fig. 4.4.4.1. Static Simulation in Solidworks on Transport Box
  2. Physical Fit and Function Test: A physical prototype was fabricated and fit-tested using the G5 Structural Model (Fig. 4.4.4.2). The CubeSat fitted with sufficient clearance for all deployables and externally mounted antennae.

    Fig. 4.4.4.2. Fit Test of G5 Structural Model with Transport Box prototype.

4.4.5. Evaluation

This CubeSat transport box demonstrates several unique features:

  • The dimensions accomodate G5 and its external deployables/solar panels
  • The ESD-safe materials allow the satellite to be powered on while inside the box.
  • Removable handles allows for portability.
  • The dedicated FPP provision allows access to the FPP for connections of umbilical connectors and power-on of the CubeSat.

4.4.6. Recommendations and Future Work (Transport Box)

The transport box is not completely airtight/dust-proof. While the acrylic panels limit particulate ingress, they do not provide a hermetic seal. Future iterations should incorporate O-rings or rubber gaskets around the acrylic panels to ensure proper sealing, which would also permit outdoor use (e.g., for RF testing) without risk of particulate contamination.

4.5. Conclusion

The 3 custom-designed MGSE effectively address each critical stage of the Galassia-5 CubeSat development process.

  • The Combined Assembly and TVAC Test Jig supports both integration (in all orientations) and TVAC testing without needing multiple jigs.
  • The Vibration Fixture offers a cost-effective, high-resonance open-frame solution for qualification of CubeSat Engineering Models.
  • Finally, the CubeSat transport box ensures safe transport while allowing access to the FPP and power-on within the ESD-safe box.

Together, these three customised, in-house solutions not only address immediate logistical challenges for G5, but also establish a robust and repeatable blueprint for MGSE in future CubeSat programs at NUS.

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