Note: This is Version 1 of the HDRM. It is currently being tested. Version 2 will be released soon, featuring significant improvements in assembly and fixes based on lessons learned from this first design.
A Hold-Down and Release Mechanism (HDRM) is a critical device used in spacecraft to securely restrain deployable components—such as antennas, solar panels, or other movable parts—during launch, and then reliably release them once the spacecraft is in orbit. HDRMs play a vital role in ensuring that sensitive or movable elements remain safely stowed during launch vibrations and accelerations, and are only deployed when needed in space.
This repository provides a fully open-source HDRM design specifically intended for CubeSat missions. All design files are included and can be freely used, modified, and manufactured by anyone interested in building their own CubeSat HDRM. By sharing these resources openly, the project aims to lower barriers for small satellite developers and support the growing ecosystem of accessible space hardware.
- ✅ Complete mechanical CAD files (STEP, PDF drawings)
- ✅ Electronics design files (schematic, PCB, Gerbers)
- ✅ Full Bills of Materials (BOM) for both mechanical and electronics
- Interface Control Document (ICD) (work in progress)
- ✅ Technical datasheet
- Assembly images and renders (work in progress)
- ✅ Demo video (watch here)
- Additional documentation (work in progress)
- ✅ Technical project paper (see
Paper/Hold-Down and Release Mechanism for CubeSats.pdf)
- Image Previews
- Specifications
- See HDRM in Action
- Build Instructions
- Post-Processing and Surface Treatment
- FAQ
- Safety Warnings
- Troubleshooting
- Glossary
- Folder Structure
With Cover:
Without Cover:
- Power Input: 5 V DC
- Current: 2 A
- Max Release Preload: ≈ 3.5 N
- Maximum Allowable Preload (Launch): ≈ 1500 N
- Actuation Time: < 2 seconds
- Vacuum Compatibility: <1% TML, <0.1% CVCM (ASTM E595)
- Dimensions: 45 × 22 × 6.5 mm
- Enclosure Material: Aluminum 6061 T6
- Connector: 3-pin Molex pico-blade
For a full list of technical specifications, please refer to the HDRM Datasheet_Ver_1.pdf included in this repository.
Watch the HDRM demonstration video (HDRM.mp4)
Below is a detailed step-by-step guide to building the HDRM. Please refer to the referenced files and drawings for specifics. An even more extensive build document will be released soon.
- Mechanical Parts:
- Fabricate all mechanical components as per the technical drawings in
Mechanical/Part Drawings/(e.g., H-Base, H-Cover, H-Slider, H-Spring, H-Bush, H-nut). - Use high-tolerance CNC milling machining for all parts to ensure precise fits and reliable operation. Tolerances should match those specified in the drawings.
- Use the [3D models](Mechanical/3D CAD/) in
Mechanical/3D CAD/for reference and CAM programming. - Recommended material: Aluminum 6061 T6 for all parts except the H-nut, which should be made from stainless steel (SS).
- Fabricate all mechanical components as per the technical drawings in
- PCB:
- Manufacture the PCB using the Gerber files in
Hardware/Horizontal_HDRM_V1 - Gerbers.zip. Gerber files are standard manufacturing files for PCBs—simply send them to any PCB fabrication service. - Use the schematic and layout in the Altium project (
Hardware/EDA Files) for reference.
- Manufacture the PCB using the Gerber files in
- Electronics:
- Procure all electronic components as listed in the Bill of Materials (BOM). The BOM is a spreadsheet listing all required parts, quantities, and recommended suppliers.
- Surface Treatment:
- Clean all parts to remove machining residues and contaminants.
- Apply MoS₂ (Molybdenum Disulfide) coating (a dry lubricant) to all sliding/contact mechanical parts. MoS₂ can be applied using the Ion Exchange Coating method or with an aerosol spray (ensure uniform coverage for best results). This prevents cold welding in space. The thickness of the coat should be ~1-2 microns
- Inspection:
- Verify all critical dimensions and tolerances per the drawings.
- Ensure all threaded holes and fits are within specification.
- Sub-Assembly:
- Assemble mechanical subcomponents (e.g., slider, spring, bush) as per the assembly drawing (
Mechanical/3D CAD/SP-RHM-000.step). - Use appropriate fasteners and ensure correct orientation of all parts.
- Assemble mechanical subcomponents (e.g., slider, spring, bush) as per the assembly drawing (
- PCB Assembly:
- Solder all components onto the PCB as per the schematic and BOM.
- Attach solderable standoffs to the PCB at the designated locations. These allow the crimp terminals from the NiTi SMA wire to be screwed directly onto the PCB for secure electrical and mechanical connection.
- Inspect for solder bridges and cold joints.
- Final Assembly:
- Integrate the PCB into the mechanical housing.
- Prepare the NiTi SMA wire: Cut to an exact length of 64 mm and crimp NiTi SMA connectors on both ends, ensuring a 64 mm gap between the crimped ends for proper function.
- Attach the crimp terminals to the solderable standoffs on the PCB and screw them in place.
- Once the PCB is placed, insert and lock the screw that secures the compression spring (also called the bias spring).
- Place the bias spring between the body and the slider as shown in the assembly drawing.
- Connect wiring, the prepared NiTi SMA wire, and the 3-pin Molex pico-blade connector.
- Secure the cover and ensure all fasteners are torqued to spec.
- Functional Test:
- Apply 5V DC and verify actuation (release mechanism should operate in <2 seconds).
- Check for smooth movement and no binding.
- Electrical Test:
- Measure current draw (should be ~2A during actuation).
- Inspect for shorts or open circuits.
- Documentation:
- Record serial numbers, test results, and any deviations.
- Mounting:
- Install the HDRM into your CubeSat structure as per your mission’s ICD.
- Connect the HDRM to the satellite’s power and control system.
- Final Verification:
- Perform a final system-level test to ensure proper operation after integration.
- Ensure all components are securely fastened and torqued and that the HDRM is in the correct state for launch.
Note: A comprehensive, illustrated build manual with photos, tips, and troubleshooting will be released soon. Stay tuned for updates!
For detailed post-processing information, refer to the file HDRM-BOM.xlsx included in this repository. Most mechanical parts are required to undergo MoS₂ (Molybdenum Disulfide) coating to prevent cold welding in space environments.
This project was fully funded by TakeMe2Space.
This project is licensed under the MIT License. See the LICENSE file for details.
For questions or support, contact: [email protected]
- Version 1: Initial release
Q: Who can use or modify this HDRM design?
A: Anyone! The design is fully open-source under the MIT License. You are free to use, modify, and manufacture it for your own projects.
Q: When will Version 2 be available?
A: Version 2 is planned for release soon and will include improvements in assembly and fixes based on lessons learned from Version 1.
Q: Where can I find detailed assembly instructions?
A: A comprehensive "How to Build an HDRM" guide will be released soon.
Q: What software do I need to view or modify the design files?
A: For electronics, use KiCad (for schematic and PCB). For mechanical parts, use any CAD software that supports STEP and PDF files.
Q: What is the purpose of the HDRM Datasheet?
A: The datasheet provides technical specifications, operational details, and key parameters for the HDRM. It is useful for engineers, integrators, and reviewers.
Q: Can I request new features or report bugs?
A: Yes! Please open an issue in this repository or contact us directly at [email protected].
Q: Where can I get an HDRM fabricated?
A: The HDRM is designed to be manufactured using widely available services:
- PCBs: You can use PCB fabrication services such as Robu, PCB Power, JLCPCB, PCBWay, or any local PCB manufacturer. Simply send them the Gerber files provided in this repository.
- Electronic Components: Components can be sourced from major distributors like Mouser, Digi-Key, LCSC, or your preferred local supplier. Refer to the BOM for part numbers.
- Machined Parts: For mechanical parts, you can approach local machine shops or use online CNC machining services. There is no single global solution—choose a supplier that can meet the tolerances and material requirements specified in the drawings. Always share the STEP and PDF files with your machinist for clarity.
Q: Are there any recommended suppliers for manufacturing?
A: While the design is open and can be manufactured by any capable supplier, we recommend reviewing the drawings for the process requirements. See the previous answer for specific suggestions on PCB, component, and machining suppliers.
Q: Is there a simulation or test data available?
A: Test data and simulation results may be included in future releases or upon request. Please contact us for more information.
Q: Where can I find the recommended torque values for fasteners?
A: The specific torquing information for all fasteners will be provided after we complete vibration testing of our HDRM. Please stay tuned for updates in future releases.
Q: What is a Hold-Down and Release Mechanism (HDRM)?
A: An HDRM is a device used in spacecraft to keep parts like antennas or solar panels locked during launch, and then release them in space when needed.
Q: What is a CubeSat?
A: A CubeSat is a small, standardized satellite, often used for research, education, or technology demonstration in space.
Q: What is a PCB?
A: PCB stands for Printed Circuit Board. It is the board that holds and connects all the electronic components.
Q: What are Gerber files?
A: Gerber files are special files you send to a PCB manufacturer so they can make your circuit board.
Q: What is a Bill of Materials (BOM)?
A: A BOM is a list of all the parts you need to build something, including quantities and where to buy them.
Q: What is CNC milling?
A: CNC milling is a way to cut and shape metal parts using computer-controlled machines for high precision.
Q: What is NiTi SMA wire?
A: NiTi SMA stands for Nickel-Titanium Shape Memory Alloy wire. It changes shape when heated and is used as an actuator in this HDRM.
Q: I have never built anything like this before. Can I do it?
A: Yes! This guide and the included files are designed to help even beginners. Just follow the steps, and don’t hesitate to look up terms or ask for help.
Q: Is there a simulation or test data available?
A: Test data and simulation results may be included in future releases or upon request. Please contact us for more information.
Q: How do I cite this project in my research or documentation?
A: You can cite the project using the repository URL or reference the technical paper included in the Paper/ directory.
- Sharp Edges: Machined metal parts may have sharp edges. Handle with care and deburr as needed.
- Electrical Safety: When testing the PCB or HDRM, always use a current-limited power supply. Avoid short circuits and do not touch exposed conductors while powered.
- NiTi SMA Wire: The shape memory wire heats up rapidly during actuation. Do not touch the wire during or immediately after activation.
- Spring Tension: The bias spring is under tension. Take care during assembly and disassembly to avoid sudden release.
- Chemicals and Coatings: Use gloves and proper ventilation when applying MoS₂ or cleaning agents.
- Eye Protection: Always wear safety glasses when working with tools, springs, or under tension.
Problem: PCB does not power up or actuation does not occur
Solution:
- Double-check all solder joints for bridges or cold joints.
- Verify correct component placement and orientation (see BOM and schematic).
- Ensure power supply is set to 5V and can deliver at least 2A.
- Check for shorts or open circuits with a multimeter.
Problem: Mechanical parts do not fit or move smoothly
Solution:
- Inspect all parts for burrs or debris; clean and deburr as needed.
- Verify all dimensions and tolerances match the drawings.
- Ensure MoS₂ coating is applied to all sliding surfaces.
- Check for correct assembly order and orientation.
Problem: NiTi SMA wire does not contract or actuate
Solution:
- Confirm the wire is the correct length (64 mm between crimps) and properly crimped.
- Ensure good electrical connection at the standoffs and terminals.
- Verify the power supply is delivering enough current (2A).
- Replace the wire if it has been overheated or damaged.
Problem: Spring or slider launches unexpectedly during assembly
Solution:
- Always assemble with the spring compressed in a controlled manner.
- Wear eye protection and keep hands clear of the spring path.
If you encounter other issues, please open an issue on GitHub or contact the project maintainers for help.
| Term / Acronym | Meaning |
|---|---|
| HDRM | Hold-Down and Release Mechanism – a device that locks and then releases parts (like antennas or solar panels) on a spacecraft |
| CubeSat | A small, standardized satellite, typically 10x10x10 cm units, used for research and education |
| PCB | Printed Circuit Board – the board that holds and connects electronic components |
| Gerber Files | Standard files used to manufacture PCBs |
| BOM | Bill of Materials – a list of all parts needed to build the device |
| CNC Milling | Computer-controlled machining process for precise metal parts |
| NiTi SMA Wire | Nickel-Titanium Shape Memory Alloy wire – changes shape when heated, used as an actuator |
| ICD | Interface Control Document – defines how the HDRM connects to the rest of the satellite |
| STEP File | A 3D CAD file format used for sharing mechanical models |
| MoS₂ | Molybdenum Disulfide – a coating to prevent metal parts from sticking in space |
| TML/CVCM | Total Mass Loss/Collected Volatile Condensable Material – measures of material outgassing in vacuum |
| SMA | Shape Memory Alloy – a metal that returns to a preset shape when heated |
| CAM | Computer-Aided Manufacturing – software for programming CNC machines |
| Standoff | A spacer used to mount the PCB securely inside the housing |
| Crimp Terminal | A connector attached to a wire by squeezing (crimping) it |
HDRM/
├── Hardware/ # Electronics and PCB design files
│ ├── electronics BOM.xls # Bill of Materials for electronics
│ ├── EDA Files # Altium project files (schematic & PCB)
│ └── Horizontal_HDRM_V1 - Gerbers.zip # Gerber files for PCB manufacturing
├── Mechanical/ # Mechanical design files and documentation
│ ├── HDRM-BOM.xlsx # Bill of Materials for mechanical parts
│ ├── RMV-RMH ICD v1.pdf # Interface Control Document (ICD) for RMV-RMH, version 1
│ ├── 3D CAD/ # Mechanical drawings (PDF)
│ │ ├── SP-RMH-001 v2.pdf # H-Base: Drawing for part SP-RMH-001, version 2
│ │ ├── SP-RMH-002.pdf # H-nut: Drawing for part SP-RMH-002
│ │ ├── SP-RMH-003.pdf # H-Cover: Drawing for part SP-RMH-003
│ │ ├── SP-RMH-004.pdf # H-Spring: Drawing for part SP-RMH-004
│ │ ├── SP-RMH-005 v1.pdf # H-Slider: Drawing for part SP-RMH-005, version 1
│ │ └── SP-RHM-006 v2.pdf # H-Bush: Drawing for part SP-RHM-006, version 2
│ ├── Part Drawings/ # 3D models (STEP format)
│ │ ├── SP-RHM-000.step # 3D model for assembly SP-RHM-000
│ │ ├── SP-RMH-001.step # H-Base: 3D model for part SP-RMH-001
│ │ ├── SP-RMH-002.step # H-nut: 3D model for part SP-RMH-002
│ │ ├── SP-RMH-003.step # H-Cover: 3D model for part SP-RMH-003
│ │ ├── SP-RMH-004.step # H-Spring: 3D model for part SP-RMH-004
│ │ ├── SP-RMH-005.step # H-Slider: 3D model for part SP-RMH-005
│ │ └── SP-RHM-006.step # H-Bush: 3D model for part SP-RHM-006
├── Paper/ # Project paper
│ └── Hold-Down and Release Mechanism for CubeSats.pdf # Full technical paper
├── images/ # Renders and photos
│ ├── cover.jpg # Render/photo with cover
│ └── no cover.jpg # Render/photo without cover
├── HDRM Datasheet_Ver_1.pdf # HDRM technical datasheet, version 1
├── LICENSE # License file (MIT)
└── README.md # This readme file