CubeSat Standard Read-Through: Mechanical Specifications (Part 1 of 2)
Channel: Build a CubeSat
Date: 11/02/2024

We start our two part read-through of the CubeSat Design Specification (#CDS) document by diving head-first into the mechanical specs. This video is for you if you have just started learning about CubeSats or if you don't usually read a lot of technical docs and want to prepare for hands-on #cubesat  development.

*Corrections*
19:09 Slight correction here: 25% recessed surface are of the rails concerns the X and Y sides, I couldn't find a spec for the diameter of the deployment switch holes on the Z ends.

*Summary*
- Purpose: "... to help ensure the success and safety of the mission, as well as provide
baseline requirements for CubeSat developers to design their spacecraft, such that they will be compatible with as many CubeSat dispensers and launch opportunities as possible."
- Launch Provider specs take precedence!
- All parts of the CubeSat shall remain attached to the CubeSat. Leave no debris behind.
- Chose only low-outgassing materials. Max. total mass loss: 1% (10g per kg)
- Appendix B is your friend! Find all relevant dimensions and tolerances in the drawings there
- Coordinate system: Z is the long edge, origin is at the geometric center
- Rails are important and need to be sized and spaced correctly. Min. 8.5mm x 8.5mm with a 1mm fillet on the outside edge and a chamfer on the contacting end. Contact surface: min. 6.5mm x 6.5mm
- Protrusions: No more than 6.5mm beyond the plane of the rails. Measure according to CIFP (link below)
- Side panels may not overlap the rails
- Z- and Z+ standoffs: 0.1mm - 7.0mm
- Z- side gets inserted into the dispenser first, so Z+ will be out first
- Just looking at the CIFP (link below) makes a lot clearer
- Deployables need to be constrained to the envelope of the CubeSat when stowed. Duh.
- Deployment switches are located in the Z+ rail ends
- Maximum mass for 2U is specified to be 4kg, but this may be less. Check launch provider specs.
- Center of gravity: +/- 20mm in X and Y and +/- 45mm in Z for 2U.
- Materials for the structure: Aluminum 6061 and 7075. I will go with 6061 for the lower price. Hard anodized for sure.
- Separation spring on the Z- face: Max. 6.7N force and more than 2.5mm stroke.

*Timestamps*
00:00 Intro
03:37 Purpose of the document
04:49 General Specifications
06:05 Outgassing
07:38 Mechanical Specifications
14:20 Protrusions and the CIFP
17:00 Deployables
17:42 Surface Roughness and Anodization
19:12 Deployment Switches
20:44 Mass budget
21:12 Center of Gravity
22:35 Material Selection and Aluminum Alloys
23:41 Separation Mechanisms

*Repo Links*
CDS Mechanical Specs Notes (stuff that needs more investigating, etc.): https://codeberg.org/buildacubesat-project/bac-docs/src/branch/main/content/s01e03/CDS-mechanical-notes.md)
CDS with my highlighting: https://codeberg.org/buildacubesat-project/bac-docs/src/branch/main/content/s01e03/CDS+REV14_1+2022-02-09-annotated.pdf)

*Links*
Cal Poly: CubeSat Design Specification (CP-CDS-R14.1): https://www.cubesat.org/s/CDS-REV14_1-2022-02-09.pdf
Cal Poly: CubeSat Interface and Fit-Check Procedures (CIFP): https://www.cubesat.org/s/CP-CIFP-20W-Public-Version.pdf

*Credits*
1. Fillet and Chamfer (Mechanical Minds): https://mechanicalsphere.blogspot.com/2018/08/fillet-and-chamfer-why-and-when-to-use_3.html
2. Deployment Switch (SUPSI Space Lab): https://tisat.supsi.ch/structeres-machanics-and-materials/

Get in touch: https://buildacubesat.space
If you are looking for a way to support this channel, leave a tip :) https://ko-fi.com/buildacubesat

Need a friendly, a non-corporate GitHub/Gitlab alternative? Check out https://codeberg.org/

#buildacubesat #episode #s01e03