🚀 CubeSats 101 – What Are They Really?

In our post #2, we briefly mentioned CubeSats while discussing the foundations of our learning kit. Now it is time to take a deeper look into what they actually are and why understanding them is essential for anyone who wants to work in the space industry.

In that article we called the following bibliography:
• What are SmallSats and CubeSats? (NASA)
• CubeSat Design Specification (Cal Poly)
• CubeSat 101: Basic Concepts and Processes for First-Time Developers (NASA)

📦 What is a CubeSat?

CubeSats started in 1999 as a collaboration between Cal Poly and Stanford University. The goal was simple yet revolutionary: reduce the cost and development time of satellites, increase accessibility to space, and enable more frequent launches.

A CubeSat is built around a standard unit (1U) defined as a 10×10×10 cm cube with a mass of up to 2 kg. By stacking these units, we can have 1U, 1.5U, 2U, 3U, 6U, and 12U configurations.

This standardization has been a game-changer for the space industry. It allows developers around the world to design satellites that can be launched using compatible deployers and fit into shared launch opportunities.

Cubesat Ilustrations and example missions (ESA)

📐 The CubeSat Design Specification (CDS)

The CubeSat Design Specification (CDS) is the main document that defines the rules of the game. It covers:
• Mechanical requirements – dimensions, rails, standoffs, mass limits, center of gravity.
• Electrical requirements – deployment switches, RBF pins, inhibits for RF and deployables, safe power-up sequences.
• Operational requirements – licensing, frequency coordination, orbital debris mitigation, and deployment timing.

Following the CDS ensures that a CubeSat can be integrated into most launch opportunities without major modifications.

📏 What Restrictions Come With Choosing 1U?

For our learning kit, we decided to base the design on a 1U CubeSat. This choice introduces specific restrictions:
• Size: Only 10 × 10 × 10 cm of internal volume. Every millimeter counts when placing PCBs, batteries, antennas, and payload.
• Mass: The total mass must be ≤ 2 kg, so structural material, batteries, and electronics must be lightweight.
• Limited Power Generation: With only four small solar panel faces, the average power budget is low. The OBC and all subsystems must be power efficient.
• Thermal Management: With such a small surface area, the satellite has less capability to radiate heat away.
• Payload Space: The payload must be compact and low-power, making mission selection a critical design trade-off.

These constraints are not a disadvantage—they are the realistic boundaries that CubeSat engineers face. They force the design to be modular, efficient, and robust.

🔌 The Role of PC/104 in CubeSat Design

To make CubeSat subsystems modular and interchangeable, most developers follow the PC/104 standard for their printed circuit boards (PCBs).

PC/104 defines:
• Board dimensions: 90.17 × 95.89 mm.
• Stackable connectors: Boards can be stacked vertically without a backplane, reducing mass and complexity.
• Electrical compatibility: Uses ISA-bus–compatible signals for data and power distribution.

This standard makes it possible to mix and match OBCs, power boards, communication modules, and payload electronics from different vendors or custom designs. It is a cornerstone of CubeSat modularity and one of the reasons CubeSats became so popular.

🛰️ Why This Matters for Our OBC

Our learning kit is deliberately designed within the restrictions of a 1U CubeSat to illustrate to users the real constraints of space system design. Understanding these limitations and the interdisciplinary nature of satellite engineering is extremely important.

Future engineers must always keep in mind that size, weight, and power are limited resources, and that every design decision affects the satellite’s ability to:
• Survive the mechanical stresses of launch
• Manage and dissipate heat in orbit
• Operate reliably with minimal power and mass

By restricting ourselves to these standards, we create a realistic context to design in, without requiring learners to build a satellite from scratch. At the same time, working inside the CubeSat Design Specification teaches the standards used by the industry—knowledge that is far from trivial for anyone entering the space field.

Following a PC/104-like approach further reduces complexity, leveraging a well-known modular standard. This not only decreases the workload but also makes it easier to understand and interface with other systems designed under the same standard.

🌍 The Bigger Picture

Now we have a clear context about the size constraints for our boards and particularly for our OBC, as well as an explanation of why we chose to follow the PC/104 standard.

With this foundation in place, it is time to move forward with the design of the OBC modules, keeping these real-world restrictions in mind so that every decision reflects the challenges of actual space hardware development.

🚀 Designing Within the Box – How CubeSat Standards Guide Our OBC