Subsystem Interdependency N² Diagram
Hover to trace who sends what to whom. Click any off-diagonal cell to see the interface details describing the flow of power, data, or thermal control between spacecraft subsystems.
An N² (N-squared) diagram is a systems-engineering tool for systematically mapping interfaces between N subsystems in a single matrix. In this diagram, each row represents the outputting subsystem and each column represents the receiving subsystem: the cell at row i, column j describes the output that subsystem i sends to subsystem j, while the highlighted column shows all inputs that subsystem j accepts. Diagonal cells represent each subsystem itself and carry no interface. The N² diagram is standard practice in systems engineering for identifying, organizing, and reviewing inter-subsystem interfaces early in design (NASA/SP-2016-6105, NASA Systems Engineering Handbook, Rev. 2, Section 6.5.1).
Simplification note: This matrix shows five core subsystems. A real spacecraft also carries Command & Data Handling (C&DH), the central computer that gathers telemetry and issues commands. Several flows shown here — for example propulsion health data and ground tracking updates — actually pass through C&DH rather than directly between the two subsystems.
Quick Glossary (plain language)
- ADCS: Attitude Determination and Control System—keeps the spacecraft pointed the right way.
- Bus: The shared power line that distributes electricity to subsystems.
- Burn: A brief thruster firing that changes speed or direction.
- Telemetry: Health and status data the spacecraft sends back.
- Downlink: Sending data from the spacecraft to Earth.
- Slew: A controlled pointing movement to a new attitude.
Inputs ↓
📝 Usage Notes & Attribution
Use this N² diagram to explore how five core subsystems trade power, heat, and data. Start by tracing the highlighted row (outputs) and column (inputs), then click an intersection to read the interface details.
Additional space system student resources can be found at spacetechchronicles.com/student-resources.
This visualization is Copyright © 2025 Dr. Daniel Singleton. All rights reserved. Please keep this attribution when sharing or adapting the material for class use.