Space Station OS (SSOS)

Overview

Space Station OS (SSOS) is an open-source platform built on ROS 2 to unify the development, simulation, and real-time control of modular space station subsystems. By simulating critical life support, thermal regulation, and power systems, SSOS provides an accessible environment for testing autonomous behaviors, validating hardware interfaces, and developing future space infrastructure software.

SSOS draws inspiration from the International Space Station (ISS) and adopts a software-defined space station philosophy. Each subsystem is modularized into ROS 2 nodes with standardized interfaces, allowing flexibility, scalability, and reusability. While SSOS is a simulation, its architecture is hardware-ready, enabling integration with future testbeds and research facilities.

Skills and Contributions

• ROS 2 middleware design with publishers, services, and action servers
• C++ and Python development for subsystem logic and GUI integration
• ISS-inspired system modeling: ECLSS, Thermal Control, EPS
• Project management: GitHub maintenance, Docker-based reproducibility, documentation
• PyQt5 GUI development for astronauts and mission control panels
• Diagnostics, telemetry, and failure injection for robust simulation

Environmental Control and Life Support System (ECLSS)

The ECLSS simulation models the core processes needed to sustain life aboard a spacecraft: air revitalization, oxygen generation, and water recovery. Implemented as ROS 2 action servers and services, these subsystems replicate ISS-inspired closed-loop functionality.

Key Subsystems

• Air Revitalisation System (ARS): Simulates the Carbon Dioxide Removal Assembly (CDRA), handling CO₂ scrubbing, contaminant management, and diagnostics. Publishes CO₂ storage telemetry and supports a service interface for CO₂ requests.
• Oxygen Generation System (OGS): Models electrolysis and Sabatier reaction, generating O₂ from water and recycling hydrogen with CO₂. Integrates with ARS and WRS subsystems, publishing diagnostics and handling failure modes.
• Water Recovery System (WRS): Inspired by the Urine Processor and Water Processor Assemblies, this subsystem purifies wastewater into product water. Implements staged purification, grey water handling, and provides a service for water requests.

Thermal Control System (TCS)

The Thermal Control System simulation abstracts the ISS Active Thermal Control System (ATCS), modeling heat transfer across avionics, tanks, and environmental hardware. It uses configurable YAML files to define thermal nodes and links, with an RK4-based solver for accurate numerical integration.

Core Features

• Thermal nodes represent equipment with temperature, heat capacity, and internal power.
• Thermal links define conduction-based heat flow between nodes.
• RK4 integration simulates dynamic thermal evolution over time.
• Cooling logic triggers when thresholds are exceeded, simulating water/ammonia loop behavior.
• Diagnostics publish overheating, loop failures, and FDIR (Fault Detection, Isolation, Recovery) events.

Electrical Power System (EPS)

The EPS simulation models ISS-style primary and secondary power distribution, including solar arrays, battery ORUs, bus switching, and regulated DC-to-DC conversion. Each component is abstracted as a ROS 2 node, reflecting real hardware operations.

Core Components

• SARJ Mock: Simulates solar array tracking and publishes solar voltage.
• Battery Manager: Models 24 Orbital Replacement Unit (ORU) batteries with charging, discharging, and voltage safety limits.
• BCDU: Action server that coordinates parallel charging/discharging of all healthy batteries. Monitors current/voltage thresholds and enters safe mode on fault.
• MBSU: Routes power from healthy channels, averages voltage, and provides input to DDCU.
• DDCU (Planned): Converts high-voltage bus to 124.5 V regulated output for station loads.

Conclusion

SSOS demonstrates how complex, safety-critical space systems can be translated into modular ROS 2 simulations for better testing, integration, and research. By blending systems engineering, software architecture, and collaborative open-source development, SSOS lowers the barrier for space station software innovation and provides a foundation for autonomous, sustainable space habitats.