Integrated Subsystems - space-station-os/space_station_os GitHub Wiki
In space station operations, no subsystem functions in isolation. Guidance, power, thermal control, life support, communications, and ground systems are deeply interconnected, sharing sensors, responding to shared conditions, and cooperating to maintain crew safety and operational integrity.
Space Station OS (SSOS) models these interdependencies explicitly using ROS 2 interfaces, enabling simulation and control of realistic cross-domain behavior.
Subsystem Interactions – Aboard the ISS and in SSOS
1. Powering Everything: EPS at the Core
The Electrical Power System (EPS) is the backbone of all subsystems. It collects energy via solar arrays, stores it in batteries, and distributes it dynamically based on demand.
- Feeds life support, communication, GNC computers, and thermal loops.
- Interacts with Thermal Control to avoid battery overheating.
- Shares telemetry with Ground Station for power budget planning.
In SSOS, EPS publishes power availability and usage stats that other systems subscribe to when deciding operational modes (e.g. GNC switching to low-power mode).
2. Keeping the Crew Alive: ECLSS + EPS + Thermal
The Environmental Control and Life Support System (ECLSS) maintains breathable air, drinkable water, and safe cabin pressure.
- Draws power from EPS for pumps, filters, and electrolysis (e.g. O₂ generation from water).
- Relies on Thermal Control to remove heat from metabolic activity and equipment.
- Uses humidity sensors, CO₂ detectors, and flow meters to monitor the environment.
Failure in EPS or Thermal can trigger ECLSS safety fallback modes (e.g., switching to passive scrubbers or dumping excess heat to radiators).
3. Orienting the Station: GNC’s Role
The Guidance, Navigation, and Control (GNC) system stabilizes and orients the station.
- Uses IMUs, gyroscopes, and star trackers for attitude estimation.
- Reacts to physical disturbances from docking, CMG failures, or thermal-induced structural shifts.
- Works with Thermal Control, since solar exposure changes depending on attitude.
- Coordinates with EPS to optimize solar panel alignment.
In SSOS, star tracker input can be simulated to feed both GNC and Navigation modules, affecting EPS power gain and ECLSS radiation shielding.
4. Managing Heat: Thermal Control in Every Loop
Space stations accumulate heat from:
- Electronics (EPS, avionics, GNC computers)
- Crew metabolism (ECLSS)
- External sunlight exposure (determined by GNC)
Thermal Control routes fluid through heat exchangers and radiators, monitoring sensors across subsystems.
- Takes temperature readings from battery packs, crew cabins, GNC units, and more.
- Uses fluid pumps and fans powered by EPS.
- Informs ECLSS if cabin temperature exceeds thresholds.
In SSOS, thermal feedback loops affect GNC CPU performance and influence EPS operational thresholds.
5. Staying in Touch: Communication & Ground Station
The Communication System links the onboard software with Earth-based mission control through the Ground Station interface.
- Sends telemetry from all subsystems: ECLSS status, GNC orientation, EPS load, etc.
- Receives commands to adjust subsystem modes (e.g. activate thermal loop B).
- Requires power and attitude: GNC must align antennas correctly, EPS must guarantee uptime.
SSOS uses a simulated Ground Station GUI that listens to telemetry topics and allows service calls to control remote systems.
Key Shared Sensors & Cross-Use Components
| Component | Used In | Description |
|---|---|---|
| Star Tracker | GNC, EPS | Used to determine absolute attitude for sun-pointing and solar panel optimization |
| IMU | GNC, ECLSS (crew motion inference) | Tracks angular rate and acceleration; used in attitude and sometimes crew localization |
| Thermal Sensors | EPS, ECLSS, Thermal Control | Monitor heat generation, battery safety, air temperature |
| CO₂ Sensor | ECLSS | Detects CO₂ buildup for air revitalization |
| Power Meters | EPS, GNC, ECLSS | Allow subsystems to report power usage and respond to low-power modes |
| Cameras & Proximity Sensors | GNC, Comms, Ground Station | Used for docking simulations, inspection, and visualization |
Summary
In SSOS, subsystems are designed to simulate realistic cooperation, not operate in isolation. This allows:
- Testing system-wide autonomy and fault responses
- Simulating power failures, attitude drift, or thermal limits
- Demonstrating how a smart habitat can manage itself
Each subsystem page dives deeper into its internal architecture, but understanding these interdependencies is crucial for developing integrated, mission-grade behavior.