Active Thermal Control System (ATCS)

Overview

The Active Thermal Control System (ATCS) module is a critical subsystem for the International Space Station (ISS). Its primary functions include:

1. Maintaining Internal Temperature: Removing heat from the pressurized cabin to sustain a stable environment.
2. Supporting Electrical Power System (EPS): Removing excess heat generated by the EPS.

This repository provides a simulation of the ATCS module, focusing on heat removal from the pressurized cabin. The simulation is implemented using ROS 2, with nodes representing various subsystems and processes of ATCS.

---

Simulation Design

The simulation is built around two main ROS 2 nodes:

1. System Temperature Node (coldplate_system)

   • Monitors the temperature of the cold plate/heat exchanger.
   • Triggers the cooling process when the temperature exceeds a critical level.
   • Publishes real-time data, including:
     • Cold plate temperature.
     • Internal coolant (water) temperature.
     • External coolant (ammonia) temperature.

2. Cooling Process Node (cooling_process)

   • Simulates the cooling process, involving:
     • Activation of pumps for the Internal ATCS (IATCS) and External ATCS (EATCS).
     • Heat transfer between the IATCS and EATCS loops.
   • Responds to temperature reduction requests.
   • Logs alerts in case of cooling system inactivation.

---

System Workflow

1. Monitoring and Publishing Cold Plate Temperature

• The coldplate_system node simulates temperature increases in the cold plate due to load variations.
• Publishes temperature data to the /coldplate_temperature topic.

2. Critical Temperature Detection

• When the temperature exceeds a critical threshold:
  • Logs a warning.
  • Sends a request to the cooling_process node to reduce the temperature.

3. Cooling Process

• The cooling_process node simulates:
  • Heat absorption from the cold plate to the internal coolant (water).
  • Heat exchange from water to the external coolant (ammonia) and finally to the radiator outside the ISS.
• Returns the updated temperatures for the cold plate, water, and ammonia.

4. Temperature Update and Publishing

• The coldplate_system node updates the cold plate temperature based on the response from the cooling_process node.
• Resumes publishing the updated data.

---

ROS 2 Topics

Published Topics

1. /coldplate_temperature
   • Type: sensor_msgs/msg/Temperature
   • Description: Publishes real-time data, including:
     • Temperature (°C) with variance.

---

ROS 2 Services

Provided Services

1. /Cooling (Cooling Process Node):
   • Type: thermal_control/srv/Cooling
   • Description: Handles temperature reduction requests.
     • Request:
       • temperature: Current cold plate temperature (°C).
     • Response:
       • success: Boolean indicating if cooling was successful.
       • message: Status message describing the result.
       • reduced_temperature: Updated cold plate temperature.
       • water_temperature: Updated internal coolant temperature.
       • ammonia_temperature: Updated external coolant temperature.

---

Parameters

Initial Parameters

• Cold Plate Temperature: 45°C
• Target Cold Plate Temperature: 30°C
• Initial Coolant Temperatures:
  • Water: 4°C
  • Ammonia: -40°C
  • Radiator: -270°C

Constants Considered

For Cold Plate (CP):

• Specific Heat Capacity (Aluminum): 900 J/kg·K
• Mass of Cold Plate: 1 kg
• Heat Exchange Efficiency (CP-Water): 0.95
• Heat Transfer Coefficient (CP-Water): 200 W/m²·K
• Contact Area (CP-Water): 0.1 m²

For Coolants:

• Specific Heat Capacity (Water): 4184 J/kg·K
• Specific Heat Capacity (Ammonia): 4500 J/kg·K
• Mass Flow Rate (Water): 1 kg/s
• Mass Flow Rate (Ammonia): 1 kg/s
• Heat Exchange Efficiency: 0.95
• Heat Transfer Coefficient (Water-Ammonia): 150 W/m²·K
• Contact Area (Water-Ammonia): 0.1 m²
• Stefan-Boltzmann Constant: 5.67e-8 W/m²·K⁴
• Radiator Emissivity: 0.9
• Radiator Area: 0.1 m²

---

Running the Simulation

Step 1: Build the Package

colcon build

Step 2: Source the Workspace

source install/setup.bash

Step 3: Launch the Nodes

ros2 launch thermal_control thermals.launch.py

---

Expected Log Output

[coldplate_system-1] [INFO] [1736625440.136587250] [coldplate_system]: Cold Plate Temperature: 48.50°C
[coldplate_system-1] [INFO] [1736625440.637731724] [coldplate_system]: Cold Plate Temperature: 49.00°C
[coldplate_system-1] [INFO] [1736625441.136917492] [coldplate_system]: Cold Plate Temperature: 49.50°C
[coldplate_system-1] [INFO] [1736625441.642691919] [coldplate_system]: Cold Plate Temperature: 50.00°C
[coldplate_system-1] [WARN] [1736625441.642796660] [coldplate_system]: Temperature exceeds 50°C. Activating cooling system...
[cooling_process-2] [INFO] [1736625441.643222008] [cooling_process]: Received cooling request: Current Temp = 50.00°C, Target Temp = 30.00°C
[coldplate_system-1] [INFO] [1736625441.643703795] [coldplate_system]: Cooling completed successfully. Cold Plate Temperature: 49.03°C
[coldplate_system-1] Water Temperature: 4.06°C
[coldplate_system-1] Ammonia Temperature: -39.86°C