Thermal Control

Introduction

The Thermal Control System’s goal is to protect AcubeSAT and its payload from the harsh space environment such as the Sun’s, IR and Albedo radiation. While the operational temperature range for each internal component varies, the subsystem needs to find a thermal control plan that would satisfy every subsystem’s needs.

Some temperature ranges for our CubeSat’s most crucial components are:

  • The microfluidics chip, where the scientific experiment is going to take place would need to have a temperature of 30±2°C.
  • CubeSat’s battery has an operational mode temperature range of 0–45°C, while if in a non-operational mode a range of -5–50°C.
  • Most electronical components, such as the ICs of our PCBs, will have an operational mode temperature range of -40–85°C and a non-operational of -50–85°C.

Passive and Active Thermal Control

To successfully maintain our components between the requested temperature ranges a thermal control plan has to be created. A thermal control design may consist of two different mechanisms, a passive and active thermal control.

 A passive control could be a material or a coating that reduces or enhances the heat transfer between the two components or areas that are separated from the material or the coating. The term passive is used because, there is no need for a power input in order for the control to work, thus using solely its thermal properties(bulk & optical properties). 

An active control is in need of a power input for it to properly function. An active control has the ability to reduce or increase a heat path, such as a passive control, but it could also provide heat energy to a component/area, or even subtract heat energy from them. 

It is also worth mentioning that active controls have an increased complexity, compared to the passive methods, thus increasing the risk for it to properly function. However, components with tight operational temperature ranges, such as our payload, need to be controlled with an active method so we can reach their demanding temperature ranges.

Thermal Analysis and Test Results

For a final decision to be made, concerning AcubeSAT’s thermal control, thermal analyses  need to take place. The software the subsystem is using for its thermal analyses is ESATAN-TMS, kindly provided by ITP Aero. 

In this software, the extreme environmental cases of the nanosatellite are being examined . These extreme cases include the hot case, in which most of the components are in operation, while Solar, IR and Albedo radiation have a maximum magnitude, and the cold case, having a minimum internal heat dissipation and minimum radiation values. 

These analyses provide the Thermal subsystem with the actual, not the required ones, temperature ranges of the components, with and without the applied passive and active thermal insulations. Comparing these two cases of temperature ranges, the actual and the required, we can decide on the final thermal control of AcubeSAT. 

Last but not least, some practical thermal tests are necessary inside a thermal vacuum chamber, verifying the thermal analysis results by minimizing the uncertainties that occured.