SEDSAT-2 Thermal
From SEDSWiki
Note: This isn't really a subsystem (although it is listed in the "Subsystems" section of the wiki frontpage, but I wasn't sure where to put a link to information on Thermal control on the satellite.
This page is a very brief overview of the issues involved in thermal control of objects in low earth orbit. Please edit it and add more detail!
Brief overview
The LEO space environment provides a challenging thermal environment for spacecraft. The temperature ranges from -100°C in the shade to +125°C in sunlight, so an understanding of how this affects the spacecraft is very important to get a satellite to work once in orbit.
The processes by which heat is transferred from one point to another are:
- Conduction - the process by which heat is transferred through a solid.
- Convection - heat transfer between a solid surface and the air - so we can ignore this for a satellite operating in the vacuum of space.
- Radiation - Thermal radiation through electromagnetic waves. For example, the sun radiates electromagnetic waves which, when they hit a surface (eg. a satellite) are absorbed and turned into heat.
Solar radiation is the primary cause of heating/cooling of the external surfaces of a satellite and through conduction, the thermal conditions experienced on the outside of a satellite are transferred to the inside of the satellite.
To attempt to control the temperature of components inside a satellite, the following techniques can be used (this isn't an exhaustive list):
- Radiators to radiate heat away
- Heaters to raise the temperature
- Insulation - attempt to prevent conduction from the surface of the satellite to the components inside the satellite
- Heat pipes - used to transfer heat from point to point
What this means
An understanding of the thermal environment in LEO is very important to getting a satellite working. After understanding the topic, it might be discovered that active thermal control isn't needed for a satellite but on the other hand if might be found that the satellite won't operate without thermal control. Maybe insulation will suffice, or maybe radiators and heaters will be needed. These questions need to be answered.
Some cubesat projects such as Merope have a dedicated Thermal Subsystem team, whereas other teams include thermal control as part one of the other teams.
Finally, the very small CanSat satellites (the size of a single Coke can!) must have addressed thermal control. There isn't much room for heaters or insulation in a coke-can, so how have they dealt with the thermal issue? It would be interesting to understand how the CanSat teams have addressed the problem, as it may provide insight that is useful for SEDSAT-2.
Update: 20071124: See the lecture notes from DTU on Cubesat Thermal Design, these are good!
References
- The Merope Cubesat team have a page of really good information on the space thermal environment and thermal control. Read this page!!
- "Fundamentals of Space Systems", Piscante et al. Chapter 7, "Spacecraft Thermal Control"
- http://www.cubesat.auc.dk/documents/Cubesat_Thermal_Design.pdf - From a lecture series on Cubesat Thermal Design!
