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ISO 29764 — Space systems — Thermal control
ISO Standard — Space systems — Thermal control — Engineering Technical Article
1. Overview of ISO 29764
ISO 29764 defines thermal control requirements for space systems, covering passive and active thermal management, material thermophysical properties, analysis verification, and acceptance testing. It applies to all spacecraft from CubeSats to large geostationary platforms.
A thorough thermal balance test with at least two extreme cases (hot and cold) is the most reliable way to validate the thermal mathematical model before flight.
2. Thermal Design Requirements
The standard specifies allowable flight temperature ranges for common spacecraft components, including batteries (0 °C to 30 °C for Li-ion), electronics (−20 °C to 60 °C), and propellant tanks (10 °C to 40 °C for hydrazine). It also requires that the thermal control system maintain these limits with a minimum of 5 °C margin at both ends.
| Component | Min Temperature (°C) | Max Temperature (°C) | Typical Control Method |
|---|---|---|---|
| Li-ion battery | 0 | 30 | Heater + MLI |
| Avionics box | −20 | 60 | Radiator + heat pipe |
| Hydrazine tank | 10 | 40 | Heater + insulation |
| Solar array | −100 | 110 | Passive (OSR) |
| Star tracker | −10 | 35 | Heat strap + radiator |
Li-ion battery temperatures below 0 °C during charging can cause lithium plating and permanent capacity loss. Independent survival heaters with thermostatic control are essential.
3. Analysis and Verification
The standard requires a thermal mathematical model correlated to within ±3 °C of thermal balance test data. Radiation analysis must account for albedo and Earth infrared flux variations. Margin policy demands a 10 °C uncertainty margin on predictions for unproven designs.
Using a dedicated thermal desktop or ESATAN-TMS model with a validated radiator sizing spreadsheet can reduce analysis cycle time by 40% while maintaining accuracy.
Passive thermal designs that rely solely on surface coatings risk catastrophic failure if the coating degrades under UV or atomic oxygen exposure — always include a heater-based backup.
4. Frequently Asked Questions
Q: Is ISO 29764 applicable to propulsion subsystem thermal design?
A: Yes, it covers propellant tank temperature control, thruster thermal constraints, and the management of heat soak-back after firing.
A: Yes, it covers propellant tank temperature control, thruster thermal constraints, and the management of heat soak-back after firing.
Q: What is the minimum margin for thermal control design?
A: The standard mandates a minimum 5 °C margin between the predicted temperature and the qualification limit, plus 10 °C uncertainty for analyses not anchored to test data.
A: The standard mandates a minimum 5 °C margin between the predicted temperature and the qualification limit, plus 10 °C uncertainty for analyses not anchored to test data.
Q: How are heat pipes qualified under this standard?
A: Heat pipes must demonstrate start-up, transport capacity, and freeze-thaw survival through qualification testing over the full predicted mission temperature range.
A: Heat pipes must demonstrate start-up, transport capacity, and freeze-thaw survival through qualification testing over the full predicted mission temperature range.
Q: Does the standard cover two-phase thermal control?
A: Yes, loop heat pipes and capillary pump loops are addressed, with specific requirements for non-condensable gas tolerance and power cycling.
A: Yes, loop heat pipes and capillary pump loops are addressed, with specific requirements for non-condensable gas tolerance and power cycling.
