Core Heat Dissipation Methods in Space: How Do Orbital Data Centers Thermal management?

I. Introduction: The Heat Dissipation Dilemma Amid the Space Computing Boom

• Essence: A "space computing cluster" — launching a large number of satellites equipped with computing chips into space via rockets to form a large-scale computing network, replacing some functions of ground data centers.
• Core Advantage: Low-cost energy — fully utilizing solar energy as the core energy source, significantly reducing energy consumption and cost pressure faced by ground data centers.

II. The Core Dilemma of Space Heat Dissipation: Why Is It Harder to Dissipate Heat in a Vacuum?

• Failure of Ground Heat Dissipation Methods: Ground data centers mainly rely on gas convection (air cooling) for heat dissipation, but space is a vacuum with no air flow, making air cooling completely ineffective.
• Only Two Remaining Heat Dissipation Paths: In space, heat can only be dissipated through thermal conduction (liquid circulation) and thermal radiation, resulting in longer and more complex heat transfer paths that require precise systematic design.

III. Thermal Control Technology for Space Data Centers: Hierarchical System Design

1. Heat Collection (Chip Level): Rapid Export of Heat from the Source

• Core Materials and Technologies: Use high-performance thermal interface materials (graphene, liquid metal, carbon fiber thermal pads, etc.) and vapor chambers inside the chip package to fill tiny gaps, reduce thermal resistance, and transfer heat efficiently.
• Auxiliary Heat Dissipation Technology: Embedded microchannel liquid cooling technology can be adopted to carry away heat with flowing liquid.
• Key Requirements: The cooling liquid must be frost-resistant and adapt to the flow characteristics of the microgravity environment; materials must consider the expansion coefficient under extreme temperature differences to avoid bursting.

2. Heat Transfer (Internal Transmission Level): Efficient Transportation of Heat

• Passive Thermal Control Technology: Mainly adopts heat pipes (especially loop heat pipes, LHP), which realize powerless heat transfer through the phase change (evaporation and condensation) of cooling working fluids (ammonia, propane, etc.), with the advantages of high heat transfer efficiency and long transmission distance; there are also variable conductance heat pipes (VCHP) that can achieve adaptive temperature control.
• Active Thermal Control Technology: Due to the excessive heat load of space data centers, it is necessary to introduce a mechanical pump fluid loop (MPFL), which drives the cooling working fluid through the cold plate via a mechanical pump to absorb heat and then transport it to the radiator.
• Technology Application: MPFL technology is mature and highly controllable, adopted by China’s Shenzhou spacecraft and Chang’e-3, and is currently continuously iterated to optimize response speed and stability.

3. Heat Radiation (External Radiation Level): Ultimate Emission of Heat

• Core Logic of Radiative Heat Dissipation: Satellites in space can only dissipate heat through radiation externally; internally, heat can be quickly transferred to the heat-dissipating surface through heat pipes or heat pumps. When the heat-dissipating surface faces deep space, the radiative heat dissipation power can be calculated by the formula: 

• Formula Parameter Explanation: \( Q_{rad} \) (radiative heat dissipation power), \( \varepsilon \) (surface infrared emissivity, usually 0.85-0.92 for thermal control coatings), \( \sigma \) (Stefan-Boltzmann constant = 5.67×10⁻⁸ W/(m²·K⁴)), \( A \) (effective area of the radiator), \( T \) (absolute temperature of the radiator surface), \( T_{space} \) (deep space background temperature ≈ 3K).

• Heat Dissipation Efficiency Reference: When the surface temperature is 50°C, the power per square meter of heat-dissipating area can reach 600-700 watts; satellites with a flat shape can dissipate heat on both sides, doubling the heat dissipation capacity.
• Radiator Design Details: Most are wing panels outside the satellite, coated with high-emissivity and low-absorptivity coatings; adopt a deployable design (folded during launch, unfolded after orbital insertion), and some are flexible film radiators; need to cope with extreme external heat flux environments to prevent "heat absorption" on the sunlit side and excessive cold on the shadow side, and can achieve adaptive heat preservation and heat dissipation through intelligent adjustment (louvers, color-changing materials).

IV. Emerging Space Heat Dissipation Technologies: Solutions for Large-Scale Computing Power

1. Phase Change Material (PCM) Heat Storage and Buffering

• Core Principle: Phase change materials can absorb and release heat near a constant temperature (melting and absorbing heat above the phase change point, solidifying and releasing heat below the phase change point), similar to a "heat storage battery".
• Application Scenario: Integrated into the heat dissipation path, it can buffer fluctuations in internal heat sources and periodic temperature differences in space (storing heat on the sunlit side and releasing heat on the shadow side).
• Key Requirements: Special adhesives are needed to bond phase change materials to heat dissipation components to ensure thermal conductivity and prevent leakage in a microgravity environment.

2. Radiative Heat Dissipation Enhancement and Wavelength-Selective Radiation

• Core Principle: Through nanostructural design, "spectral selective radiators" are manufactured, which have high emissivity in the mid-infrared wavelength band (atmospheric window) and high reflectivity in the sunlight wavelength band.
• Technical Advantage: Theoretically, it can increase heat dissipation efficiency several times, greatly optimizing the effect of radiative heat dissipation.
• Key Requirements: The bonding of nano-coatings to the radiator surface requires special adhesives to ensure compatibility and low thermal resistance, and guarantee coating stability.

3. Evaporative Heat Dissipation and Material Emission

• Core Principle: In extreme cases, heat is carried away by spraying volatile working fluids (such as water) into the vacuum environment.
• Application Limitations: The working fluid consumption is large, so it is only suitable for short-term, high-intensity emergency heat dissipation; a sustainable "ice making-evaporation" cycle can be established on celestial bodies with ice resources (such as the moon) to achieve heat dissipation for the entire system.
• Key Requirements: The fluid storage and delivery system needs to be sealed with vacuum-compatible adhesives to prevent leakage in the vacuum environment.

4. System AI Intelligent Regulation

• Core Principle: Use AI algorithms to predict heat loads and dynamically adjust pump speed, valve opening, or louver angle to realize adaptive optimization of the heat dissipation system.
• Technical Advantage: It can maintain the highest efficiency of the heat dissipation system in the complex and changing space environment, ensuring stable operation of equipment.
• Key Requirements: The bonding and sealing of precision sensing and control components require radiation-resistant adhesives to ensure stable work in the cosmic radiation environment.