Vapor Compression Heat Pump
Space-Rated Vapor Compression Refrigeration Unit
A space-rated vapor compression heat pump is an active thermal control unit that uses a compression, condensation, expansion, and evaporation cycle to cool electronics bays and cryogenic transition zones below ambient temperatures. Utilizing a variable-speed hermetic scroll compressor and brazed plate heat exchangers, these units achieve a coefficient of performance of 2 to 4. Lunar deployment introduces specific physical constraints: reduced gravity alters two-phase flow behavior inside the evaporator and condenser, while the ambient vacuum eliminates convective cooling, requiring strictly radiative heat rejection and complete, zero-leak working fluid containment.
Vapor compression heat pump providing active cooling for zones requiring sub-ambient temperatures
Purpose
Actively cool electronics bays and transition zones between ambient and cryogenic areas
Context
Child of L2-TCS-HPMP in the Active Thermal Control System
Principles
- ▸Vapor compression cycle: compression, condensation, expansion, evaporation provides active cooling
- ▸COP (Coefficient of Performance) of 2-4 typical for space-rated heat pumps
- ▸Variable-speed compressor allows capacity modulation for varying heat loads
- ▸Working fluid selection (R-134a replacement, CO2, or hydrocarbon) affects performance and life
Typical implementations
- ▸Honeywell space-rated vapor compression systems for ISS Future Habitats
- ▸JAXA JEM thermal control vapor compression development
- ▸Sunpower free-piston Stirling coolers for space applications
- ▸Emerson Copeland scroll compressors adapted for reduced gravity
Lunar considerations
- ▸No convective cooling available for condenser - must use radiative rejection only
- ▸Compressor reliability over 100 years requires redundant units and robotic replacement
- ▸Working fluid containment critical in vacuum - zero-leak hermetic system required
- ▸Reduced gravity affects two-phase flow behavior in evaporator and condenser
Specifications
Functional
| primary function | Vapor compression heat pump providing active cooling for zones requiring sub-ambient temperatures |
Physical
| materials | Hermetic scroll compressor, Brazed plate heat exchangers, R-1234yf or CO2 refrigerant |
Interfaces
Provides
- Active cooling for sub-ambient temperature zones
Requires
- Electrical power for compressor motor (~500W-2kW)
Cite this entry
Lunar Ark Codex. "Vapor Compression Heat Pump" (L3-TCS-HPMP-VCMP). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-TCS-HPMP-VCMP
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.