Radiator Surface Coating
High-Emissivity Thermal Control Coating System
Radiator surface coatings are specialized exterior treatments—such as AZ-93 inorganic white paint with an absorptance of 0.16 and emissivity of 0.92, or quartz optical solar reflectors—applied to radiators to maximize infrared heat rejection while minimizing solar absorption. In the lunar environment, maintaining this low absorptance-to-emissivity ratio is difficult because solar ultraviolet radiation degrades organic coating formulations, adhering lunar dust alters radiative properties, and micrometeorite strikes expose bare substrate. Because these degradation mechanisms steadily compromise thermal rejection over a 100-year settlement lifespan, maintenance relies on periodic robotic recoating.
Specialized surface coatings maximizing radiator emissivity and minimizing solar absorptance
Purpose
Maintain optimal alpha/epsilon ratio for maximum heat rejection throughout mission life
Context
Child of L2-TCS-RAD in the Active Thermal Control System
Principles
- ▸White thermal coatings (alpha_s<0.2, epsilon>0.9) minimize solar heating while maximizing IR emission
- ▸Coating degradation from UV, atomic oxygen, and particle radiation tracked by alpha/epsilon ratio
- ▸Second-surface mirror coatings provide excellent alpha/epsilon with good durability
Typical implementations
- ▸AZ-93 white thermal paint (alpha=0.16, epsilon=0.92, NASA standard)
- ▸Optical Solar Reflectors (OSR) quartz mirror tiles
- ▸AeroGlaze Z306 black polyurethane for non-solar-facing surfaces
- ▸SG121FD white silicone thermal coating
Lunar considerations
- ▸No atomic oxygen on Moon but UV degradation of organic coatings still occurs
- ▸Lunar dust adhesion changes effective alpha/epsilon ratio over time
- ▸Coating reapplication may be needed over 100-year mission via robotic painting
- ▸Micrometeorite impacts create local coating damage exposing bare substrate
Specifications
Functional
| primary function | Specialized surface coatings maximizing radiator emissivity and minimizing solar absorptance |
Physical
| materials | AZ-93 inorganic white paint, OSR quartz tiles, Z306 polyurethane |
Interfaces
Provides
- Optimized emissive surface for heat rejection
Requires
- Replacement coating materials for reapplication
Cite this entry
Lunar Ark Codex. "Radiator Surface Coating" (L3-TCS-RAD-COAT). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-TCS-RAD-COAT
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.