Variable Emittance Coating
Electrochromic Variable Emittance Coating
An electrochromic variable emittance coating is a solid-state thermal control surface composed of a tungsten-oxide film, an indium tin oxide transparent electrode, and a solid electrolyte that dynamically regulates radiative heat rejection by shifting infrared emittance between 0.2 and 0.85 under an applied voltage. In lunar environments where 300 K temperature swings and abrasive regolith cause mechanical thermal louvers to seize or degrade, this coating eliminates all moving parts. Consuming 1 W of power at a mass of 8 kg, the device switches states in 60 seconds and provides a 25-year operational lifetime with a mean time between failures of 500,000 hours.
Electrochromic variable emittance coating (VECs) — switchable IR emittance allowing dynamic thermal control without moving parts.
Purpose
Electrochromic variable emittance coating (VECs) — switchable IR emittance allowing dynamic thermal control without moving parts.
Context
Child of L2-PTC-COAT within the Lunar Ark system
Principles
- ▸Tungsten-oxide / vanadium-oxide variable emittance
- ▸Switchable emittance 0.2-0.85 with applied voltage
- ▸Active control allows thermal load matching without louvers
- ▸Solid-state — no moving parts
- ▸Long-life electrochemical reversibility
Typical implementations
- ▸Eclipse Energy Variable Emittance Coatings
- ▸NASA Glenn variable emittance R&D
- ▸Aerospace VEC heritage (small satellites)
Lunar considerations
- ▸Replaces mechanical louvers (no moving parts)
- ▸Long mission benefits from no-mechanism design
- ▸Low control power
Specifications
Functional
| primary function | Electrochromic variable emittance coating (VECs) — switchable IR emittance allowing dynamic thermal control without moving parts. |
| emittance range | 0.2, 0.85 |
| switching time s | 60 |
Physical
| mass kg | 8 |
| materials | WO3 electrochromic film, ITO transparent electrode, Solid electrolyte |
| vacuum compatibility | True |
Operational
| power consumption w | 1 |
| thermal range c | -40, 70 |
| lifetime years | 25 |
| mtbf hours | 500000 |
Interfaces
Provides
- Variable emittance surfaces
Requires
- Switching power (~1 W per panel)
Cite this entry
Lunar Ark Codex. "Variable Emittance Coating" (L3-PTC-COAT-VAR). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-PTC-COAT-VAR
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.