Spacecraft MLI Effective Emittance Calculator
Space thermal insulation: Calculate Multilayer Insulation (MLI) effective emittance (ε*), parasitic heat leak, layer count scaling, and seam/penetration degradation.
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Frequently Asked Questions
What is effective emittance (ε*) in spacecraft MLI blankets?
Because an MLI blanket combines radiation shielding across dozens of thin foils with solid contact conduction through spacer netting, engineers model the complex heat transfer using a single lumped parameter called effective emittance (ε*). Flight-quality blankets typically achieve ε* = 0.02 to 0.04.
Why do MLI blankets only work in high vacuum?
MLI relies entirely on eliminating gas convection and gas conduction between layers. In atmospheric air, gas molecules easily conduct heat between foils, rendering the blanket useless. Only in space vacuum (pressures < 10⁻⁴ torr) does radiative shielding become the dominant thermal barrier.
Why does adding more than 30 layers provide little benefit?
The theoretical radiative resistance scales with the number of shields (1/N). However, as blankets become thicker and heavier, gravity and tension increase contact pressure between adjacent layers, causing conductive heat transfer through spacer netting to rise. Above ~30 layers, conductive gains cancel out radiative gains.