Satellite Eclipse Heater Power Calculator
Spacecraft power budgets: Calculate lumped-mass thermal cooldown during orbital shadow eclipse, minimum transient temperature, and survival heater wattage.
Eclipse Duration & Thermal Inertia
Transient Cooldown & Heater Requirement
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
Why do spacecraft components experience severe thermal stress during eclipse?
In sunlight, spacecraft receive over 1361 W/m² of direct solar flux. When passing into Earth's shadow (eclipse), solar flux instantly drops to zero while the spacecraft continues radiating intensely to deep space. Temperatures plummet rapidly unless mitigated by high thermal inertia (aluminum cold plates) or thermostatically switched survival heaters.
What is the "thermal capacitance" (thermal flywheel effect)?
Thermal capacitance is the product of mass and specific heat (C_th = m · C_p). Massive components (e.g. solid aluminum avionics chassis or heavy battery cells) store substantial thermal energy that slows down transient temperature drops (dT/dt = -Q_rad / C_th), acting as a passive thermal flywheel across 35-minute LEO shadows.
Why are survival heaters a major driver of battery sizing?
During eclipse, the solar arrays generate zero power. All electrical survival heaters, payload standbys, and avionics must run exclusively from the electrochemical battery bank. A 50 W survival heater operating across a 72-minute GEO eclipse consumes 60 Watt-hours per cycle, directly increasing battery mass.