Engineers are designing a radiative cooling system for a spacecraft
PHYSICS · Multi-part · ISC · Physics · Heat and Thermodynamics · Heat and Thermodynamics
Problem
Engineers are designing a radiative cooling system for a spacecraft. Four identical square radiator panels, each of area 0.60 m2, fold out once the craft reaches orbit. During each 90 min orbit the panels are
• sun-lit for the first 55 min, during which their surface temperature stabilises at 330 K,
• in Earth’s shadow for the remaining 35 min, during which their surface temperature drops and stabilises at 290 K.
Assume each panel maintains the stated temperature for the entire duration of its respective interval and that no other heat-transfer mechanisms are significant. Let σ=5.67×10−8Wm−2K−4.
(a) Determine the radiant power emitted by a single panel during the sun-lit portion of the orbit.
(b) Determine the radiant power emitted by a single panel during the shadow portion of the orbit.
(c) Calculate the total thermal energy radiated by all four panels during one complete 90 min orbit.
(d) Compute the average power that the radiator system removes from the spacecraft over an orbit. Explain how this average power would change if the shadow duration increased while the sun-lit duration decreased but panel temperatures remained the same.