1. simple analysis detailed analysis control methods
Thermal Control
simple analysis
detailed analysis
control methods

2. Simple Analysis spherical cow approach simplify geometry
thermal inputs
(internal)
thermal inputs
(external)
approximate spacecraft
thermal output

3. Radiative Heat Transfer
In steady-state, Qin = Qout [energy/time]
qin [energy/area/time]
from solar flux (S ~ 1.35kW/m2 at Earth’s distance from Sun)
Qin =  SAexposed + Qinternal ( = absorptivity)
Qout = qoutAtotal
Stefan-Boltzman Law: qout = T4
 = emissivity

4. Example Qinternal = 100 W. Atotal = 4 r2, with r = 2 m.
dist. from Sun = 1.25 au
= 1.87108 km
=  = 0.90
Aexposed = 0.5 Atotal = 25.1 m2
Qin = 100 W SAexposed(R/R)2
= W.
Qout = T4Atotal
 T = oK = 21 oC = 70 oF r
Aexposed
internal sources
Atotal

5. Detailed FE Analysis
Consider individual internal components (placement and thermal properties) and external geometry
TRASYS -- builds input file for SINDA
SINDA – calculates temperatures of components

6. Control Methods Passive Active MLI (multi-layer insulation)
surface coatings
louvers
heat pipes
Active
electric heaters
thermal fluid loops

7. Design Procedure Develop list of requirements
min/max temperatures that components can tolerate
special thermal rqts for some instruments?
Estimate worst case hot/cold conditions
Initially, use simple steady-state analysis
Later, use FE analysis
Select and size thermal control method(s)