Space Technology Special Report - Version B. July 2023 - 9

Thermal Modeling
of
Small
Satellites
validation and verification of each simplification that goes
into a reduced model is obviated. Of course, working directly
with the CAD is going to lead to a greater computational
cost: a CAD-based numerical model will subdivide the
geometry of the satellite into thousands, or even millions, of
different computational elements, so there is a tradeoff.
Historically speaking, the lumped modeling approach had a
lot going for it. Computers used to be relatively slow, so having
the numerical analyst spend time semimanually reducing
the computational complexity was important for getting
results quickly. This approach is still relevant for the
modeling of very large structures like the International
Space Station, but for small satellites - especially
as computational costs continue to drop - it is
now becoming increasingly attractive to start
at the other end of the modeling spectrum.
In practice, a thermal analyst will want to
work somewhere on the spectrum between a wholly
simplified and a full-fidelity model. For example, it might
be desirable to replace the CAD description of each screw and
fastener with a lumped thermal resistance at the surface between
the joined components. Similarly, it might make sense to reduce
an electronic component such as a chip or battery to a block
of material with averaged properties and internal dissipation.
Important Modeling Considerations
Regardless of the modeling approach taken certain
aspects, as described below, need to be considered.
The geometric description of the satellite. The CAD design
and thermal properties (thermal conductivity, density, and
specific heat) of the materials being used in each component
determine the total thermal mass of the satellite as well as the
conductive heat transfer between parts. The relative orientation
of the satellite faces also determines the view factors, describing
how well one surface can see another surface. This is needed
when computing radiative heat transfer. Along with the CAD
design, there is additional information that is related to the
geometry. For example, the mating surfaces between two parts
might have a thin coating, or a bonding material, that alters
SPACE TECHNOLOGY SPECIAL REPORT
JULY 2023 9
Space Technology Special Report - Version B. July 2023

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