Am I right in thinking that if the Hyperion is roughly cylindrical,
then the heat flow between the inner and outer surfaces is calculated as in
A hollow cylinder
<http://en.wikibooks.org/wiki/Heat_Transfer/Conduction#A_hollow_cylinder>
For a cylinder of length L : inner R1 at T1, outer R2 at T2
Q = 2 pi k (T1 - T2) / ln ( R2/ R1 )
Since this cylinder is surrounded by another insulating cylinder we
don't have to worry how it gets rid of the heat
(radiation,convection,conduction) to the surrounding air.
(I think I'll have another go with the Elmer FEM program).
