rickman wrote in :

I think the barbeque effect is because the capsule does not spread the
heat very evenly. The temperature of space (including the sun's
radiation) at earth's orbit is about the temperature of the surface of
the earth.

That fits. I think they were just averaging it on that basic principle. (And
specifically, protecting the oxygen tanks above pretty much all else, if I
remember the books right, I read a few at one point, over ten years ago).