Summary: Starting from version 2020.0, Optistruct is able to simulate radiation to space. Unlike conduction and convection, radiation is a method of heat transfer that doesn’t rely on any contact between the heat source and the heated objects. Radiant exchange happens between the surface element (CHBDYE) and a black body space node (ambient node defined by SPC). You can find a presentation attached to this article containing an overview of solver capabilities, as well as an FE example model.