There are some unusual but otherwise plausible ways to reject heat at incredible scale without involving a lot of mass. https://en.wikipedia.org/wiki/Liquid_dr

There are some unusual but otherwise plausible ways to reject heat at incredible scale without involving a lot of mass. https://en.wikipedia.org/wiki/Liquid_droplet_radiator https://en.wikipedia.org/wiki/Liquid_droplet_radiator Space has many downsides, but it also comes with a few advantages.