Ah, for a radiator, you can use both sides; one side exposed to the solar system north, and the other side facing south. So the 1.55 km on a side gets reduce b

Ah, for a radiator, you can use both sides; one side exposed to the solar system north, and the other side facing south. So the 1.55 km on a side gets reduce by a factor of sqrt(2), to 1.1 km on a side.