Passive heat sinks would work so much better in space where you can radiate heat out to the universe (background temperature of about 3 degrees above absolute zero). Just keep the sun side insulated.
Passive heat sinks require an extremely large area for high-power, low-temperature applications, so you'd likely be using up most of your payload mass for just the heat sink. It's not a very efficient use of resources.
Is this the Star Trek section of the forum?
It's the Speculation section. We're speculating on the viability of asteroid mining and the effect it will have on the Bitcoin economy.