ok, next question: how do you make sure you have a good mix?
Didn't see any additional options, other than "load troops at nearest"
You can garrison troops at the colony through the troop menu to prevent ships from picking them up. Garrison a good chunk of all unit types so there's a desired mix of units being loaded on board. I'm honestly not sure how the game decides what troops to pick up when told to load the ships.
If you're invading a colony and meet an insane level of resistance (like on homeworlds with fifteen+ billion people), sometimes it's worth it to kill a few people or five billion with nuclear bombardment to lower their strength enough so you can invade with a reasonable army. I keep a few ships armed with nuclear devastators for just such an occasion.
EDIT: I think the Distant Worlds equivalent of World War II just started. In a matter of three days, war was declared over twenty times between different empires. This'll be fun to watch.
The game determines what units to carry via the percentages in the policy tab, I think.
I just noticed a couple tabs and was about to make a post on it.
Anyway, troop loadout is determined by percentages on the ship/fleet screen. Go to the fleet menu and select the fleet, then set the percentage of whatever units you want in the boxes at the bottom-middle of the screen. If it's a lone ship, find it on the ships menu and click the "troops & characters" tab, which has a column of boxes similar to the fleet menu.
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Korabbian Spice is worth quite a lot, apparently, like Zentabia Fluid. I had actually discovered one source of both in the galaxy, both of which were already in other empires' areas of influence, so I didn't bother at the time. However, when I was finished rubbing out the Fire Gang and most of the Mortalu Council, I decided to take a shot at it.
The Korabbian Spice was covered by the Enton Domain's area of influence, who didn't exactly like me. They didn't claim the moon it was on, though. I guess they never discovered it and the other resources on the moon were too worthless to justify building a mining station. The other problem was that it was halfway across the galaxy, smack in the middle. I got over this obstacle for the most part by parking a few resupply ships in caslon nebulae between my space and theirs.
I first started with money. I had a couple million excess credits so I showered them in wealth. I also granted them mining and refuelling rights. Eventually, with enough cash, I managed to get our relationship up to the positives and they gave me mining rights. I swooped in with a construction ship and built a mining station, claiming the Korabbian Spice for the Gizurean Collective! They were pretty pissed off after being stood up, it seems, because they demanded the station from us multiple times, to which our response was "go fuck yourselves." It's occasionally crippled by the neverending sand slugs, even with its twenty railguns, but it's repaired at a good enough pace. The civilians rabidly selling the spice and my refusal to let it go to any other empire has crashed the price from 600 to 329 in a matter of five years.
An ongoing war has given the Khulum Confederacy control over a nearby colony, placing the spice mine in their sphere of influence. They
immediately demanded it from us, to which the response was the same. A resupply ship is being moved to the gas giant the moon orbits and combat vessels are being deployed to maintain control over this valuable asset. The Confederacy will be crushed before that mine is lost. The Zentabia Fluid source is held by another, even more hostile empire. I won't bother with trying to wrench that from them just yet.
Other things of note include the relocation of alien races in the Collective's space to frontier slave worlds, a hot war between half the galaxy and the Shakturi (to which we support the Shakturi via massive piles of cash), the explosion of the civilian and state fleets alike, a massive chain of declarations of war in response to the Shakturi incident, and the Collective approaching seventy-five billion members of almost purely Gizurean citizens. The year is 2191 and the Collective has yet to stumble, much less fall.