Civilian Shipping lines are like gremlins, if you feed them they will grow. Colonizing a world like Venus or Titan that requires significant infrastructure will feed the shipping lines as they transport the demanded infrastructure so they will build more ships. If you stick to colonizing terraformed or low cost worlds then the growth will be more reasonable and the civilian lines will be less of a hassle.
This!
I got a conventional start, gave me the Trans Newtonian base tech via SM. Starting with 500M pop 5 RL and 1x 1k Tons Naval shipyard.
Colonized Luna even without minerals on it. And set 1 Day autoturns. This really boosts shipping lines. The Travel time between Earth and moon is nearly non-existent, wich leads to fast trading.
Also the 1 Day increments lead to vast amount of trades. I think this is because of Orderqueue of the civs. They get trade order to transport colonist/infrastructure from Earth to Luna. when done they seem to wait for the next increment to set a new task. This leads at 30Day Increments to 1 trade per ship and month. at 1 Day increments They check every day for a new task. So this happens:
1 Day increment: 30 Day increment:
Loadings infra from earth (10 hours) Loadings infra from earth (10 hours)
Move to Luna (5 min) Move to Luna (5 min)
Unload infra at Luna (10 hours) Unload infra at Luna (10 hours)
Wait for next increment (3h 55min) Wait for next increment (29d 3h 55min)
check for next availible trade check for next availible trade
= =
Potential trades per month: 30 potential trades per month: 1
Now in Year 33 and have this:
Dangel Transport Corporation: 195 ships 8 544 650 Tonnage
Trattner Company: 137 ships 6 214 600 Tonnage
Welke Colony Group: 15 ships 678500 Tonnage
Hamburg Lines: 7 ships 301800 Tonnage