Honestly, I made this on a whim and haven't ever used it practically myself either! The basic concepts are the same as "cars on belts", and there are a bunch of YouTube videos about how to set those up.
You might find the Inventory Sensor mod useful to detect when a container is present and what's in it.
The containers will always need to travel in a one-way loop, even if part of this loop enters and exits a SE spaceship. The gate-belt allows you to build spaceship door over the belt. If you make the belt travel through the center of a 3-wide door/gate, and control the gate with circuit signals, it acts as a valve for the container flow. You can also use circuit-disabled belts to pause the container flow, so the most important function is entering spaceships.
There are other idiosyncrasies, like if containers back up at a corner, sometimes the long line of waiting containers will push one off the corner. You can use other entities (and containers) as walls as containers go around corners to make sure they stay on the belt and are on the center of the belt after the corner. Again, all trucks from the cars-on-belts bases.
If you come up with any good applications, let me know!
