While most settled planets in the Alliance are self-sufficient, very few can produce everything they need, and offplanet luxuries are by definition from another planet. For obvious reasons, this leads to a lot of interplanetary and interstellar trade.
In-system trade largely consists of basic commodities being transferred as needed. Typically, this means food, complex machinery, and other necessities from a habitable world being exchanged for raw materials gathered on an uninhabitable world or asteroid belt. There is also a fair amount of passenger travel involved.
Interstellar trade typically involves cargoes with much denser value than basic foodstuffs or raw materials. High-tech machinery, exotic merchandise made nowhere else, unique artwork and other artifacts, information, strange animals, and other small, extremely valuable cargoes are the norm when traveling between the stars. That isn’t to say food and other less valuable cargoes aren’t shipped over interstellar distances, but these are outliers. A newly-founded colony will often have regular shipments of food dropped off while they get established, for example.
If a transport in the Alliance is capable of atmospheric operations, it’s also almost always amphibious. Properly paved, reinforced spacecraft facilities are expensive both in materials and labor, but every planet yet discovered by the Alliance or Gliror that can support life as we know it has large oceans. For this reason, an inhabitable world’s primary starport is usually located on a coast and incorporates a seaport. When a starship isn’t using a dock, ordinary surface vessels are free to. It also streamlines surface trade; the starship unloads its cargo, usually in shipping containers, the cargo is warehoused in the port, and if it needs to be loaded onto a surface ship it’s right there. If the cargo is to be delivered using surface shipping, the same facilities a boat would use are readily available.
There are other advantages to sea landings and launches as well. Reentry using aerobraking gets a hull hot and landing in a large body of water helps cool it off. Standard hybrid ramrocket propulsion systems can use water as reaction mass, and refueling is a snap if the ship is already floating in an ocean. Such a ship operates in atmosphere using air as reaction mass, then switches to water at high altitude to reach and then break orbit. Seawater is easily purified using a ship’s life support system to replenish potable water stores.
And if the crew’s number is up, designated landing areas are far enough from population centers to limit the death toll from a crash.
The Alliance being what it is, there are uncountable “standard” shipping container sizes, and even more custom-made containers. There are also sizes that have gained traction in interstellar shipping. Of these, the most common are one-meter, six-meter, and twelve-meter containers. The six and twelve-meter containers have a 2.5-meter square cross-section, while the one-meter is a cube. Six- and twelve-meter containers are used for standard bulk shipping, while one-meter cubes are intended for secure shipping of valuable and/or fragile goods. All of them are sturdy, corrosion-resistant, and vacuum sealed, suitable for being carried inside a cargo hold or bolted to the hull of a starship.
While a standard container is a basic box, they can be modified almost infinitely. Common modifications include refrigeration systems, plumbing for liquid cargoes, internal racks for anything from meat to vehicles, hoppers for free-flowing dry goods like grain or ball bearings, and secure locks. Locks and thicker shells are especially common on one-meter cubes to secure valuables.
For transport, containers can be stowed in a cargo hold, attached to the hull of a suitably equipped starship, or plugged into special sockets. Most freight transports intended to handle shipping containers will have internal cranes and attachment points to move and secure the containers. All the client has to do is drop it off outside and the transport can do the rest.
External attachment is usually done in space rather than on the ground, but there are starships with sunken decks on the roof and suitable ramps to allow containers to be stacked while on the ground. Some of these ships will have retractable roofs to provide a certain amount of heat shielding for reentry, but since dropping out of orbit is usually belly-first it isn’t really necessary in most cases.
A number of lighter transports have a socket system to load a small number of containers semi-internally. They have doors on the underside to either expose a single socket or the whole array and cranes to lift the containers into the socket. The advantages to this system over fully external attachment are twofold: the doors provide protection to the containers, and they’re much quicker and easier to load and unload. In n emergency, a container can be “unloaded” by opening the doors and dropping it. Its advantage over internal storage is that the containers can’t be accessed from within the ship without cutting through the socket wall and opening the doors while spacewalking will alert the ship’s computer.
The same qualities that give them their intended utility have led to used containers being appropriated and repurposed across the Alliance. Six- and twelve-meter containers make comfortable housing if furnished and properly modified. Inventors and tinkerers have used one-meter cubes to make the housings for all manner of devices. They also make solid end tables and nightstands, and people have been using them as safes since they were introduced.