Cyclers

Interplanetary travel is quite a common form of space travel. Ships travel between planets and other locations to trade, mine, conduct war, or otherwise do a variety of things. But most ships owned by individuals cannot do this, they simply lack either the fuel, power, air, or all above to do so. In that light, there emerged a solution. Cyclers. Cyclers are ships that cycle between two places. There's two varieties. Interplanetary and interstellar. Cyclers have been around since the 2100s, and are a staple in space travel.

Interplanetary

Interplanetary ones are ones that cycle in an orbit between two major locations in a solar system, most commonly planets. They nearly exclusively transport cargo. The most common form of cargo is refined materials, consumer goods, and other such products. They also transport ships and people. If a ship can't travel an interplanetary distance, it can be loaded aboard a cycler, and can go on that. It's a lot faster, easier, and actually doable.
Cyclers typically operate on trips of a couple of weeks to a few months, depends on distances, and have a set path. For example, there are two cycler routes between Ochtotne Prime and Jett, linking the two planets and their civilizations. Comparatively, the Sol system has thousands of routes all over, and trips like Earth-Mars or Earth-Jupiter are even more congested. Most cyclers are quite old, and often have been operating for a long while, some being around since the early days of space travel.

Interstellar

Interstellar cyclers are even bigger, and are nearly always tradeships. The Void Traveler, for example, is one. These ships often route between clusters. The Core Worlds are often the most popular start, end, or pass-through point, but plenty others exist.
These ships are very big, the smallest ones being in the five-ten kilometer range and the biggest ones dwarfing habitats and stations. The routes the biggest ones take are hundreds of lightyears long, and the longest one is almost two thousand lightyears long. These routes also take centuries to complete, and before FTL, not a single one of the longer ones had been finished.

Common designs

Interstellar cyclers were, before FTL, very big tubes with engines on both ends. They generated gravity via rotation, and the inner layers were often used for cargo while the outer ones were where the crew worked, the few there are. These immense ships used to travel between stars at around 0.7c, via large antimatter engines strapped a small distance away from the hull. There are two sets, because you need to decelerate as well, which, like acceleration, often took years. They would also use a shaped cone of ice in front of the ship to be more aerodynamic, because that does matter at those speeds. It also served as a fine supply of hydrogen and oxygen.
Nowadays, the big trade cyclers have FTL drives fitted in, and those drives are quite powerful. This also makes the engines somewhat overkill, as now all they're needed for is in-system travel.
Interplanetary cyclers are very much small versions of interstellar cyclers. They have a similar front-back engine setup, and are tube-shaped with the same cargo location. They're just smaller. Their thrusters are often only fusion thrusters, and they are very rarely fitted with FTL drives.

Crew

Cyclers of both varieties are highly automated. In fact, many only have a small crew of less than ten. Among interstellar tradeships, Modes are disproportionately common, largely due to the wealth of the crew and the ready access to advanced modifications and the like from their travels.
The crew is most often divided into:

Leadership, be that a single captain, or some group like a triumvirate.

Maintenance, often a few people, overseeing the various maintenance systems.

Navigation, often working in conjunction with the leadership to plan routes and travels.

Resource management, taking care of the ship's monetary affairs and oversees the stores of stuff like food, fuel and oxygen.

Communication, communicates trade deals, legal affairs like habitat approach permissions, and similar.

The crews are often tight-knit due to spending so much time together, but absolutely not always.