So you've decided you're going to run a science fiction game that takes place in space. And for that you're going to need a ship. I am a scifi gamer and a navy brat, so here are a few things I'd like you to consider.
The purpose of a ship is to transport some sort of payload to a destination. The nature of that payload will dictacte a large part of the ship's design.
A cargo ship's payload is its cargo. Capacity is usually more important than speed, and you only need a large enough crew to handle the ship and the cargo. If your cargo is packed in some sort of standardized container, then fewer crew members are needed to handle it. The crew could be a single pilot or it could be a robot ship that doesn't have to worry too much about life support. That is not to say you couldn't also carry passengers, you simply do not have as much room for them.
NOTE: A few movies/tv series have suggested a 'space rig', where a tractor module connects in some way to one or more separate trailer modules. The movie Alien had the Nostromo connected to a massive robotic refinery that processes the raw cargo into a usable form while the crew is hybernating. The movie Space Truckers and the anime Cowboy Bebop episode "Heavy Metal Queen" have a tractor module that connects to modular cargo pods. The Eagle from Space: 1999 is another example of a space rig.
A passenger ship's payload is people. People who will eat, sleep, breathe, and demand more in the way of entertainment if they are not in hybernation. The more people you are transporting, the larger your crew will need to be. This is not to say you cannot carry cargo, it's just with the passenger needs, you will not have as much room available.
A Military Battlewagon's payload is weapons. Larger warships are usually more heavily armored and have bigger weapons - more guns and missiles, but tend to be slower as a result of all that mass they have to move around. Smaller ships depend more on speed than armor to protect them and may not be as heavily armed.
Some warshps are more specialized. Carriers carry fighters, which greatly extends the reach of a battle group, but the carriers themselves are usually only lightly armed, depending on their fighters and the support of the rest of the battle group to protect it. Carriers in today's modern navy are considered to be capital ships, and as such they usually are escorted by destroyers or cruisers - they never go anywhere by themselves.
NOTE: Drones are becoming an important part of modern warfare. Future space navies may depend more on ship-controlled drones to take the fight to an enemy rather than a manned fighter.
Another specialized warship is the Assault ship, which uses shuttles to transport troops and armored cars to the surface. Once again, only lightly armed, so they depend on another warship such as a cruiser or destroyer to help protect it from a threat. Assault ships may have a few fighters (or drones) to give it and the shuttles some protection.
Military ships tend towards larger crews, to allow for crew loss during battles, damage control, as well as 24x7 monitoring of the area around them.
The setting of your game is also important, as it will determine what's available for you to use. If this is an interplanetary game, you don't need an interstellar drive. Going into an atmosphere? Then the ship has to be sufficiently streamlined or the characters need to use something else like shuttles or teleports to get to the surface.
No teleport? Shuttles then.
What about gravity? In zero gravity, astronauts start losing bone density, so for something long-term, you want some sort of gravity. Centerfugal force works, but it requires a portion of your ship to be spinning. Or do you have a gravity generator?
Communication - how do you talk to someone on another ship or on a planet's surface? How do you contact someone who's on a different planet in a different system? Or even a different compartment on board your ship?
Is there special equipment to worry about, like powered armor or armored cars? Or ISO cargo containers?
Knowing the setting helps you design your ship.
Crews and passengers will want a lot of the same things - a comfortable environment that's not to hot or cold, air to breathe, food to eat, a way to relieve themselves, and someplace to sleep or sit down as needed. So we will explain some of the usual terms.
Environmental Systems or Life Support are those elements that regulate temperature and the air on board a ship. This can be as simple as oxygen tanks and COČ scrubbers, Algae tanks, or a complete biosphere.
The Hull is the outer layer of the ship. Some ships may have an inner hull, separated from the outer hull by a gap. Hulls are usually armored to protect against radiation and micro-meteor damage. There may be a separate heat sheld to protect the ship during re-entry.
Bulkheads are vertical walls that separate the ship into multiple sections, at least three, as a way to contain damage and to prevent loss of atmosphere if one section becomes open to space.
Decks are like the floors in your house or a building.
Compartments are the rooms inside a ship.
Passage ways are like the connecting hallways in your house or building.
Hatches are reinforced doors that allow a bulkhead, deck, or compartment to be sealed to prevent loss of atmosphere. Not all doors aboard a ship will be hatches.
Airlocks are small chambers with hatches at either end, with pumps that can remove air from the chamber to allow crew access to and from the ship from the outside. Most airlocks are set up so that for one hatch to be opened, the other must be closed.
Bathrooms on board ship are refered to as the "Head", dating back to ancient sailing ships where the "bathrooms" were all the way forward on the ship, on either side of the bowspirit where the figurehead was fastened.
The Galley is the ship's kitchen. Officers have their own kitchen known as the Pantry.
The Crews' Mess or Mess Decks is the crew dining compartment. Officers have a separate compartment known as the Wardroom.
Sick Bay - the ship's hospital or medical clinic.
Berthing is a compartment that has sleeping racks and lockers for the crew. A ship typically will divide the crew between several berthings to minimize loss. Each berthing compartment will have its own bathroom or "head".
Cabins are officer offices/sleeping compartments. Typically, only senior officers will have their own private bathroom or "head", the rest share a common bathroom.
The Bridge is where the ship is controled. The Captain usually has a cabin near the bridge.
Turret - this is a weapon pod, usually situated on a reinforced section of the hull known as a "hard point". Turrets are usually remotely controlled by an operator at a dedicated console inside the ship, not in the turret.
4. THE "WOW" FACTOR
Sometimes called the "Cool" factor, this is some aspect of the ship's appearance that will hopefully make your players want to have their characters on board.
This is just a brief introduction to starship design, I will be covering other topics later.
Some interesting information here. I will have to come back to it when my brain can comprehend it. But the little I read was good.