The expert system approach for design was taking too long to develop for not much improvement. Instead I've adapted my existing scripts with hard-coded routines for spawning decks large enough for a forest or orchard. There is enough ambiguity in the design that if I find I need some sort of oversized amenity, I have a volume of the ship to draw from in which that would fit. After the script runs, I then check its work in Sql making sure that enough deck area was allocated to match my design estimate spreadsheets.
In the end I went with a vessel that is about 1km across. A vessel that size will support up to 1600 people. 160 members of that population are Specialists. The vessel will launch with 288 civilians and 160 specialist. It will take the ship about 80 years to fill to capacity. The civilian population will grow, but the specialist population will remain constant.
The vessel uses the island population model, but because we have built the ship to support far more people than it is launching with, the housing surge is well within the design capacity of the ship. We also have the specialists to balance out the workforce.
My design history is thus: The economy in which this ship was built can very easily and cheaply construct massive vessels. But people for crews are in short supply. The threat of war has placed premium on anyone with a skill. Thus the only crews that are made available for deep space missions are surplus 20 somethings who already live in the asteroid belt colonies, or fresh migrants from Earth. Neither of whom have decades of experience running a ship. And even they are not available in massive numbers. Because the ship really only needs them for genetic diversity, they don't even have to be anyone's first choice for recruiting.
This vessel was launched for 2 missions. One to establish a forward operating base at a star system that is currently out of the range of ISTO's militaristic rivals the Krasnovians. The second, secret mission, is to collect data about the Krasnovian expedition/outpost that happens to be on the way. That outpost is outside the range of where intelligence says that Krasnovian outposts can be supplied from, and depending on estimate, Krasnovian ships can even return from.
The Iliad is based on an existing colony design (The Gilgamesh class deep space colony). That tried and true design can support itself independently for decades. Ships of the Gilgamesh class are currently used to mine comets for heavy water. The ships are large, some 1000m across. But the design has proved robust, and crew morale on board them is generally better than even luxury communities back on Earth.
This new Iliad class of vessel takes the habitation design of the Gilgamesh class, and mates it with a new propulsion system capable of accelerating the vessel at 1 g for years at a time. Travel range is limited only by spare parts and fuel.
The structure of the vessel, as well as engines and key systems, were constructed at the asteroid Psyche. The vessel then made its way to Ceres to take on topsoil, cattle, crops, and crew. The fuel requirements of the vessels mission were such that she was only given enough fuel at Ceres to get out to the Oort cloud to refine her own heavy water from comet material.
Five years of gathering fuel gave the crew a chance to train, grow, and shake down all of the systems on board. She carries enough heavy water and lithium to allow her propel herself to her intended destination, and back. There is also enough fuel to sustain the colony for up to a century if rescue should be needed. (A scenario where she arrives, has engine trouble, finds the system barren, and has to call for help, it would take 50 years for the message to get back to Earth and a century for the rescue mission to arrive. Yes, only 20 years would have passed on the rescue ship, but 100 years will pass on both the Iliad and on Earth.)
The star system she is headed out to is a sun-like system, with a G class star slightly younger than our own sun. The system is too distant to determine if it has a comet cloud like Sol's and/or minor planets like Ceres that could be mined to sustain a new colony. Thus the exploratory nature of the ship. And the enormous resources dedicated to making sure the vessel has the means to deal with contingencies.
If all goes well, and the system can support a colony, all of that fuel on hand means the ship can operate for a few decades before having to leave the material rich interior of the system to mine the outer reaches for more fuel. Fuel is generally located in the outer reaches of a solar system. Getting out there, finding the comets, and returning is a process that can take years.
The player's character is one of the specialists on board. Specialists are test-tube babies that are given an accelerated rate of growth, as well as cybernetic enhancements. The enhancements allow the fetus to be subjected to neural stimuli during the incubation process. These stimuli allows a specialist to emerge from an artificial womb after 2 years as a fully formed adult with a doctorate level education. Specialist development is also shaped to include neural abnormalities documented in the geniuses of the field in which they work.
A staff of artificial intelligences supervises the development of the specialists, and act as parents and mentors for them. But in their own peculiar robot sort of way. Despite all that well meaning love and care, specialists grow up to have the same range of quirks and insecurities that are normally associated with abused orphans.
Legally, Specialists are wards of the ship until their 20th birthday. (21 being the age of majority with 1 years credited for training during incubation.) Each specialist is commissioned to perform a specific role. After their commission has elapsed, a specialist joins the civilian population. They may continue on with their commissioned vocation, pick a new field entirely, or simply decide to live under a tree and commune with nature. They have served their vessel, and have earned the right to live a "normal" life.
Until their 20th birthday, while it's inevitable a specialist may fall in love, they are not permitted to marry or have children. (And there are legal means to prevent the former and technical means to prevent the later.) The specialist aging process is a little different than civilians. They don't age outwardly, but they seem to suffer premature aging internally. At their 20th birthday the have the health of a 30 something in age. On their 30th birthday, their internals function like a civilian of 50. On their 40th birthday, they function like an 80 year old. It's rare for a specialist to see their 50th birthday. Competing theories blame the accelleration technology used to produce them, the stress of the occupations they encounter, or simply that the fire that burns twice as bright burns half as long. They always seem to leave a good looking corpse, though. Most deaths for specialists are actually accidents or suicides.
Specialist are never told what they were created for. Part of their integration process is to discover what they were created to be. This is partly to familiarize themself with the community. Mostly because the best lies are the ones you tell yourself. Someone who discovers they like to be a waste management engineer, and has to fight to be a waste management engineer, is far more likely to be sane at the end of 20 years of being a waste management engineer than someone who wakes up, is assigned the job "Waste Management Engineer", and told never to question it. (Oddly enough, Krasnovians, as draconian as they are, have a similar policy.)
This game will be about discovering who you are, and what your purpose is in this world. And then, of course, subverting that. It'll be fun, trust me. ;-)