# Basic Size of Habitats or Starbases

#### Cordane

##### GW/SC/PD/Flak Wonk
I've been diving back into reading Leviathan Wakes, book 1 of The Expanse series of novels. One of the major settings in that novel (less so in later novels) is the asteroid/dwarf planet Ceres, which at the beginning of the novel was described as having a (near) human population of around 6 million residents and another million or so in transitory population. The Wikipedia article for actual Ceres puts its rough volume at 434 million cubic-kilometers, or a mean diameter of approximately 940 km. Now the usable internal volume is likely MUCH smaller than that (maybe as little as 100 meters cubed, 1M cubic-meters per person, or 7 trillion m^3 / 7,000 km^3 for 7M humans), but even an artificial body (like a Stellaris Habitat or other station) would be a bit larger in terms of enclosed volume versus usable internal volume (maybe 20-25% larger, 8,400-8,800 km^3, 25.4 km diameter sphere).

When looking at the Habitats in Stellaris, I was curious as to how large they would realistically be (this is trying to get my head around their size, not to specifically ask for any change in their costs or construction times). I've often estimated that a single Pop would be somewhere on the order of 250 million human analogues (e.g., 100 Pops on a planet would be equal to 25 billion humans). A basic Habitat is indicated as housing 4 Pops, or 1 billion humans by my estimation - around 143x as many humans as The Expanse's Ceres. Assuming a linear relationship, my 1M m^3 estimate per person extrapolated out only comes out to 1.23M km^3 or a diameter of "just" 132.9 km - Death Star 1 was stated to have a diameter of 160 km, with crew and passengers of only around 1.2 million, so I might have errored quite a bit smaller. Changing the internal volume to 1 km cubed per person (or a little more than half of the ratio of the Death Star 1) puts the enclosed volume for the Habitat at 1.23 billion km^3 or a diameter of 1,328.8 km (our Moon has a diameter of 3,474.8 km in comparison).

Now looking at the Stellaris Wiki, it puts the cost of a 4-Pop Habitat at 150 Influence and 1,500 Alloys, while a Starbase at Star Fortress level is either 2,050 alloys (if the costs for the tiers below are added in) or 1,250 alloys (if not). I'm not thinking those are intended to be comparable costs, but does anyone have any thoughts on how big they are and how large of a Pop-fraction they contain? What about Mining or Research stations?

#### LordQulex

##### Sergeant
I think one option you're possibly overlooking is an answer of, plainly, zero. Every robot portrait is leaps and bounds ahead of where we are now. We have the technology for each individually, but getting them to work together and programming them is tricky. So when you consider the possibility that we MAY get Stellaris quality "robots" in our lifetime, you begin to understand the complexity and capability of automation. There is a decent chance that strike craft, construction ships, mining stations and research stations are un-manned/remote-control drones.

After that, is it really a stretch to believe that starbases could be automated as well? We have automated hydroponic farms now, so a starport with a hydoponics bay and a pair of anchorages could be crewed by perhaps merely a handful of administrators and techs (perhaps with their families), while larger maintenance fleets arrive every so often for larger repair or upgrade tasks.

#### CaesarVincens

##### Lt. General
A couple notes: basic habitats don't house 4 pops, but allow 4 districts. Habitation districts provide 8 housing each, "work" districts provide 3 housing each, and the upgraded habitat "capital" building provides 5, so that is nominally 29 pops for max housing habitat, or 17 for max work habitat.

Second, while certain numbers work as pop to individuals ratios in some contexts, it will never work universally, without giving too large or too small amounts for one end or the other. That is a "pop" is an abstracted unit of population, even if using the standard human template.

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#### HFY

##### Field Marshal
Really depends what number of individuals you imagine are in a Pop, and then how much population density you imagine for the Habitat.

Are these people living like planetside suburbanites?

Or are the more like a submarine crew?

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#### SirBlackAxe

##### Lt. General
Really depends what number of individuals you imagine are in a Pop, and then how much population density you imagine for the Habitat.

Are these people living like planetside suburbanites?

Or are the more like a submarine crew?

Given the 70% base habitability rating on habitats, I'd figure closer to suburbanites.

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#### Cordane

##### GW/SC/PD/Flak Wonk
Really depends what number of individuals you imagine are in a Pop, and then how much population density you imagine for the Habitat.

Are these people living like planetside suburbanites?

Or are the more like a submarine crew?

That's why I talked about the occupancy ratios of both The Expanse's Ceres and Death Star 1. Both of those seem to be very high to me, but I didn't want to discount those entirely out of turn.

There's also a very big difference between sleeping accommodations and all of the space needed for the systems to keep people alive, fed, protected, and productive. And I really don't think that hot-racking in triple bunks is what a happy populace is signing up for.

#### HFY

##### Field Marshal
And I really don't think that hot-racking in triple bunks is what a happy populace is signing up for.

Maybe that's the 70% habitability rating.

The near-total lack of privacy could explain why pop growth is often very low on Habitats.