Very Large Spacecraft

[AlexanderHowl]

I think Red Dwarf probably would mass between 30 billion metric tons and 300 billion metric tons (depending on the density of the ship) which would mean that it would be between SM+23 and SM+25.

[Dalillama]

Most of it is gonna be cargo holds; we know there was enough room in those for a cat civilisation, and the crew was only 1169 people (in the TV series, it was ~10x larger in the books)

[ericthered]

I've got several versions of a SM+18 ship known as a "rotalith migrator" floating around in my notes. It was when I was first using spaceships and I was deliberately ignoring fuel requirements. Its essentially a generation ship for a slow-metabolism alien species that is more comfortable on asteroids than on planets.


All versions have 4 systems of rock armor on the front, and at least 2 house-ruled engines that can get Ion drive efficiencies using rock.

[The Colonel]

IIRC The Culture's GSVs were as much as hundreds of kilometres in size and home to up to billions of people (although given the ... culture ... of The Culture I can't guarantee that they were all extant biologicals.

Of course, since a large part of a GSV apparently consisted of force fields and could adjust its size, that might be a bit tricky to model.

[AlexanderHowl]

One issue is that there is that large spacecraft can support many, many more people than most authors seem to expect. Using five cabins per person (a luxury cabin with total life support and an office), my SM+31 design is capable of supporting 600 billion people, and it only allocates twenty percent of its volume to Habitats and Open Spaces. A lot of the large spaceship designs in fiction are going to be capable of supporting much larger populations that their designers suggested.

For spacecraft with planet killing lasers though, a SM+30 spinal battery or a SM+31 major battery seems to be the minimum required size. With 100 EJ of output, the 500,000 dDR for a planet like Earth halves to 250,000 dDR, meaning that an average of 100,000 points of d-damage goes through every turn. With around 170 million d-HP for a planet like Earth, a 100 EJ weapon can turn wreck a planet in less than ten hours and turn it to an asteroid belt in less than sixty hours. While it is not as impressive as the Death Star, it is still pretty frightening to think that it could literally destroy a planet in less than three days.

Against smaller targets, the spacecraft is quite capable of annihilating them with one blow. Even against a similar vehicle, despite its armor and forcefield, it is able to cripple it with one attack and destroy it with a few more. Against a m-scale superheros, its tertiary weapons are capable of vaporizing them in one hit.

[Phantasm]

A few thing I've posted to the forums:

Ishtar Station, an SM +21 O'Neill colony in one of Venus's Lagrange points.

The Death Star, an SM +32 mobile base city, based off its stated diameter and accounting for it being a sphere rather than any mass figures (which I distrust).

[AlexanderHowl]

I generally like using mass because I use the density of liquid hydrogen to determine the volume because it gives realistic amounts of space for people in habitats and open spaces, but each to their own.

[strange7person]

Originally Posted by AlexanderHowl

One issue is that there is that large spacecraft can support many, many more people than most authors seem to expect. Using five cabins per person (a luxury cabin with total life support and an office), my SM+31 design is capable of supporting 600 billion people, and it only allocates twenty percent of its volume to Habitats and Open Spaces. A lot of the large spaceship designs in fiction are going to be capable of supporting much larger populations that their designers suggested.

Sure, if you've got about one person per 20,000 cubic feet of habitable space. By volume that would be an order of magnitude denser than modern Manhattan from bedrock to about a thousand feet above sea level, which is already far more crowded than most people can stand. Star Wars Episode 4 depicted the Death Star's interior with chase scenes in long broad hallways, deep chasms, and other wide-open spaces which were almost completely unoccupied, not an elbow-to-elbow labyrinth like the Kowloon Walled City.

[Varyon]

For my space opera setting, I'm considering having the flagship (which is also where the owner often resides) of the setting's largest company (which is actually an independent nation, with a military that can be hired as mercenaries) be a scaled-up version of their already-quite-large capital ships. Seeing as those capital ships are intended to be a linked pair of SM+15 vessels (one is a proper ship, the other is a giant cannon, with the cannon typically detaching prior to firing), the flagship would need to be larger than SM+15, but I haven't decided upon an actual size yet (nor a proper design for the smaller ships, other than their cannon halves having a 10-module Spinal Battery of sorts and an External Clamp). Some of the biological ships of the setting's "aliens" (actually engineered lifeforms based on Earth stock, but almost nobody in the setting knows that) might exceed SM+15, but I'm leaning toward no on that.

[Phoenix_Dragon]

Originally Posted by strange7person

Sure, if you've got about one person per 20,000 cubic feet of habitable space. By volume that would be an order of magnitude denser than modern Manhattan from bedrock to about a thousand feet above sea level, which is already far more crowded than most people can stand.

That's kind of a strange way of measuring that. Almost all of that volume you're citing is open, unusable sky, and most travel is done on one or two levels at most. There are more than 40,000 buildings in Manhattan; only eleven reach 1,000 feet. Barely 100 buildings in all of New York City reach 600 feet. Less than 7,000 buildings in all of New York City break 115 feet.

20,000 cubic feet is larger than the inhabitable volume (Including garage) of the entire house I grew up in, with my entire family. It's about three times the volume of the apartment I currently live in with three other adults. And this is for one person. Four to twelve times the amount of living space per person is a lot of room, especially when you're not so confined in where you put all your traffic.