Re: Coolant [Spaceships]
 

Come to think of it, since they use the Emperor as a psychic navigation beacon during warp travel they do indirectly sacrifice souls for FTL.

I'm only really familiar with the main game fluff, but don't they have a lot smaller warp capable space ships in the RPG spin offs? The product blurbs make it sound like they would.

Re: Coolant [Spaceships]
 

No, not for the Imperium anyway. The smallest spaceships were only in the millions of metric tons while the largest were in the hundreds of millions of metric tons (ranging from a minimum of SM+15 to a maximum of SM+19 in GURPS terms). Of course, Orks used hulks, which were even larger, as they were often made of small asteroids, wrecked warp-capable spaceships, and stranger things.

Re: Coolant [Spaceships]
 

SM+19 sounds a bit small for the top end. For example the battleship Macragge's Honour is supposedly 26 km long, which is SM+26 I think (since it's an elongated box).

Re: Coolant [Spaceships]
 

Unfortunately, the larger ships in the Imperium do not make sense because they have a low density.

Re: Coolant [Spaceships]
 

Reminds me of someone (who was working on a Honorverse game) doing the math on superdreadnaughts and figuring out that they had lower density than air or something, and Weber actually changed their sizes in the back of a later book (in that section where they tend to have technical information, etc).

Re: Coolant [Spaceships]
 

Yes, a SM+26 spaceship should mass around 1 trillion metric tons. Its major weapon batteries would be capable of dealing 3d×5,000 damage, would require a crew of 100 million people, and would cost around $6 quadrillion. If the Imperium of Man was capable of fielding such monsters, it would have utterly destroyed its enemies thousands of years ago, though it really would make more sense to field 1,000 SM+20 spaceships instead.

Re: Coolant [Spaceships]
 

You can't really say anything about it's weapon batteries as it isn't designed using GURPS Spaceships. :) But yeah, in general, being a 40k author is all about throwing out random large numbers to sound impressive.

I haven't found a mass number for Macragge's Honour but some BFG ships have them.
Sword-class Frigate: 1.6 km, 6 M tonnes, 26 k crew
Claymore-class Destroyer: 1.4 km, 5.9 M tonnes, 21 k crew.
Lunar-class Cruiser: 5 km, 28 M tonnes, 95 k crew.

Re: Coolant [Spaceships]
 

A Lunar-Class Cruiser is the 'typical' 40K warship. At ~30 megatons, it would be SM+17, so 95k crew would be about right

Re: Coolant [Spaceships]
 

That suggests the Sword-class is comparable to a WWII era warship in terms of crosssection and density, and a Lunar-class is either shaped like a needle or made out of balsa wood. I would not look to WH4K for inspiration if hoping to find sensible numbers.

Re: Coolant [Spaceships]
 

My 40K spaceship conversions focus on the mass, not the dimensions. It just works better.