My two pennyworth on crew sizes was around 1500-2000 per damage point for Imperial and Chaos capital ships (adjust down a bit for Eldar and up a bit for Orks), but only around 2-500 total for escorts. Space Marine ships, as had been mooted, I would imagine to benefit from a lot of automated systems and wired in servitors to reduce their crew requirements to a minimum and increase their state of readiness in comparison with Navy ships. I would imagine that most Imperial and Chaos capital ships could find transport capacity for troops equal to about 1/3 to 1/2 their crew compliment. Tanks, artillery, Titans etc would need specialist transports to carry in any significant numbers.
A far more interesting way of looking at crew numbers is summed up in this excerpt from a short story I've been writing for my own amusement.
Nathan woke to the sound of screaming.
He lurched up with a half-strangled yelp, almost braining himself on the bottom of Kron's bunk. He stared wildly about him, gulping for breath. The oppressive redlight of the bunkroom still surrounded him, the cloying odour of sour sweat and grease still fought the sharp tang of coolant in the air down here. The room was quiet save for the drip of the condensers and the sussurance of night noises made by forty sleeping men.
Nathan wiped a shaky hand across across his eyes and peered over towards Hendriks. If anyone had screamed it would have been Hendriks, he had nightmares nearly every sleep-shift. They all did, but Hendriks just couldn't take it. Perhaps he had a guilty conscience, or perhaps he was just some dumb farmer who was completely terrified by being shut up in one of the Emperor's warships.
The scream came again, but it was tinny and distant, carried along by the conduits from another bunkroom. Pity the poor devils in there, thought Nathan, every one of them wide awake and praying the screamer didn't go berserk and start clawing and biting at them. Didn't turn into a wild beast like Fetchin had.
Nathan lay back in the narrow bunk and tried to recapture sleep. He tried to imagine all the other shipmen doing the same. Start with this gundeck. Forty guns with forty(ish) crews each, thats sixteen hundred, another gundeck on the port side for three thousand two hundred. Then there were the lance turrets, port and starboard, nobody seemed to know just how big the crews for those beasts were, call it another sixteen hundred a piece. This was working well, his eyelids were drooping. That was six and a half thousand souls (give or take). The torps probably had a crew bigger than a single gun but less than a whole deck - maybe a thousand. That made seven and a half... engines must be at least two or three thousand more...
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