How Many Humans were at Hell's Gate?

[Human No More]

Originally Posted by Ashen Key

I actually would be surprised if the population of Hell's Gate was more than a 1000 - a) most of the base is taken up by hangars and the airfield and the plant-to-make-things (forget what it is actually called) and b) a lot of things would be mechanical/automated in the future. Far more than now. So you wouldn't actually NEED that many people - and they are probably running at fewer staff than optimal, because that's what businesses tend to do. Also, refer to Wainfleet being both Trudy's gunner AND in charge of the unit of AMP-suit drivers. I wouldn't be surprised if there were a lot of double-ups like that, pilots also being mechanics, etc.

Well said, I mostly agree here.

Well, the ISV carries around 200 passengers, plus crew. For the sake of convenience, if we assume ALL the scientists stayed, then that gives 200 people, excluding them. Equally, we could assume all the marines who went with Quaritch died and only the few that remained at Hell's Gate survived (we can see 2-3 getting onto the shuttle), then the remaining ~200 people would be enough for the miners, maintenance staff and control room staff. As mentioned above, people seem to do more than one job, and we already know that passenger and cargo transport is extremely expensive so it would make sense to keep numbers as low as practical.
As for passengers on the shuttle, it is mentioned that a shuttle can carry up to 100 passengers with two loads of cargo in a single trip, or six with no passengers (which seems about right with the numbers seen at the start with cargo in the middle), so presumably it took two trips to load everyone onto the ISV.

Since the shuttle can carry up to 100 people and cargo, then the AMPsuits in the attack were in the cargo section, there are 12 of them in total (6 from the dragon, 6 from the shuttle), plus marines from the shuttle and perhaps 30 more getting off the Samsons. Each scorpion and Samson has one pilot, plus two in the shuttle, while each samson dropped off what could be assumed to be 5-6 marines, so there were maybe 140-150 marines, of which it can be safely assumed that the vast majority of which were killed. For the avatar drivers, there are 10 links in the main link room, in addition to mobile sites, and while it wasn't shown at 100% utilisation, they will be doing other things as well, so I would guess 10-15 avatar drivers, plus maybe 20-30 support staff. Either way, both of those groups can be ruled out for returning as mentioned above.
Other than that, maybe 100 total general/maintenance staff could be considered a plausible number, maybe another 75 for mining (since it is largely automated and they just drive vehicles), leaving around 25 control room staff, all still fitting into a return ISV.